Effect of Previous Crop Residues on The Growth and Development of Squash Plants

The seedlings of Squash (Cucurbita pepo L.) were irrigated with aqueous extract of crop residues of barley, wheat or oat, at a concentration of 50 g.L-1, or olives at 25, 50, 75 and 100 g.L-1, in addition to the control treatment (tap water) until the flowering stage. A completely randomized design was used with the treatments. The results showed that the fresh and dry weight of the shoots decreased by (27, 26, 33%) and (26, 35, 44%), and the number of leaves and flower buds (20, 20, 25%) and (28, 24, 40%) and leaf petiole length (38, 41, 47%), when treated with aqueous extract of the residues of each of barley, wheat, or oats, respectively, compared to the control. The results also showed the effect of the aqueous extract of olive residues on the growth measurements of squash plants, and the rate of decrease was directly proportional to the increase in the concentration of the aqueous extract, and thus both the fresh and dry weight of the shoots decreased by 51% and 42%, roots 43% and 25%, plant length 40%, number of leaves 29%, and leaf area 70%, respectively, compared to the control. The results obtained show that the aqueous extract of different plant residues have a clear role in reducing the growth of squash plants, and thus, this will be reflected in productivity later. This type of effect is clearly due to the presence of an "allelopathic" effect from growth-inhibiting substances present in the tissues of previous plant residues or their presence simultaneously with squash plants in the field.