Evaluating the Yield of Three Legume Crop Varieties under Hawaii’s Micro-Climates

Abstract

Hawaii is known for its diverse micro-climates, making the evaluation of varieties at different locations an important strategy to determine the best varieties for each climate zone. Demand for dry beans in Hawaii has been rising due to the increase in production of value-added goods made from legumes. Initial field trials in 2017 were conducted to determine the best sowing date for dry beans in Hawaii since there were no previous such determinations. Field trials were conducted between 2018 and 2021 to evaluate 24 varieties of chickpea (Cicer arietinum), 21 varieties of common bean (Phaseolus vulgaris), and 10 varieties of cowpea (Vigna unguiculata) for their suitability and yield variability under Hawaii’s micro-climates. Preliminary sowing date trials were conducted in 2017, and a variety of trials were conducted between 2018 and 2021; seven field trials were conducted, including two in each of Oahu, Maui, and Hawaii County, and one in Kauai County. The trials were conducted in a randomized complete block design (RCBD) with three replicates. For all the study sites, 20-20-20 NPK fertilizer was applied at 30, 13, and 25 kg/ha N-P-K, respectively. A drip irrigation system was used in all locations as supplemental irrigation. Irrigation was used when needed and turned off 2weeks prior to harvest. The results showed highly significant (p < 0.01) differences in yield between the varieties of each legume crop. Highly significant (p < 0.01) differences in yield were also found between the study locations. There was a significant (p < 0.05) decline in yield by 28% and 45% in chickpea and by 32% and 43% in common bean when planted 1 and 2 months, respectively, after the optimal mid-February planting on Oahu and Maui County. A decline of 21% and 50% in chickpea and 30 and 48% in common bean was recorded when planted 1 and 2 months, respectively, after the optimal mid-March planting in Hawaii County. The study results lead to developing site-specific recommendations for varieties and planting dates from each of the legume crops for each county. However, more studies are needed to develop site-specific recommendations for the micro-climates within each county.