Assessment of the performance of Maize (Zea mays L) intercropped with Jack bean (Carnavalia ensiformis) under subtropical conditions.

Abstract

Food demand in Sub-Saharan Africa continues to rise, while soil fertility declines, climatic conditions remain uncertain, and farming systems rely heavily on chemicals. Sustainable cropping practices such as cereal legume intercropping are needed to address these challenges. This study therefore evaluated productivity of maize (Zea mays L) intercropped with jack bean (Canavalia ensiformis) under subtropical conditions of Mpumalanga Province, South Africa, to determine whether intercropping maize with jack could improve soil fertility and increase yield of maize. A randomized complete block design was used with sole maize, sole jack bean, and intercrop treatments. Growth and yield traits of both crops were measured, and soil samples were taken before planting and after planting. Seed quality were determined for protein, fat, fiber, and carbohydrate contents. One-way ANOVA and correlation analysis were used for comparisons. Intercropping markedly produced different outcomes across every growth and yield metric when compared with sole maize (p < 0.001). Specifically, intercropped maize demonstrated greater performance in various metrics, including protein content, chlorophyll content, plant height, stomatal conductance, leaf index, moisture content, and stem diameter. Intercropped maize had protein contents of 10.88% in season 1 and 8.12% in season 2, compared with 9.61% and 7.87% for sole maize in the same season. Furthermore, the intercropped treatment produced a land equivalent ratio (LER) exceeding 1, highlighting its efficiency in land use compared to monocropping. Intercropped maize averaged higher values across all yield components. Furthermore, cob length was 28.09 cm, kernel count averaged at 546.7 per cob, 100-seed weight was 0.5164 kg, and total seed weight amounted to 4.435 kg per block. Although yields declined in Season 2 due to drier conditions, intercropped maize still maintained an advantage with longer cobs (25.34 cm), more kernels (471.1 per cob), and higher seed weight (0.795 kg per block). Additionally, root nitrogen concentration was greater in intercropped maize than in sole maize during both seasons, intercropped roots averaged at 0.53% N versus 0.46% in sole maize in season 1, and 0.43% versus 0.40% in season 2. Additionally, intercropping maize with jack bean has significantly enhanced soil mineral nutrients, resulting in an average increase of 30kg N/ha in nitrogen, a 25% increase in phosphorus content and improved potassium stability. In addition, jack beans are underutilized, with no commercial varieties available and limited awareness among farmers. Research should focus on breeding adapted varieties, promoting its use in food and feed, and assessing its potential for poverty reduction.