Influence of low light intensity on growth and yield of four soybean cultivars during wet and dry seasons of northeast thailand

Abstract

Crop is commonly grown in intercrop combinations of which cereal/legumes are the most widespread in tropical countries. The availability of low light inten-sity due to shading is the critical factor in determin-ing legume yield in intercropping. The experiment searches of better soybean cultivar for intercropping. A field experiment was conducted at the experimen-tal farm of Khon Kaen University in 2005. The objec-tives of this study were to determine the influence of light regimes (30% of normal light, 50% of normal light and normal light) on the growth and yield of four soybean cultivars (early, medium and late ma-turity) under artificial shading at 35 days after seed-ing until harvest in the wet and dry seasons. The re-sults showed that grain yield was significantly (p<0.05) decreased under the low light intensity at 30% of natural light both in wet and dry season. This was mainly due to low light intensity at 30% of natural light decreasing the number of pods per plant in the dry season. For cultivars, grain yield was sig-nificantly difference (p<0.05) among cultivars both in the wet and dry seasons. The cultivar KKU 74 (me-dium maturity) gave maximum grain yield both in wet and dry season under the low light at 30% of natural light. The KKU74 cultivar is better adapted to shading environment than other cultivars. This was due to the KKU74 cultivar produced higher chlorophyll b concentration in leaves after the plant experienced to shading. This physiological character can be used for soybean breeding program in shading tolerance. Therefore, the cultivar KKU 74 had a higher potential yield advantage in intercropping systems in which low light intensity is a major limit-ing factor on grain yield.