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| Lambert, Dayton M.; Lowenberg-DeBoer, James; Malzer, Gary L.. |
| Site-specific application of manure has the potential to improve crop production and environmental quality. If manure is applied where it is needed, in the quantity required by the crop, over application, with attendant runoff and leaching problems can be reduced. To implement this approach growers need site-specific crop response information. Increasing availability of site-specific yield information offers a way to estimate such crop responses. The objective of this study is to develop a methodology for estimating site-specific response of corn and soybeans to manure given soil test information, and to use that methodology to analyze an on-farm manure management trial conducted near Sleepy Eye, Minnesota. Both quantity and quality of the crop is... |
| Tipo: Conference Paper or Presentation |
Palavras-chave: Research Methods/ Statistical Methods. |
| Ano: 2004 |
URL: http://purl.umn.edu/20091 |
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| Malzer, Gary L.; Hurley, Terrance M.; Kilian, Bernard. |
| Confirming the precision agriculture hypothesis for variable rate nitrogen applications (VRA) is challenging. To confront this challenge, researchers have used increasingly sophisticated statistical models to estimate and compare site-specific crop response functions (SSCRFs). While progress has been made, it has been hampered by the lack of a conceptual framework to guide the development of appropriate statistical models. This paper provides such a framework and demonstrates its utility by developing a heteroscedastic, fixed and random effects, geostatistical model to test if VRA can increase nitrogen returns. The novelty of the model is the inclusion of site, spatial, treatment, and treatment strip heteroscedasticity and correlation. Applied to data... |
| Tipo: Working or Discussion Paper |
Palavras-chave: Crop Production/Industries. |
| Ano: 2004 |
URL: http://purl.umn.edu/14111 |
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| Lambert, Dayton M.; Lowenberg-DeBoer, James; Malzer, Gary L.. |
| Understanding the relationship between soil fertility dynamics and crop response is conceptually appealing. Even more appealing is comprehension of the spatial and temporal heterogeneity of these connections over a production surface and across seasons. Knowledge of these interactions is complicated because nutrient carryover dynamics and crop response to inputs are determined simultaneously on the one-hand, and sequentially on the other. A second problem enters when crops are rotated, for example, in the corn-soybean system commonly practiced in the Corn Belt. This paper examines the nutrient carryover-crop response nexus using data from a corn-soybean, variable-rate nitrogen (N) and phosphorous (P) experiment conducted over five years. Site-specific corn... |
| Tipo: Conference Paper or Presentation |
Palavras-chave: Crop Production/Industries. |
| Ano: 2005 |
URL: http://purl.umn.edu/19452 |
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| Hurley, Terrance M.; Malzer, Gary L.; Kilian, Bernard. |
| Confirming the precision agriculture hypothesis for variable rate nitrogen applications (VRA) has proven challenging. To confront this challenge, researchers have begun to use increasingly sophisticated statistical models to estimate and compare site-specific crop response functions. While progress has been made, we believe it has been hampered by the lack of a clear conceptual framework to guide and motivate the development of appropriate models and methods. The purpose of this paper was to provide such a framework, while demonstrating its utility. The framework was used to develop a heteroscedastic, fixed and random effects, geostatistical model to test the potential for VRA to increase nitrogen returns. The model was implemented with data collected... |
| Tipo: Conference Paper or Presentation |
Palavras-chave: Crop Production/Industries. |
| Ano: 2003 |
URL: http://purl.umn.edu/21950 |
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| Lambert, Dayton M.; Malzer, Gary L.; Lowenberg-DeBoer, James. |
| This paper compares two estimation methods of a three-stage least squares (3SLS) system of equations, corrected for spatial autocorrelation. The modeling approach is novel in that it is an extension of Anselin's (1988) seemingly unrelated regression (SUR) space-time spatial error model for panel data. An empirical comparison of the quasi-maximum likelihood (QML) estimation of the equation system, and Kelejian and Prucha's general moments (GM) estimation approach is presented. The model and estimation procedures introduced in this study are easily extended to other economic, agronomic, or biological models that must incorporate spatial and temporal effects in the model specification, and overcome simultaneous equation bias. The empirical example used in... |
| Tipo: Working or Discussion Paper |
Palavras-chave: Research Methods/ Statistical Methods. |
| Ano: 2004 |
URL: http://purl.umn.edu/28667 |
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