Exploring practical nutrition options for maximizing seed yield and protein concentration in soybean

Abstract

Soybean seed yield and protein concentration are functions of the genetic, environmental, and management interactions. Both traits are frequently reported as negatively correlated since increases in seed yield are normally not accompanied by increases in seed protein concentration. The main goal of this study was to explore the impact of practical management decisions like (i) nutrition at sowing, and (ii) foliar fertilization at the beginning of seed-filling on seed yield and protein concentration of GMO and non-GMO soybean, across two regions with contrasting historical seed yield and protein concentrations: (i) high yielding and low protein region – Central region, and (ii) low yielding and high protein region – North-West region of Argentina. Within regions, fields were further classified as high and low productivity according to farmers' expertise. For Central region, improved nutrition at sowing yielded 5.4% (p < 0.05) and showed 0.9% more seed protein concentration than conventional treatment (p < 0.001). Non-GMO genotypes presented 9.6% less seed yield but 0,7% more seed protein concentration than GMO ones (p < 0.01). Seed yield differences between foliar treatments were variable between field productivities (p < 0.05) with no effects on seed protein concentration. High productivity fields showed ∼16% more seed yield and 0.7% higher seed protein concentration than low productivity fields (p < 0.001). For North-West region, seed yield was not affected by sowing treatments. Seed protein concentration of improved treatment was 0.3% higher than conventional treatment at sowing (p < 0.05). Likewise, non-GMO genotypes showed 0.7% more seed protein concentration than GMO ones (p < 0.001). Regardless of the region, changes in seed protein concentration due to the changes in tested factors were not correlated with changes in seed yield (p > 0.05). Our findings highlighted that (i) fertilization and inoculation constitute practical options for farmers to modify soybean productivity and seed quality, (ii) the effectiveness of changes in some input practices like foliar fertilization depended on the region where soybean was cultivated and (iii) not all changes in tested factors that allowed increased yields, impacted negatively on soybean seed protein concentration.