Nitrogen uptake of winter wheat from different soil depths under a modified sowing pattern

Aims A modified sowing pattern (MSP) consisting of wider seedling strips has been shown to improve the nitrogen (N) use efficiency of winter wheat by enhancing N uptake from soil. However, the effects of MSP on root size, 15 N-uptake efficiency, and N uptake from different soil depths have not been yet elucidated. Methods The seedling strip width in the MSP was 8–10 cm compared with 3–4 cm in the conventional sowing pattern, with a fixed row spacing of 27 cm. Both were used to investigate root size, root spatial distribution, and N uptake from different soil depths. Results The increased intra-row spacing of the MSP resulted in increases in the number of tillers and roots and in dry matter per unit area. The total root weight increased due to the higher root/shoot ratio induced by the enhanced nutrient requirements. Together with the increase in root number, the greater total root weight led to increases in root length and surface area, with a constant specific root length and surface area based on the total root weight. The absolute increases in root length and surface area densities declined with soil depth. Root 15 N-uptake efficiency based on root length and surface area decreased in the topsoil but increased or remained unchanged in the subsoil. Conclusions 15 N-uptake from each soil layer increased, with the largest increase occurring in the 40 to 80 cm soil layer. Due to the enhanced N uptake, particularly from the subsoil, the MSP may be used to reduce N inputs without penalizing yield.