abstract
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Most research explored gains in wheat yield over time within the scope of yield components [e.g., kernels per area, kernel weight, and harvest index], usually ignoring the dynamics of nutrient accumulation and partitioning. With the objective of understanding historical changes in wheat N,P, K, and S uptake and partitioning as affected by breeding (G), management(M), and their interaction, we established a complete factorial experiment with eight winter wheat cultivars and two fertilizer practices. Cultivars’ date of release ranged from 1920 to 2016, and fertilizer practices were i) no infurrow fertilizer or ii) 112 kg ha-1 of in-furrow 12-40-0-10-1. The trial was established in a split-plot design with variety as whole plot and fertility as sub-plot in two Kansas locations during the 2017 and 2018 harvest seasons, for four site-years. We collected aboveground biomass five times during the growing season (tillering, jointing, anthesis, soft dough of grain development, and harvest maturity) and each sample was partitioned into plant components(leaves, stem, chaff, and grain) and analyzed for N, P, K, and S concentration. Nutrient accumulation was the product between biomass and nutrient concentration. Grain yield was measured by combine-harvesting at maturity. For most measurements, G and M were significant but G × M was not. Grain yield increased in ~300 kg ha-1 due to in-furrow fertilizer, and at 29 kg ha-1 yr-1. However, this increase was not linear: a sigmoidal model suggested that most of the yield gain occurred between 1960 and 1990. Varieties did not differ in whole-plant biomass at most of the growth stages, but biomass allocation during the post-anthesis period was greater in the grains for modern semi-dwarf varieties and greater in the stems for historical tall varieties. The relationship between biomass and macronutrient concentration was negative exponential for all nutrients. Whole-plant N, P, and S concentration increased over time while K concentration decreased over time. In-furrow fertilizer increased concentration of all nutrients. Accumulation of N, P, K, and S in the leaves and grain followed a similar trend as that measured for grain yield, with a sigmoidal increase in recent years (greater increases in grains as opposed to leaves). Macronutrient accumulation in the stem and chaff decreased over time and was more apparent in the stem. Our data suggests that increases in yield over time were driven by greater concentration of N, P, and S, and greater accumulation of macronutrients in the grain.