Effects of Biochar and Vermicompost Amended Soil on Yellow Squash Yield under Deficit Irrigation in Bangladesh

Soil fertility management and efficient irrigation system could contribute in sustainable vegetable production in Bangladesh. This study evaluated the effects of soil amendments and irrigation levels on the growth, yield, and water use efficiency (WUE) of yellow squash (Cucurbita pepo L.). A field experiment was conducted at the Sylhet Agricultural University (SAU) campus, Sylhet, using a randomized complete block design consists of six treatments with three replications. Treatments included loamy soil (control), loamy soil with vermicompost, and loamy soil with biochar, each under 60% (deficit) and 80% (deficit) field capacity irrigation. Field level data were collected from sample plants of each plots. Collected data were analyzed by SPSS version 23.0 software. Results demonstrated that integrating organic amendments with loamy soil under adequate irrigation improves yellow squash productivity, soil fertility, and water efficiency. Among treatments, LCFI80 (vermicompost + loamy soil at 80% field capacity) was identified as the most effective strategy for maximizing fruit yield and plant growth, while LBFI80 (biochar + loamy soil at 80% field capacity) offered the greatest advantage in improving WUE. However, soil amendments and deficit irrigation levels significantly impacted on squash growth and yield. Fruit weight ranged from a minimum of 614 g in LSDI60 (60% field capacity with control soil) to a maximum of 980 g in LCFI80 (80% field capacity with vermicompost-amended soil). Fruit diameter showed a similar trend, with values ranging from 13 cm (LSDI60) to 27 cm (LCFI80). Water use efficiency (WUE) was strongly influenced by soil type: biochar-amended soil showed superior efficiency, ranging from 42 g L⁻¹ in LSFI80 to 53 g L⁻¹ in LBFI80, reflecting its enhanced water-retention capacity. These results of the study provide a practical guidance for soil fertility management through using biochar in vegetable production systems in Bangladesh.