Zhijie Shan, Weixia Zhao, Huanjie Cai, Wei Qin, and Zhaoyan Wang
Non-pressure irrigation, crop-pan coefficient, soil matric potential threshold
Non-pressure irrigation is an efficient micro-irrigation technique, which has the lower system investment and higher irrigation water use efficiency. In this text the irrigation scheduling based on pan evaporation and soil matric potential threshold was made for greenhouse tomato under non-pressure irrigation technique. Soil matric potential was measured by tensiometer and threshold was designed as -25 kPa. Pan evaporation was measured by 20 cm standard pan and crop-pan coefficients (Kcp) were designed as 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2. Tomato yield, irrigation water-use efficiency, plant growth and biomass allocation were studied to identify suitable crop-pan coefficient. Irrigation frequency and soil matric potential were analyzed to study the characteristic of irrigation application based on tensiometer and pan. For all Kcp used, there was significant difference in tomato yield between Kcp = 1.2 and other treatments, whereas there was no significant difference among Kcp = 0.2~0.8 treatments. Irrigation water-use efficiency was the highest when Kcp = 0.2. Higher irrigation water amount had no significant influence on plant height, while it increased stem diameter and biomass accumulation. Root system was concentrated in the top 40 cm of the soil and independent of Kcp used. Irrigation application was frequent and low volume. The hysteresis of irrigation water amount calculation based on pan evaporation and the validity of tensiometer location were two main factors affecting the consistency between irrigation application and plant water consumption.
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