Acta Agriculturae Scandinavica, Section B — Soil & Plant Science 2015, Vol. 65(2): 132–140
The cause for low maize yields in rain-fed production systems is usually associated with water stress due to
perceived suboptimal seasonal precipitation. A modeling study using Agricultural Model Intercomparison and
Improvement Project modeling framework was conducted to determine the magnitude of rain-fed potential
yield and yield gap of maize in the Wami River sub-basin, Tanzania. Primary and secondary data on soils,
weather, management, and crop yields and cultivars were used. Data matrix search technique was used to
calibrate CERES-Maize Crop System model against reported yield for each of 168 farms involved in this study.
Then the individual farms’ simulated yields, actual reported yields, and the resultant yield gaps were aggregated
into ward-level averages. Model calibration was robust as there was a very close agreement between reported
and simulated yield (R2 = 0.9). Actual yields reported from farm survey ranged from 50 kg ha−1 to 3600 kg ha−1
with an average of 860 kg ha−1. Simulated rain-fed potential yield was between 2073 kg ha−1 and 5443 kg ha−1
and a mean of 4033 kg ha−1. It is apparent therefore that there exists a wide maize yield gap of 79% with current
management under rain-fed conditions. This suggests that there is a large scope of improving maize yields
under rain-fed conditions. Narrowing the yield gaps would require an intensive soil fertility improvement in the
study area.