Economic and agronomic evaluation of using excreta-derived plant nutrients sources (latrine dehydrated and pasteurised pellets, struvite and nitrified urine concentrate) as agricultural fertilisers.
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Faecal sludge can be recycled and processed into usable products such as the Latrine Dehydrated and Pasteurised (“LaDePa”) pellets and urine into Nitrified Urine Concentrate (NUC) and struvite, which can be used as fertilisers. The financial costs and benefits and the agricultural-effectiveness of using LaDePa, NUC and struvite as fertilisers in South Africa and the wider sub-Saharan African region have not been empirically quantified. A study was carried out using experimental data to quantitatively establish the cost-effectiveness of using LaDePa, NUC and struvite for maize production. The costs per hectare of using these products to meet crop nutrient requirements for maize and achieve a specified target yield were determined and compared with the costs per hectare of using recommended commercial fertilisers. The financial feasibility was determined using partial budgets. The income per hectare of using these products was determined and compared with that of the commercial fertilisers. Pot trials in a tunnel were also carried out to determine the agricultural-effectiveness of the products compared with the commercial fertilisers and crop growth parameter results analysed statistically using GenStat. The results showed that LaDePa, NUC and struvite are financially viable, if used in place of the organic fertiliser studied. Their net income (gross income less total calculated costs) per hectare was also higher compared with that of commercial fertilisers analysed. On the agronomic side, the products also proved to be very effective for crop growth and might be better than the assessed commercial fertilisers. On top of being a viable nutrient source, LaDePa is even more cost-effective if it is used as a soil amendment to improve soil physical properties. The use of NUC and struvite as nitrogen and phosphorus sources, respectively, was shown to be financially viable. If one is to add the environmental benefits of recycling waste products as fertilizers, the products will be even more economically viable. However, there is a need for more research on consumer acceptance of the agricultural goods produced this way.