土壤含水率监测位置对温室滴灌番茄耗水量估算的影响

Estimation of water consumption as affected by measurement locations of soil water content in drip irrigated tomato in solar greenhouses

土壤水分传感器埋设位置的选择是局部灌溉条件下获得作物根区代表性土壤含水率数据，从而制定滴灌灌溉制度的关键。本文以日光温室滴灌番茄为对象，研究滴灌线源土壤湿润体内含水率分布状况，通过对比距滴灌带不同位置处土壤含水率监测结果估算番茄耗水量的差异，探讨土壤含水率监测的合理位置。结果表明，番茄生育期内14～25mm的灌水定额主要用于增加0～40cm土层的土壤含水率，湿润体内日平均土壤含水率分布在75％～100％田间持水率。作物生育期内连续多次滴灌条件下，沿滴灌带单个灌水器形成的湿润土体会充分叠加，形成近似均匀的土壤含水率带状分布，且作物生育期内沿深度方向0～40cm土层土壤含水率均值无显著性差异，距滴灌带不同水平距离的土壤含水率随时间的变化趋势具有同步特点，无明显的滞后性。以集中80％总根量的土壤深度作为滴灌番茄水分渗漏下界面时，14～25mm的灌水定额会导致深层渗漏，且深层渗漏量表现出一定的空间变异性。番茄生育期内深层渗漏量约占灌水量的13％。距滴灌带不同位置处的番茄耗水量除在番茄苗期和开花座果期有较大差异外，其余生育阶段的差异均在10％以内。对温室滴灌番茄来说，滴灌高频少量的灌溉特征有利于维持作物根系层适宜的土壤水分状态，监测1个含水率剖面即可满足估算作物耗水量的要求。

Placements of soil moisture sensor have been key considerations in obtaining representative soil water content in crop root zones for irrigation schedules. In this article, the distribution of soil water content in the wetted volume from a line source was studied in drip irrigated tomato in solar greenhouse condition. Through comparison of tomato water consumption determined from measured water content by moisture sensors at different locations, suitable placements of sensors were discussed. The results indicated that irrigation quota range of 14-25 mm increased soil water content in the 0--40 cm soil layer, and daily mean soil water content in wetted soil volume was 75%-100% field capacity throughout tomato growth season. Wetted soil volumes generated by adjacent emitters along the drip lines fully overlapped after several sequential irrigation events, forming lateral zones with approximately uniform distribution of water content around the drip lines. There was no significant difference between mean soil water content along the depth of 0-40 cm layer. The variation tendency of soil water content with time at different horizontal locations from drip lines was synchronous in character, without any obvious hysteresis quality. Assuming that the 0-40 cm layer was the root zone with 80% root concentrated, an irrigation quota range of 14-25 mm caused deep percolation from the bottom of the root zone with a certain spatial variability. Seasonal deep percolation accounted for 13% of irrigation amount during tomato growth season. The differences in tomato water consumption at different locations from drip lines were within 10%, except for the seedling and blossom fruiting stages. The experimental results suggested that high frequency drip irrigation sustained suitable soil watercondition in the root zone. One profile of soil water content measured in the proximity of drip lines was adequate for the proper estimation of water consumption of drip irrigated tomato in solar greenhouse conditions.