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Spatially-Explicit Effects of Maize Intensification in Tanzania

Spatially-explicit simulation of input intensification in Tanzania showed that scopes exist to double maize yields, despite spatial heterogeneity in economic benefits.
Percentage change in district-scale simulated partial profit (net value) between the baseline (local seed cultivar and 10 kg N ha−1) and more intensive practices of improved seed cultivar and 40 kg N ha−1 for maize monoculture in different districts of the Mbeya region of Tanzania.
Figure 3. Percentage change in district-scale simulated partial profit (net value) between the baseline (local seed cultivar and 10 kg N ha−1) and more intensive practices of improved seed cultivar and 40 kg N ha−1 for maize monoculture in different districts of the Mbeya region of Tanzania.

Colleagues from IFPRI recently published an ex-ante impact assessment study on the maize intensification options in Southern Tanzania in the Land Use Policy journal. The study, led by Adam Komarek, used an integrated, spatially-explicit modeling framework linking the DSSAT Cropping System Model and the Dynamic Research Evaluation Model (DREAM), to estimate the biophysical and economic potential of intensifying smallholder farmers’ maize farming in the Mbeya region in Southern Tanzania. The study found that modest changes in seed cultivars and fertilizer application rates can sustainably double productivity without having a negative effect on its stability.

Abstract
Slower than desired growth in crop yields coupled with rising food demand present ongoing challenges for food security in Africa. Some countries, such as Tanzania, have signed the Malabo and Abuja Declarations, which aim to boost food security through increasing crop productivity. The more intensive use of seed and fertilizer presents one approach to raising crop productivity. Our simulation study examined the productivity and economic effects of planting different seed cultivars and increasing fertilizer application rates at multiple spatial scales for maize in Tanzania. We combined crop simulation modeling with household data on costs and prices to examine field-scale and market-scale profitability. To scale out our analysis from the field scale to the regional and national scale (market scale) we applied an economic surplus model. Simulation results suggest that modest changes in seed cultivars and fertilizer application rates can double productivity without having a negative effect on its stability. The profitability of applying extra fertilizer, calculated as its value-cost ratio, increased if improved seed cultivars replaced local seed cultivars. Rankings of district-scale profits differed from rankings of district-scale yields, highlighting the importance of considering economic factors in assessments of input intensification. At the national scale, simulation results suggest the total benefit could be US$ 697 million over 5 years if there was a 39 percent adoption rate of planting an animproved seed and applying extra mineral fertilizer. Providing economic assessments of input intensification helps build evidence for progressing the Malabo and Abuja Declarations.

Komarek, A. M., Koo, J., Wood-Sichra, U., & You, L. (2018). Spatially-explicit effects of seed and fertilizer intensification for maize in Tanzania. Land Use Policy78, 158-165. https://doi.org/10.1016/j.landusepol.2018.06.033