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1. Nitrogen and Phosphorus Fertilization of Cool Season GrassStudies were initiated at two locations on cool season grass in central South Dakota to evaluate the effects of nitrogen and phosphorus on forage and seed yields. Nitrogen rates (0,30,60,90,120,1501b Nacre) and phosphorus rates (0,30,60,90,180 Ib P,Odacre) were applied to established crested or intermediate wheatgrass once and harvested for either two or three years depending on location. Nitrogen increased dry matter yield by 48 and 62% at the two locations and seed yield by 166 percent. Phosphorus... |
2. 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... |
3. Changes in Iowa's Soil Test P and K Interpretations and RecommendationsResearch results from long-term and short-term experimentation in Iowa have been consistent in the response or lack of response of Iowa field crops to applications of fertilizer phosphorus (P) and potassium (K) at various soil test levels for P and K. Analyses of the research data have established critical soil test values for P and K and the most economic soil test range for P and K to maintain (Mallarino, Webb, and Blackmer, 1991a and 1991 b; Mallarino and Blackmer, 1992 and 1994; Webb, Mallarino,... |
4. Delivering Continuing Education to Ag Professionals- The Crop Adviser InstituteContinuing education is essential for agricultural professionals, whether required by a certifjmg organization or completed voluntarily as a supplemental educational opportunity. Agricultural continuing education has traditionally been delivered on-site, but temporal, geographical, and other constraints often prevent individuals from attending these courses. The Crop Adviser Institute (CAI) has been established to provide an alternative method of delivering continuing education. Implementation of... |
5. Estimating Second- and Third Year Nitrogen Availability from Dairy manure: It is common practice to repeatedly apply dairy manure to the same fields. To accurately assess the total plant availability of rnanure nutrients, it is necessary to account for the nutrients remaining in soil fiom previous years applications. A corn (Zea mays) field experiment has continued since 1998 on a Plano silt loam. Residual manure N availability was estimated for two and three years after a single rnanure application fiom differences in whole-plant N uptake using 1) fertilizer N equivalence... |
6. Nitrous Oxide Emissions in Claypan Soils Due to Fertilizer Source and Tillage/Fertilizer PlacementNitrogen fertilization for agricu ltural production is a major contri butor to increased soil nitrous oxide emissions. These emissi ons may contribute to global warming and ozone depletion. Nitrogen fertilizer source and placeme nt can influence soil nitrous oxide (N 2O) emissions by affecting the concentration of ammonium and nitrat e available for nitrification and denitrification throughout the growing season. The objectives of this research were to quantify the effect of tillage / fertilizer... |
7. Topsoil Thickness Effects on Phosphorus and Potassium Dynamics on Claypan SoilsDue to variable depth to claypan (DTC) across landscapes, nutrient supply from subsoils, and crop removal, precise P and K fertilizer management on claypan soil fields can be difficult. Therefore, a study was performed to determine if DTC derived from soil apparent electrical conductivity (ECa) could be used to improve P and K management for corn (Zea mays L.) and soybean (Glycine max [L.]). Research was conducted on a claypan soil at the University of Missouri’s... L. Conway, M. Yost, N. Kitchen, N. Kitchen, K. Sudduth |