Assessing risk associated with N fertilizer recommendations in the absence of soil tests

Barreto, H. J.; Bell, Matthew

doi:10.1007/bf00750463

Cited by 9 publications

(7 citation statements)

References 4 publications

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“…This differential result could be attributed to a higher N mineralization rate resulting from warmer temperatures and higher soil organic mater contents in environments at relatively low altitudes (2). These results are similar to those (1) reporting that the soil's ability to mineralize the soil organic matter and annual weather conditions have a strong influence in determining annual variability in wheat responses to N fertilizer applications. This variation, according to b 1 parameter from Eq.…”

Section: Nitrogen Ratesupporting

confidence: 91%

“…Grain Yield (bu/acre) = a 1 + b 1 *N, if N fertilizer < critical N rate [1] Grain Yield (bu/acre) = a 2 + b 2 *N, if N fertilizer ≥ critical N rate [2] where N is the rate of N application in lb/acre; and a's (intercepts), b's (linear coefficients, grain yield response to N fertilizer application), and critical rate of N fertilization (occurs at the intersection of the two linear regressions) are constants obtained by fitting the model to the data and are estimated using SAS software with the PROC NLIN option (16).…”

Section: Field Studiesmentioning

confidence: 99%

“…However, this approach may provide varying results as different statistical models can be used to fit the response curve to N application. For example, results from a study (1) using a quadratic regression model for a year‐location study with wheat in the central highlands of Mexico showed that economic optima for responsive sites to N varied between 68 and 192 lb N per acre. However, the current N fertilizer recommendation from the National Institute for Forestry, Agricultural, and Livestock Research (INIFAP) is to apply a flat rate of 71 lb N per acre.…”

Section: Introductionmentioning

confidence: 99%

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Nitrogen Fertilizer Management and Recommendations for Wheat Production in Central Mexico

Limón-Ortega

Villaseñor-Mir

2006

Crop Management

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The current N fertilizer recommendation for wheat (Triticum aestivum L.) production in the central highlands of Mexico is to apply 71 lb N per acre. However, this N rate appears to exceed current crop needs. Therefore, research activities in farmers’ fields to estimate the optimum N rate and timing were initiated in 1999 and continued until 2002. A field trial was conducted at eleven location‐years representing the major wheat production areas of central Mexico. Four N rates were applied (0, 36, 63, and 89 lb N per acre) under three N timing strategies; basal at planting, end of tillering‐early jointing, between 30 and 60 days after planting, and split (one third at planting and the remaining two thirds at the end of tillering‐early jointing). To estimate the critical N fertilization rates for optimum grain yield in each environment, yield data was fitted to a linear plateau model on N fertilization rates. Results indicated that the critical N rate for optimum wheat production is lower than current N fertilizer recommendation. According to the regression model used, predicted critical N fertilization, that explained 47% of the optimum grain yield variability, ranges from 28 to 66 lb N per acre. For grain yield goals below 45 bu/acre (± 3.1 bu/acre), farmers do not have to apply N fertilizer. For grain yield goals above this threshold, farmers have to apply 2.6 lb N per acre for every additional bushel expected. Nitrogen fertilizer application at the end of tillering‐early jointing (Feekes scale 6) showed a tendency to increase grain yield by means of increasing the number of spikes per unit area.

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Section: Nitrogen Ratesupporting

confidence: 91%

Section: Field Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nitrogen Fertilizer Management and Recommendations for Wheat Production in Central Mexico

Limón-Ortega

Villaseñor-Mir

2006

Crop Management

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“…In the above‐mentioned studies, the reliability was defined as the probability that one treatment yields higher than the other by more than a certain amount of grain. The major difference with our use of CPDs, however, is that we focus our analyses on incremental comparisons of several N rates rather than on a comparison of one specific fertilizer rate to a control without N as described by Barreto and Bell (1995)…”

Section: Resultsmentioning

confidence: 99%

Characterizing and Classifying Variability in Corn Yield Response to Nitrogen Fertilization on Subfield and Field Scales

2009

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A gronomy J our n al • Volume 101, I s sue 2 • 2 0 0 9 269 ABSTRACT Marked spatial and temporal variability in yield response to N fertilizer observed in individual yield response trials creates a high degree of uncertainty when estimating economic optimum rates (EORs) of N for a group of trials and when extrapolating these rates from one location to another. A survey was conducted to characterize and classify variability in yield response to N on subfi eld and fi eld scales. Fertilizer N was applied at fi ve rates (56, 84, 112, 140, and 168 kg N ha -1 ) in many (6-12) replicated strips within three 18-to 24-ha no-till fi elds during two corn (Zea mays L.) growing seasons. Yield responses or yield diff erences between two adjacent strips were measured in 22 to 25 grid cells ha -1 within each fi eld. Cumulative probability distributions (CPDs) were used to estimate the probability that a given N rate produces a yield response less or equal to a specifi ed quantity. Th e yield responses were classifi ed into potential categories with diff erent N fertilizer requirements using apparent soil electrical conductivity (EC a ), digital soil map units, and relative elevation. Analysis indicated that the classifi cations explained <3% variability in yield response to N applied in the near-optimal range, where probabilities of receiving positive and negative marginal returns were the same. Presenting probabilities of yield response observed at diff erent ranges of N fertilization may provide the basis for assessing the uncertainty associated with the variable eff ects of weather and variable supply of N when assessing economic risk and benefi ts of N fertilization in large-scale on-farm studies. P.M. Kyveryga, On-Farm Network, Iowa Soybean Association, 4554 114th Street, Urbandale, IA 50322; A.M. Blackmer, in memory, Dep. of.

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“…The challenge, however, consists in determining how to use a given EONR value (or range of values) to make reliable predictions of corn N needs for another field, another farm, or the next growing season. The need for developing a reliable decision‐making process when using EONRs under uncertainty has been discussed (Barreto and Bell, 1995; Bullock and Bullock, 2000) but such systems have not been developed and implemented as N fertilizer recommendations.…”

mentioning

confidence: 99%

Predicting Risk from Reducing Nitrogen Fertilization Using Hierarchical Models and On‐Farm Data

et al. 2013

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Current systems for developing N recommendations for corn (Zea mays L.) lack methods to quantify the effects of factors influencing yield responses to N and quantify the uncertainty in N recommendations. We utilized hierarchical modeling and Bayesian analysis to quantify the risk from reducing N to corn using on‐farm observations. Across Iowa, farmers conducted 34 trials in 2006 and 22 trials in 2007. Each trial had a farmer’s normal N rate alternating with a reduced rate (by about 30% less) in three or more replications. Yield losses (YLs) from reduced N were calculated at 35‐m intervals. Posterior distributions were used to identify across‐field and within‐field factors affecting YL and to quantify the risk of economic YL (>0.31 Mg ha−1) from reducing N in unobserved fields. In 2006 (dry May and June), the economic YL for corn after soybean (C‐S) was predicted to be 20% larger than that for corn after corn. Also in 2006, C‐S fields with above‐normal June rainfall had economic YLs 35% larger than those with below‐normal June rainfall, and sidedress applications were about 20% riskier than spring applications. In 2007 for C‐S, N reductions with above‐normal spring rainfall were riskier than with below‐normal spring rainfall. Areas with higher soil organic matter (SOM) had economic YLs about 20% smaller than those with lower SOM. Many on‐farm trials can be conducted across the state and the use of the proposed statistical methodology can improve decisions on where to reduce N applications across and within fields.

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Assessing risk associated with N fertilizer recommendations in the absence of soil tests

Cited by 9 publications

References 4 publications

Nitrogen Fertilizer Management and Recommendations for Wheat Production in Central Mexico

Nitrogen Fertilizer Management and Recommendations for Wheat Production in Central Mexico

Characterizing and Classifying Variability in Corn Yield Response to Nitrogen Fertilization on Subfield and Field Scales

Predicting Risk from Reducing Nitrogen Fertilization Using Hierarchical Models and On‐Farm Data

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