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1. Corn and Soybean Grain Yield and Concentration of Potassium in Plant Tissues and Soil as Affected by Potassium FertilizationResearch in the Midwest has shown that K fer tilization tends to increase plant K uptake by corn and soybean and the K concentration of vegeta tive tissues. Several studies found that K fertilization usually increases the K concentrati on of vegetative plant parts, often regardless of the soil-test K (STK) level a nd grain yield response (Malla rino et al., 1999; Borges and Mallarino, 2000; Yin and Vyn, 2002a, 2002b; Borg es and Mallarino, 2003; Yin and Vyn, 2003). It is well known that the K concentration... |
2. Identification of Reasons for High Temporal Soil-Test Potassium VariationExtensive research has focused on potassium (K) fertlization and soil K testing during several decades in the Corn Belt. IN Iowa, more t han 200 conventional or on-farm strip trials were conducted since the iddle 1990s until the early 2000s. Results of this research were used to update Iowa State University (ISU) K recommendations in 1999 and in 2002. In spite of increasd knowledge about soil-test K calibration, K fertilizer placement meethods, and needed K fertilizer rates, this research demonstrated... |
3. Agronomic and Environmental Assessment of Cover Crops in IllinoisCrop production systems have been changing for thousands of years and new ideas and practices are being implemented every day. In recent years, the practice of cover cropping systems has come into the spot light, and though research has been in effect, the practice has been slow to take root for producers in Illinois. Benefits of cover crops primarily center around increases in soil organic matter, which can lead to higher soil productivity, but the long-term agronomic, environmental, and economic... |
4. The Effects of 40 Years of Tillage and Fertility Practices on Soil Organic Carbon and Fungal PopulationsSoil organic carbon plays an integral role in long-term soil productivity. In cultivated systems, potential productivity is directly related to soil carbon concentrations, highlighting the need to protect current organic matter levels and develop management practices that will enhance soils with declining soil carbon contents. There have been variable responses in soil carbon levels to both tillage and fertility treatments. Tillage alters the physical and chemical properties of the soil environment... |
5. Iowa Soybean Nitrogen Fixation Consider in Nitrogen BudgetsSoybean (Glycine max) is one of the most important agricultural commodities grown in Midwestern states of the US and some other parts of the world. Like many other legumes, soybean can associate symbiotically with nitrogen (N) fixing bacteria, which can transform the N2 from the atmosphere into NH3 a more available N form, through a process known as biological N fixation (BNF). However, BNF is an energy expensive process for soybean that requires carbohydrates from... S. Cordova, R. Dietzel, M. Licht, S. Archontoulis, M. Castellano |
6. Examination of Topography and Soil Health Properties and Their Relationship to Corn Yield Stability in Central Iowa Agricultural FieldsCroplands in the North Central region are managed for high crop yields that are stable across years and fields. Nevertheless, yields fluctuate from year to year. Moreover, the magnitude of these fluctuations can vary across the field such that yield in some portions of the field is relatively stable and relatively variable in other portions of the field. Previous research has found that yield stability can be partially explained by topographic variables, but potential relationships between yield... L. Makens, M. Castellano |