The influence of spatial arrangement and planting dates on the growth and yield of soybean and sorghum in intercropping systems

Abstract

This study investigated the effects of spatial arrangement and planting date on the growth and yield of soybean (Glycine max L.) and sorghum (Sorghum bicolor L.) in an intercropping system. The experiment was conducted over two cropping seasons (2020 and 2021) at the Teaching and Research Farm of Joseph Sarwuan Tarka University, Makurdi, Nigeria, using a split-plot design fitted into a randomized complete block design with three replications (33 plots in all). Three spatial arrangements (S1: both crops on the ridge crest; S2: soybean on the ridge crest and sorghum by the side of the ridge; S3: alternate rows of soybean and sorghum) and three planting dates for sorghum (D1: simultaneous planting; D2: sorghum sown two weeks after soybean; D3: sorghum sown four weeks after soybean) were evaluated, alongside sole crops of each species. Planting date significantly affected plant height, leaf number, branching, pod number and yield of both crops, while spatial arrangement significantly affected most of these traits. Soybean seed yield was highest when sorghum was sown four weeks after soybean (D3), with the S2D3 combination (soybean on the ridge crest, sorghum by the ridge side four weeks later) and S1D3 giving the highest yields among the intercrop treatments. Sorghum grain yield per hectare was highest under S2 and when sorghum was sown two weeks after soybean (D2), while the longest panicles were produced under alternate rows (S3) with simultaneous planting (D1). The study concludes that spatial arrangement and planting date are critical determinants of productivity in soybean-sorghum intercropping, and recommends the S2 arrangement with sorghum introduced four weeks after soybean where soybean is the priority crop, or two weeks after soybean where sorghum is the priority crop.