The wide gap between potential and actual yields of maize in Tanzania, due to low productivity is the major
constraint to improvement of food security and livelihood of farmers. The objective of this study was to
evaluate the potential of the use of small amount of nitrogen fertilizer as a measure to reduce maize yield
gap under rain fed conditions. Field experiments were conducted at Sokoine University of Agriculture,
Morogoro during the dry and rainy seasons of 2012/2013 using Maize cultivar PIONEER PHB 3253.
The nitrogen application rates were 0 (control), 15 (low N dose) and 80 kg N ha-1 (recommended rate).
Three water application regimes were tested. Irrigation water was applied from crop establishment up to;
grain filling; 50% anthesis; and between 50% anthesis and grain filling. The treatments were applied in a
completely randomized block design, in factorial layout for the dry season experiment. Nitrogen treatments
were repeated during the 2012/2013 rain season under rain-fed conditions. Both experiments were
replicated three times. In a dry season experiment, the water application regimes significantly (P≤0.05)
increase biomass at both 50% and harvest maturity stages. Total tissue N content decreased under nonstressed
water regime relative to water-stressed treatments. The interaction between irrigation and nitrogen
treatments significantly (P≤0.05) affected grain yield. Application of recommended N rate did not result into
yield increase when water was limiting. In the rainy season experiment, recommended N rate resulted in
highest biomass at end of juvenile (1 t ha-1), 50% anthesis (7.7 t ha-1) and harvest maturity stages (13.1 t ha-
1
). Total tissue N content and grain yield increased significantly with increase in N application rates during
the rainy season. Under water stress conditions, low N dose produced an extra 1000 kg ha-1 grain yield over
absolute control treatment. Under water stress conditions, recommended N rate, a 54% reduction of yield
gap was observed, which could not sufficiently reduce yield gap. However, under adequate soil moisture
conditions, recommended N rate attained up to 26% yield gap, suggesting that it would be beneficial to
apply nitrogen fertilizer when water is not limiting to close the yield gap. Small nitrogen doses can be an
effective strategy towards narrowing yield gaps for resource poor farmers especially in drought prone
areas. Further study should be done to extend the results beyond experimental site to test and validate the
approach under farmers’ paradigms.