Developing functional relationships between temperature and soybean yield and seed quality

Temperatures that vary spatially and temporally over the soybean growing areas affect soybean seed yield and quality. Five day/night temperature, 21/13, 25/17, 29/21, 33/25, and 37/29°C, effects on total biomass, yield, and seed quality parameters were investigated on indeterminate (Asgrow AG5332, AG) and determinate (Progeny P5333RY, PR) soybean cultivars. The cultivar × temperature interaction was significant for total biomass, seed yield, protein, oil, palmitic acid, oleic acid, linolenic acid, raffinose, and stachyose. Quadratic functions best described the response of yield to temperature, where the optimum temperature for maximum yield was 26°C for AG, and 23°C for PR. Temperature affected all seed quality parameters in both cultivars. Seed protein concentration was slightly higher at the two lower and higher temperatures than at 29/21°C. Seed oil concentration increased with temperature up to 26°C for AG and 25°C for PR and declined at higher temperatures. Palmitic acids showed quadratic responses to temperature with a significant interaction between cultivars, while stearic acid showed a similar quadratic response in both cultivars. Oleic acid increased with increasing temperature while linolenic and linoleic acids declined linearly with temperature. Sucrose concentration declined with an increase in temperature in both the cultivars. Raffinose and stachyose concentrations in the two cultivars responded differently to temperature and declined with increasing temperature. The effects of temperature on yield and seed quality that are described in this research can be used to improve crop growth models and the management of soybean under climate change.