不同水分下限对温室膜下滴灌甜瓜开花坐果期地温的影响

土壤水热状况是影响甜瓜生长及坐果的重要因素.本文以膜下滴灌为供水方式，在开花坐果期设计了重度亏缺（55%田间持水量，T₁）、中度亏缺（65%田间持水量，T₂）、轻度亏缺（75%田间持水量，T₃）和不亏缺（85%田间持水量，CK）4种水分控制下限处理，研究了不同水分控制下限对温室滴灌甜瓜耕层温度的影响，在此基础上探讨了耕层（0～20 cm）不同水热比值对甜瓜生长发育及坐果情况的影响.结果表明；甜瓜在开花坐果期间，耕层的平均地温为T₁＞T₂＞T₃＞CK，地温与土壤含水率呈反比.晴天、阴雨天及灌水后的地温日最大变幅均出现在膜内地表，最小变幅出现在膜外地表以下20 cm处；地温极值与土壤深度密切相关，地表极值与地下10和20 cm的极值差异显著.该阶段选择T₃作为灌水标准，即水热比值为1.62 mm·℃^-1时，植株的生长速率最快，坐果历时最短且坐果率最高.综合考虑温室膜下滴灌甜瓜在开花坐果期的土壤水分与地温的关系，认为T₃处理可使耕层土壤水热比值（水热比值为1.62 mm·℃^-1）达到最佳状态，更有利于甜瓜的生长发育和坐果.

Effects of irrigation threshold on soil temperature in blossom and fruit-set periods of muskmelon under mulching-drip irrigation in greenhouse.

It is very significant for muskmelon growth and production to maintain optimal conditions of soil moisture and temperature, especially during blossom and fruit bearing periods. The object of this study was to analyze the effects of different soil water thresholds (T₁: 55% of the field capacity, T₂: 65% of the field capacity, T₃: 75% of the field capacity, CK: 85% of the field capacity) on soil temperature under mulching drip irrigation in greenhouse. Moreover, effects of the ratio of soil moisture to heat in the plough layer (0-20 cm) on muskmelon growth and fruit setting were investigated. Results indicated that during the flowering and fruit bearing periods, the order of mean soil temperature in the plough layer for the different treatments was T₁＞T₂＞T₃＞CK. There was an inverse correlation between soil temperature in the plough layer and moisture. The maximum one day variations for soil temperature on sunny day, rainy day and after irrigation were observed in the soil surface under the plastic film mulch, while the minimum happened in the soil layer of 20 cm outside the mulch. The soil temperature extreme was closely related with soil depth, and the difference in the extreme soil temperature between the soil surface and the soil layers of 10 and 20 cm was significant. The treatment T₃, with the fastest plant growth rate, the minimum duration of fruit bearing and the maximum fruit setting rate, could be selected as the optimal treatment, and the ratio of soil moisture to heat in T₃ was 1.62 mm·℃^-1. Therefore, taking into consideration the relationship between soil moisture and temperature during flowering and fruit bearing periods of muskmelon under mulching drip irrigation, the ratio of soil water to heat in the plough layer should be kept at 1.62 mm·℃^-1. The result would be very meaningful for drip-irrigated muskmelon production and management in greenhouse in North China.