Crop Science

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Aerial phenotyping tp identify superior sugarcane genotypes.
(2024) Hoffman, Natalie.; Joshi, Sheilesh Vinanay.; Singels, Abrahams.
Sugarcane is a globally important food and bioenergy crop which necessitates continual improvement through breeding to ensure its sustainable production under increasingly challenging environments. Compared to other major crops, yield gains in sugarcane have stagnated worldwide in recent years. This could be attributed to the resource-intensive and time-consuming nature of breeding a genetically complex crop with long growth cycles and large, diverse populations. The primary objective of sugarcane breeding is to develop superior genotypes with enhanced genetic gains, securing sustainable production for the future. Aerial phenotyping (AP) with high-throughput phenotyping sensor technologies and unmanned aerial vehicles (UAVs, commonly known as drones) could assist breeding by increasing selection efficiency and accuracy, uncovering genetic variation for yieldpromoting traits, and expediting large-scale trial screening. Key physiological traits governing canopy development and water use, namely green canopy cover (GCC) and stomatal conductance (gs), can be estimated from the aerially measured Normalized Difference Vegetation Index (NDVI) and canopy temperature (Tc), respectively. While promising, further research is required to evaluate the efficacy of AP in breeding. The study aimed to develop and test an AP procedure for identifying superior genotypes in sugarcane breeding. The specific objectives were to: (1) determine the impacts of ground (GCC and gs) and aerially measured traits (NDVI and Tc), on stalk dry mass yield (SDM) under well-watered (WW) and water deficit (WD) conditions; (2) develop an AP procedure for estimating gs, GCC and SDM from Tc and NDVI; (3) determine the genetic variation and broad-sense heritability of ground and aerially measured traits; (4) evaluate the feasibility and potential benefit of implementing AP to identify superior genotypes in breeding. These aims and objectives were addressed in three experimental phases. An unreplicated pilot trial with two genotypes grown under WW and WD conditions (~ 200 m2 in total) was used to establish preliminary relationships between ground and aerially measured traits under varying canopy and moisture conditions. Key findings were that FIPAR (fractional interception of photosynthetically active radiation - a surrogate measure of GCC) measured on the ground could be reliably estimated from NDVI, though the relationship required further investigation at partial canopy cover. Tc could be used to distinguish differences in measured gs between water treatments under moderate to severe stress conditions only. Overall, the experiment was used to formulate a preliminary AP protocol, with recommendations for further improvement in the subsequent phase. A replicated field trial with 54 genotypes, grown under WW and WD conditions (~ 3 ha in total) in plant and first ratoon crops, was used to assess trait correlations, genetic variation and broad-sense heritability of traits, and to refine the AP procedure. In line with previous research, the study confirmed FIPAR and gs as influential traits for determining SDM. FIPAR, measured at 2-3 months after crop start, could be used to identify high- and lowyielding genotypes, and could be predicted well from NDVI, at partial canopy for wellwatered crops. Breeding programs for irrigated environments could benefit from the early identification of superior genotypes if traits with high heritability, like FIPAR, can be accurately and rapidly phenotyped. Furthermore, results suggested that high gs benefits wellwatered crops, while relatively low gs could be advantageous in dry environments, though this requires further validation. Phenotyping of gs from Tc was mostly unreliable, and its practical application in breeding programs requires further evaluation on a larger, genetically diverse population with improved measurement procedures. It was concluded that NDVI and Tc, which both showed significant genotypic variation and moderate to high heritability, could be used to identify high- and low-yielding genotypes when measured early in the crop cycle in young, partially canopied, well-watered crops planted in multi-row plots. Novel results also showed potential for screening of drought tolerance using water treatment differences in Tc and SDM, which has not been reported previously for sugarcane. Overall, this research was used to establish an AP procedure for subsequent use in breeding trials. Lastly, the AP procedure was implemented in two rainfed early-stage breeding trials, with 1770 to 2130 genotypes, planted in replicated single-row plots over ~3.5 – 6 ha. This validation phase was used to test the utility of AP for enhancing selection accuracy and efficiency and contribute to yield improvement. The limited number of flights in the first trial prevented adequate capture of temporal and genotypic variations in aerially measured traits, which are necessary for accurate yield prediction. In the second trial, early estimates of NDVI and Tc, measured approximately 1.5 to 3 months after crop start in partially canopied, well-watered crops, showed significant genotypic variation, moderate to high heritability, and significant correlation with yield. Tc was also significantly correlated with yield when measured shortly after canopy closure but before row overlap due to crop growth. Despite these promising results, the AP procedure implemented in these early-stage breeding trials did not achieve the precision required for genotype selection. A comparison of direct (SDM-based) and indirect (based on aerially measured traits) selection approaches showed that the number of positive matches was mostly offset by a larger number of incorrectly identified genotypes using aerially measured traits. It was concluded that the effectiveness of AP in breeding is currently hindered by limitations in the precision of aerial measurements and challenges in breeding trial execution. The findings from this study highlight the potential and limitations of AP for physiological breeding. AP holds great promise for identifying genetic variation in yield-promoting traits, which could be leveraged in breeding for the identification of superior genotypes in irrigated environments, however further research is required to fully realize this potential. It is recommended to modify the design of early-stage trials by increasing plot length, number of rows, and row-spacing to facilitate accurate estimation of aerially measured traits using the developed AP procedure. Further efforts are also needed to overcome challenges inherent in breeding trial execution, such as lengthy planting periods introducing biases in early vigour, and variability in field soil composition, which directly and indirectly affect the quality of ground and aerially measured data. Should these recommendations be implemented, early screening of trials using AP could lead to shorter breeding cycles, the discovery of novel genetic variations, and improved selection efficiency, ultimately reducing the resourceintensive nature of traditional methods through early elimination of inferior genotypes from the program. In conclusion, this study demonstrates the potential of AP to enhance sugarcane breeding by facilitating the early detection of important yield-promoting traits, particularly in wellwatered crops. While AP shows promise to enhance sugarcane breeding, further work in refining its application is essential to fully realize its benefits. These research findings provide a strong foundation for future efforts to develop innovative breeding strategies and precision agriculture technologies.
Agro-morphological, nutritional and genetic diversity analyses of Bambara groundnut (vigna subterranea (L.) Verdc)
Hlanga, Nokuthula Cherry.; Modi, Albert Thembinkosi.
Bambara groundnut (Vigna subterranea (L.) Verdc) is a legume crop with potential to address food insecurity in sub-Sahara Africa. However, a lack of agronomic, genetic and nutritional information on the crop hinders its full potential utilization. Nineteen Bambara groundnut lines were evaluated in the field in 2017 and 2018 at two sites. The lines showed significant differences (P<0.05) for all the measured traits. Lines such as IITA686, Cream and Uniswa Red-R were found to have superior performance for multiple traits such as number of seeds per plant, seed mass per plant, plant height and mid-leaf width. The genetic variation among the Bambara groundnut lines was assessed using 20 polymorphic SSR markers The markers exhibited an average polymorphic information content (PIC) of 0.57 and the observed heterozygosity was 0.58, showing that the lines exhibited a considerable level of outcrossing. The lines were clustered into three groups based on the principal coordinate analysis. The highest genetic distance was 0.60 between Tiganecuru and S19. Lines such as IITA686, Cream and Uniswa Red-R that had good performance for multiple agronomic traits occurred within a genetic distance of 0.40 making them genetically divergent enough for generating crosses for Bambara groundnut improvement. The ash, fat, proteins, starch, calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), phosphorous (P), sodium (Na), copper (Cu), and zinc (Zn), acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were determined in the Bambara groundnut lines using combustion and chemical digestion procedures. The nutritional content varied significantly (p<0.05) among the lines with lines S19, Gresik, Pong-Br-UNK, Pong-Cr exhibiting high means for starch and protein content ranging from 11.05 to 11.94%. Genotypes Mix, Pong-Br-UNK, 42-1, Gresik, Uniswa Red-R, and Brown were clustered together based on their high starch, Na, Ca, fat, and Mn contents. The negative correlations among some of the nutritional content would be a challenge for simultaneous selection to breed nutritious Bambara groundnut lines. The lines with high content for multiple nutritional elements such as 211-57, Pong- Br-EN and Uniswa Red-G were recommended for production. It was imperative to determine interrelations among agronomic traits and nutritional content with seed mass for indirect selection. Among the agronomic traits, number of seeds (NS r=0.58, p<0.01), number of healthy seeds (NHS, r=0.51, p<0.05) and plant height (PH, r=0.45, p<0.05) exhibited the strongest associations with seed mass. These traits had NS, NHS and PH high direct effects on seed mass of 2.04, 1.72 and 0.60, respectively. These findings provide a means to facilitate indirect selection of genotypes with high seed mass productivity via proxy. Overall, the study found significant agro-morphological and genetic variation among the Bambara groundnut lines, which would be a prerequisite for Bambara groundnut improvement. The superior lines identified for multiple traits and genetic divergence were IITA686, Cream and Uniswa Red-R. Key words: Agro-morphology; Bambara groundnut; Genetic variation; Seed quality
Agronomic and physiological approaches to improving productivity of selected sweet potato (Ipomoea Batatas L.) cultivars in KwaZulu-Natal : a focus on drought tolerance.
(2014) Mgcibelo, Motsa Nozipho.; Modi, Albert Thembinkosi.
Sweet potato (Ipomoea batatas L) is a resilient food security crop with wide adaptation characteristics and hence can fit well under smallholder production. Its importance as a food security crop in relation to drought is still underestimated and fails to attract sufficient attention from agricultural researchers. The adaptive responses of different sweet potato cultivars to different agro-ecological areas may vary, and sweet potato is an important crop for small-holder farmers in KwaZulu-Natal (KZN) of South Africa, which has diverse agro-ecological areas. Adaptive responses of sweet potato cultivars in KZN’s ecological regions are not known. The possible varying adaptive responses may impact on the food and nutrition security role of sweet potato. This study evaluated the ecophysiology, growth, yield and nutritional composition of three locally bred sweet potato cultivars in response to a range of climates and soils from KZN, South Africa. With the help of smallholder farmers, field experiments were conducted at three sites located in three different agro-ecological areas (Deepdale, Umbumbulu and Richards Bay) of KZN. Agronomic, physiology and yield data were collected. Harvested roots were further analysed for selected nutrients (starch and β-carotene) and other metabolic responses to drought stress. A separate study on physiological and yield response of sweet potato to water stress was conducted under controlled environment. Metabolic analyses were conducted continuously during plant growth. Plant growth, physiological responses and yield were significantly (P ≤ 0.05) influenced by growth environment. Drought stress in Richards Bay resulted in poor plant growth, low yields and low nutritional content (starch and β-carotene content). High temperatures and evapotranspiration (ETo) were associated with drought stress. The other locations (Deepdale and Umbumbulu) where ETo was low showed increased plant growth, yields and nutritional content. The cultivars’ ecophysiology, growth and yield were not suitable for the Richards Bay agro-ecology/bioresource group. They were more suitable for Umbumbulu and Deepdale agro-ecology/bioresource groups. Under controlled conditions, the cultivars adapted to water stress through reduced canopy size. When fully-irrigated, they increased vegetative growth than storage root growth, thus resulted in low storage root yield. This suggested that the cultivars were drought tolerant and suitable for production in marginal areas. Leaf phytochemical content was high in sweet potato leaves compared to other common leafy vegetables. It was even higher in leaves of water stressed plants. This indicated that both leaves and storage roots can be utilised for improved food and nutrition security. Under marginal areas where storage root yield is compromised, the leaves can contribute to food and nutrition security. In areas where rainfall is not limited, communities can benefit from both storage roots and leaves.
Agronomic characterization and evaluation of pigeon pea landraces in KwaZulu-Natal Province of South Africa.
(2015) Hluyako, Lindah London.; Magwaza, Lembe Samukelo.; Odindo, Alfred Oduor.
Abstract available in PDF file.
Agronomic performance of sugarcane varieties derived from tissue culture (NovaCane®) and conventional seedcane under rainfed conditions.
(2017) Shezi, Sbonelo Nicholus.; Ramburan, Sanesh.; Modi, Albert Thembinkosi.
The use of tissue culture (TC) plants have been promising for the production of true-to-type, disease free planting material. However, TC plants have been shown to possess an altered phenotype (high tillering and thinner stalks) compared with conventionally propagated sugarcane from setts (hereafter referred to as conventional or Con). Limited information is available for the response of different varieties to the TC process. Additionally, the effects of any altered phenotype in subsequent stages has not been evaluated. Three field experiments were conducted under rainfed conditions at South African Sugarcane Research Institute (SASRI) Mount Edgecombe experiment station to gain insights into these factors. The aim of experiment 1 was to investigate growth and yield differences between the TC and the Con plants for different varieties. Here, a field trial was established as a randomised block design with four replications of four varieties (N12, N31, N41, and N48) planted using three methods: 1) TC derived plants (spaced at either 30 (TC30) or 50 (TC50) cm apart; 2) conventional hot water treated seedcane setts (Con); and 3) single-budded sett derived plants (speedlings) planted 50 cm apart (SP50). The aim of experiment 2 was to investigate the effects of different in vitro procedures on several phenotypic and agronomic characteristics of TC plants of sugarcane. A field trial was established as a randomised block design with four replications consisted of two varieties (N41 and N48) derived through three variations of the in vitro NovaCane® procedure, namely i) the standard procedure, ii) plantlets exposed to CoCl2 (NovaCane® (CoCl2)) and iii) plantlets that underwent a secondary meristem excision process (NovaCane® (secondary)) from in vitro material. The plantlets from all three treatments were planted using two (30 and 50 cm) plant spacings. The aim of experiment 3 was to compare the performance of seedcane obtained from TC (stage 1) and Con when planted at different planting rates. The seedcane for experiment 3 was derived from the corresponding treatments in experiment 1, which were: 1) stalks derived from TC50 and planted at a lower planting rate (TC50 low); 2) stalks derived from TC50 and planted at a higher planting rate (TC50 high); 3) stalks derived from TC30 and planted at a lower planting rate (TC30 low); 4) stalks derived from TC30 and planted at a higher planting rate (TC30 high); and 5) stalks derived from Con and planted at a normal planting rate. Yield and yield component measurements for these experiments were taken at harvest and data were analysed by ANOVA. For experiment 1, there were no significant differences in cane yield, stalk height and stalk mass between propagation methods for all varieties in both crops harvested. For varieties N12 and N31, both TC treatments produced significantly thinner stalks and higher stalk population compared with the Con treatment when averaged across crops. Variety N48 was insensitive to the TC process, indicating that the phenotype of this variety was maintained during the TC process. The TC30 and TC50 treatments did not differ significantly for any parameter in both crops for all varieties, showing that plant spacing did not affect growth. The SP50 treatment produced significantly thicker stalks compared with the TC50 for varieties N12, N31 and N41 in the plant crop. For experiment 2, the plants produced through the NovaCane® (CoCl2) procedure resembled those produced through NovaCane® for all phenotypic and agronomic characteristics in the plant and first ratoon crops. The plants produced through the NovaCane® and the NovaCane® (secondary) procedures differ significantly for stalk population only, with the NovaCane® treatment having significantly lower stalk population compared with the NovaCane® (secondary) treatment for variety N41. Planting at closer (30 cm) or wider (50 cm) spacings did not have an effect on plant growth and to the response of varieties to the in vitro treatments. For experiment 3, crop derived from TC had a significantly higher mean cane yield and TERC compared with the crop derived from the Con. The crop derived from TC had a significantly higher mean stalk population compared with the crop derived from Con. This was observed for varieties N12 and N41 in particular. The crop derived from TC produced significantly thinner and taller stalks compared with the crop derived from Con. The effects of planting rates and TC source (TC30 vs TC50) were not significant for any parameter. Varieties responded differently to the TC process (N48 did not show phenotypic variations). As a result, screening of varieties for phenotypic to TC is recommended to make grower aware of expected changes in the phenotype. This should mitigate the risks of possible poor adoption of varieties based on thin stalks. It is recommended that TC plants be propagated using wider (50 cm) plant spacings, as this is more economical. The lack of differences between in vitro procedures suggests that propagation of new genotypes through standard NovaCane® procedures for commercial release should continue. The seedcane derived from the TC at stage 1 can be used as planting materials for commercial production without any negative effects on productivity in subsequent propagation stages. This is despite persistence of the reduce stalk diameter, higher stalk population phenotype. Lack of differences between the higher and the lower planting rates of TC-derived crops suggests that lower planting rates should be used for economic reasons.
Agronomic performance of wild mustard in an intercropping with green beans.
(2005) Phiri, Nathan.; Modi, Albert Thembinkosi.
Wild mustard (Brassica spp.) is used as an edible wild leafy vegetable by indigenous people in South Africa. The potential of wild leafy vegetables in agriculture is not well understood, because there is generally no agronomic research on their production practices. The objective of this study was to examine the performance of three wild mustard species (herein referred to as I, K and M) over four cropping seasons in an intercropping system with green beans (Phaseolus vulgaris L. cv. Imbali). The crops were grown with and without organic fertiliser under dryland conditions at two sites (The University of KwaZulu-Natal Research Farm, Ukulinga and in a rural area of Umbumbulu, KwaZulu-Natal within the farmers' locality) during autumn, winter, spring and summer of 2004 to 2005. Plant development (leaf number, plant height and fresh biomass) during the first six weeks after sowing and seed yield were used to determine agronomic performance of each species. Nutrient status of the rhizosphere soil was determined at 42 days after sowing for each species to determine what effect growing the species would have on mineral availability. Wild mustard production significantly (P < 0.01) performed better at Ukulinga than Umbumbulu. Polyculture was beneficial for wild mustard leaf accumulation and green bean production as determined by land equivalent ratios greater than one for all species combinations, regardless of fertiliser application. Cool environmental conditions occurring in autumn and spring were more favourable (P < 0.05) for wild mustard and green bean biomass accumulation than summer and winter conditions. However, wild mustard seed yield was highest in winter compared with autumn and spring, and there was no measurable seed production in summer. Soil analysis results at 42 days after sowing showed an increase in P, K, Cu and Mg in the rhizosphere of wild mustard without organic fertiliser. Polyculture improved Zn, Cu, Mn and K in wild mustard leaf tissue. It is concluded that wild mustard can be grown as a leafy vegetable throughout the year, but it requires cool environmental conditions to enhance seed yield. Species M significantly yielded better biomass and seeds than species I and K during all the seasons. However, species K performed the least in all aspects.
Alleviation of cotyledonal cracking in green beans (Phaseolus vulgaris L.) by calcium seed treatment.
(2003) Mazibuko, Tholakele Gladness.; Modi, Albert Thembinkosi.
Cotyledonal cracking is a physiological disorder of common beans, and rarely, soybeans that occurs as transverse fissures across the cotyledons. The phenomenon is generally referred to as transverse cotyledonal cracking (TVC). Although TVC has been known for decades now, factors contributing to its occurrence, and how the disorder can be alleviated, are still not well understood. The objective of this study was to investigate the effect calcium seed treatment on cotyledonal cracking in green bean (Phaseolus vulgaris L.) seeds. Six cultivars (Imbali, Sodwana, Outeniqua, Elangeni, Tokai and Tongati) were examined for water absorption patterns during a 6-h imbibition in distilled water. Cultivars were categorised according to the rates of water absorption, in the presence of seed coat, and there was a significant correlation between seed size and water absorption rate. To examine seed predisposition to TVC, seeds were imbibed with and without seed coats and TVC was scored every hour for the 6-h duration of imbibition. There was a significant positive correlation between water absorption rate and TVC. Genetic analysis of the cultivars using SDS-PAGE revealed that there are possible differences between the resistant cultivars and sensitive cultivars, with respect to protein patterns. Imbali, one of the small cultivars (-1.5 g seed -1) that imbibed water uniformly, was resistant to cotyledonal cracking compared to the largest cultivar (Sodwana -2.5 g seed -1), which also had a high rate of water absorption. Priming seeds with calcium (CaS04, Ca(N03)2 and CaCl2) osmolarities (0, 1, 10, 50, 100, and 100 mM) increased seed calcium content and reduced susceptibility to TVC. Comparison of priming and seed coating with respect to field emergence, TVC, stand establishment and seed yield showed that coating was better than priming. However, greenhouse studies showed that the effect of priming in the progeny of treated seeds was significantly better than that of coating, with respect to TVC reduction. In both laboratory and field studies, it was clear that applying calcium concentrations greater than 50 mM was not necessary to alleviate TVC and improve seed performance. Seed germination and emergence were reduced at calcium concentrations greater than 50 mM. It is concluded that calcium is effective in controlling TVC under both laboratory and field conditions. The effect of calcium is associated with regulation of imbibition and improvement of seed calcium content. Enhanced seed calcium content likely improved cell wall integrity.
Application and evaluation of aquacrop, dssat and simple model in modelling yield water use of selected underutilised cereal crops.
(2021) Nzimande, Thembelihle Nkosingiphile Millicent.; Mabhaudhi, Tafadzwanashe.; Chimonyo, Vimbayi Grace Petrova.
The study compared yield, biomass, and water use (WU) for maize, sorghum, and millet simulated using three crop models of varying complexity: AquaCrop, DSSAT and the SIMPLE model. The hypothesis was that there is no significant difference between simple and complex models of estimating yield, biomass and WU. A standard set of crop parameters was used to develop crop files for all three models. Similar soil, climate and management descriptions attained from the Ukulinga Research Farm were used across the models. Six general circulation models (GCMs) were used as climate input data to model past, present, mid-, and late-century climate change impacts on cereal crops. The effect of irrigation (as a management practice) on yield and water use was assessed using the mid-century projections. The performance of the three models was observed to be statistically different. Based on the mean bias error, all models overestimated yield, but the lowest overestimation was with AquaCrop (0.22 t/ha) followed by DSSAT (0.24 t/ha) and the SIMPLE model (0.69 t/ha). Other statistical indicators, viz., RMSE and R2, illustrate that the simulation of yield and WP in AquaCrop was more satisfactory than DSSAT and the SIMPLE model. Across all the time scales, it was observed that AquaCrop simulated the highest yield and biomass, and the SIMPLE model simulated the lowest yield across the GCMs, which were inconsistent. Applying a higher amount of irrigation at more frequent intervals resulted in higher yield, biomass and WP. AquaCrop showed the highest simulated mean yield for maize (8.34 t/ha), millet (6.86 t/ha) and sorghum (5.28 t/ha). Highest WP was observed under AquaCrop for maize (21 kg/ha/mm) and millet (15.10 kg/ha/mm), the SIMPLE model for sorghum (13.37 kg/ha/mm). The study confirms that DSSAT requires relatively more input data but does not always perform more satisfactorily. The SIMPLE model requires fewer input requirements than AquaCrop and DSSAT; however, it is less sensitive to management changes. AquaCrop had relatively incomparable results to DSSAT and the SIMPLE model and was observed as the most suitable model for simulating yield, biomass, and WU of the selected cereal NUS under climate change and irrigation management scenarios. Before their application, it is essential to calibrate crop growth parameters for local conditions or use parameters from local field studies when applying complex crop models such as DSSAT specifically for marginal environments, such as South Africa. On the other hand, AquaCrop performed reasonably well with minimal input requirements, confirming its application in datalimited and marginal environments. However, it is recommended that there must be calibration for all the models using inputs specific to locations.
Artificial soil profile for vegetable production: a potential case of urban agriculture.
(2020) Phungula, Nosipho Precious.; Modi, Albert Thembinkosi.
A significantly large population of South Africa migrates from rural to urban areas, leaving opportunities for small-scale subsistence agriculture for a perceived better livelihood. Food insecurity and poverty seem to increase in the peri-urban areas because of poor opportunities for food production and the inescapable need for money to survive. The advantages of urban farming have been published in the literature for many years, but there are still opportunities to introduce innovative methods that are confirmed by scientific findings. This study aimed to determine the efficiency of portable bags and artificial soil profiles on year-round production of common vegetables in South Africa, namely, Swiss chard, lettuce, onion, beetroot, and green pepper. Artificial soil profiles were created in the bags using commonly found urban homestead common organic garden refuse (grass and wood) garden soil and collected rock, respectively. One vegetable, lettuce was used to represent fertilizer requirements and three recommendations (0, 50, and 100%) were applied. Measured crop growth parameters included plant height, leaf number, stomatal conductance, chlorophyll content index, leaf area index, and photosynthetically active radiation. Soil moisture content, soil water potential, and soil temperature were also determined. Crop biomass yield and mineral content at harvest were also determined. The artificial environment was compared with soil plot environment (sandy loam soil with 110 mm depth) under rainfed conditions, with limited supplemental irrigation during dry periods. Results showed that vegetable production is possible all year round in both artificial and real profile conditions. The vegetable yield was reduced in non-soil artificial profiles, but the fertilizer application supported it all year round. Vegetable nutritional value, in terms of selected minerals, differed significantly between seasons and less between normal and artificial profiles, where even no fertilizer application produced yield all year round. The study concludes that disposable bags have a potential role for vegetable production in urban areas, where land area is limited. Potential food security benefits are linked more to nutrient access than quantity access. There is a need to test the findings of the study a different environmental and socio-economic conditions, to influence government policy. Keywords: artificial soil profile, fertilizer, season, temperature, vegetable nutrient content.
Assessing nutritional water productivity of selected African leafy vegetables using the agricultural production systems simulator model.
(2020) Kunene, Thobeka Gladness.; Modi, Albert Thembinkosi.
Food and nutrition insecurities are regarded as one of the main challenges in the Sub-Saharan region. While substantial progress has been made to address food and nutrition challenges, this progress has varied across the region and over time in response to climate change hazards. Agriculture has been used as the main driver to improve food and nutrition security; however, productivity in these marginalised communities remains low. African leafy vegetables (ALVs) provide an unprecedented opportunity to ensure food security, lessen poverty and diversify farming systems while improving human health and increasing income. Crop modelling can generate information about the crop's growth, development, water, and nutritional needs. The primary objectives of this study were (i) to assess the growth and productivity of selected ALVs (amaranth (Amaranth spp), cowpea (Vigna unguiculata), sweet potato (Ipomoea batatas) and wild mustard (Sinapis arvensis)) under different management practices, and (ii) assess water productivity (WP) and nutritional water productivity (NWP) of the selected ALVs. Desktopbased research was conducted to achieve the mentioned objectives. Here, information on the studied crops' agronomy secondary data was gathered through a careful literature search. This secondary information was then used to model growth and productivity and quantify nutritional water productivity at different management practices. The Agricultural Production Systems Simulator (APSIM) was used to simulate growth and productivities under different management scenarios of planting date, plant density, fertiliser application and irrigation. We used the soil and climatic data from the University of KwaZulu-Natal's research farm (Ukulinga Research Farm) situated in Pietermaritzburg, South Africa (29°37′S; 30°16′E; 775 m a.s.l.), to calibrate the model. All data analysis was done using descriptive statistical analysis (R software). All mean values were subjected to a t-test set at p<0.05 significance. The results showed that depending on crop species. Different management practices can be relevant to achieve optimum growth and productivity for various purposes. The investigated ALVs were found to have high nutrient content. Compared to one another, amaranth was more nutrient-dense and wild mustard the least dense crop. On the other hand, NWP was comparatively high on both amaranth and cowpea.
Assessing the effect of crop intensification in improving aricultural productivity in smallholder farmers' fields : a case study of northern KwaZulu-Natal, South Africa.
(2017) Mthembu, Hloniphile.; Odindo, Alfred Oduor.
Crop intensification is adopted by different countries to address their challenges, which may include low standards of food and nutrition security, limited arable land and land degradation. To assess the effect of crop intensification in improving agricultural productivity in smallholder farmers in Northern KwaZulu-Natal, a qualitative study and in-field experiment were conducted. In a qualitative study the Participatory Rural Appraisal (PRA) tools namely, focus group discussions, transect walks and key informant interviews was used. A random purposive sample of 249 smallholder farmers from 5 local municipalities of uMkhanyakude district was undertaken. The following information was explored: different farming systems; landscape; availability of irrigation systems or water sources; classification of farming soil types; perception of soil fertility; planting and rainfall patterns. Smallholder farmers’ demographics, socio-economic status, typical farming systems, differences between backyard gardens and crop fields, water sources, knowledge and skills on farming systems and practices, understanding and benefits of mixed farming, crop mixing and intercropping, soil fertility and soil acidity management were also explored. The findings of the study revealed that the age of the smallholder farmers ranged between 40-65 years. About 90% of the smallholder farmers who participated in this study were females. 45% of smallholder farmers’ households are headed by females. A typical household of the smallholder farmers, is characterised by more than two dwelling places in one household compound with mixed farming. Water is a serious problem in uMkhanyakude district. 70% of the farmers primarily used indigenous knowledge and acquired their skills on farming systems and practises from generation to generation indigenous knowledge system. In-field experiment was conducted. It was laid out in a randomized complete block design (RCBD) with three replicates having a net plot size of 3.6m x 5m. The following treatments were evaluated: Maize intercropped with beans (T1), Maize intercropped with pumpkins (T2), Maize intercropped with beans and pumpkins (T3), Maize sole crop control (T4), Beans sole crop control (T5), Pumpkins sole crop control (T6) and Bean intercropped with pumpkins (T7). Productivity was measured using the following indices: Land Equivalent Ratio (LER), Area Time Equivalent Ratio (ATER), Competition Ratio (CR), Relative Crowding Coefficient (K) and Aggressivity (A), Actual Yield Lost (AYL), Intercropping Advantage (IA) and Monetary Advantage Index (MAI). The study revealed that the intercropping system with three crop species in all three location showed greater values of LER (1.8, 1.9, and 1.7) and ATER (1.8, 1.9, 1.7). The crowding coefficient (K) was the highest in Mtubatuba and Hluhluwe treatment 3 (maize/bean/pumpkin) (80.72 and 61.78) respectively. Intercrops showed positive Agressivity, and greater competition ratio and actual yield loss when compared with the main crops. Intercropping advantage (IA) and monetary advantage (MAI) in treatment 3 (maize/bean/pumpkin in all locations showed greater values (58327, 12850, 5532) and (54573, 59487, 19606) respectively. The productivity of the intercropping system where there are more than two crops is considered greater in terms of land equivalent ratio (LER), area time equivalent ratio, (ATER).
Assessing the fertiliser value of co-composted biochar compost made from black soldier fly larvae faecal residue.
(2021) Nkomo, Nqobile.; Odindo, Alfred Oduor.; Missengue, Roland.
The Black Soldier Fly Larvae (BSFL) technology can treat faecal sludge emptied from full Urine Diverting Dry Toilets (UDDT’s). A residue containing residual mineral elements such as nitrogen (N), phosphorus (P), potassium (K), and high organic matter, pathogens, and potentially heavy metals is left behind. Improper disposal of the residue can pose a challenge and lead to environmental pollution and health threats. However, there is potential for recycling BSFL Residue. The fertiliser value of BSFL Residue as an organic fertiliser has not been studied in South Africa. This study was carried out to evaluate the use of co-composted biochar compost made from BSFL Residue as a plant nutrient source for maize production. The residue was pyrolysed for 120, 90, and 60 minutes at 300 °C, for 60 and 45 minutes at 400 °C, and 60, 45, and 30 minutes at 500 °C. Biochar pyrolysed at 300,400, and 500 °C for 60, 45, and 30 minutes, respectively, was not burned and was analysed for physico-chemical, and biological characteristics. Biochar yield decreased significantly with increasing pyrolysis temperature. Surface area, pH, extractable phosphorus (P), exchangeable bases, trace metals significantly increased with pyrolysis temperature. Pathogens were destroyed with pyrolysis. Biochar pyrolysed at 500 °C for 30 minutes was chosen based on its characteristics as a bulking agent in the co-composting experiment. Co-composting of the residue was carried out, and chemical and physical characteristics of BSFL Residue composts (COMBI (compost with biochar) and (COMP (compost without biochar)) were compared to chicken manure (CM) and BSFL Heated Residue (HR). pH and exchangeable bases in BSFL Residue COMBI were higher than BSFL Residue Compost but less than BSFL HR and CM. Composting with biochar significantly increased trace elements, water holding capacity, total P, and total N in the BSFL Residue COMBI compared to BSFL Residue Compost. The BSFL Residue COMBI, BSFL Residue COMP, BSFL Residue, HR, CM, Chemical Commercial Fertiliser (CCF), and control were incubated in a sandy Cartref soil over a 112-day incubation period to determine phosphorus and nitrogen release patterns. Phosphorus decreased in all treatments during the first 21 days except for the control. Phosphorus release started after day 21, and the pattern for BSFL Residue COMBI and BSFL residue Compost were comparable, indicating the potential of using these amendments for crop production. Chicken manure had the least phosphorus released at the end of the incubation. Ammonium decreased with a concomitant increase in nitrates for all treatments. Nitrate release was lower for BSFL Residue COMBI compared to BSFL Residue Compost. An additional source of N is needed if BSFL Residue COMBI is to be used as a fertiliser based on P. The highest nitrate release was observed in CM. Amendments used in the incubation were used at the recommended and double recommended application rate to grow maize in a greenhouse pot trial. Statistically similar yields were obtained in grain harvested from COMBI, COMP CCF, and CM. More researchshould be carried out on the residual effect of BSFL COMBI on subsequent maize growth to establish possible residual fertility on the second cycle of growth. Keywords: biochar; biochar co-compost; black soldier fly larvae;faecal matter; fertiliser-value; nutrient recycling; phosphorus; pyrolysis; crop growth.
Assessing the potential use of struvite and effluent from decentralized wastewater treatment systems (dewats) as plant nutrient sources for early maize ( zea mays) growth.
(2021) Sokhela, Fortunate Sthabile.; Odindo, Alfred Oduor.; Muchaonyerwa, Pardon.
The Decentralised Wastewater Treatment System (DEWATS) effluent has been shown to contain considerable concentrations of mineral elements such as nitrogen (N) and phosphorus (P), which are important for plant growth. The use of effluent for agriculture as a sole nutrient source is limiting in terms of macronutrient and micronutrient content supplied to plants. There is little information about the effects of combining the effluent with struvite and commercial fertilizer for crop production. The study aimed to determine the effect of applying struvite and DEWATS effluent as nutrient sources combined or in combination with urea/single superphosphate (SSP) fertilizers on the growth, nutrient uptake, and biomass production of maize. The specific objectives were: (1) to determine N and P release pattern of struvite when applied solely or combined with urea relative to SSP fertilizers combined with urea in a sandy soil, (2) to determine N and P release pattern of DEWATS effluent applied solely or combined with struvite and or SSP fertilizers in a sandy soil, (3) to investigate the effect of applying struvite and DEWATS effluent as nutrient sources combined together or with urea/SSP fertilizers on the growth, nutrient uptake and biomass production of maize. Two soil incubation experiments were set up under controlled room temperature at 25oC and 80% atmospheric humidity to determine the N and P release pattern of human excreta derived materials (HEDMs) (struvite and DEWATS effluent) with supplementary chemical fertilisers urea and SSP. The first experiment was laid out as a single factor analysis with the following treatments: (i) struvite alone, (ii) urea alone, (iii) SSP alone, (iv) struvite + urea, (v) SSP + urea. Each treatment was replicated 3 times to give 15 experimental units (in 5 litre ventilated containers). The second experiment was also laid out as a single factor comprising the following treatments: (i) effluent alone, (ii) struvite + effluent, (iii) effluent + SSP, and (iv) a control, all replicated 3 times to give 12 experimental units (in 5 litre ventilated containers). The fertiliser materials were applied to achieve an equivalent of 200 kg N/ha and 60 kg P/ha to meet maize nutrient requirements from the Cartref (sandy soil). The effluent in the study was applied as an irrigation source to achieve a 100% soil water holding capacity while supplying nutrients at the same time. Data was collected on the ammonium N, nitrate N, and extractable P release weekly, for 56 days. A pot trial was set up in 20 litre pots in the tunnel at 26oC air temperature and 65% atmospheric humidity to determine the effect of applying struvite and treated effluent from the anaerobic filters (AF) on growth, nutrient uptake, and biomass production of maize. The pot experiment was set up as a 9 x 2 factorial experiment in a completely randomised design (CRD) with the following treatments: fertilizer combinations (8 levels- (i) struvite + urea (recommended rates); (ii) ) struvite + urea (half recommended), (iii) struvite + effluent (recommended rates); (iv) struvite + effluent (half recommended); (v) SSP + effluent (recommended rates); (vi) SSP + effluent (half recommended); (vii) SSP + urea (recommended rates); (viii) SSP + urea (half recommended) and the control. The second treatment was maize variety with 2 levels –‘Colorado’ and ‘IMAS’. The treatments were replicated three times. Three maize seeds were planted per pot and were thinned 3 weeks after planting to one plant per pot. The amount of water applied as irrigation was based on Cartref soil water requirements. Soil moisture was maintained at 70-100% field capacity. The soil incubation experiment showed that there were significant (P<0.05) differences among treatments- struvite (S), effluent (E), SSP (P), urea (U), struvite + urea (SU), struvite + effluent (SE), effluent + SSP (PE), SSP + urea (PU) and zero fertilizer. The combination of HEDMs and commercial nutrient sources released higher ammonium-N and nitrate-N than sole applications and when commercial SSP + urea was applied together. Ammonium N declined over time and nitrate N increased rapidly over time. The findings suggested that the fertiliser combination of HEDMs and commercial fertiliser increased nutrient N availability to the soil. Phosphorus did not change over time in all treatments. The pot experiment result showed that there were significant (P<0.05) differences observed in plant height, leaf number, chlorophyll content, dry matter, N and P uptake, and grain + cob yields among the different fertiliser combinations (SE, SU, PE, PU) at both recommended and half recommended application rates. In conclusion, optimising N and P supply through a combination of the effluent and struvite or with inorganic fertilisers could potentially be considered as a better option for providing a balanced supply of nutrients than when applied separately.
Assessing variability in yield performance and nutritional quality of citron watermelon (citrullus lanatus var. citroides (L.H. Bailey) mansf. ex greb.) genotypes under drought conditions.
Mandizvo, Takudzwa.; Odindo, Alfred Oduor.; Mashilo, Jacob.
Research is needed to investigate the potential of Neglected Underutilized Crop Species (NUCS) such as citron watermelon, to increase crop diversity and mitigate the effects of prolonged drought because of climate change. Little is known about citron watermelon’s food quality attributes (seed popping yield, nutritional value, and lignin content). In addition, there is a need to understand the agro-morphological, physiological and biochemical characteristics associated with drought tolerance in citron watermelon. Therefore, the objectives of this study were: (1) to assess citron watermelon genotypes for food quality attributes (popping yield, chewability and nutritive value) of seeds based on visual appearance, (2) to screen citron watermelon accessions for drought tolerance using morphological and physiological traits, (3) to study the root system architecture of citron watermelon accessions and identify droughtadaptive root traits for cultivar improvement under water-stressed environments and (4) to reveal how citron watermelon responds to combined stress (water deficit and high temperature) with respect to growth, water status, reserve mobilization and metabolite partitioning at seedling stage. The first study determined whether citron watermelon seed’s nutrient composition and physical properties are related to the visual appearance of seed coat. Brown and red-coloured seeds have a higher popping yield than dark-coloured seeds with poor popping ability and are prone to burning during roasting. Seed coat thickness was closely related to hemicellulose contents and cellulose across all seed coat colours. High hemicellulose, cellulose and lignin contents were found in dark and red seeds associated with thick seed coats and increased chewing strength than white seeds. From a nutritional perspective, dark and red seeds were good sources of Cu, Zn, nitrogen and sulfur than brown seeds. Dark and brown seeds were good Mg sources, whereas dark and red seeds were vital sources of potassium. The second study determined variation in drought tolerance among South African citron watermelon landrace accessions for selection and use as genetic stock for drought-tolerance breeding in this crop and closely related cucurbit crops such as sweet watermelon. The forty citron watermelon accessions evaluated showed varying levels of drought tolerance based on morphological and physiological traits. These allowed five distinct groupings, namely: A (highly drought-tolerant), B (drought-tolerant), C (moderately drought tolerant), D (droughtsensitive) and E (highly drought-sensitive) based on various drought tolerance indices. The following accessions (WWM02, WWM-05, WWM-09, WWM-15, WWM-37(2), WWM-39, WWM-41 (A), WWM-46, WWM-47, WWM-57, WWM-64, WWM-66, WWM-68 and WWM-79) were categorized as highly-drought tolerant and accessions WWM-03, WWM-08, WWM-14, WWM-21, WWM-33, WWM-35(1), WWM-35(2), WWM-67 and WWM-76 as drought tolerant. These are useful genetic stocks for improving drought tolerance in this crop and related cucurbit crops, including sweet watermelon. The third study examined citron watermelon accessions’ root system architecture and identified drought-adaptive root traits for cultivar improvement under water-stressed environments. The study showed that plasticity and biomass allocation shift according to genotype, presumably to optimise the use of limited resources. The study found significant phenotypic variation in root architecture among citron watermelon accessions that may relate to differences in water uptake. The following traits of root system architecture (RSA) (total root length, root system width, convex hull area and total root volume) were associated with drought tolerance. Further, RSA traits such as root dry mass and root shoot mass ratio were highly correlated with root branch count, root system depth, total root length and leaf number. These traits are useful selection criteria for breeding and developing water-efficient citron watermelon accessions for cultivation in drought-prone environments. The fourth study identified multiple abiotic stress-induced modifications in different phytosterols (campesterol, sitosterol and stigmasterol) in the seedling axis (embryonic leaf and root) of genetically distinct citron watermelon accessions. Detailed evaluation of phytosterols was done and the effects of the changes observed in stressed plants were discussed.
Assessment of bambara groundnut (vigna subterranean L. verdc) recombinant inbred lines (rils) for agro-morphological traits, cooking quality properties and nutritional composition.
(2022) Ruzive, Amanda.; Mabhaudhi, Tafadzwanashe.; Shayanowako, Admire Isaac Tichafa.; Govender, Laurencia.
Bambara groundnut response to controlled environment and planting date associated water stress.
(2011) Sinefu, Fikile.; Modi, Albert Thembinkosi.
Bambara groundnut is a protein-rich legume, with food security potential in drought-prone regions. It has been grown for many centuries and has remained an important crop to most African subsistence farmers. However, despite its high nutritional status and yield advantages in poor soils, it remains one of the neglected crops by science. There have now been recent efforts to study underutilised crops, with the aim of promoting them as healthy alternatives for people facing resource and environmental challenges and to contribute to food security. In order to do this, there needs to be information that can be used to advise farmers on the agronomic aspects of producing the crop. The overall aim of the study was to evaluate the response of bambara groundnut landraces to drought under controlled environment and field conditions. Seeds were initially collected from subsistence farmers in Jozini, KwaZulu-Natal, and characterised into three seed lots distinguished by seed coat colour: red, white and brown. In the initial study (Chapter 2) seed quality of bambara groundnuts was evaluated. Seed lots were used for standard germination (SG) and cold test (CT). Seeds were germinated under two conditions, 25°C for 8 days (SG) and 4°C for 7 days followed by 8 days at 25°C (CT). Germination percentage, seedling size and mass were determined. Desiccation tolerance was evaluated by suspending 30 seeds of each seed lot over saturated salt solutions of NaCl, LiCl, KNO3 and H2O (control) for 0, 2, 4, 8, 24 and 48 hours. Five seeds were sampled at each interval and stored at -21°C for 7 days. Samples were ground and analysed for proline content. In addition, early establishment performance of bambara groundnut was evaluated under controlled environment conditions in seedling trays using two water regimes (Chapter 2). The experimental design had three factors: seed lot (colour), priming (NaCl, LiCl, KNO3, H2O and control) and water regimes [25% and 75% Field Capacity (F.C.)]. The experiment was replicated three times. Seedling emergence was determined daily for 21 days. Seedling height and leaf number were determined weekly for three weeks, thereafter, seedling leaf area, root and shoot mass (fresh and dry), root and shoot lengths and root to shoot ratio were also determined. Seedlings were later transplanted in 90 pots for a pot trial in order to evaluate growth responses of bambara groundnut to water stress; plant height, leaf number and yield components were determined (Chapter 3). Lastly, the use of planting date selection as a management strategy for managing the occurrence of water stress under field conditions was evaluated in field trials. The experimental design was a split-split-plot design with planting date as main factor (early, optimum and late), irrigation and rainfed as sub-main factor, and seed colour as sub-plots (brown, red and white) arranged in a randomised complete block design (RCBD), with three replications. There were three planting dates: 7 September (early planting), 24 November (optimum planting) and 19 January (late planting). Results from Chapter 2 showed that the brown seed lot had the highest germination across treatments, followed by red and white seeds, respectively. There were significant differences between seed lots (P < 0.05) and salt solutions (P < 0.05) with respect to proline content. Seed proline content increased from 0 to 8 hours and later declined; NaCl was associated with the highest proline accumulation. There were highly significant differences (P < 0.001) between seed colours, priming treatments and F.C., as well as their interaction, with respect to seedling emergence. White seeds had the highest emergence, followed by brown and red, respectively. Priming seeds improved their emergence compared to the control, with highest emergence being observed in seeds treated with LiCl. Priming also improved emergence under water stress; 25% F.C. had the highest emergence compared to 75% F.C. Results from Chapter 3 showed that, seeds primed with NaCl and KNO3 resulted in tallest plants with the highest number of leaves per plant. However, NaCl and KNO3 were also the most affected under water stress. Priming was shown to improve germination and early crop establishment of bambara groundnut landraces under water stress. However, yield per plant did not improve in response to either halo- or hydro-priming. Results from field trials showed that in terms of the measured plant growth parameters (plant height, leaf number and LAI), bambara groundnut landraces were sensitive water stress. Water stress decreased yield components, and hence yield. However, selection of planting dates was shown to be a useful management tool for managing water stress under water limited field conditions. Choice of planting date significantly affected both plant growth and yield. The optimum planting date resulted in the best crop growth for all measured plant growth parameters followed by late and early planting dates, respectively. Seed quality was shown to be associated with seed lot colour. Darker coloured (red and brown) seeds performed better than light (white) seeds with respect to germination. Priming was also shown to improve germination and early crop establishment of bambara groundnut landraces under water stress. However, yield per plant did not improve following priming. Growth of bambara groundnut landraces was shown to be sensitive to water stress. Water stress decreased yield components and hence yield under both controlled and field conditions. Choice of planting date significantly affected both plant growth and yield. The optimum planting date was shown to be the best performing planting date. The findings of this study suggest that bambara groundnut seed performance in terms of germination, stand establishment and productivity is associated with seed lot colour. Seed priming improves seed performance and enhances crop capacity to withstand water stress. If the optimum planting date for groundnuts (late spring to early summer) is missed, better crop performance and yield are obtained from late planting (late summer to early spring) compared with early planting (early spring). Bambara groundnut has a potential for production under water stress conditions in controlled and field environments.
Chemical mutagenesis of wheat for herbicide resistance.
(2012) Ndou, Vuledzani Nico.; Shimelis, Hussein Ali.; Odindo, Alfred Oduor.
Weed infestation is one of the yield limiting factors in crop production. Weeds have negative effect on crop growth and productivity due to competition, allelopathy or hosting other harmful organisms. For large-scale wheat production, the use of wide spectrum pre-emergence or post-emergence herbicides remains the most valuable weed control tool. In South Africa, annual grass weeds are a major wheat production constraint, which is usually managed through application of pre-emergence herbicides. Due to limited water availability and low soil moisture content, these herbicides can often become ineffective and result into high weed infestations, which then have to be managed by manual cultivation or post-emergence herbicidal applications. However, there are no effective selective post-emergence herbicides available to control grass weeds in wheat. There is also limited option to use broad-spectrum post-emergent herbicides because they non-selectively kill the crop and weeds. Consequently, the use of herbicide resistant crops is a viable weed management system in wheat production. Breeding herbicide resistant crop varieties would allow farmers to safely use post-emergence herbicides without damaging the crop. Subsequently yield and quality losses will be reduced significantly. Thus, the development of herbicide resistant crop varieties through mutation breeding is a novel approach for effective weed management under both small-scale and commercial farmers. Mutagenesis has been recognized as one of the most efficient method to induce genetic variation in plants. Through induced mutations, development of new variants is possible that could be manipulated in plant breeding programs. Mutation leads to alteration of various traits in crop plants including plant height, improved nutritional quality, shorter growing period, increased tolerance or resistance to abiotic and biotic stresses. Ethylmethanesulphonate (EMS) is one of the most widely used chemical mutagens to induce mutagenesis in crop plants. The objectives of this study were to: 1) determine the optimum EMS concentration, treatment temperature and duration that would provide desired germination percentage and vigorous and healthy seedlings for effective mutagenesis in wheat, 2) investigate variations in agro-morphological traits in two selected wheat varieties (SST56 and SST875) after EMS mutagenesis and 3) select herbicide resistant wheat germplasm after inducing genetic variation using EMS using two selected wheat varieties (SST56 and SST875). The objectives were achieved through three independent studies as outlined below: In the first study seeds of four selected wheat varieties (B936, B966, SST387 and SST875) were treated in two replicates with three EMS concentrations (0.3, 0.5, and 0.7%), three temperature regimes (30, 32.5 and 35 °C) at four time durations (0.5, 1, 1.5 and 2 hrs). Results showed highly significant interactions (P<0.01) among varieties, EMS concentrations, temperature and exposure time on seedling emergence, germination and seedling height. Seeds treated with the highest EMS dose (0.7%), temperature (35ºC) and long exposure time (2 hr) showed delayed emergence by 18 days. At 30ºC, 0.5hr and 0.3% EMS varieties B936, B966 and SST875 had early emergence (6 days). B936 and SST387 had 50% while B966 and SST875 had 53% and 57% germination, respectively. These results were observed at EMS level of 0.7%, 300C and 1.5 hr exposure time in B936 and EMS at 0.5%, 350C and 1.5 hr in B966. SST387 and SST875 required EMS dose at 0.5%, 32.50C and 2 hr treatment time. Other low or high treatment combinations were invariably ineffective comparedto untreated control. During the second study two selected varieties (SST56 and SST875) were subjected to EMS mutagenesis using 0.5% v/v EMS at 32.5oC for 1 hr. Field trials were carried out at Ukulinga research farm of the University of KwaZulu-Natal in the randomized complete block design with two replicates. Data on nine important agro-morphological traits were collected and analyzed using the analysis of variance (ANOVA), correlation and principal component analysis (PCA) procedures. Significant variations were found among the agro-morphological traits between M1 individuals compared to untreated checks. The mutagenesis significantly reduced seed germination in the field at 40% in both varieties. The treatment significantly delayed days to heading by 8 days and shortened days to maturity by 13 days in both varieties. EMS treatment also significantly reduced plant height at 18 cm in SST56 and 21 cm in SST875 and spike length reduced by ~2.5 cm in both varieties. Plant height had positive and significant correlation with number of tillers, number of seeds per spike, flag leaf length and 100 seed weight. However, it had negative correlation with the number of days to maturity. The PCA revealed that three principal components (PC1, PC2 and PC3) accounted to 57% of the total variations among the agro-morphological traits in both varieties. PC1 alone contributed to 27.7% of the variation which was well-correlated with plant height (0.767), tiller number (0.812), number of seeds per spike (0.599) and seed yield (0.720). PC2 explained 15.6% of the variation and well-correlated with germination percentage (0.784), spike length (0.554) and flag leaf length (0.772). PC3 accounted to 12.4% of the variation and had negative correlation with days to maturity (-0.730). In the last study, seeds of two selected wheat varieties (SST56 and SST875) were treated with EMS at 0.5% concentration for 2 hr at 32.5ºC. Treated seeds and comparative controls were planted at the experimental farm of the University of KwaZulu-Natal using the randomized complete block design. Four weeks after planting M1 plants and untreated standard checks were sprayed with two herbicides, i.e. metsulfuron-methyl and bromoxynil at three different doses viz. 2x, 4x and 8x above the recommended rate of 4 g ha-1 and 2 kg ha-1, respectively. Two weeks after the treatment herbicide resistance were assessed. Results showed significant difference among varieties, tested herbicides and doses used. The EMS treated wheat lines showed variable degree of herbicide resistance compared to untreated controls. Overall, the study established the requirement of variety specific EMS dose and treatment temperature and duration that could be used for inducing large-scale mutation to select targeted mutant individuals in wheat. Further, the study found that EMS has the potential to increase agro-morphological variations in wheat to select useful and novel mutants with desired phenotypic traits and herbicide resistance which will be subjected for further selections to identify stable and herbicide resistance lines.
Climate change and variability impacts on crop production in the low potential smallholder farming regions of Zimbabwe.
(2016) Jiri, Obert.; Mafongoya, Paramu L.; Chivenge, Pauline.
Climate change and variability is one of the most serious global problems affecting many sectors in the world. It is considered to be one of the most serious threats to sustainable development with adverse impact on environment, human health, food security, economic activities, natural resources and physical infrastructure. Southern Africa is one of the most vulnerable regions to climate change in the world, particularly because of widespread poverty, recurrent droughts, inequitable land distribution, over-dependence on rain-fed agriculture and low adaptive capacity. Yet rural farmers in southern Africa have managed to survive the vagaries of climate change over the years. The central argument in this study was that coping and adaptation strategies to climate change by local smallholder farming communities in Zimbabwe who traditionally relied on indigenous knowledge systems are at risk and less effective because the use of indigenous knowledge systems is becoming unreliable due to climate change and variability. The main objective of this study was to identify local smallholder farmers’ perceptions to climate change and variability and the influence of indigenous knowledge systems in deciding and adopting coping and adaptation strategies. This study used a combination of participatory and field data collection tools in Chiredzi District, one of the areas affected by climate change impacts in Zimbabwe. Household surveys, focus group discussions and key informant interviews were done in selected wards in the district. Field trials were done to identify climate smart cropping options to assist farmers in coping and adapting to climate change and variability. The results indicate that farmers use a variety of local indicators for weather forecasting and climate prediction, for adapting to climate change and variability. Integrating indigenous knowledge systems with climate scientists’ efforts can contribute to effective on-farm adaptation initiatives. One objective of this research was to identify IKS used by farmers to predict seasonal weather patterns, and the subsequent adaptation strategies. The information was collected using focus group discussions, household survey, and ethnographic interviews. Most farmers (72.2%) indicated that low rainfall is the major limitation to agricultural production. Without reliable local scientific weather forecasts the farmers use tree phenology, animal behaviour and atmospheric circulation as sources of local knowledge to predict the onset and quality of the season. These forecasts are then used for designing crop choices, planting dates and agronomic practices. Study results obtained show that the use of IKS in local farming communities is an effective way of building coping and adaptation strategies. The results revealed that IKS are being eroded and becoming less accurate in seasonal weather prediction. Therefore, future studies on IKS should use multiple methods that combine indigenous knowledge and scientific weather data in order to obtain more complete and accurate information for local area season quality prediction. Another study objective was to examine farmer perceptions on climate variability, current adaptive strategies and establish factors influencing smallholder farmers’ adaptation to climate change. The results showed that farmers perceived that there has been a decrease in annual rainfall and an increase in average temperatures. A linear trend analysis of rainfall and temperature data from 1980 to 2011 corroborated the farmers’ perceptions. Farmers’ adaptation options included adjusting planting dates and crop diversification. Off-farm income has reduced the dependence of the farmers on agriculture. A multinomial regression analysis showed that socio-economic factors such as gender, age, number of cattle owned, land size and average crop yields influenced farmer adaptation strategies. We conclude that although farmers are diverse in their socio-economic attributes, they exhibit homogeneous perceptions on changes in climate, which are consistent with observations of empirical climate data. These perceptions help to shape smallholder farmer coping and adaptation strategies. The variability of climate demands the use of a variety of agronomic strategies and crop choices in order to reduce vulnerability and increase resilience and adaptive capacity to climate change and variability. Traditional drought tolerant crops such as sorghum are often chosen when drought seasons are anticipated. However, there are certain crops, originating elsewhere, that could help the smallholder farmers increase diversity of crops that can be grown in changed climates. One such crop is tepary bean (Phaseolus acutifolias). Resource poor farmers, affected by drought effects of climate change, can adopt climate smart crops to achieve food, nutritional and heath security from combinations of cereals and legumes. This study revealed that these rural farmers are highly vulnerable and resilient, largely using indigenous knowledge systems to cope and adapt to climate change. Availability and access to scientific weather information to make cropping and other decisions at the local level remain key issues to usage of climatic data by rural farmers. One the other hand, indigenous knowledge is what they have been using but is also becoming unreliable due to climate change, increasing vulnerability and demanding more resilience. Integration of indigenous knowledge and scientific seasonal forecast seems to be a key possible thrust to reduce vulnerability, enhance resilience of rural farmers and increase their adaptive capacity. This study concludes that farmers can use indigenous knowledge systems to make adaptation decisions. However, there is need to integrate indigenous knowledge systems and scientific knowledge to reduce vulnerability and increase adaptive capacity of smallholder farmers. Climate smart crops provide a useful option for farmers affected by climate change and variability to improve food and nutritional security and livelihoods.
Closure of the Umlazi landfill : meeting statutory requirements for engineering and plant cover.
(2008) Mannie, Neeraj Mannie.
This study investigated the establishment of vegetation cover planted in plug and seedling form in the closure phases of the Umlazi Landfill. It also investigated the various facets of the closure process of the Umlazi Landfill and the effect these have on the establishment and choice of vegetative cover, and the grass technology used to make the establishment of vegetation a success. The setting up of trials and the gathering of basic data were undertaken to assess the alternative vegetation options available to researchers. The cover provided by the grasses was assessed in the investigation. The capping of landfill sites is a relatively new approach and it is soon to become a mandatory requirement by the Department of Water Affairs and Forestry (Minimum Requirements for Waste Disposal) (DWAF, 1998). This systematic investigation used in the closure of the Umlazi Landfill, will provide a model for the capping of landfills in South Africa. Seeing that this was the first hazardous (H:h) landfill site in the country to be closed according to the Minimum Requirements for Waste Disposal (DWAF, 1998), every attempt was made to ensure that all aspects in the closure of the site met with the Minimum Requirements. The Minimum Requirements document mentions only briefly that the landfill must be vegetated with some grass type. Prior to 1994, capped landfill sites were usually planted with traditional grass seed mixes and these were not widely successful, as seen on many older landfills that have been partially or completely capped, and where vegetation cover is sparse. There is much literature in the developed countries on the closure of landfills (e.g., Erickson, During the site inspections in June 2001 and February 2002, it was noted that many species of alien plants had established themselves in the poor soil conditions. This made it even more important to find indigenous vegetation to vigorously establish itself that would prevent the establishment of alien invaders. Samples of grass species established on some part of the site were also taken for identification. The dominant grass was identified as Cynodon dactylon. In view of establishing a balanced vegetative cover on top of the Umlazi Landfill, Acacia karoo trees (in seedling form) were also planted. Three bunch grass species, Melinis nerviglumis, Melinis minutiflora and Hyparrhenia hirta, were tested to see if thatching grass could be grown on the site to generate a cash crop for local residents of Umlazi township. Preparation and planting of the capped areas took place in the latter part of 2003 and were completed in early 2004. Measurements and field data were recorded and statistically analysed. The trials revealed three key findings: Firstly, both creeping grasses studied, namely Cynodon dactylon var. “Sea Green” and Panicum natalense var. ”Natal Buffalo Grass” grew well on the site. Initially P. natalense grew faster but after a month, C. dactylon overtook it. At the end of the trial (six months, P. natalense provided a higher level of soil cover. However, C. dactylon grew more consistently over this period. Hence both species provided good growth and cover on this site. Secondly the three bunch grasses, Melinis nerviglumis, Melinis minutiflora and Hyparrhenia hirta, all grew well and had similar survival rates. Hence the potential for growing these grasses as a cash crop has potential. Thirdly, all the Acacia karoo trees survived, i.e., they achieved 100% survival. The average height increase and stem width was similar in all trials and growth was consistent over the six month growing period. Hence the tree species would be a good choice for planting on landfills in its ecologically suitable zones. It is therefore feasible to envisage the planting of a mixture of grasses under the cover of A. karoo trees, to provide a balanced mixture of indigenous grasses to cover a freshly capped landfill. Such a system should provide for stable growth of vegetation for many years.
Comparative responses of fodder and grain teff (Eragrostis tef (Zucc.) Trotter) cultivars to spatial, temporal and nutritional management.
(2002) Kassier, Sigrun Barbara.; Greenfield, Peter L.
Teff has its origin in Ethiopia as grain crop, while in South Africa it is primarily a forage crop for hay and recently as summer grazing pasture. The response of teff herbage and grain production to planting date, growth stage at cutting, seeding rate and N fertilizer application was studied. Previously limited research data were available for teff production in South Africa. Spring plantings (September to October) are required to maximise total herbage yield with 9.40, 8.48 and 7.64 t DM ha -1) recorded for 1996/97, 1997/98 and 1998/99 respectively. Summer plantings (November to December) give maximum herbage yield from the first cut, yielding 4.42, 4.72 and 3.78 t DM ha -1) for 1996/97, 1997/98 and 1998/99 respectively. The exact planting date is season dependent. Temperature and rainfall determine the beginning of the growth season regarding favourable conditions for teff germination and growth. Herbage yield of cut 1 increases with advancement in growth stage at cutting. Cutting at the vegetative and piping stages gives most number of cuts , up to five yielding 7.45 t DM ha -1) (1996) while the full flowering stage gives the least (one or two cuts , 4.75 and 7.72 t DM ha -1 in 1996 and 1997 respectively). Yield is also affected by environmental conditions influencing germination, biomass accummulation and regrowth after cutting and by lodging. A trade-off results between herbage quantity and quality. Yield increases while quality decreases with advancing phenological stage, resulting in reduced digestibilty and CP and increased fibre content. Seeding rate differences were manifested primarily in weed infestation level, which varied between cultivars depending on leafiness and associated sward density. Nitrogen application levels gave maximum response between 75 and 150 kg N ha -1, with some cultivar differences. Split N application according to expected yield distribution related to planting date is recommended. Grain yield response to seeding rate and N fertilization levels could not be established. Heavy grain losses through thunderstorms and wet conditions at grain maturity precluded yield measurements. Teff yield responses are influenced by day length, environmental factors, such as temperature and rainfall. and phenological stage at cutting. These variables influence biomass accumulation and regrowth.

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