Impact of applying organic fertilizers on nutrient content of soil and lettuce plants, yield quality and benefit-cost ratio under water stress conditions

The possible scarcity of available water for irrigation, climate change implications and environmental issues created the motivation for investigating new ways of increasing water use efficiency for crops. A field experiment was conducted, during two growing seasons, under open field conditions at Agricultural Research Center, Egypt. The study aimed to determine the effect of different irrigation water levels (60, 80 and 100% of crop evapotranspiration (ETc)) and fertilization (mineral fertilizers (control), farmyard manure (FYM), biochar, compost and vermi-compost) on growth, yield, water use efficiency and nutritional status of lettuce (Lactuca sativa L.). The experimental design was split plot; the irrigation water levels located at main plots and fertilization types located at sub-plots. Applying different irrigation water levels and fertilizers significantly affected the vegetative growth and yield traits, i.e., no. of leaves, weight, head length and width, and total chlorophyll, as well as nutrient contents (N, P and K) and total soluble solids (TSS). Data revealed that using vermi-compost fertilizer reduced irrigation water requirements of lettuce plants, compared with control treatment. Also, vermi-compost treatment gave the highest values of the studied plant traits, during the two tested seasons. Increasing irrigation level up to 80% of ETc enhanced the yield, with additions of organic fertilizer treatments, and increased water use efficiency. Moreover, the treatment of vermi-compost + 80% of ETc gave the highest benefit-cost ratio (BCR values were 3.08 and 2.77 during the two tested seasons, respectively), while the lowest ones (0.85 and 0.93) were recorded by applying the treatment of mineral fertilizers+ 60% of ETc during the two studied seasons, respectively.