Effects of gibberellic acid and cytokinin application on morphological development, growth, quality and yield of french beans grown under different irrigation schedules
Ikiba, Lawrence Kalawa
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French bean (Phaseolus vulgaris L.) is an increasingly important vegetable crop in Kenya accounting for a significant proportion of foreign exchange earned from horticulture. Farmers in Kenya experience insufficient and unreliable rainfall that affects yields and subsequent family incomes. Attempts to address this situation have been further hampered by poor rainfall distribution. Integration of plant growth regulators in French bean production are among the options that have been suggested for mitigation of water scarcity. Phytohormones can stimulate crop growth, morphological development and improve yield under conditions of poor moisture. There are different growth regulators that manifest varied physiological effects on crop development. In this study the effects of two commercial growth regulators gibberellic acid (GA3) and cytokinin (CK) on French beans grown under different irrigation schedules were evaluated. The parameters of study were aspects of French bean growth yield and quality. The study also assessed the effects of growth regulators under different irrigation schedules with an objective of establishing potential of growing French beans with less water. The study was conducted at the Kenyatta University Research and Demonstration Farm, Nairobi County, Kenya. The experiment was laid out in a Randomized Complete Block Design (RCBD) with split- plot arrangement where Irrigation schedules (1, 2 and 3-day intervals) formed the main plot factor and hormones at different rates (Cytokinin at 0, 0.250, 0.500 and 0.750 ml/L, and Gibberellic acid at 0, 0.225, 0.450, and 0.675 ml/L) formed the subplot factors. The data was subjected to Analysis of Variance and where there were significant differences among treatments, means were separated using Fishers Least Significance Difference (LSD). The daily irrigation led to the highest growth rate, quality and the yield of French beans while irrigation every three days had the lowest indicating stressed crop growth. The 0.225 ml/L gibberellic acid and 0.50 ml/L cytokinin led to the highest potential growth, quality and yield of the French bean irrespective of irrigation regimes. It was however noted that under depressed conditions of moisture (irrigation once in 3 days), application of 0.225 ml/L gibberellic acid or 0.50 ml/L cytokinin enabled the crop to eventually produce significantly higher pod fresh weight yields (48.67 and 58.14 g per plant respectively) with cytokinin having a greater effect compared to gibberellic acid. In addition, use of the phytohormones even where water is sufficient improved growth yield and quality of French beans. It is thus recommended that farmers especially in water deficient production systems of French beans to incorporate the use of these hormones.