Proceedings
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1. Challenges for making intensive soil sampling and VRT Pay. Ongoing Iowa Studies with PhosphorusSoil fertility evaluation and management can be greatly improved with the use of precision agriculture technologies. Differential global positioning systems @GPS), yield monitors, various forms of remote sensing, geographical information system (GIs) computer software, and variable rate technologies are available for use to producers. Intensive soil sampling, crop scouting, and other practices complete the new technological package. Soil testing is a diagnostic tool especially adapted for site-specific... |
2. Phosphorus Loss with Runoff after Applying Fertilizer or Manure as Affected by the Timing of RainfallPublic concerns about agriculture impacts on water quality and the likelihood of further government regulation have been increasing. Phosphorus usually is the nutrient that limits and controls algae growth and eutrophication in freshwater bodies. The uninformed public and many in regulatory agencies see reducing fertilization rates as an effective way of reducing nutrient loss from fields and improving water quality, especially when animal manure is applied. Soil testing for P is a useful, although... |
3. Do Soil Nitrogen Tests Relate to Nitrogen Mineralization in First-year Corn Following Alfalfa?Corn (Zea mays L.) is the most frequent first-year crop grown following alfalfa (Medicago sativa L.) in the Upper Midwest. In the majority of cases, first-year corn does not respond to fertilizer N, but sometimes large amounts are needed to optimize yield. The pre-sidedress and Illinois soil N tests (PSNT and ISNT, respectively) are early-season tests used to predict corn yield response to fertilizer N. These tests measure specific fractions of soil N and define a critical concentration to separate... |
4. Correlation of the Weak Organic Acids Test of a Soil Health Tool with Crop Yield Response to Phosphorus FertilizationThe field correlation of a soil P test with yield response to P fertilization is the foundation for sound soil-test interpretations and fertilizer recommendation guidelines. Weak organic acid extractants have been used to measure soil P for decades in some northeastern states of the US and other countries, but not in Iowa or the Midwest. A new test based on a mixture of malic, oxalic, and citric acids (H3A) was developed as a component of a Soil Health Tool to measure soil P and K. The H3A... A. Mallarino, J. Jones |
5. Effects of Sampling Time and Extraction Method on Soil-Test and Nonexchangeable Potassium in Iowa SoilsMore research is needed to better understand K cycling and high short-term temporal soil-test K (STK) variation. The objective of this research was to study soil-test K and nonexchangeable K pools across Iowa soils managed with corn-soybean rotations as affected by K application rates, soil properties, parent materials, and time of sampling. Three-year field trials that included a control and several broadcast K fertilizer rates were conducted at 35 Iowa sites. Soil samples (6-inch depth) were... R. Oltmans, A. Mallarino |
6. Nitrogen and Potassium Interactions in CornExtensive research in the North Central region has investigated separately nitrogen (N) and potassium (K) fertilizer management for corn. However, there is scarce information available about how N and K interactions affect corn grain yield and nutrient uptake. The objective of this study was to evaluate the effects of various combinations of N and K rates on corn yield, N and K tissue concentrations, and N and K removed with grain harvest. Two trials with continuous corn were conducted from 2013... J. Hirniak, A. Mallarino |
7. Evaluation of Agricultural Lime and Pelleted Lime to Increase Soil pH and Crop YieldAgricultural lime (aglime) is applied to increase pH of acidic soils to values optimum for crop production, and its effectiveness is affected mainly by it calcium carbonate (CaCO3) equivalent (CCE) and fineness. Availability and use of pelletized limestone has increased in recent years, but there is limited information about its effectiveness. Six field trials were established in 2014 at acidic Iowa soils (pH 4.9-6.1) with contrasting texture and organic matter. Treatments replicated three times... A. Mallarino, M. Haq |
8. Influence of Source and Particle Size on Agricultural Limestone Efficiency at Increasing Soil pHExcessive soil acidity is known to have potential negative impacts on crop production. The chemical and physical characteristics of a liming material determine its capacity to neutralize soil acidity. The calcium carbonate (CaCO3) equivalent (CCE) and estimates of particle size impact on the efficiency at increase soil pH are considered when assessing a material’s liming value. The reaction of limestone particles within the soil depends largely on the soil pH and the material surface area... J. Jones, A. Mallarino |
9. What Can Long Term Experiments Provide for Improving Phosphorus and Potassium Management?Agricultural research utilizes both short-term and long-term experiments. Short-term experiments provide useful information on how a system is affected at the time of management changes, and evaluate short-term responses by the soil or crop. Agricultural systems are complex systems with multiple components that operate on different time scales of response, however. Therefore, the initial response of either the whole system or individual components may not necessarily indicate the direction or... A. Mallarino |