Abstract
Nitrogen (N) losses negatively impact groundwater quality. Spring wheat genotypes varying in N-fertilizer recovery were studied (by using lysimeters) for their potential to minimize NO3-N leaching during spring and summer, over a three-year period. Additionally, we examined to what extent root growth and NO3-N leaching explain the well-known difference found between apparent and isotopic N recovery. The genotypes were grown under low (2 g m−2) and high (27 g m−2) N fertilizer supply. On average, the apparent and isotopic recoveries of N fertilizer by wheat were 43% and 51%, respectively. The three genotypes varied in fertilizer N recovery but not in NO3-N leaching, which only accounted for 15% of the applied N fertilizer. The differences in N uptake, fertilizer N recovery and root growth among the genotypes were not associated with the leached NO3-N because root growth and N uptake were not well synchronized with NO3-N leaching. Already at stem elongation 70% to 98% of the season-long NO3-N leaching had already taken place. Thus, the ability to minimize in-season NO3-N leaching by using spring wheat genotypes with higher fertilizer N recovery was limited because maximum N leaching occurred in the early crop season.
Highlights
Understanding the processes that affect the uptake and utilization of nitrogen (N) by wheat is of major importance because these processes determine grain yield, quality, production costs, and the environmental burden of wheat cropping
The estimates ofConditions the parameters of the logistic growth curve used to approximate the root density (RD) were calculated
The genotypes varied in fertilizer N recovery, but not in NO3 -N leaching
Summary
Understanding the processes that affect the uptake and utilization of nitrogen (N) by wheat is of major importance because these processes determine grain yield, quality, production costs, and the environmental burden of wheat cropping. To obtain high grain yields while achieving the quality requirements of the bread-making industry, fertilizer N is supplied at rates that exceed demand by wheat. This strategy is expected to influence N leaching, and agricultural N losses negatively impact groundwater quality [1,2]. The most often used method to determine the N fertilizer recovery is the apparent method [4], in which the amount of fertilizer taken up by the crop is calculated as the difference between fertilized and unfertilized plots. The estimated recovery of fertilizer N is often higher when the apparent method is used rather than the 15 N dilution method [6,7]. Smil [8] argued that the 15 N dilution method provides a more accurate estimate of Agronomy 2016, 6, 29; doi:10.3390/agronomy6020029 www.mdpi.com/journal/agronomy
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