Effect of Humic Acid on Growth and Development of Squash under Saline Stress Conditions in Benghazi

Abstract

Two experiments were carried out to cultivate the squash plants (Cucurbita pepo L.) cultivar "Alexandria" in pots of 3 liters in the research farm of the Faculty of Agriculture - University of Benghazi in the Plain of Benghazi during the planting season in the region during 2018 and 2019, in order to study the effect of salinity of irrigation water in concentrations 500, 1000, 2000 and 3000 (ppm) and humic acid at concentrations of 0, 100, 200, 300 and 400 (ppm) and different interactions between factors on vegetative growth characteristics of plants, water relationships of plants, leaf content of chlorophyll, leaf content of protein, content Leaves of mineral elements (N, P, K, Na, Cl) and total yield and its components. Salinity negatively affected the characteristics and water content of the vegetative growth as well as leaf content of chlorophyll, also the leaves content of nitrogen, phosphorus and potassium decreased, while their content of sodium and chloride increased, the leaf content of protein decreased, and also led to the reduction of the characteristics of reproductive growth and plant yield, the soil EC value increased by increasing the salinity concentration, and the control treatment of salinity gave the greatest value for vegetative measurements regardless of humic acid concentration. On the other hand the treatment with humic acid had a positive effect on the characteristics of vegetative growth and water content and leaf content of chlorophyll as well as the leaves content of nitrogen, phosphorus and potassium, while the content of sodium and chloride decreased, the leaf content of protein increased, the number of flower buds and plant yield increased, and the 107 soil PH value decreased due to the addition of humic acid, the greatest value of total chlorophyll was from treatment of 100-300 and control-400 (ppm) of salinity and humic acid during the first and second season, respectively. Salinity led to increase the EC value of soil, which increased the water potential of the soil solution, which makes it difficult to absorb water and nutrients and thus decreased the vegetative and reproductive growth of the plant, and the addition of humic acid mitigated the effect of salinity due to its contribution in raising the value of water potential of plant cells and its ability to link to thesodium, which helps the plant to withstand high salt concentrations and avoid osmosis problems.