The fertilizer NH4NO3 was applied to maize at 0, 40 and 60 kg/fd, and to barely at 0, 40 and 60 kg/fd from water of one-source sprinkler of 24 m circle (RAINBIRD 30, with operating pressure 0.25 mega-pascal Mpa) more than half of the water fell within 4 m of the sprinkler head. Water application rate at 2, 4, 6, 8 and 10 m from sprinkler was 4.4, 4.2, 3.1, 2.4 and 0.6 mm/h respectively. Soil moisture, mineral N and maize grain yield also decreased with distance from sprinkler. Highest yield of 4048 kg/fd was at 2 m, the lowest of 494 kg/fd was at 12 m. Barely grain yield increased towards medium yield and moisture in soil; the highest of 1672 kg/fd being at 8 m, and the lowest of 1004 kg/fd at 12 m. Highest N rate gave highest maize yield, but lower barely yield than that given by the 40 kg/fd. Mineral N in non-fertilized soils was around 25 ppm NH4-N and 160 ppm NO3-N in fertilized one. There was more NO3-N in subsurface than in soil surface. Lowest efficiency of fertilizer N, measured as fertilizer recovery, uptake, was at circle periphery and highest was in middle areas. Special care in designing sprinkler network is vital in minimizing variations along the radius so as to have positive response to water and fertilizers far from the centre |
