Variable Rate Nitrogen Application on Corn Fields: The Role of Spatial Variability and Weather

Abstract

Meta-response functions for corn yields and nitrogen losses were estimated from EPIC-generated data for three soil types and three weather scenarios. These metamodels were used to evaluate variable rate (VRT) versus uniform rate (URT) nitrogen application technologies for alternative weather scenarios and policy options. Except under very dry conditions, returns per acre for VRT were higher than for URT and the economic advantage of VRT increased as realized rainfall decreased from expected average rainfall. Nitrogen losses to the environment from VRT were lower for all situations examined, except on fields with little spatial variability.

Stochastic Corn Yield Response Functions to Nitrogen for Corn after Corn, Corn after Cotton, and Corn after Soybeans

“…Researchers have found the quadratic response plateau (QRP, also called quadraticplus-plateau in the literature) to be the most suitable response function for modeling corn yield response to N (Bullock and Bullock, 1994;Cerrato and Blackmer, 1990;Roberts et al, 2002). Bullock and Bullock (1994) compared a QRP and a quadratic function and determined the QRP to be the more appropriate response function.…”

Nitrogen response models for winter cereals grown for forage

“…Models from literature 1 Most economic rate of N (MERN) Max (pY(N) − wN) Bullock and Bullock (1994) 2 Quadratic E{Y(N)} = a + bN + cN 2 Bullock and Bullock (1994) 3 Quadratic plateau E{Y(N)} = a + bN + cN 2 , N < M a + bM + cM 2 , N ≥ M Isfan et al (1995) 4 Linear plateau E{Y(N)} = a + bN, N < M a + bM, N ≥ M Isfan et al (1995) 5 Square root E{Y(N)} = a + bN + cN 0.5 Llewelyn and Featherstone (1997) 6 Exponential (Mitscherlich) E{Y(N)} = q(1 − e −r(N+s) ) Cerrato and Blackmer (1990) and National Academy of Sciences (1961) Models for study (Table 1). Plateau functions can be useful as they reflect an increase in yield up to a certain level beyond which additional fertilization has little to no effect on yield (Alivelu et al, 2003;Bullock & Bullock, 1994;Cerrato & Blackmer, 1990;Gagnon & Ziadi, 2010;McSwiney & Robertson, 2005;Roberts, Mahajanashetti, English, Larson, & Tyler, 2002). Stochastic functions have been used to account for year to year variation across trials (Boyer et al, 2013;Brorsen & Richter, 2012).…”

“…The five statistical models commonly used to analyze N rate studies are all deterministic yield response functions, including the quadratic (Equation 2), quadratic plateau (Equation 3), linear plateau (Equation 4), square root plateau (Equation 5) and exponential (Mitscherlich) (Equation 6) models (Table ). Plateau functions can be useful as they reflect an increase in yield up to a certain level beyond which additional fertilization has little to no effect on yield (Alivelu et al., ; Bullock & Bullock, ; Cerrato & Blackmer, ; Gagnon & Ziadi, ; McSwiney & Robertson, ; Roberts, Mahajanashetti, English, Larson, & Tyler, ). Stochastic functions have been used to account for year to year variation across trials (Boyer et al., ; Brorsen & Richter, ).…”

Estimating Soil Solution Nitrate Concentration from Dielectric Spectra Using Partial Least Squares Analysis

“…Although precise application of N is attainable through variable-rate technology, a great challenge facing its widespread utilization is the lack of a robust and fast measurement system for real-time monitoring of NO 3 dynamics in soil water (Zhang et al, 2002). In situ monitoring of NO 3 -N concentrations can help to optimize the application of N-rich fertilizers, reduce the risk of NO 3 -N leaching to water bodies, and evaluate the effi ciency of best management practices targeted on the improvement of N uptake by plants during the growing season (Roberts et al, 2002(Roberts et al, , 2010Koch et al, 2004). Traditional methods for measuring soil NO 3 concentration are accurate, but at the same time they are labor intensive, time consuming, expensive, and destructive, which limits their application in real-time in situ monitoring for large areas.…”