Opportunities to Improve Smallholder Maize Productivity and Nitrogen Use Efficiency in Manica, Mozambique.

Projections by the FAO suggest that food production in the 21^st century will have to increase 50-70% in order to meet the demands of an increasingly crowded and globalised world. These pressures are exacerbated in sub-Saharan Africa due to high population growth and the current low-levels of food production. A number of studies examining the challenges for African agriculture have identified lack of nutrients – most notably nitrogen – as the most limiting factor for subsistence farmers. This study used a combination of farmer questionnaires and crop systems modelling using APSIM to examine the magnitude and causes of gaps in maize farm productivity and nitrogen fertilizer use efficiencies (NUE) in the Manica province of central-western Mozambique. The potential production and economic benefits from N input investment, as well as its seasonal variability, were calculated. Maize yields in farmers' fields were found to be highly variable within sites even when accounting for differences in nitrogen input use, indicating distinct farm productivity groups. Results of model analysis indicated that gaps in yields and input NUE between farms and fields were largely explained by differences in soil fertility status and basic agronomic management (primarily sowing density and residue management). Deficiencies in local extension advice relating to recommended sowing density and recommended residue and fertilizer management were identified. Optimal maize sowing density was found to be relative to N inputs (ranging from 1-3.5 plants/m²), and regardless of N input levels highest simulated maize yields occurred at sowing densities well below locally recommended rates (7.4 plants/m²). Further, the blanket recommendation on residue applications to improve soil organic matter status was shown to be highly detrimental to maize yield where farmers are unable to invest in N fertiliser. Estimates of the potential return on N input investment found that from a profitability perspective these inputs were suitable for the medium and higher performing farms in each district, providing application is on highest performing fields.