[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 · °C(-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 · C(-1). The result would be very meaningful for drip-irrigated muskmelon production and management in greenhouse in North China.