Evaluation of Soybean (Glycine max (L.) Merr.) Varieties for Tolerance to Relay Intercropping with Chili (Capsicum annuum L.) in Coastal Sandy Land

The relay intercropping of soybean (Glycine max (L.) Merr.) planted between rows of chili (Capsicum annuum L.) in coastal sandy soils presents a potential strategy for increasing soybean production in Indonesia. This study aimed to evaluate the performance of soybean varieties for tolerance to relay intercropping with chili in coastal sandy lands based on yield, yield index, and plant growth. The research was conducted at Samas Beach, Bantul Regency, Yogyakarta, from January to May 2023, using a randomized complete block design with two factors and three blocks. Five soybean varieties ('Anjasmoro', 'Dena 1', 'Demas 1', 'Grobogan', and 'Malika'), and two cropping systems (monoculture and relay intercropping) were evaluated. Water was irrigated when rainfall was insufficient to maintain adequate soil moisture levels. Data were analyzed using t-test, ANOVA, Principal Component Analysis, Cluster Analysis, and Pearson’s correlation. The results showed that relay intercropping significantly enhanced the seed yield of all soybean varieties compared to the monoculture, with 'Anjasmoro' showing the highest increase of 443.39%. Differences among the varieties under the relay intercropping system showed that 'Anjasmoro', 'Malika', 'Demas 1', and 'Dena 1' consistently outperformed 'Grobogan' in terms of yield and growth. The varieties were grouped into high-yielding ('Anjasmoro', 'Malika', 'Demas 1', and 'Dena 1') and low-yielding ('Grobogan'). High-yielding varieties had high positive correlations with the yield index (r=0.98), harvest index (r=0.61), and 100-SW (r=0.64). These findings suggest that utilizing high-yielding soybean varieties in relay intercropping with chili could significantly enhance soybean yields in coastal sandy lands.