Effects of Growth Regulators on Yield and Quality of Vegetable Soybean cv. DOA Chiang Mai84-2

Abstract

The demand for vegetable soybean cv. DOA Chiang Mai84-2 has been increasing in the market. Increasing the yield of this soybean by extending the planting area was not practical due to the limitation of appropriate planting areas. To increase yield, the effects of spraying growth regulators at the flowering stage on the yield and quality of vegetable soybean cv. DOA Chiang Mai84-2 were investigated. The experiment was conducted at the Chiang Mai Field Crops Research Center in two dry seasons during the years 2022-2023. A randomized complete block design of six treatments with 4 replications was applied. The treatments were comprised of spraying soybean at the flowering stage (R1) with different growth regulators: 1) brassinolide 0.01 ppm, 2) gibberellic acids (GA₃) 1 ppm, 3) abscisic acid (ABA) 1 ppm, 4) kinetin 5 ppm, 5) naphthalene acetic acid 10 ppm and 6) spraying water (control). The results showed that spraying all growth regulators gave a total yield of 1,397-1,511 kg/rai, a marketable yield of 1,335-1,464 kg/rai, and a standard pod yield (grade A) of 530-623 kg/rai, which were slightly different. The ABA spraying gave the highest grade A pod yield of 623 kg/rai, which was not different from other growth regulators but significantly higher than that of GA₃ spraying. All growth regulator spraying treatments gave higher yields than that of water spraying, causing marketable yield increases of 19.5-31.1%. Nevertheless, all growth regulator treatments did not affect other yield components. The benefit-cost ratio of all spraying treatments was greater than 1, indicating that the investment was worthwhile. Therefore, spraying these growth regulators was recommended as an alternative method to increase the yield of vegetable soybean cv. DOA Chiang Mai84-2.