关键词: 水稻, 高温热害, 灌溉水源, 温度, 能量平衡

Abstract: Heat stress is one of the common agrometeorological disasters in the rice production in the middle and lower reaches of the Yangtze River in China. To mitigate the effect of heat stress on rice growth, irrigation with pond or well water was usually adopted, and which is considered to be an effective measure. In this paper, the effect of the irrigation with different water sources was evaluated by a field experiment conducted in Nanjing from August 12th to 18th, 2016, during which time a heat stress had just occurred. The rice variety Liangyoupeijiu was used in the experiment and three daily irrigation treatments, set as T1, T2 and CK, were implemented. For T1 and CK, pond water was used for the irrigation, and well water was used for T2. For all treatments, the irrigation started from 8：00 and stopped when the height of water layer reached about 10 cm. For T1 and T2, the paddy water was drained out at 18：00; but for CK, the water was kept with a height between 5 and 10cm. The average temperature was about 30.5℃ and 18.2℃ for pond and well water respectively. Since CK kept the water in the field, the average temperature of the paddy field water at 8：00 was about 28.2℃. The temperature and humidity within the rice canopy at four different heights (40cm, 80cm, 120cm and 130 cm), leaf temperature at the canopy top, and solar radiation above the canopy were measured. With the observations, the diurnal variation of each energy balance component in the paddy field was calculated using the Penman-Monteith stratification model. The micrometeorological characteristics of the paddy fields were analyzed. The results showed that from 8：00 to 18：00, the order of canopy temperatures for three treatments were T1>CK>T2. However, the difference of the canopy temperatures among the treatments decreased with the height within the canopy. Similarly, the difference of paddy soil temperatures among the treatments decreased with the depth in the soil. From 18：00 to 8：00, the difference of soil temperature at 5cm depth was the most obvious among the treatments. The difference of the canopy temperature at 40cm height within the canopy was the second one. The analysis indicated that the relationship between the changes of the energy balance of paddy fields and the irrigation water was close. The order of the heat storage in water (Q) was T2 >CK >T1. And the orders of soil heat flux (G), sensible heat flux (H) and latent heat flux (LE) were T1>CK >T2. These results suggested that irrigation with pond water could aggravate the heat stress on rice, while irrigation with well water is benefit to reduce the effect of heat stress on rice growth.

Key words: Rice, Heat stress, Irrigation water source, Temperature, Energy balance