The effects of biochar properties on crop growth are little understood. Therefore, biochar was produced from eight feedstocks and pyrolyzed at four temperatures (300°C, 400°C, 500°C, 600°C) using slow pyrolysis. Corn was grown for 46 days in a greenhouse pot trial on a temperate and moderately fertile Alfisol amended with the biochar at application rates of 0.0%, 0.2%, 0.5%, 2.0%, and 7.0% (w/w) (equivalent to 0.0, 2.6, 6.5, 26, and 91 t biochar ha −1 ) and full recommended fertilization. Animal manure biochars increased biomass by up to 43% and corn stover biochar by up to 30%, while food waste biochar decreased biomass by up to 92% in relation to similarly fertilized controls (all P<0.05). Increasing the pyrolysis temperature from 300°C to 600°C decreased the negative effect of food waste as well as paper sludge biochars. On average, plant growth was the highest with additions of biochar produced at a pyrolysis temperature of 500°C (P < 0.05), but feedstock type caused eight times more variation in growth than pyrolysis temperature. Biochar application rates above 2.0% (w/w) (equivalent to 26 t ha −1 ) did generally not improve corn growth and rather decreased growth when biochars produced from dairy manure, paper sludge, or food waste were applied. Crop N uptake was 15% greater than the fully fertilized control (P<0.05, average at 300°C) at a biochar application rate of 0.2% but decreased with greater application to 16% below the N uptake of the control at an application rate of 7%. Volatile matter or ash content in biochar did not correlate with crop growth or N uptake (P>0.05), and greater pH had only a weak positive relationship with growth at intermediate application rates. Greater nutrient contents (N, P, K, Mg) improved growth at low application rates of 0.2% and 0.5%, but Na reduced growth at high application rates of 2.0% and 7.0% in the studied fertile Alfisol.

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.

Corn (Zea mays L.) nitrogen (N) rate trials conducted in North Carolina over a recent 10‐year time frame (2001–2011) were reviewed to potentially adjust yield goals (realistic yield expectations [RYE]) and their associated N rate recommendations in the North Carolina RYE database. The analyzed trial data provided evidence that corn yields increased by 15, 18, and 31% in the Coastal Plain, Piedmont, and Mountain regions, respectively. To reflect these increases, realistic yield expectations in the database were adjusted upward by 20%. However, linear‐plateau regressions confirmed that the current N rate recommendations in the RYE database were appropriate for obtaining optimum agronomic yields and therefore were not adjusted. While our approach does not permit direct statistical comparison of different tillage methods or crop rotations, long‐term no‐till (>10 years) was the only tillage category with higher measured optimum yields and significantly lower calculated N factors (amount of N applied per unit of yield [lb N bu−1] at the optimum N rate) than the standard RYE database values. However, measured yields and optimum N rates between conventional and no‐till (>10 years) were similar. For corn following soybean [Glycine max (L.) Merr.] rotations (but not corn following corn), mean optimum yield was higher and the value of the N factor was lower than the standard values.

Core Ideas Environmentally Smart Nitrogen (ESN) and ESN mixtures with ammonium sulfate did not increase grain yield over urea–ammonium nitrate. Effects of ESN timing varied due to year and physiographic region. Environmentally Smart Nitrogen does not appear to provide agronomic benefit to wheat in North Carolina. Winter wheat (Triticum aestivum L.) field trials were conducted from 2013 to 2015 to evaluate effectiveness of Environmentally Smart Nitrogen (ESN) in two different physiographic regions in North Carolina: Coastal Plain and Piedmont. Trials were designed to (i) determine the effectiveness of ESN alone or in blend with ammonium sulfate compared with standard fertilizer applications; and (ii) identify optimum timing of application. At plant, all plots received starter fertilizer as urea–ammonium nitrate (UAN) at the rate of 30 lb N acre−1. An additional 105 lb N acre−1 was applied as one of six treatments in the winter (late January through early February) and/or spring (early March). Winter treatments consisted of 100% ESN, or blends with ESN providing either 75 or 50% of total N (ammonium sulfate provided the remainder). A fourth treatment consisted of spring ESN application providing 50% of the total N (the remainder from ammonium sulfate). Two final treatments provided N from UAN and ammonium sulfate, either as split application (late winter and early spring) or spring application. Compared with fertilizer applications without ESN, ESN treatments did not differ for grain or straw yield, or grain, straw, or crop N uptake in the Piedmont. In the Coastal Plain, 2013–2014 ESN treatments returned higher yields when applied in spring than in winter applications; spring‐applied treatment without ESN had higher yields than ESN treatments. In 2014 to 2015, there were no yield differences between the ESN treatments and the non‐ESN treatments. Environmentally Smart Nitrogen does not appear to provide an agronomic benefit to wheat production in North Carolina.

Winter wheat field trials were conducted from 2013 to 2015 to evaluate effectiveness of Environmentally Smart Nitrogen (ESN) in the North Carolina Coastal Plain and Piedmont regions. Trials were designed to (i) determine the effectiveness of ESN alone or in blend with ammonium sulfate compared with standard fertilizer applications and (ii) identify optimum timing of application. Earn 1 CEU in Nutrient Management by reading this article and taking the quiz at http://www.certifiedcropadviser.org/education/classroom/classes/514.