[Effects of water and nitrogen management on photosynthetic matter production and yield of wheat].

The shortage of water resources and the irrational application of nitrogen fertilizer restrict the synergistic enhancement of yield and water- and fertilizer-use efficiencies of wheat in the Huang-Huai-Hai region. In this study, we conducted an experiment following two-factor split zone design with three irrigation levels and four nitrogen application rates. The relative water content of the 0-40 cm soil layer was supplemented to 65% (W₁), 75% (W₂), and 85% (W₃) of field water capacity at the jointing and anthesis stages of wheat. The rates of nitrogen application were 0 (N₀), 150 (N₁), 180 (N₂), and 210 (N₃) kg·hm^-2. We analyzed the effects of these different managements on post-anthesis photosynthetic matter production, yield, and water- and nitrogen-use efficiencies. The results showed that yield first increased with increases in the levels of irrigation and nitrogen application, peaking under the W₂N₂ treatment (9103.53 kg·hm^-2). However, further increases in water and nitrogen input did not have further enhancement of wheat yield. Under the same nitrogen application condition, compared with W₁ treatment, the canopy light interception rate, chlorophyll relative content and actual photochemical efficiency after anthesis increased by 4.5%-6.0%, 19.7%-28.2%, and 7.5%-9.8% in response to the W₂ treatment, respectively, without any difference between the W₂ and W₃ irrigation levels. At the same irrigation level, post-anthesis dry matter accumulation in repose to the N₂ treatment increased by 80.1%-88.9% and 16.7%-22.2% compared with N₀ and N₁ treatments, respectively, without significant difference between the N₂ and N₃ treatments. Both the irrigation water-use efficiency (IWUE) and the nitrogen partial factor productivity declined with increases in the levels of irrigation and nitrogen application. Under the W₁, W₂, and W₃ treatments, the values obtained for IWUE were 16.23, 11.01, and 7.91 kg·hm^-2·m^-3, respectively, whereas in response to the N₁, N₂, and N₃ treatments, N partial factor productivity was 50.8%, 48.4%, and 42.5%, respectively. In all, based on soil moisture measurements and assessments of wheat yield and water- and nitrogen-use efficiencies, the optimal water and nitrogen management strategy for enhancing wheat yield in the Huang-Huai-Hai region is supplementation of water content of 0-40 cm soil layer at the jointing and anthesis stages to 75% field capacity combined with the application of 180 kg·hm^-2 nitrogen (W₂N₂). This approach could achieve high yield and efficiency and promote conservation of water and fertilizer.