Search

The anaerobic potentially mineralizable N (PMN) test combined with the preplant (PPNT) and presidedress (PSNT) nitrate tests may improve corn (Zea mays L.) N fertilization predictions. Forty‐nine corn N response experiments (mostly corn following soybean [Glycine max (L.) Merr.]) were conducted in the U.S. Midwest from 2014–2016 to evaluate the ability of the PPNT and PSNT to predict corn relative yield (RY) and N fertilizer over‐ and under‐application rates when adjusted by PMN. Before planting and N fertilization, PPNT (0–30, 30–60, and 60–90 cm) and PMN (0–30 cm) samples were obtained. In‐season soil samples were obtained at the V5 development stage for PSNT (0–30, 30–60 cm) in all N rate treatments and PMN (0–30 cm) in only the 0 and 180 kg N ha−1 preplant N treatments. Increasing NO3–N sampling depths beyond 30 cm with or without PMN improved RY predictability marginally (R2 increase up to 0.20) and reduced over‐ and under‐application frequencies up to 14%. Including PMN (preplant only) with PPNT or PSNT improved RY predictability minimally (R2 increase up to 0.10) only for coarse‐ and medium‐textured soils, but N fertilizer over‐ and under‐application frequencies were not substantially reduced (≤12%). These marginal improvements in RY predictability and N fertilizer over‐ and under‐application frequencies, regardless of the variables used (e.g., fertilization, sampling depth, soil texture, and growing degree‐day categories), demonstrate that including PMN with soil NO3–N alone does not improve corn N fertilization need predictions enough to recommend their use. [ABSTRACT FROM AUTHOR]

Understanding the variables that affect the anaerobic potentially mineralizable N (PMNan) test should lead to a standard procedure of sample collection and incubation length, improving PMNan as a tool in corn (Zea mays L.) N management. We evaluated the effect of soil sample timing (preplant and V5 corn development stage [V5]), N fertilization (0 and 180 kg ha−1) and incubation length (7, 14, and 28 d) on PMNan (0–30 cm) across a range of soil properties and weather conditions. Soil sample timing, N fertilization, and incubation length affected PMNan differently based on soil and weather conditions. Preplant vs. V5 PMNan tended to be greater at sites that received < 183 mm of precipitation or < 359 growing degree-days (GDD) between preplant and V5, or had soil C/N ratios > 9.7:1; otherwise, V5 PMNan tended to be greater than preplant PMNan. The PMNan tended to be greater in unfertilized vs. fertilized soil in sites with clay content > 9.5%, total C < 24.2 g kg−1, soil organic matter (SOM) < 3.9 g kg−1, or C to N ratios < 11.0:1; otherwise, PMNan tended to be greater in fertilized vs. unfertilized soil. Longer incubation lengths increased PMNan at all sites regardless of sampling methods. Since PMNan is sensitive to many factors (sample timing, N fertilization, incubation length, soil properties, and weather conditions), it is important to follow a consistent protocol to compare PMNan among sites and potentially use PMNan to improve corn N management. [ABSTRACT FROM AUTHOR]

Estimates of mineralizable N with the anaerobic potentially mineralizable N (PMNan) test could improve predictions of corn (Zea mays L.) economic optimal N rate (EONR). A study across eight US midwestern states was conducted to quantify the predictability of EONR for single and split N applications by PMNan. Treatment factors included different soil sample timings (pre-plant and V5 development stage), planting N rates (0 and 180 kg N ha-1), and incubation lengths (7, 14, and 28 d) with and without initial soil NH4--N included with PMNan. Soil was sampled (0-30 cm depth) before planting and N application and at V5 where 0 or 180 kg N ha-1 were applied at planting. Evaluating across all soils, PMNan was a weak predictor of EONR (R² ≤ 0.08; RMSE, ≥67 kg N ha-1), but the predictability improved (15%) when soils were grouped by texture. Using PMNan and initial soil NH4--N as separate explanatory variables improved EONR predictability (11-20%) in fine-textured soils only. Delaying PMNan sampling from pre-plant to V5 regardless of N fertilization improved EONR predictability by 25% in only coarse-textured soils. Increasing PMNan incubations beyond 7 d modestly improved EONR predictability (R² increased ≤0.18, and RMSE was reduced ≤7 kg N ha-1). Alone, PMNan predicts EONR poorly, and the improvements from partitioning soils by texture and including initial soil NH4--N were relatively low (R² ≤ 0.33; RMSE ≥ 68 kg N ha-1) compared with other tools for N fertilizer recommendations. [ABSTRACT FROM AUTHOR]

Nitrogen provided to crops through mineralization is an important factor in N management guidelines. Understanding of the interactive effects of soil and weather conditions on N mineralization needs to be improved. Relationships between anaerobic potentially mineralizable N (PMNan) and soil and weather conditions were evaluated under the contrasting climates of eight US Midwestern states. Soil was sampled (0.30 cm) for PMNan analysis before pre-plant N application (PP0N) and at the V5 development stage from the pre-plant 0 (V50N) and 180 kg N ha-1 (V5180N) rates and incubated for 7, 14, and 28 d. Even distribution of precipitation and warmer temperatures before soil sampling and greater soil organic matter (SOM) increased PMNan. Soil properties, including total C, SOM, and total N, had the strongest relationships with PMNan (R2 < 0.40), followed by temperature (R2 < 0.20) and precipitation (R2 < 0.18) variables. The strength of the relationships between soil properties and PMNan from PP0N, V50N, and V5180N varied by .10%. Including soil and weather in the model greatly increased PMNan predictability (R2 < 0.69), demonstrating the interactive effect of soil and weather on N mineralization at different times during the growing season regardless of N fertilization. Delayed soil sampling (V50N) and sampling after fertilization (V5180N) reduced PMNan predictability. However, longer PMNan incubations improved PMNan predictability from both V5 soil samplings closer to the PMNan predictability from PP0N, indicating the potential of PMNan from longer incubations to provide improved estimates of N mineralization when N fertilizer is applied.

Sulfur is applied to irrigated corn (Zea mays L.) grown on sandy soils. The objective of this study was to evaluate the sprinkler-irrigated corn response to S. Treatments were a factorial combination of 0, 14, 28, and 42 kg S ha-1 as (NH4)2SO4 applied on the soil surface at four locations at planting and in season (V5). Tissue samples were collected at V8 and R2 and evaluated along with corn grain yield and soil pore water SO4 2--S concentration measured at 60 cm with suction tube lysimeters. Application of S increased V8 plant mass, V8 whole plant S concentration and S uptake, and R2 leaf S concentration but did not increase corn grain yield. Decreased V8 plant mass was a result of S deficiency and was only corrected when some S was applied at planting. A total of 28 kg S ha-1 was sufficient to ensure adequate plant growth and S uptake whether S was applied at planting, in-season, or as a combination of the two timings. Concentrations of S were elevated in soil pore water from at planting and in-season S application indicating a portion of the S applied were still available for most'and at the end of'the growing season. Sulfur fertilizer is crucial early in the growing season for irrigated corn to ensure optimal corn growth. Rate of application is more important than time of S application in irrigated corn production. Incidental applications of S may reduce the need of S fertilizer for irrigated corn.

Acrylamide is a potentially harmful compound when consumed in the human diet and is formed during potato (Solanum tuberosum L.) processing from the precursors reducing sugars and asparagine. The objective of this study was to determine the effects of N rate (135-404 kg ha-1) on tuber yield and quality and tuber reducing sugars and asparagine concentrations in newly released cultivars Easton and Dakota Russet, relative to the standard cultivar Russet Burbank. Tuber samples were collected at intervals from initial set through harvest during two growing seasons. Tuber yield of all cultivars increased quadratically with increasing N rate. Highest yield was produced by Easton, followed by Russet Burbank and Dakota Russet. Russet Burbank had more tubers per plant than the new cultivars. Specific gravity decreased with increasing N rate and was lowest in Russet Burbank both years. The new cultivars had a lower hollow heart incidence than Russet Burbank when environmental conditions were favorable for hollow heart development. Tuber-reducing sugars changed during the growing season but were related more to cultivar and growing conditions than N rate. New cultivars had lower reducing sugars than Russet Burbank. In contrast to reducing sugars, asparagine increased with increasing N rate and was less affected by environmental conditions during the growing season. Easton had slightly lower asparagine concentrations than Russet Burbank and Dakota Russet. This study indicates that cultivar and growing conditions have a dominant effect on tuber-reducing sugars, while N rate has a more consistent effect on tuber asparagine. [ABSTRACT FROM AUTHOR]

Polymer-coated ureas (PCUs) can reduce N leaching in potato (Solanum tuberosum L.) production while maintaining yields. However, damage to the polymer coating during handling increases N release and potentially affects leaching and crop response. A 2-yr study was conducted to develop a quick test of PCU damage, compare its results with N release under field conditions, and determine damage effects on N uptake and yield in field experiments. A 24-h water immersion procedure was developed to measure N release differences from two sources of the PCU fertilizer Environmentally Smart Nitrogen (ESN) handled in different ways: ESN(C), dealer grade undamaged control, and ESN(A), damaged by air boom spreader application. Nitrogen release from ESN(A) was more rapid in both the 24-h test and during in situ soil incubation. Quick test results were positively correlated with N release during the first 7 d of field incubation (R² = 0.91, adjusted R² = 0.86). Differences in prill damage between ESN(C) and ESN(A) were greater in 2010 than 2011. Limited crop response differences occurred in 2011, but in 2010 petiole nitrate-N was more stable and higher late in the season for ESN(C) than ESN(A), and tuber, vine, and total N uptake were significantly greater for ESN(C). Tuber yield and size were not significantly affected by ESN damage. Based on these results, the quick test provides an accurate assessment of potential differences in N release during the growing season due to coating damage and can be used to evaluate leaching potential and possible need for fertigation. [ABSTRACT FROM AUTHOR]

Maize ( Zea mays L.) stover and cobs are potential feedstock sources for cellulosic ethanol production. Nitrogen (N) fertilization is an important management decision that influences cellulosic biomass and grain production, but its effect on cell wall composition and subsequent cellulosic ethanol production is not known. The objectives of this study were to quantify the responses of maize stover (leaves, stalks, husks, and tassel) and cob cell wall composition and theoretical ethanol yield potential to N fertilization across a range of sites. Field experiments were conducted at rainfed and irrigated sites in Minnesota, USA, over a 2-year period. Stover cell wall polysaccharides, pentose sugar concentration, and theoretical ethanol yield decreased as N fertilization increased. Stover Klason lignin increased with N fertilization at all sites. Cob cell wall composition was less sensitive to N fertilization, as only pentose and Klason lignin decreased with N fertilization at two and one site(s), respectively, and hexose increased with N fertilization at one of eight sites. Cob theoretical ethanol yield was not affected by N fertilization at any site. These results indicate variation in stover cellulosic ethanol production is possible as a result of N management. This study also demonstrated that cell wall composition and subsequent theoretical ethanol yield of maize cobs are generally more stable than those with stover because of overall less sensitivity to N management. [ABSTRACT FROM AUTHOR]

The nitrogen sufficiency index (NSI) can be used for in-season variable rate management of nitrogen (N) fertilizer to maintain productivity of potato ( Solanum tuberosum, L.) while reducing leaching losses. The objective of this study was to evaluate the implications of using high spatial resolution broad-band imagery for determining N prescriptions at different growth stages. Aerial images were obtained for research plots, as well as for a commercial potato field (59 ha) near Becker, Minnesota on 30, 56 and 79 days after emergence (DAE) with a Redlake MS4100 multispectral camera. In research plots, experimental treatments included five N treatments with varying rates and timing of N fertilizer, and two potato varieties, Russet Burbank and Alpine Russet. Spectral indices investigated in this study adequately predicted N stress based on leaf N concentration ( r values within dates ranged from 0.49 to 0.82). On 56 and 79 DAE, the Green Ratio Vegetation Index (GRVI) normalized by an NSI that used the recommended rate and timing from the research plots as a reference showed that most areas of the commercial field did not require supplemental N fertilizer (using an NSI over-sufficiency threshold of 120 %). Based on regional guidelines, N was over-applied to the commercial field, but in situations where N is applied more sparingly, a GRVI NSI threshold of 80 % should be used to identify areas that are most suitable for supplemental N fertilizer. A practical approach and the implications associated with using spectral data for in-season N management are proposed. [ABSTRACT FROM AUTHOR]

Irrigation and N fertilizer management are important factors affecting crop yield, N fertilizer recovery efficiency, and N losses as nitrous oxide (N2O) and nitrate (NO3-). Split application of conventional urea (split-U) and/or one-time application of products designed to perform as enhanced-efficiency N fertilizers may mitigate N losses. The objective of this study was to compare the effects of controlled-release polymer-coated urea (PCU), stabilized urea with urease and nitrification inhibitors (IU) and split-U on direct soil- to-atmosphere emissions, NO3- leaching, and yield for fully irrigated and minimum-irrigated corn in loamy sand. Indirect emissions due to NO3 - leaching were estimated using published emission factors (EF5). Split-U increased yield and N uptake compared with preplant-applied PCU or IU and decreased NO3- leaching compared with PCU. Direct emissions were significantly less with IU or split-U than with PCU, and there was a trend for greater emissions with split-U than with IU (P = 0.08). Irrigation significantly increased NO3- leaching during the growing season but had no significant effect on direct emissions. After accounting for significantly increased yields with irrigation, however, N losses expressed on a yield basis did not differ and in some cases decreased with irrigation. Post-harvest soil N and soil-water NO3- in spring showed the potential for greater N leaching in minimum-irrigated than fully irrigated plots. Indirect emissions due to NO3- leaching were estimated to be 79 to 117% of direct emissions using the default value of EFy thus signifying the potential importance of indirect emissions in evaluating management effects on emissions. [ABSTRACT FROM AUTHOR]

Abstract: A survey was conducted in the spring of 2010 to characterize the use of nitrogen (N) fertilizer on corn (Zea mays L.) by Minnesota farmers in the 2009 growing season. Detailed information on synthetic N fertilizer management practices was collected from interviews with 1496 farmers distributed across all of the corn growing regions in the state. The total amount of corn they grew represented 6.8% of the ha of corn harvested in Minnesota in 2009. This report summarizes data on: (1) N fertilizer rates, (2) major N sources (excluding manures), (3) application timing of the major N source, (4) use of nitrification inhibitors, additives, and specialty N fertilizer formulations, (5) fertilizer placement and incorporation practices, (6) use of starter fertilizer, split and sidedress applications, and other N sources such as ammonium phosphates, (7) N fertilization of irrigated corn, and (8) use of soil testing as a fertility management tool. Many of the survey results are reported as statewide averages, but where regional differences occurred the data are broken down and presented separately for different parts of the state. This survey provides the most comprehensive set of data on N fertilizer use on corn that has been collected in Minnesota. The information can be used to target research and education programs to improve N management for both production and environmental goals. The statewide average N fertilizer rate was 157kgNha−1. Variable rate application was used to apply N by 23% of farmers. About 59% of surveyed farmers applied the majority of their N fertilizer in the spring before planting, 32.5% made their main N application in the fall, and 9% sidedressed the majority of their N after corn emergence. Most farmers used anhydrous ammonia (46%) or urea (45%) as their major source of N fertilizer, while 6.5% used a liquid N formulation as their primary N source. Soil testing was used as a fertility management tool on 84% of the surveyed fields in the last 5years. Overall results indicate that N fertilizer use by Minnesota corn farmers is generally consistent with University of Minnesota Extension N management guidelines. Fertilizer N use could probably be improved by taking adequate N credit for previous soybean crops. In the South Central region of the state, fertilizer N recovery could potentially be improved by increased use of nitrification inhibitors with fall-applied anhydrous ammonia or by delaying anhydrous ammonia application until spring. [Copyright &y& Elsevier]

The article presents a study on the impact of polymer-coated urea (PCU) on the maintenance of groundwater nitrate concentrations in the potato production regions of the U.S. The agricultural products retailer Agrium Inc. had developed a type of PCU called Environmentally Smart Nitrogen, wherein its potential to reduce nitrate leaching has not been scrutinized in a potato. A comparison of four PCUs were studied during the leaching years of 2006 and 2007, and measurements of nitrate leaching, fertilizer nitrogen (N) recovery, N use efficiency (NUE) and residual N soil were determined.

The article discusses field studies intended to determine the effects of sugar beet by-product application on nitrogen release and crop yields over the course of two growing seasons. This research was conducted due to the fact that the land application of food processing wastes has become an acceptable practice because of nutrient value and fiscal savings. The control treatment was fertilized with nitrogen fertilizer. Wheat was grown in one year, and sugar beets were grown in the subsequent year.