Effects of Irrigation with Micro-sprinkling Hoses on Canopy Temperature and Humidity at Filling Stage and Grain Weight of Wheat

Abstract

We carried out a two-year field experiment in 2012–2013 and 2013–2014 growing seasons of winter wheat, with treatments of no irrigation(W0), border irrigation(W1), and irrigation with micro-sprinkling hoses special for wheat(W2). The W2 treatment was conducted at different time of a day in early or late grain filling stage with different amounts of irrigation in the middle and late filling stages. The results showed that the spike layer temperature of W2 decreased by 6.8–11.3°C after irrigating with micro-sprinkling hoses at 10:00 a.m. in early grain filling stage, and the decline was significantly greater than that of W1. However, no significant difference in temperature of spike layer was observed between W2 and W1 from the 2nd day to the 4th day after irrigation and between W2 and W0 at the 4th day after irrigation. The leaf water potential on the irrigation day was significantly higher in W2 than in W1. In contrast, leaf photosynthetic rate on the irrigation day, as well as leaf water potential and leaf photosynthetic rate on the next day were similar between W2 and W1. As a result, the grain weight and the grain yield in W2 and W1 were higher than that in W0 treatment. Besides, the irrigation water use efficiency of W2 was significantly higher than that of W1. When 5 or 10 mm of water was sprayed by micro-sprinkling hoses at 10:00, 12:00, and 14:00 hours in the late grain filling, the canopy temperature decreased significantly whereas the canopy relative humidity, the flag leaf water potential, and the canopy apparent photosynthetic rate tended to increase. During a day, earlier irrigation resulted in better improvement of water status and photosynthetic performance for wheat leaf. Our results suggest that supplementary irrigation with micro-sprinkling hoses should be conducted at early grain-filling stage or at 10:00 on a day during middle-to-late grain filling with 5–10 mm water spray each time when daily high temperature is forecasted.