Proceedings
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1. Aglime for Corn and Soybean ProductionLiming acid agricultural soils has been a long-time proven practice to maintain/improve crop yields, particularly forage legumes, and to favorably affect soil chemical, biological and physical properties. Summaries of soil test results from the Iowa State University Soil Testing Laboratory for the past 35 years have shown a consistent 2 to 3 percent of soil samples with a soil pH below 5.5 and 14 to 16 percent with soil pH between 5.6 and 6.0. There has been an increasing percentage (from 21 to ... |
2. Assessing Crop Nitrogen Needs with Chlorophyll MetersTissue testing of corn leaves for nitrogen (N) concentration is not widely used because it is easier and perhaps more economical to apply sufficient fertilizer than to risk a yield reduction because of an N deficiency. Environmental concerns related to N fertilizer will require producers to improve N management practices to reduce the potential for nitrate leaching. Applying fertilizer N on an "As Needed" basis rather than using a "Lump Sum" approach has both environmental and economic implicati... |
3. Best Management Practices for Nitrogen in MinnesotaAtrention to nirrogen (N) nlanagemerzt and to rhe influence of N on ground- rvarer qzraliry was significanrly enhanced in Minnesota wirh the passage of the Conlprehensive Groundwater Protection Acr in 1989. That legislative act mandated the fonnarion of u Nirrogen Fertilizer Task Force whose duty was ro study the eflecrs and impacrs on water resources fro,n N fenilizer use so rhar besr management practice (BMPs), a fenilizer managenlenr plan, and N fem'l- izer use regulations could be developed... |
4. Economic Perspective on Variable Rate FertilizationSoils form a continuum across every farmer's field, constantly changing in both physical and chemical characteristics. Sometimes these changes are visible; sometimes they are completely masked to the eye. Variables such as organic matter, water-holding capacity, pH, and soil nutrient levels differ, and combined, they affect crop yield goals. In either case, these differences should result in different management practices, including fertilizer applications, being recommended for different soils ... |
5. Evaluation of Soil Profile NO3-N for Prediction of N Fertilizer RequirementsCurrent N recommendation systems based on yield goal with adjustment for previous legume crop or manure applications have worked well in many situations. In the example given in Table 1, multiplying the 8 year average yield times 1.2 lb N/bushel would result in a recommendation within 20 Ibs N/acre of the optimum in 6 of the 8 years. As expected, this system resulted in significant over recommendation in the 1988 and 1989 drought years. While these results provide confidence that the system wor... |
6. Foliar Fertilization of Soybeans in MissouriSoybeans may benefit from foliar fertilization during the reproductive phase of growth. Foliar fertilizers consisting of factorial combinations of boron, calcium, magnesium and phosphorus were applied to soybeans every other week for eight weeks beginning at flowering at three locations. The foliar fertilization treatment containing B+Mg (1.0 lb/acre B + 2.0 lb/acre Mg total) and split into four applications at Mt. Vernon and the Delta Center increased yields by 8 and 4 bulacre, respectively. Th... |
7. Ground Water Quality Research and Demonstration Projects in NebraskaTwo projects were initiated in Nebraska in 1990 to address concern with increasing levels of nitrate in ground water as part of USDA's Water Quality Initiative. The Nebraska Management Systems Evaluation Area (MSEA) Water Quality Project is a joint effort of USDA Agricultural Research Service (ARS) and University of Nebraska-Lincoln scientists. One phase of the project is investigating the direct impact of four management systems on ground water quality. Another phase of the project is evaluatin... |
8. Missouri Grid Soil Sampling ProjectA grid soil sampling project has been conducted over the past three years in S.E. htissouri for creating a database to provide for variable fertilizer application within fields. Results have shown widely varying soil test levels in excess of 100% variation for P and K. Gross returns to variable spreading of P and K are estimated using an expected soil test and nutrient response function. As may be anticipated, returns to variable fertilization application within a field are also highly variable... |
9. 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. Phosph... |
10. 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 re... |