Proceedings
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1. A Field Study of Soil Test Variability, Its Effects on Accuracy of Fertilizer Recommendations, and the Subsequent Effect of Variable Rate Fertilizer Application on Soil Test ValuesThree 2.5 acre blocks were selected for intensive soil sampling from within an approximate 90 acre field which had been partitioned into 35, 2.5 acre blocks by a farm supply dealer. The 2.5 acre blocks had previously been sampled on a central composite grid basis and a variable rate fertilizer spreader (VRS) programmed for fertilizing the field. Three other more intensive sampling techniques were used to sample the 3 blocks selected for more detailed studies. Results obtained showed that soil te... |
2. Alfalfa Response to K Rate, Source and Time of ApplicationThe potassium (K) requirement of alfalfa is greater than that for any other nutrient. Potassium influences several systems within-alfalfa plants, including enzyme activity, carbohydrate production and transport, stomata1 activity: photosynthesis through chlorophyll content and CO, exchange rate, and nitrogen fixation (Munson, 1985). Potassium also markedly influences alfalfa agronomically through yield increases and improvements in forage quality, disease resistance, and overwinter survival. A s... |
3. An Evaluation of Methods for Determining Site-Specific Management ZonesNumerous procedures have been examined for identifymg management areas within fields. Traditional soil surveys give a general understanding of the effects soil mapping units have on crop productivity. In the USA. county soil surveys report the average grain yield of major crops by soil series. Slope position and landform are topographic features thal also have been used to explain water and crop productivity relationships (Mulla et al., 1992; Sudduth et al., 1997). Generally, footslope positions... |
4. Dietary P Management to Reduce Soil P Loading from Pig ManureThe potential use of phosphorus (P) based land application limits for animal manure has increased the importance of optimizing animal feed P management. The specific objectives of this study were to determine the impacts of using high available P (HAP) corn and phytase on 1) P uptake and excretion by young pigs, and 2) total P, PA-P, and water-soluble P (WSP) levels in fiesh manure generated by these pigs during a seven day digestibility trial. Our results show that, compared to the control diet... |
5. Effect of Potassium Rates and Placement on Soil Test Variability Across Tillage SystemsExperiments were conducted from 1994 through 1996 at the Dixon Springs Agricultural Center and the Belleville Research Center to evaluate K rates (60, 120, and 180 Ib KzO per acre) and placement methods in a corn and soybean rotation using chisel tillage (CT) and no-till (NT) practices. Four placement methods were used: surface broadcast, dribble, 10-inch wide surface band over each row, and banding 30 Ibs K20 per acre 2 inches to the side and 2 inches below the planted seed (remainder of the K ... |
6. Effect of Tillage, Rotation, and Nitrogen Rate on Rainfed Corn Yield and Nitrogen UptakeDetermining the long term effect of tillage, rotation and nitrogen rate in typical cropping sequences is important in making sound agronomic decisions. In northeast Nebraska rainfall is the major deternlinant of yield. In 1956 a tillage study was initiated to determine the effect of tillage. rotation and nitrogen rate on corn and soybean yields. Spring plow. disk and no-till treatments were applied to continuous corn and co1-n follo\ving soybeans on a Kennebec silt loam. Five nitrogen rates (0. ... |
7. Effect of Time and Rate of N Application on N use Efficiency and Surface Water Contamination with NitratesNitrate levels in excess of the public health standard of 10 mg N/1 in public water supplies along - with concern about hypoxia in the Gulf of Mexico have drawn renewed interest to improving fertilizer N use efficiency. Prior research has indicated that some farmers may be unkaowingly contributing to these problems. The objectives of this research were to: determine the effect of rate and time of N application on nitrate-N concentrations in water from tile lines and to evaluate the effect of pre... |
8. Foliar Fertilization of SoybeansExtensive research addressed foliar fertilization of soybeans at reproductive stages during the 70s and 80s. The soybean plant has been characterized by markedly reduced root activity during late seed development and increased translocation of nutrients and metabolites fiom other tissue into the seed. This depletion of numents from leaves could result in decreased photosynthesis. leaf senescence. and lower grain yields. Researchers theorized that if nutrients were applied directly to the foliage... |
9. Identifying Critical Sources of Phosphorus Export from Agricultural WatershedsPhosphorus (P) is an essential element for plant and animal growth, and its input to agriculture is necessary to maintain profitable crop and animal production. Eutrophication, the natural aging of lakes or streams brought on by nutrient enrichment, can be accelerated by P inputs to fresh waters from human activities (Carpenter et al., 1998; Schindler. 1977). Eutrophication has been identified as the main problem in surface waters withimpaired water quality (USEPA. 1996). It restricts water use ... |
10. Influence of Sulfur Source on CornSulfur is an essential plant nutrient. Medium and fine texture high organic matter soils in South Dakota usually supply adequate levels of sulfur to plants. Very sandy soils are less capable of supplying sulfur to plants but even these soils usually provide adequate sulfur for plant needs. However, in recent years above average precipitation may have caused leaching of sulfur, possibly resulting in sulfur deficiencies. In addition, spring soil temperatures have stayed cool, likely slowing decay ... |
11. Low-Phytate Corn- A Genetic Approach to Manure-P ManagementManaging nitrogen (N) and phosphorus (P) contained in manure produced by monogastric animals (primarily poultry and swine) is complicated because the N:P in corn grain is 6: 1 but only 3: 1 or less, in the manure. The P content in manure fiom monogastric animals becomes elevated because corn grain and many other feed sources contain most of their P as phytic acid (phytate) which is unavailable to these species because they lack the intestinal enzyme, phytase, needed to metabolize phytic acid-P. ... |
12. Nitrogen Fertilization of SoybeanNitrogen (N) requirement of soybean is high because of the high protein seed produced. One bushel of soybean requires over 3.5 pounds of N in the grain alone. Symbiotic Nz fixation supplies N for soybean, but Harper (1 974) reported that only 25 to 60% of the N in a marure soybean piant comes from N fixation while the other 40 to 75% comes from the soil. However. application of N fertilizer to soybean remains a very controversial issue because of mixed results of previous research.... |
13. Nitrogen Management in Irrigated Corn Using Remotely-Sensed Imagery and Small-Plot ExperimentsNitrogen management for irrigated corn (Zea mays L.) grown along the Arkansas River Valley in Kansas is a concern due to the hig&ly leachable soils and high water tables (ranging fiom 10-50 A). Irrigated corn usually requires a high input of N fertilizer to achieve maximum yields, and most farmers in this area have been applying a uniform rate of nitrogen across their fields every growing season based on the following KSU N recommendation. N Rec = [YG * 1.35 lbs bu-'1 STA - PCA - PYM - PNST N Re... |
14. Optimizing Nitrogen Managament in Manure CornfieldsAnimal manure can provide N needed for production of corn. A major problem. however. is that manure is not perceived to be a reliable source of plant-available N. Much of the manure-N is known to be lost soon after application to soils, and much of the remaining N is known to persist as forms that are not readily available to the next crop. Recent studies involving 148 on- farm trials show that the late-spring test for soil nitrate has great potential for addressing this problem. The test involv... |
15. Remotely Sensed Crop Indices for Nitrogen StressCrop nitrogen (N) stress has a strong influence on plant vigor and growth. Under field conditions, crop N stress is frequently expressed through spatial variability in biomass production and grain yield. Remote sensing serves as a useful tool to monitor crop N status by characterizing canopy reflectance because certain wavebands (i-e., colors) are sensitive to chlorophyll and crop growth. Unfortunately, interpreting reflectance data in terms of crop stress is still an inexact science. Several in... |
16. Soybean Nitrogen Aquisition and UtilizationBecause of its high seed protein concentration soybean has a huge nitrogen demand, about 350 IbdA for a 65-bu/A crop. The nitrogen is supplied by two acquisition systems that operate in tandem. In early season the plant uses soil nitrate; later its nitrogen is acquired largely through Nz fixation. On highly fertile, Midwestern soils nitrate utilization peaks at about R3 and then declines sharply. With heavy nitrogen fertilization peak nitrate utilization can be extended through R5, but ordinaril... |
17. 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... |
18. Spring Wheat Response to Copper Fertilization in North DakotaTraditionally, copper responses have been tllought to be associated with organic soils. However, recent Canadian research has found that copper responses by wheat are possible on low organic matter, coarse textured soils. A yield response to copper in spring wheat was found in North Dakota on a coarse textured, low organic matter soil. Yield responses were not found in similar copper soil test levels of higher organic matter, heavier textured soils. A two-tiered recommendation strategy is sugges... |
19. The Potential use of Polymer-Coated Urea as a Spring Nitrogen Source for WheatMost of the soils in Northwest Ohio are medium to fine texture with poor internal drainage. Tile drainage has improved these fields, but nitrogen loss still often occurs from denitrification, especially during cold and wet springs. Growers compensate for this potential loss by applying more N at green-up or split spring applications. both of which add costs. -4 slow release N fertilizer may reduce the need for more N or split applications. One of the new time release N products is polymer-coated... |
20. The Potential use of Polymer-coated Urea as an In-Furrow Fertilizer for CornMost of the soils in Northwest Ohio are medium to fine texture with poor internal drainage. Tile drainage has improved these fields, but nitrogen loss still often occurs from denitrification, especially during cold and wet springs. The use of no-till practices has accentuated the problem. Starter fertilizers at planting have often improved the early growth of corn under these cold and wet conditions. IIowever, weather conditions may prevent timely sidedressing after planting, and cause N deficie... |
21. Tillage and Potassium Effects on Potassium use Efficiency in a Corn-Soybean RotationA field study was conducted from 1994 through 1996 at the Dixon Springs Agricultural Center @SAC) on a Bonnie sil soil and at the SlU Belleville Research Center (BRC) on a Herrick sil soil. No-till (NT) and spring chisel tillage (CT) systems were compared in a corn-soybean rotation. Within each tillage system, potassium (K) rates of 60, 120 and 180 Ib K20 per acre were combined with four placement methods that included surface broadcast, 10-inch surface band over the intended row, surface dribbl... |
22. Variability of Soil Test Phophorus and Management of Phosphorus FertilizerSoil avdable phosphorus (P) can have appreciable spatial variation wluch could result in inefficient ferthzer use. The hlgh cost of mapping ttus variab&ty may make sit2 spedc management of P uneconomic. Seed-placing a small amount of P fertrli2er has been shown to increase gain yield of corn. Therefore. it may have potential for improving P use efficiency. Ah txperiment was conducted to evaluate the spatial pattern of soil test P and the spatial response of applied P fertilizer. The scale of P v... |