Effects of reduced nitrogen application and supplemental irrigation on photosynthetic characteristics and grain yield in high-yield populations of winter wheat.

Abstract

A field experiment was conducted to study the effects of reduced nitrogen application and supplemental irrigation on the light environment, photosynthetic characteristics and yield components in high-yield wheat population. The treatments included three irrigation schedules [no irrigation (W1), medium irrigation (W2, the soil relative water content of 70%±5% after jointing stage), well-irrigation (W3, the soil relative water content of 85%±5% after jointing stage)] and three nitrogen application levels [no nitrogen (N1), reduced nitrogen (N2,195 kg N·hm-2), high nitrogen (N3, 270 kg N·hm-2)]. The results indicated that the N2W2 treatment significantly improved the light environment of high-yield wheat populations, the photosynthetically active radiation (PAR) and the light transmission rate at the region of 20-30 cm canopy increased by 34.5% and 10.8%, respectively, when compared with the high nitrogen-supplementary water treatments (N3W2, N3W3). The leaf area index (LAI) of N2W2 was the highest among all treatments tested, which decreased slowly at grain filling stage, and the period with higher LAI value (>7.6) was 3-4 days longer than that of high-nitrogen and non-nitrogen treatments, as well as, the leaf photosynthetic potential was increased by 9.7% on average. Under the treatments of N2W2 and N2W3, the photosynthetic rate (Pn) was relatively higher at grain-filling stage, while the difference was not significant compared with the treatment of N3W2. The apparent quantum yield in flag leaves of N2W2 reached 0.1 μmol CO2·m-2·s-1, Pn value kept on the level of 27.692 μmol CO2·m-2·s-1 and the light compensation point (LCP) was relatively lower, which demonstrated a stronger photosynthetic productivity. The grain yield of N2W2 was the highest among all treatments.