Model based Estimation of Resource Use Efficiency in Maize Production Systems in Nigeria

Understanding the resource use and resource use efficiencies of current production systems could help to identify possibilities of producing more with the available resources and to address the variability in crop production to address the food security issues in a sustainable manner. Estimation of Water Use Efficiency (WUE) and Agronomic Fertilizer Use Efficiency (FUE) will allow farmers to adapt their production practices to climate variability under rain-fed and low-input agriculture production systems especially in Africa. Moreover, quantifying the relationships between WUE, FUE, and grain yields would facilitate the elucidation of crops' physiological responses, breeding, and improvement in the area.

A gridded data set was built; covering the major maize producing region of Nigeria. Within the SIMPLACE modelling framework, a combination of the LINTUL5 crop model with a detailed soil water balance model (SLIM) was used to simulate the yield and biomass of dominant maize varieties with prevailing agri-management practices. The simulations were run at 25 x 25 km grid cells and WUE and FUE were calculated for each simulation grid and aggregated from the simulation grid to the district level for comparing them with the statistics.

The WUE increases whereas, FUE decreases with the higher amount of fertilizer application. Highest WUE was estimated at 11.9 kg mm^-1 under 135 kg ha^-1 N application. Highest FUE under current fertilizer application (i.e., on an average 9 kg ha^-1 N) was estimated at 74 kg kg^-1 and lowest was in the tune of 61 kg kg^-1 across the states in Nigeria. The spatial variability in FUE values across the states in Nigeria was attributed to the cumulative precipitation amount in the crop growth period.

Results obtained suggest that water would be most efficient in Maize production in Nigeria when combined with 135 kg ha^-1 N fertilizer application. The calculations of optimal application rates at the state level should not be applied to individual farms, because at this level, the soil endowment of a farm is a decisive factor.