Effect of Nitrogen, Row Spacing, and Plant Density on Yield, Yield Components, and Plant Physiology in Soybean–Wheat Intercropping

Abstract

The introduction of cultivars with earlier development and greater productivity has raised questions about the effect of management practices on soybean [Glycine max (L.) Merr] yield in a no‐till (NT) system. The objective of the study was to evaluate the interaction between N fertilization, row spacing, and plant density on photosynthetic index, yield components, yield, and nutritional status of soybean–wheat (Triticum aestivum L.) intercropping. For soybean cultivation, three N rates, three row spacing, and three planting densities were assessed during two growing seasons, while for wheat, 17.5‐cm row spacing and no N fertilization were used. No significant effects of row spacing and plant density were detected. The yields for 0 and 40 kg N ha−1 rates were similar, while applying 20 kg N ha−1 reduced, on average, soybean yield by 14.5%. The planting densities, row spacing, and N rates did not affect wheat yield, or oil and protein content in soybean seeds. Soil temperature (ST), intercellular carbon dioxide concentration (Ci), and intrinsic water use efficiency (IWUE) increased, while plant height, chlorophyll content (CC), and transpiration rate (Trmmol) decreased with increasing spacing of soybean. Plant density changed ST, Ci, chlorophyll content, and stomatal conductance (gs). Leaf tissue analysis indicated adequate nutrient levels in soybean and wheat. The current management practice with 50‐cm row spacing, no N fertilization to complement biological nitrogen fixation (BNF), and 333,000 plants ha−1 is adequate for soybean cultivation, while N supplied from soil organic matter (SOM) and BNF is sufficient to meet requirements of associated wheat crops.