Dry matter production and 15N recovery in spring wheat as affected by placement geometry of the fertilizer band

Abstract

The growth and nitrogen (N) uptake of spring wheat as affected by placement geometry was studied in a pot experiment. The pots were covered by a mobile shelter to prevent disturbance from natural precipitation. The 15N-labeled ammonium nitrate was applied in a band parallel to a single row of the growing crop. The fertilizer was banded in 12 combinations of depth (1, 5, or 10 cm) and distance from the crop row (1, 5, 10, or 15 cm), or broadspread on the soil surface. Plants were sampled at the elongation phase (5 treatments only) and at ear emergence (all treatments) and dry matter, apparent N recovery and 15N recovery in the crop were measured. In addition, the number of shoots and a vegetation index were measured on the first sampling date, and the numbers of ears were counted on the second sampling date. Regression analysis by distance from the crop row and depth from soil surface were carried out. There was a negative effect of increased distance and a positive effect of increased depth for all parameters. The effects were more pronounced when the parameters were measured in the elongation phase. The distance by depth interaction was insignificant for parameters measured on the second sampling date, but the estimated negative interaction was significant for the number of shoots and the simple vegetation index measured on the first sampling date. Deeper placement of the N fertilizer band was not able to mitigate the negative effect of increased distance for the measured parameters. The distance from crop row should not exceed 6–7 cm and the depth below soil surface should exceed 4–5 cm to ensure a positive effect of N placement under adverse conditions, such as low precipitation.