Can we profitably double maize yields in southern Tanzania? Environment and Production Technology Division, International Food Policy Research Institute December 7, 2016

Context Slower than desired growth in crop yields coupled with rising populations present an ongoing challenge to the food security of some African countries Some countries like Tanzania have signed the Malabo declaration, which aims to double food productivity by 2025 This study examined the productivity and economic effects of different seed and fertilizer practices in Mbeya, Tanzania

Research questions For maize in the Mbeya district of southern Tanzania: How does seed and fertilizer management affect the yield and profit of maize? What are the marginal value-cost ratios of fertilizer use for different seed practices?

Methods Simulated how fertilizer and seed practices effect maize grain yields computed economic and risk indicators of alternative practices

Methods Crop management factorial simulated: 10 or 30 kg N ha-1 Traditional or improved maize cultivars Traditional or improved sowing dates No manure, 80% crop residues removed from field Used DSSAT from 2009 to 2009 in six maize-growing districts of Mbeya

Methods Profit: value of grain production minus the cost of production. District-level prices used Agronomic efficiency: change in yield divided by change in quantity of fertilizer applied Marginal value-cost ratio: agronomic efficiency multiplied by ratio of grain to fertilizer price

Results: historical and extrapolated grain yield

Results: simulated yields and profits

Results: agronomic efficiency and price ratios

Results: value-cost ratio

Results: probability of the marginal value-cost ratio (MVCR) associated with using more fertilizer exceeding different thresholds Practices Probability MVCR >1 (%) Probability MVCR >2 (%) Traditional seed and planting date 80 59 Traditional seed and sowing with a lower AE or higher fertilizer price 73 43 Traditional seed and improved planting date 100 Improved seed and improved planting date

Conclusion Changes in seed and fertilizer application can help double yields and increase profits Heterogeneity exists in profitability of fertilizer application Questions remain if it is more cost effective to lower fertilizer prices or increase agronomic efficiency by an equivalent percentage Questions remain why farmers don’t use more fertilizer given the MVCR we calculated