Optimal subirrigation quota for cucumber at different growth stages in protected field

The optimal irrigation quota of sectional subirrigation for cucumber in protected field was studied by measuring the yield and water use efficiency under different soil moisture ratios.The cucumber growth period was divided into two stages as earlier stage and later stage,and the irrigation was based on the upper irrigation control limit and lower control limit for each growth period.The results showed as follows:when the buried depth of subirrigation pipe was 25 cm,the planned wetting soil zone is 15-40 cm(25 cm in depth),the upper irrigation control limit and lower control limit were 6 kPa (soil water suction)and 30 kPa respectively,the optimal soil moisture ratio of planned wetting soil zone for earlier stage of cucumber was 0.37-0.38 (irrigation quota was 54-56 m3·hm-2)and later stage was 0.34-0.37 (irrigation quota was 50-55 m3·hm-2)for sandy clay loam,and at these wet ratios the yield and water use efficiency were optimalizing.