Nitrogen recovery and dry matter production of silage maize (Zen mays L.) as affected by subsurface band application of mineral nitrogen fertilizer

Fertilizers, including nitrogen (N), may be better available to crops when they are placed close to the crop's root system. Therefore, from 1991 to 1994 the effects of subsurface band application of mineral N fertilizer on the N recovery and dry matter (DM) yield of silage maize were studied in nine field experiments on sandy and clay soils. In the early crop stages and especially in the clay soil experiments, banded N had a significant negative effect on the N uptake and DM yield compared to broadcast N, possibly due to salt damage. At final harvest, however, banding significantly increased the N uptake and DM yield in most of the experiments. The apparent N recovery increased by circa 20-25% (absolute). The positive effects indicated that band application improved the efficiency of the N fertilizer. It could be calculated that banding allowed a reduction in the N rate of 20-30% without significant effects on the N uptake and DM yield of the silage maize. Benefits of banding were positively (P<0.001) related to the accumulated precipitation in the whole growing season. When N was broadcast, soil mineral N measurements showed that, initially, N was preferably taken up from soil compartments near the maize row resulting in lateral gradients, that sometimes even persisted until final harvest. Band application resulted in strong lateral gradients in the early crop stages, decreasing during the growing season due to N uptake by the maize crop. Root countings in two experiments showed that banding also seemed to affect root proliferation. Effects were, however, not consistent. Relatively more roots were found near the banded N in 1991 while in 1992 roots tended to avoid soil compartments with high N concentrations.