Effects of border irrigation and fertilization timing on soil nitrate nitrogen distribution and winter wheat yield

In border irrigation, an optimal pattern is necessary for high irrigation and fertilization uniformity, nitrogen storage efficiency and crops yield. This paper aims to explore the effects of different border specifications and fertilization methods on the distribution of soil NO3--N and the yield of winter wheat. Therefore, a field experiment was conducted in 2017-2018 at the winter wheat season. Three experimental factors were selected, including the border width of field (1.5, 2.3, and 3.2 m), border length (40, 60, and 80 m) and the fertilization timing (first half liquid fertilizer application, second half liquid fertilizer application, full liquid fertilizer application). Three factors were set by orthogonal experiment design, and twelve treatments were established, including three traditional broadcasting fertilization as control treatments (border width of 1.5, 2.3 and 3.2 m at 80 m border length with spreading application). The content of soil NO3--N, the uniformity of NO3--N distribution, nitrogen storage efficiency and winter wheat yield were measured in this study. The results showed that the concentrations of soil NO3--N increased in different soil layers after irrigation, compared with those before irrigation, while soil NO3--N concentrations decreased with the increase of soil depth. In liquid application treatments, the accumulation of soil NO3--N in the root layer was 0.27%-27.97% higher than that in the spreading application treatments. The border width, border length and fertilization timing all significantly determined the fertilization uniformity and storage efficiency of NO3--N in border irrigation. In the wheat reviving stage, the contribution rate of border length to the uniformity of irrigation and fertilization was the maximum (91.64%), whereas the contribution rate of fertilization timing on nitrogen storage efficiency was the highest (44.2%). In the flowering stage, the border length and border width were the main factors that affected the uniformity of irrigation and fertilization, and the nitrogen storage efficiency, where the contribution rates were 92.67% and 53.6%, respectively, indicating that the border length dominated in this case. The uniformity of irrigation and fertilization under 60 m border length treatments was higher than that under 40 m and 80 m of border length treatments. The contribution rates of border width, border length, and fertilization timing to the crop yield were 37.2%, 37.3%, and 23.9%, respectively. The highest yield (7869.2 kg/hm2) was achieved under the border width of 3.2 m, border length of 60 m and full liquid application treatment. The finding demonstrated that the liquid application can improve the distribution uniformity of soil NO3--N, and soil NO3--N accumulation in the root layer of winter wheat, while avoid soil NO3--N leaching. The optimal treatment mode can be the combination of 3.2 m border width, 60 m border length and full liquid fertilizer application for the uniformity and accumulation of soil NO3--N, as well crop yield. The results of this study can offer a theoretical basis to select border dimensions and fertilization timing for the winter wheat in North China Plain. © 2020, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.