Abstract
Bio-organic amendments have great potential to improve the performance and quality of crops grown under different environmental conditions. Thus, the effect of bio-organic amendments, comprising humic acid (HA), a cellulose decomposing bacterium (CDB) and wheat straw (WS), on squash was investigated under arid land conditions in the 2019/20 and 2020/21 planting seasons. 16S ribosomal RNA gene sequencing revealed that CDB was Geobacillus stearothermophilus. The independent application of HA, CDB and WS significantly (p <= 0.05) improved Lebanese summer squash fruit weight and number in both seasons despite the field's temperature (18.2-35 degrees C), rainfall (0-23.6 mm) and relative humidity (8-95%) ranges. Percentage increments in fruit weights were between 32.5% and 30.62% for HA, 10.32% and 5.44% for CDB, and 17.86% and 10.64% for WS in 2019/20 and 2020/21 planting seasons, respectively. Furthermore, HA, CDB and WS significantly (P <= 0.05) increased vitamin C content in both seasons averagely by 77.7%, 16.6%, and 54.5% compared to control (0 L/ha of HA, without CDB and 0 t/ha WS), respectively. Total soluble solids (TSS) and titratable acidity (TA) were significantly (P <= 0.05) increased by all the treatments. Percentage increments in TSS were between 145.5% and 146.5% for HA, 30.6% and 50.5% for CDB, and 630.4% and 297.4% for WS in both planting seasons, respectively. At the level of the interaction, the combined application of HA and WS improved the number of fruits, average fruit weight, and vitamin C content while HA and CDB improved vitamin C and fruit's pH. Three-ways interaction of the treatments also had a significant (P <= 0.05) effect on TSS. Overall, the use of bio-organic amendments under arid land conditions in Saudi Arabia significantly improved squash fruit yield and quality.