Responses of yield and water use efficiency of drip-irrigated cucumber in greenhouse to water stress

Abstract: To optimize the drip irrigation schedule of greenhouse cucumber is of great significance for achieving efficient use of agricultural water, promoting high yields and quality of facility crops and improving farmers' living standards. The greenhouse cucumber was planted in 2017 (autumn-winter planting season) and 2018 (spring-summer planting season) in the Venlo-type greenhouse of Modern Agricultural Equipment and Technology of Jiangsu University. Irrigation treatments were designed based on the cumulative water surface evaporation of 20 cm standard pan and they included three irrigation levels of full irrigation (T1), light deficit irrigation (T2) and moderate deficit irrigation (T3). In the spring-summer season, the coefficients of evaporating pan were 0.8, 0.6 and 0.4 at the development stage of cucumber for the treatments of T1, T2 and T3, respectively and 1.2, 1.0 and 0.8 at the middle and later stages of cucumber for the treatments of T1, T2 and T3, respectively. In the autumn-winter season, the coefficients of evaporating pan were 0.9, 0.75 and 0.45 at the development stage of cucumber for the treatments of T1, T2 and T3, respectively and 1.2, 0.9 and 0.6 at the middle and later stages of cucumber for the treatments of T1, T2 and T3, respectively. Soil moisture, evapotranspiration, yield and water use efficiency were determined. Stem flow rate, photosynthetic rate and stomatal conductance were also measured. The results showed that the cucumber yield and water use efficiency had a decreasing trend with the decrease of irrigation amount. Different degrees of water deficit had certain inhibitory effects on the evapotranspiration in different growth stages of cucumber. Water deficit at any growth stage of cucumber decreased the sap flow rate, photosynthetic rate, stomatal conductance and decreased the accumulation of dry matter of cucumber. The average fruit weight, fruit stem diameter, fruit length and fruit number per plant decreased with the decrease of irrigation amount. The proportion of cucumber fruit malformation increased with the increase in water deficit at different growth stages. The response of yield, evapotranspiration and water use efficiency of greenhouse cucumber in different planting seasons to different irrigation amount showed that the yield of greenhouse cucumber for T1 treatment were higher than T2 and T3 treatments by 22.0% and 51.2% in the spring and summer planting seasons, respectively and by 54.2% and 73.9% in autumn and winter planting seasons, respectively. The evapotranspiration for T1 treatment was higher than T2 and T3 treatments by 17.4% and 34.9% in the spring and summer planting season, and by 24.0% and 48.0% in the autumn and winter planting seasons, respectively. The water use efficiency of T1 treatment was higher than T2 and T3 treatments by 5.5%and 25% in the spring and summer planting seasons and by 39.7% and 50.0% in the autumn and winter seasons, respectively. The irrigation scheme with 0.8 times the cumulative evaporation amount during the development stage and 1.2 times the cumulative evaporation amount during the middle and later stage was recommended for greenhouse cucumber cultivation. This study is of great significance for efficient use of agricultural irrigation water and the improvement of yield and quality of facility crops.