Interactive effects of deficit irrigation and vermicompost on yield,quality, and irrigation water use efficiency of greenhouse cucumber

Water scarcity is the most significant barrier to agricultural development in arid and semi-arid regions. Deficit irrigation is an effective solution for managing agricultural water in these regions. The use of additives such as vermicompost (VC) to improve soil characteristics and increase yield is a popular practice. Despite this, there is still a lack of understanding of the interaction between irrigation water and VC on various crops. This study aimed to investigate the interaction effect of irrigation water and VC on greenhouse cucumber yield, yield components, quality, and irrigation water use efficiency (IWUE). The trials were done in a split-plot design in three replicates in a semi-arid region of southeastern Iran in 2018 and 2019. Three levels of VC in the experiments, i.e., 10 (V₁), 15 (V₂), and 20 t/hm² (V₃), and three levels of irrigation water, i.e., 50% (I₁), 75% (I₂), and 100% (I₃) of crop water requirement were used. The results showed that the amount of irrigation water, VC, and their interaction significantly affected cucumber yield, yield components, quality, and IWUE in both years. Reducing the amount of irrigation water and VC application rates reduced the weight, diameter, length, and cucumber yield. The maximum yield (175 t/hm²) was recorded in full irrigation using 20 t/hm² of VC, while the minimum yield (98 t/hm²) was found in I₁V₁ treatment. The maximum and minimum values of IWUE were recorded for I₁V₃ and I₃V₁ treatments as 36.07 and 19.93 kg/(m³?hm²), respectively. Moreover, reducing irrigation amount decreased chlorophyll a and b, but increased vitamin C. However, the maximum carbohydrate and protein contents were obtained in mild water-stressed conditions (I₂). Although adding VC positively influenced the value of quality traits, no significant difference was observed between V₂ and V₃ treatments. Based on the results, adding VC under full irrigation conditions leads to enhanced yield and IWUE. However, in the case of applying deficit irrigation, adding VC up to a certain level (15 t/hm²) increases yield and IWUE, after which the yield begins to decline. Because of the salinity of VC, using a suitable amount of it is a key point to maximize IWUE and yield when applying a deficit irrigation regime.