Using the DSSAT-CROPGRO model to simulate gross margin and N-leaching of cowpea fertigated with human urine

Abstract

This study simulated the biophysical, economic and environmental implications of cowpea fertigated with human urine (equivalent to 60 kg N ha-1) as source of organic N. The DSSAT CROPGRO model was used to simulate harvested cowpea yield, N (leached) , N (uptake) , monetary returns or gross margins in ($) under two different treatments: without fertigation or human urine (T 0) and with fertigation (T 1). Biophysical analysis using the Cumulative Probability Distribution (CPD) showed a 50% probability of the harvested cowpea yield under T 1 being higher than under T 0 at 1060 and 600 kg ha-1 respectively, accounting for a 43.4% difference. The Mean Gini Stochastic Dominance (MGSD) analysis was used to assess the gross margin and helped in deciding on the best strategic and management option. The findings of this study revealed a 50% probability (CPD 0.5), of higher gross margin under T 1 at $-215 higher than under T 0 at $285. This was a $70 difference per season under T 1 and so enhancing a faster payback and a larger monetary return on overall investments. Similarly, seasonal analysis with fertigation showed that at CPD 0.5 , the N (leached) was still < 4 kg N ha-1 per season and so posed no environmental risks. The simulation results also showed higher a probability of N (uptake) of about 270 kg N ha-1 during fertigation compared to about 95 kg N ha-1 under T 0. Therefore, the DSSAT CROPGRO model can be used to successfully forecast future cowpea yields, gross margin, N (leached) , N (uptake) under different management practices to enable smallholder farmers in South Sudan make informed decisions on sustainable cowpea production.

Climate Change Impact on Management Practices of Maize Yield: Case of Mount Makulu, Zambia

“…The DSSAT models can be applied to predict variations and identify trends in biophysical indicators [95,96]. Further, unsustainable or sustainable management options can be identified and evaluated.…”

“…Further, unsustainable or sustainable management options can be identified and evaluated. The Mean Gini Stochastic Dominance (MGSD) analysis has been used by Lomeling and Huria [96] to evaluate the gross margin and assisted in deciding on the appropriate management options. The authors concluded that the DSSAT models could be applied to forecasting future cowpea yields, gross margin successfully, and nutrient use under diverse management options assisting farmers to make knowledgeable decisions on sustainable crop productivity.…”

Scalability constraints in Disruptive Agricultural Technologies (DATs) along Value Chain on agricultural production in South Sudan

“…Agricultural production in S. Sudan is still very subsistence with yields as low as 0.97 tons/ha for cereals and about 1.2 tons/ha for cowpeas (Lomeling and Huria, 2020) obtained from relatively small farms 0.4-1.5 ha in size. Lack of entrepreneurial mentality, poor market access and marketing information system, lack of microfinancing institutions and infrastructure are only a few of the sales and marketing constraints limiting intensive agricultural production in S. Sudan.…”

“…Estimated level of agricultural production of cowpeas (kg/ha) from marginal probabilities of different input variables under best case scenario. (calibrated with a 50% CPD production level of 700 kg/ha; Lomeling and Huria, 2020). were chosen to illustrate this point.…”

“…The conditional probability, here in the form of agricultural production, is a function of both joint probabilities of all discrete variables in the domain. Using calibrated value of cowpeas at 50% CPD (Lomeling and Huria, 2020) as 700 kg ha -1 , the BBN forecasted value for worst case scenario was about 692.9 kg ha -1 . Scaling up the marginal probabilities of both financial resources and agrotechnology from 0.015 to 0.003 (50% increase) and 0.025 to 0.1 (40% increase), respectively, while keeping other variables constant increased agricultural production to 783.14 kg ha -1 , a 12% increment.…”