Nutrient Use Efficiency Contribution to Corn Productivity: A Global and Historical Overview.

Global food security faces dual challenges of improving crop yields and delivering biofortified grains. Water and nutrients are frequently the primary yield-limiting factors separating actual farm from potential yields (i.e. yield gap). The contribution of nutrient use efficiency to corn production was analyzed for a compendium of public-sector research (>160 studies with >2000 observation/treatment-means for each plant trait). Historical and geographic analyses of research reporting corn yield and nutrient uptake (N, P, and K) at maturity were performed. Geographically, the main comparison was between USA and the rest of the World (named as “World”), while historical periods (named as “Eras” for studies conducted from late 1800’s to 2012) were also compared in each region. Five points are noteworthy from this review: i) at community-scale, corn grain yield and plant nutrient uptakes were superior for USA vs. the World in each Era, and reflected greater physiological efficiency (PE, yield to plant nutrient content) for N, P and K; ii) at plant-scale (adjusted by plant density for each specific treatment-mean), differences for the yield-nutrient uptake relationships were negligible between geographic clusters; iii) historical PEs improvements were primarily achieved by reductions in grain nutrient concentration at comparable plant-yield (“nutrient dilution process”); iv) overall nutrient ratios for NP (5-6:1) and NK (1:1) were comparable across Eras and geographies; v) nutrient use efficiency for N, P and K (grain yield to fertilizer applied) was greater for USA vs. the World as an outcome of better nutrient synchrony reflected in superior fertilizer recovery and plant physiological use; and vi) apparent nutrient budgets were close to neutral for N and P for USA, but greater nutrient asynchrony was apparent for the World. There is still considerable scope, particularly outside USA, for better nutrient management practices to help close corn yield gaps and improve PE for these macronutrients.