Role of humic acid and some spraying treatments in improving vegetative growth parameters, chemical components of leaves and yield of hot pepper plants (Capsicum annuum L.) planted in unheated plastic houses conditions

The experiment was implemented through the winter agricultural season 2020-2021 in one of the unheated greenhouses with dimensions (9 x 50) m and an area of 450 m² following to the fields of the department of horticulture at the college of agriculture and marshes-Dhi Qar University, south of Iraq, with the aim of research the impact of adding humic acid, spraying sevsral treatments, on vegetative growth parameters, chemical components of leaves and yield of two kind hybrids of hot pepper plants (Barbarian F1and Kizil F1). Experiment included 30 factorial treatments which were the possible combinations of two hybrids(Barbarian F1and Kizil F1), three proportions of humic acid 0, 1, 2 g. l−1 and five foliar spray treatments (aqueous extract of jujube leaves at a proportion (75) g. l−1, aqueous extract of pomegranate peels at a proportion of 5 ml. l−1, calcium at a proportion of 1.5 ml. l−1, arginine acid 200 mg. l−1 in addition to control treatment (spraying with distilled water only). Factorial experiment was designed out according to the split-split plot design in R.C.B.D with three replicates. The results were analyzed by the analysis of variance and mean values were contrast using the Revised Least Important Difference Test at 0.05 probability. Results appear that the Barbarian F hybrid superiority on plant height, leaf area, chlorophyll and nitrogen,. Adding humic acid at the proportion of 2 g. l−1 led to important raise in the plant height, the proportion of total chlorophyll, while the proportion of 1 g. l−1 caused an increment in the percentages of nitrogen, the proportion of total chlorophyll and the yield per plant. Spraying arginine acid 200 mg. l−1 led to raise the proportion of total chlorophyll, whereas the treatments of arginine acid 200 mg. l−1 and calcium at a proportion of 1.5 ml. l−1 were the best in growing the leaf area. The application of extract of pomegranate peels at a proportion of 5 ml. l−1 gave the highest yield per plant.