LAUSR

Abstract The middle and lower reaches of Yangtze River present high rainfall and always have a high water table. Recently drip fertigation has been introduced and widely used for vegetable production in this area. To investigate the effect of shallow groundwater and the newly-developed fertigation on the cucumber water and nitrogen (N) requirement, experiments were carried out in plastic tunnels in Yangzhou, Jiangsu, China, during the 2016 and 2017 growing seasons using a randomized block design with three replicates. Four N rates, 4 irrigation amounts and 2 irrigation intervals (2 d and 4 d) were applied in this experiment. The results showed that irrigation amount of 75% of estimated plant evapotranspiration (ETc) was optimal to obtain the highest yield, indicating shallow groundwater had a considerable contribution to the cucumber plant evapotranspiration in this condition. Fertigation technology improved the irrigation water use efficiency (IWUE) and N use efficiency (NUE) and 75% of the recommended N rate (calculated according to a traditional local nutrient balance method) optimized cucumber yield. Frequent irrigation with low water volume had a beneficial impact on the improvement of cucumber yield, IWUE, NUE and reduced the N leaching. According to this work, the recommended fertigation strategy is 0.75 of recommended N, 0.75 estimated ETc and 2 d irrigation interval in this experiment, in which cucumber yield of 105.4 Mg ha−1, IWUE of 41.1 kg m-3 and NUE of 356.4 kg kg−1 were achieved.