Path and Stability Analyses of Yield and Yield Components of Soybean (Glycine Max. L Merr.) Varieties Intercropped with Maize
Wanjala, Wanyama Patrick
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Soybean production in Kenya is estimated at 9,061MT. This is low compared to the annual demand of 100,000MT. This large deficit is met through importation which puts a strain to the economy’s foreign exchange. Soybean has the highest protein content (40-42%) among the food crops with oil content of18-22% comprised of 85% unsaturated fatty acids. These attributes make it an inexpensive source of proteins and desirable human diet. Released soybean varieties in Kenya have been evaluated based on sole-cropping system. However, commercial production is mainly through intercropping with either maize or sugarcane. The most common advantage of intercropping is the production of greater yield on a given piece of land by making more efficient use of the available growth resources. Research on intercropping has been concerned with effects of agronomic manipulation but there is limited information on soybean varieties suitable for intercropping. Therefore, this study aimed to compare grain yield and yield components of soybean under intercropping and sole cropping, select varieties of soybean for increased yields under intercropping and to determine the genotype by environment interaction in soybean. The study was conducted in three sites: KALRO-Alupe, in Busia County; KALRO-Kakamega, in Kakamega County; and Sang’alo Institute of Science and Technology, in Bungoma County. Ten recommended varieties of soybean were evaluated in randomized complete block design in split plot arrangement with three replications. The main plots were cropping systems (soybean sole crops and maize-soybean intercrop); the sub plots were the ten soybean varieties. The maize variety used was H513. Data was collected on grain yield and yield components of soybean. All measured variables were statistical analyzed by ANOVA using SAS software. Treatment means were separated using the LSD at α = 0.05. The results indicated that the yield and yield components were significantly different between the varieties in each site and in combined environment. In intercrops, the varieties were significantly different in all three sites; Kenysoy009, DPSB8, DPSB19 and EAI3600 were the best varieties in Alupe, Kakamega, Sang’alo and combined environments respectively. In sole cropping system DPSB8, SC Saga, Salama and Kensoy009 were the highest yielding varieties in Alupe, Kakamega, Sang’alo and across sites respectively. Across the environments under intercropping system, harvest index, 1st pod height and leaf area were positively correlated to grain yield while days to maturity were negatively correlated with yield. In path analysis, the number of branches had the highest direct effect of 0.55 followed by harvest index of 0.35. However, days to maturity had negative direct effect on grain yield. Therefore, an early maturing variety with many branches and high harvest index should be selected for intercropping. In sole cropping system; 1st pod height and number of leaves were negatively correlated to grain yield while the other characters were positively correlated to grain yield. Path analysis in sole crops indicated that seeds per pod had the highest direct effect of 0.60 followed by 100 seed weight. Therefore, seeds per pod and 100seed weight should be considered when selecting varieties for sole cropping system. The highest yielding varieties for intercropping were EAI3600 and DPSB19 and therefore are recommended for intercropping by farmers.