Diversification of neglected legumes into cropping systems of South Africa.

Abstract

Neglected legumes (Bambara groundnut, cowpea, pigeon pea) are fundamental to global food systems, contributing to agricultural sustainability, enhancing food security and strengthening the resilience of smallholder farming systems. However, they remain underutilized and have historically received limited attention in terms of cultivation, research, and market development, despite their significant nutritional, agronomic and environmental potential. Therefore, this study's objectives were (1) to assess the socioeconomic factors influencing crop diversification among smallholder farmers in Bergville, South Africa; (2) to investigate the socioeconomic factors influencing smallholder farmers' willingness to cultivate neglected legumes and their selection of suitable planting dates; (3) to determine the effect of planting date on agronomic performance of neglected legumes under rainfed conditions; and (4) to evaluate the effect of cropping systems on the adaptability of neglected legumes in rainfed conditions. The first study on the socioeconomic factors influencing crop diversification among smallholder farmers in Bergville, South Africa, revealed that farmers in the study area practice crop diversification. However, the findings indicated that, socioeconomic factors play a crucial role in shaping diversification decisions within smallholder farming systems. This study confirms that, limited access to land, water availability, market access, and education level constrain farmers’ ability to diversify their crop choices. The second study findings indicate the vital role of socioeconomic factors in shaping adoption decisions and integrating these crops into existing cropping systems. Limited access to land, water availability, market access, and marital status influence farmers' willingness to cultivate neglected legumes. Household size, participation in legume-related training, and access to irrigation water influenced the selection of suitable planting dates. The limited cultivation and adoption of neglected legumes were not primarily due to resource constraints but rather a lack of awareness and knowledge regarding their nutritional and health benefits. The third study on the effect of planting date on agronomic performance of neglected legumes under rainfed conditions indicated a significant variation in agronomic performance across planting dates, with early planting generally associated with improved emergence, timely flowering, and higher yield potential while the fourth study demonstrated that cropping systems significantly influenced the adaptability of neglected legumes under rainfed conditions. Intercropping systems, particularly those involving cereallegume combinations, have enhanced the growth performance, yield, and resource use efficiency of neglected legumes compared to sole cropping. The improved adaptability observed under intercropping is attributed to the complementary utilisation of resources and microclimatic benefits that mitigate water stress.

The contribution of neglected legumes to food and nutrition security remains limited due to the socio-economic challenges faced by farmers, which contribute to the underutilization of these legumes. Integrating neglected legumes into cropping systems would broaden the basket of options, and the net effect would be increasing resilience. Crop diversification is a vital strategy for achieving sustainable agriculture and food security; however, its adoption rates remain low. This study first objective examined the socioeconomic factors influencing crop diversification among smallholder farmers. A two-stage sampling procedure was employed to collect data from 161 farmers who specialised solely in crop production. A structured questionnaire was used to collect data, analysed using descriptive statistics. The multiple linear regression and multivariate probit regression models were applied to assess the socioeconomic factors influencing diversification. The results revealed that smallholders primarily focused on vegetable cultivation (87%), followed by cereals (56%) and legumes (43%). Education level, household size, market access, and the perceived benefits of diversification significantly influenced diversification decisions (p < 0.05). Also, sources of irrigation water, age, marital status, and farm size were key factors in vegetable diversification, while farming experience, farm size, and perceived benefits influenced legume diversification. Only marital status and farming experience were positively linked to cereal crop diversification. Furthermore, 48.4% of farmers practice intercropping, integrating maize with pumpkins or sugar beans, while 33.5% still rely on monoculture, predominantly maize, due to limited resources. These findings underscore the need for policies and extension support to address socioeconomic barriers and promote the wider adoption of crop diversification strategies. The second objective of the study was to assess socioeconomic factors influencing farmers’ willingness to cultivate neglected legumes and their selection of suitable planting dates in Bergville, South Africa. A simple random sampling procedure was used to collect data from 150 farmers who specialised exclusively in crop production. An action research design was implemented, comprising structured training sessions on neglected legumes and trial demonstrations. Data were collected through a structured survey questionnaire, focus group discussions, and key informant interviews. Descriptive statistics were used for analysis, and a multivariate probit model was employed to determine the socioeconomic factors influencing farmers' willingness to cultivate neglected legumes including Bambara groundnut (Vigna subterranea), cowpea (Vigna unguiculata), pigeon pea (Cajanus cajan), and common bean (Phaseolus vulgaris) and their selection of suitable planting dates. Findings confirmed that, the majority of smallholder farmers primarily focus on vegetable cultivation, followed by cereals, while a smaller

proportion engage in legume farming. The results also revealed that, limited knowledge and resources, along with the lack of training programs and extension services, specifically targeting neglected legumes, are significant barriers hindering their adoption and cultivation in the region. Furthermore, the study revealed that a majority of smallholder farmers had never received training in legume production. Additionally, marital status, farm size, market access, and water sources for irrigation were significant socioeconomic factors influencing farmers' willingness to cultivate neglected legumes, while household size, participation in legume training, and water sources for irrigation had a significant effect on farmers' selection of suitable planting dates. These findings underscore the need for targeted interventions, including tailored training programs, improved access to resources, and enhanced extension services, to overcome these barriers and promote the adoption of neglected legumes into smallholder farmers' cropping systems. The third objective examined the effect of planting date on the agronomic performance of the selected neglected legume crops. Field trials were conducted over two consecutive summer growing seasons (2022/23 and 2023/24) using a split-plot randomized complete block design with three replications. Phenological traits (emergence, flowering, podding, and senescence) and yield components (pod mass, and grain yield) were recorded and analysed using GenStat® and principal component analysis. Significant effects of planting date, legume species, season, and their two- and three-way interactions (P ≤ 0.05) were observed for all measured traits. Early planting demonstrated enhanced crop establishment and vegetative development, while reproductive traits were strongly influenced by the synchronization of phenological stages with prevailing climatic conditions. Cowpea and Bambara groundnut demonstrated stable phenological and reproductive performance across planting dates and seasons, with high emergence rates of 90.2% and 85.63%, respectively, suggesting strong resilience under climate variability. Pigeon pea showed greater sensitivity, particularly to delayed planting. Delayed sowing increased grain yield in common bean, cowpea, and Bambara groundnut, whereas pigeon pea showed a decline. These findings underscore the importance of aligning planting dates with species- specific phenological responses to optimize the productivity and resilience of neglected legumes in rainfed systems. The fourth objective evaluated the effects of cropping systems on the adaptability of neglected legumes in rainfed environments. Field trials were conducted over two consecutive summer growing seasons (2022/23 and 2023/24) using a split-plot randomized complete block design with three replications. Phenological traits (emergence, flowering, podding, and senescence),

yield components (pods per plant, seeds per pod, pod mass, 100-seed weight and grain yield (t ha⁻¹)), and land equivalent ratios (LER) were recorded and analyzed using GenStat® and principal component analysis. Significant effects of cropping system, cultivar, season, and their two- and three-way interactions (P ≤ 0.05) were observed for all measured traits, confirming that legume-based intercropping systems significantly influenced the adaptability and productivity of neglected legumes under rainfed conditions. Intercropping enhanced early emergence and accelerated reproductive development in legumes such as Bambara groundnut, cowpea, and common bean, while pigeon pea showed reduced establishment under sole cropping due to competitive suppression. Pod production, pod mass, seed number per pod, 100- seed weight and grain yield consistently increased under intercropping. Cowpea and Bambara groundnut exhibited stable responses across seasons, whereas common bean and pigeon pea showed greater variability, highlighting the importance of genotype and species-specific compatibility with intercrop designs. Land equivalent ratios (LER) consistently exceeded 1.0 under intercropping confirming the superior land-use efficiency and yield potential of intercropping in smallholder agroecosystems. These findings underscore the importance of strategic selection of legume species with complementary phenology, growth dynamics, and resource requirements to optimize interspecific interactions and enhance system productivity. Keywords: Smallholder farmers; socioeconomic attributes; rainfed agriculture; legumes adoption; intercropping; agronomic performance; optimal planting date; multivariate probit regression model; PCA