Proceedings
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1. Evaluation of Phosphorus and Potassium Fertilization on Corn and Soybean Yields and Soil Test Levels in OhioThe most recent fertilizer phosphorus (P) and potassium (K) recommendations for corn and soybean grown in Ohio were established in the mid-90s and research is required to verify the appropriateness of these recommendations after 20 years. In this study, corn and soybean rotations were established and maintained at three sites from 2006 to 2014 and fertilizer P and K were applied at 1) zero rates, 2) estimated nutrient removal rates and 3) twice the estimated nutrient removal rates for each rotation.... |
2. North Central Regional Nitrate Soil Testing ProjectAlthough preplant soil nitrate (NO -N) tests have a long history of 3 successful use in semi-arid regions of the Western and Great Plains region of the United States (Hergert, 1987), soil NO -N testing in humid 3 regions is currently receiving substantial research attention. One of the most promising approaches to KO testing in the higher rainfall areas 3 of the Midwest and Eastern states is use of the pre-sidedress soil NO test (PSNT) (Magdoff et al., 1984). Research conducted in the humid 3 regions... |
3. Predicting Subsoil Nitrate Content from Surface MeasurementsPreplant soil profile nitrate (NO,-N) tests are effective for I predicting corn (Zea mays L.) responsk to applied N. The difficulty of obtaining profile soil samples is one of the main obstacles to more extensive use of preplant tests. One approach to overcoming this barrier is to develop and use models to predict subsoil NO -N contents 3 from surface soil NO -N measurements. Data from 2295 routlne field 3 samples submitted to the University of Wisconsin Soil and Plant Analysis Laboratory from 1989... |
4. Soybean Nitrogen Contributions and Rotation EffectsCorn-soybean rotations are widely used in Midwestern grain production. These rotations usually produce higher corn yields and require less supplemental nitrogen (N) than corn grown following corn. The yield benefits are usually attributed to rotation effects, although the precise mechanisms responsible for the yield enhancement are often not well defined. Nitrogen contributions from soybean in rotations are also not well understood because nitrogen budgets for soybean show that soybean harvested... |
5. Nitrogen Recommendations and Optimum Nitrogen Rates- How Do They CompareThe goals of University N recommendations for corn are to suggest adequate amounts of N to maximize economic return to the grower and simultaneously avoid excess N additions that can contribute to water quality problems. With increasing concerns about the contributions of aoricultural N to groundwater nitrate and to hypoxia in the Gulf of 3 Mexico. the appropnateness of N recomn~endations and their research basis are increasingly questioned. In addition, University N recommendations are often being... |
6. Yield Goal Versus Delta Yield to Predict Nitrogen Need in CornFertilizer nitrogen (N) needs of corn can vary widely both among and within fields. Many states use a yield goal to identi@ differences in fertilizer N need combined with an N credit system to adjust for N provided by the soil from sources such as soil organic matter, residual inorganic N and crop residues. Some have questioned yield-goal derived fertilizer N recommendations because of its poor correlation with fertilizer N need, leading some states to eliminate yield goal from their N recommendation... |
7. Long-Term Nitrogen Fertilization Effects on Corn Yields and Soil PropertiesA long-term experiment (1 958-2002) provides information about the sustainability of long-term nitrogen (N) fertilizer use and continuous corn production in the northern Corn Belt. The experiment includes three N rates (none, medium, and high) applied annually in a randomized complete block design with four replications. Nitrogen rates in the medium and high categories increased over time and are currently 125 and 250 lb Nlacre. Lime treatments were imposed on the long-term N rates in 1985 using... |
8. Measuring Water-Extractable Phosphorus in Manures to Predict Phosphorus Concentrations in RunoffWater-extractable phosphorus (WEP) in manures can influence the risk of P losses in runoff when manures are land applied. There is some uncertainty about how WEP in manures should be determined. Specifically, are WEP measurements affected by manure sample handling before analysis, and what manure extraction procedures are most appropriate for predicting potential P runoff losses after manure application? We evaluated several manure handling and extraction variables in determinations of WEP in manures... |
9. Determining Economic Optimum Nitrogen Rates with the Illinois Soil Nitrogen Test and Soil Organic Nitrogen FractionsDevelopment of a diagnostic test to estimate soil N supplying capability is a continuing research need. The Illinois soil nitrogen test (ISNT) has been proposed as a method for adjusting corn (Zea Mays L.) N recommendations for to account for soil organic N contributions. We evaluated the ISNT as a tool for predicting corn N response in Wisconsin by comparing ISNT values and corn N response data from-81 experiments conducted between 1984 and 2004 with a range of crop rotations, management histories,... |
10. Validating the Wisconsin P Index with Measured Runoff P Losses From Agricultural FieldsPhosphorus (P) indices have been developed by most states in the USA for use as planning tools to assess the risk of P loss and identify appropriate management alternatives to control these losses where needed. Little information is available on the relationshp between P index values and actual P runoff losses in the field. We compared annual P losses in runoff measured at 2 1 field or sub-watershed locations with Wisconsin P index values calculated for the same areas. The research sites included... |
11. An Environmental Assessment of Sensor-Based Variable-Rate Nitrogen Management in CornIn order to address the problem of nitrate contamination of surface and ground waters, various methods have been used to try to account for spatial variability of N within agricultural fields. One approach to account for this variability and thereby reduce nitrate pollution is in-season site- specific N application according to economic optimal N rate (EONR). Recently, active crop canopy sensors have been tested for mid-season, on-the-go N fertilizer application in corn. This 2004 and 2005 study... |
12. Nitrogen Mineralization Estimates for N Rate SuggestionsTo improve the accuracy of N rate recommendations for corn, reliable estimates of soil N supplying capability are needed. The important influence of soil N supplying capability on estimating corn N needs is illustrated by a recent compilation of data on corn yield response to N fertilization fiom over 300 experiments in Illinois, Iowa, Minnesota, and Wisconsin showing that 50 to 70% of the observed corn yield was produced with N supplied by the soil alone (Sawyer et al., 2006). The soil available... |
13. What are the Benefits of Canopy Sensing for Variable-Rate Nitrogen Corn Fertilization?Canopy reflectance sensing for assessing crop N health has been proposed as a technology on which to base top-dress variable-rate N applicat ion. The objective of this research in Missouri was to evaluate the economic a nd environmental benefit of activ e-light crop-canopy reflectance sensors for corn N rate decisions. A total of 16 field-scale experiments were conducted over four seasons (2004-2007) in three major soil areas. Mu ltiple blocks of randomized N rate response plots traversed the length... |