Nutrient Accumulation Patterns in Soybean Cultivars Released Over 90 Years.

Advancements in soybean production has occurred through plant breeding and agronomic techniques over the past century. Soybean genetics and soil fertility are inherently related in production and research, but little research has documented changes in plant nutrition over this history. Our objective was to determine seasonal uptake of nutrients by soybean cultivars released over the last nine decades. We selected 26 cultivars from maturity group (MG) II and 26 cultivars from MG III that were released over the past 90 years and were representative of these decades. These cultivars were grown in nutrient-rich soil of west-central Indiana in 2011. Each MG set was arranged in a randomized complete block design replicated three times. Cultivars were sampled at V4 (four expanding trifoliates), R2 (full bloom), R4 (full pod), R6 (full seed), and R8 (physiological maturity) and were partitioned by leaves, stems, pods, and grain. Plant partitions were weighed and analyzed for macro- and micro-nutrients. Total biomass at V4 and R2 was similar for MG III cultivars regardless of release year, but modern cultivars began to produce more biomass at R4 and continued to produce more biomass until, physiological maturity. Modern, MG III cultivars partitioned more biomass into leaves and stems during R4 and R6. Whereas modern, MG II cultivars produced more total biomass than older cultivars during late reproductive development, especially during the grain fill period. Leaf concentrations of P and K in MG III were consistent across release years within each sampling time. Leaf N concentration increased over release years at V4 and R6 (dramatically after 1950). However, N concentrations were similar in the leaves during R2 and R4, and in the grain at harvest. These modern cultivars seemed to acquire and allocate nutrient resources better than older cultivars, which resulted in higher harvest index and grain yield.