Profitability of variable rate nitrogen application in wheat production

TLDR: In this article, the authors used plant sensing to determine the amount of nitrogen (N) to apply to increase profits in wheat (Triticum aestivum) production by reducing N cost or by increasing grain yield.

Abstract: Using plant sensing to determine the amount of nitrogen (N) to apply has the potential to increase profits in wheat (Triticum aestivum) production by reducing N cost or by increasing grain yield. The objective of this paper was to determine if yields and profits from experimental trials that used a precision N applicator to apply N were significantly different from trials that applied pre-determined amounts of N. Across Oklahoma, USA, experiments were designed to test 10 N treatments that included two variable rate treatments (VRT), two uniform rate treatments (URT) where the level of N applied was based on optical reflectance measurements (ORM), and six conventional treatments (i.e., pre-determined uniform rates of N). Data included treatments during 2005–2009 from eight different locations. Results indicated no statistical difference in yields between the conventional treatments that apply 90 kg ha−1 of N and the VRT and URT treatments. On average, the conventional treatment that applied 90 kg ha−1 of top-dress N produced the largest yield, with a VRT treatment producing the third largest yield. Profits were calculated for each treatment using a partial budget. On average, the treatment that received 90 kg ha−1 of top-dress N was the most profitable even though the pre-plant N (anhydrous ammonia) had a cost advantage relative to top-dress N (urea and ammonium nitrate).