Evaluation of Nitrogen‐Loss Prevention Amendments in Maize and Wheat in North Carolina

Abstract

Core Ideas Fertilizer additives to decrease N losses did not provide consistent yield advantages. Plots treated with N‐loss products did not increase N use efficiency or N uptake. Agronomic optimum N rates observed in the field aligned with North Carolina recommendations. To reduce environmental losses of N and increase crop use, it is critical to optimize N fertilization rates and determine if N‐loss prevention amendments increase yields. Research objectives were to: (i) determine N‐release patterns of three N‐loss amendments (urea ammonium nitrate [UAN] treated with NBPT+DCD, nitrapyrin, or an organo‐Ca) and UAN through a laboratory incubation; (ii) determine effectiveness of these four products for maize (Zea mays L.) and winter wheat (Triticum aestivum L.) produced in two to three regions of North Carolina; and (iii) determine agronomic optimum N rate for wheat and corn compared to state‐recommended rates. Nitrogen release was measured in three soils (coastal plain, piedmont, and mountains) during the incubation experiment. Field experiments were randomized complete block designs (four replications of six maize N rates and five wheat N rates), with each rate applied as one of four product treatments (UAN and UAN+ one of three N‐loss prevention amendments). In the incubation experiment, soils treated with UAN+nitrapyrin or UAN+NBPT+DCD delayed nitrification longer than soils treated with UAN or UAN+organo‐Ca. There was no significant effect of product on maize grain yield (coastal plain and mountains) and wheat yield (coastal plain and piedmont). A year × product interaction occurred for maize grain yield in the piedmont. Agronomic optimum N rates mostly aligned with current North Carolina N fertilizer recommendations. Despite positive laboratory results, N‐loss amendments did not have a significant effect on yield in 9 of 10 site‐years, indicating that proper N rates are a more effective nutrient management strategy.

Optimum Nitrogen Rates for Maize and Wheat in North Carolina

“…Compared to the agronomic best treatment, the average RYE recommended rate was within 5 kg ha −1 both years, however RYE yields were 1040 kg ha −1 less than measured. These results combined with previous work (Rajkovich et al, 2017) support that yield revisions in wheat are needed.…”

“…Compared to the agronomic best treatment, the average RYE recommended rate was within 5 kg ha -1 both years, however RYE yields were 1040 kg ha -1 less than measured. These results combined with previous work (Rajkovich et al, 2017) support that yield revisions in wheat are needed. The average N rates selected in maize were 48 kg ha -1 higher than recommended by RYE and yielded 1558 kg ha -1 grain more (Table 4).…”

“…Data development was a collaboration between North Carolina State University, the Natural Resource Conservation Service, the North Carolina Department of Agriculture and Consumer Services, the North Carolina Division of Soil and Water Conservation, and many local partners and farmers. The data tables were updated in 2015 for higher-yield maize varieties (Rajkovich et al, 2015) and recent data confirmed maize and wheat N recommendations (Rajkovich et al, 2017). Morris et al (2018) have detailed the strengths and weaknesses of N recommendations made from yield goals and have suggested that adaptive N management be used by farmers to potentially augment and refine N rate decision-making.…”

“…Data development was a collaboration between North Carolina State University, the Natural Resource Conservation Service, the North Carolina Department of Agriculture and Consumer Services, the North Carolina Division of Soil and Water Conservation, and many local partners and farmers. The data tables were updated in 2015 for higher‐yield maize varieties (Rajkovich et al, 2015) and recent data confirmed maize and wheat N recommendations (Rajkovich et al, 2017).…”

Soft Red and White Winter Wheat Response to Input‐Intensive Management

“…However, NBPT can also be detrimental to wheat growth due to increased incidence of urea leaching and NH 4 -N toxicity (Joo et al, 1991;Britto and Kronzucker, 2002;Dawar et al, 2011). Positive NBPT yield responses are often inconsistent and not widely reported due to cool soil temperatures, increased precipitation frequency during peak wheat growth, or lack of NH 3 -N volatilization conditions during winter wheat spring N application timings (Mckenzie et al, 2010;Grant, 2014;Mohammed et al, 2016;Rajkovich et al, 2017).…”