Predicting Economic Optimal Nitrogen Rate with the Anaerobic Potentially Mineralizable Nitrogen Test (original) (raw)
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Theory to predict potentially mineralizable nitrogen in soils
Soil Biology and Biochemistry, 1994
Estimates of mineralizable N with the anaerobic potentially mineralizable N (PMN an) 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 PMN an. 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 NH 4-N included with PMN an. 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, PMN an was a weak predictor of EONR (R 2 ≤ 0.08; RMSE, ≥67 kg N ha −1), but the predictability improved (15%) when soils were grouped by texture. Using PMN an and initial soil NH 4-N as separate explanatory variables improved EONR predictability (11-20%) in fine-textured soils only. Delaying PMN an sampling from pre-plant to V5 regardless of N fertilization improved EONR predictability by 25% in only coarse-textured soils. Increasing PMN an incubations beyond 7 d modestly improved EONR predictability (R 2 increased ≤0.18, and RMSE was reduced ≤7 kg N ha −1). Alone, PMN an predicts EONR poorly, and the improvements from partitioning soils by texture and including initial soil NH 4-N were relatively low (R 2 ≤ 0.33; RMSE ≥ 68 kg N ha −1) compared with other tools for N fertilizer recommendations. Disciplines
Determination of potentially mineralizable nitrogen in agricultural soil
Biology and Fertility of Soils, 1996
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 (PMN an) and soil and weather conditions were evaluated under the contrasting climates of eight uS Midwestern states. Soil was sampled (0-30 cm) for PMN an analysis before pre-plant N application (PP 0N) and at the V5 development stage from the pre-plant 0 (V5 0N) and 180 kg N ha −1 (V5 180N) 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 PMN an. Soil properties, including total C, SOM, and total N, had the strongest relationships with PMN an (R 2 ≤ 0.40), followed by temperature (R 2 ≤ 0.20) and precipitation (R 2 ≤ 0.18) variables. the strength of the relationships between soil properties and PMN an from PP 0N , V5 0N , and V5 180N varied by ≤10%. Including soil and weather in the model greatly increased PMN an predictability (R 2 ≤ 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 (V5 0N) and sampling after fertilization (V5 180N) reduced PMN an predictability. However, longer PMN an incubations improved PMN an predictability from both V5 soil samplings closer to the PMN an predictability from PP 0N , indicating the potential of PMN an from longer incubations to provide improved estimates of N mineralization when N fertilizer is applied.
Soil Science Society of America Journal
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 (PMN an) and soil and weather conditions were evaluated under the contrasting climates of eight uS Midwestern states. Soil was sampled (0-30 cm) for PMN an analysis before pre-plant N application (PP 0N) and at the V5 development stage from the pre-plant 0 (V5 0N) and 180 kg N ha −1 (V5 180N) 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 PMN an. Soil properties, including total C, SOM, and total N, had the strongest relationships with PMN an (R 2 ≤ 0.40), followed by temperature (R 2 ≤ 0.20) and precipitation (R 2 ≤ 0.18) variables. the strength of the relationships between soil properties and PMN an from PP 0N , V5 0N , and V5 180N varied by ≤10%. Including soil and weather in the model greatly increased PMN an predictability (R 2 ≤ 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 (V5 0N) and sampling after fertilization (V5 180N) reduced PMN an predictability. However, longer PMN an incubations improved PMN an predictability from both V5 soil samplings closer to the PMN an predictability from PP 0N , indicating the potential of PMN an from longer incubations to provide improved estimates of N mineralization when N fertilizer is applied.
Nitrogen mineralization: a review and meta-analysis of the predictive value of soil tests
Accurate estimation of mineralizable nitrogen (N) from soil organic matter is essential to improve fertilizer management in agricultural systems. Mineralizable N refers to the amount of N in soil that is released during a certain period (ranging from 1 week to the length of a growing season). It has been estimated from increases in inorganic N during incubation or from N uptake by plants grown in a greenhouse or field. Many chemical soil tests measuring extractable organic N (EON) fractions have been proposed to predict mineralizable N. We evaluated the predictive value of these soil tests, using 2068 observations from 218 papers. Meta-analysis was used to find the best soil test, to analyse differences between field and laboratory experiments, and to determine whether their predictive value is affected by extraction intensity (% of total soil N that is extracted). The concentration of EON was positively related to mineralizable N, explaining on average 47% of the variation. It did not, however, explain more of the variation than total N. Best predictions (57% < R 2 < 74%) were obtained when EON was extracted with hot CaCl 2 , acid KMnO 4 , acid K 2 Cr 2 O 7 , hot water or hot KCl. Extraction intensity was not related to the strength of the above-mentioned relationship. Predictions of mineralizable N were significantly worse when mineralization was measured in the field compared with measurements under controlled conditions. We found no evidence of a causal and direct relationship between EON and mineralizable N. Accuracy of soil testing may improve when the current 'single soil test approach' changes to a more complex approach, which includes different soil tests, soil properties and environmental conditions.
Field Crops Research, 2020
The goal of most fertilizer decision support tools is to help maize farmers estimate the most profitable nitrogen (N) rate for a given fertilizer N/grain price ratio, known as the economically optimum N rate (EONR). While maximizing profitability, to our knowledge the environmental performance of the EONR has not been fully assessed using a process-based model that can jointly predict yield, N uptake, and multiple N loss pathways (leaching, nitrous oxide emissions, volatilization). The objective of this study was to construct a full N budget when the EONR is applied, and to measure how N management influences both grain yield and the environmental performance of the EONR. The DeNitrification and Decomposition model (DNDC) was calibrated and validated using measurements from a long-term N rate trial from Elora, ON, Canada (2009-2016). DNDC was then used to simulate N applications at the EONR when two different N sources (urea and urea ammoniumnitrate), two N placements (broadcast or incorporated) and four N timings (100 % at planting, 100 % at V6, 50 % at planting and 50 % at V13, and 50 % at V6 and 50 % at V13) were used. Depending on N management, mean EONR (2009-2016) was highly variable, ranging from 158 to 185 kg N ha −1 while grain yield was stable across N management choices. The use of urea over urea ammonium-nitrate (UAN), and the decision to broadcast versus incorporate, increased the EONR, yield-scaled N/ losses at the EONR, and N surplus. When applied inseason, N applications modestly reduced leaching N losses at the EONR but did not significantly impact the amount of N applied at the EONR or yield-scaled N losses. In all 16 management combinations, simulated mean (2008-2016) N surplus never exceeded 50 kg N ha −1 , and yield-scaled N losses never exceeded 8 kg N Mg −1 grain. In conclusion, the EONR delivers strong environmental performance relative to established benchmarks for N surplus and yield-scaled N losses, while N management decisions such as N source and N placement will still affect in-season N losses and consequently the amount of N applied at the EONR.
Evaluation of optimal time and parameters for measuring potentially mineralized nitrogen in soil
Zbornik Matice srpske za prirodne nauke, 2008
Our research was done on brown forest soil with long-term experiments and with a system of fertilizing which is in use for 40 years. Experiment variants with an increasing dose of nitrogen fertilizer were chosen for this research. Two experiments have been performed: experiment in pots supplied with ammonium nitrate labeled with a stable isotope 15N (11.8%) and experiment in the field. The aim of the research was to establish which plant and soil parameters group (obtained in the controlled conditions and/or in the field) could be considered as reliable for evaluation of aerobic and anaerobic incubation and of the best time for estimation of potentially mineralized nitrogen in soil. According to the determined correlative dependence, it could be concluded that reliability of aerobic incubation should be estimated in October by plant and soil parameters from field, anaerobic incubation should be estimated in early spring (March) by plant and soil parameters, from controlled condition...
Evaluation of the Illinois Soil Nitrogen Test in the North Central Region of the United States
Agronomy Journal, 2008
Recently the Illinois soil nitrogen test (ISNT) was proposed as a means to identify fi elds where corn (Zea mays L.) will not respond to additional N fertilizer and which may also be used to predict the economic optimum N rate (EONR). Data from 96 corn N rate response trials across Iowa, Illinois, Michigan, Minnesota, Nebraska, and Wisconsin were compiled to evaluate the usefulness of the ISNT in identifying nonresponsive fi elds, predicting EONR, and estimating mineralizable N. At each trial site, multiple rates of fertilizer N were applied, including zero N and nonyield limiting rates. Corn was grown following several crops. Th e ISNT could not accurately predict nonresponsive sites, nor could it reliably estimate EONR. Subsetting the data based on soil drainage class and previous crop did not improve the predictive capability of the ISNT even though ISNT values were significantly diff erent among previous crops and soil drainage classes. Th e ISNT was strongly correlated to soil organic matter (OM) and was apparently measuring a constant fraction of total soil N (TN). Th e lack of correlation between the ISNT and relative N uptake (check plot N uptake/N uptake at the maximum N rate) suggests that the ISNT is not measuring the readily mineralizable fraction of soil N. Based on results of this project, the ISNT is not suggested for use in adjusting N rate recommendations for corn in the North Central Region (Corn Belt) of the United States.