Soybean Seed Composition as Affected by Seeding Rates and Row Spacing

Research on the effects of seeding rates (SDR) and row spacing (RS) on soybean [Glycine max (L.) Merr.] seed composition is almost nonexistent. The objective of this research was to investigate the effect of SDR and RS on soybean seed protein, oil, fatty acids, sugars, and minerals using four soybean cultivars (P 93M90 and AG 3906, maturity group[MG] III; P 94B73, MG IV; and V 52N3, MG V) tested in 2006 and 2007. Seeding rates for P 93M90 and AG 3906 ranged from 247,000 to 592,800 seeds ha(-1) and for P 94B73 and V 52N3 ranged from 60,000 to 180,000 seeds ha(-1). Row spacings were 38 and 76 cm. Protein, oleic acid, sugars, P, and B concentrations increased with the increase of SDR in P 93M90 and AG 3906. However, after the maximum concentrations of these constituents were reached, a decrease was observed at the highest SDR. This trend was mainly observed in 2006 and depended on RS. In 2007, the opposite trend of protein and oleic acid concentrations was observed, where the protein and oleic decreased with SDR. In cultivars P 94B73 and V 52N3, results showed that protein concentration increased with SDR in 2006 and 2007 for both 38 and 76 cm RS. Oleic acid increased and linolenic acid decreased with SDR in 2006. The different trends of protein and oleic concentrations between years may be due to temperature and drought stress differences. This research showed that SDR and RS can alter seed constituents, and the magnitude of this effect depended on cultivar and environmental factors, especially temperature and drought.