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Conservation Tillage Systems and Liming Materials Report for Third Year (2004) Gene Stevens and David Dunn The adoption of conservation tillage systems continues to increase across Missouri. However, no-till and strip-till farmers have expressed concern that lime may need to be incorporated with conventional tillage equipment to neutralize soil acidity below the 0 to 2-inch soil depth. Research at the University of Tennessee Milan Experiment Station showed that surface applied lime on a no-till field effectively increased soil pH in the soil profile. However, this study was conducted on a loessial silt loam soil with good internal drainage. Whether the same would be true on a poorly drained Sharkey clay soil is not known. Solubility of the liming material may also be a factor. Tests with conventional till cotton at the University of Missouri Delta Center showed that dolomitic lime increased soil pH slower than calcitic lime, but both types of lime resulted in the same amount of cotton yield increase. A study was begun in 2002 to determine the soil depth that surface applied lime in conservation tillage systems will neutralize soil acidity on clay and silt loam soils. Research activities in 2004: Tests were conducted at four locations. Fields on the University of MissouriDelta Center with Dubbs silt loam (average initial pH salt 5.2) and Tiptonville silt loam soils (average pH salt 5.3) were used. Two fields with Sharkey clay soil (average initial pH salt 4.6) at the University of Missouri Lee Farm were also used. A corn-soybean rotation system was used at the silt loam and clay sites. A split-plot design was used with no-till, strip-till and conventional till main plots. Soil pHsalt and Woodruff buffer pH were used to determine the recommended amount of ENM needed to raise the pH to the 6.1 to 6.5 range. Liming materials were obtained from local dealers and tested for ENM value. Sub-plot treatments were the recommended rate of calcitic (white) lime, recommended rate of dolomitic (red) lime, and an untreated check. Liming materials were applied in the April 2002 on the silt loam sites and April 2003 on the clay sites. These were surface applied before any tillage was done. In September or October each year, soil cores were collected from the 0 to 6-inch soil depth. The cores were cut into 2-inch increments (0 to 2-inch, 2 to 4-inch, and 4 to 6-inch soil depths) and tested for soil pH and extractable Mn. Plots will be mechanically harvested for yield. Conclusion We found no consistent soil pH or yield results indicating tillage is needed to incorporated lime in soybean or cornfields (Tables 1 and 2 ). Yield response to liming materials was generally positive but no always statistically significant compared to the untreated check. Soil tests from the 0 to 6-inch depth showed that dolomitic and calcitic lime both increased soil pH and reduced extractable Mn levels (Figures 1 and 2). Low soil pH increases Mn and Al availability (toxic at high levels) and decreases the availability of important nutrients like P. Although Mn is an essential element, Mn toxicity is more common in Missouri than Mn deficiency. We will continue the experiment on the Sharkey clay soil in 2005 without funding to gain more results and publish the information from both soils in a scientific journal. Table 1. Effect of lime material on soybeans and corn at the MU Delta Center Marsh Farm averaged from 2002 to 2004 on a Reelfoot sandy loam soil with initial soil pHsalt of 5.2. Tillage Lime No tillage Dolomitic Calcitic Check Dolomitic Calcitic Check Dolomitic Calcitic Check Strip tillage Conventional Grain yield † Corn Soybean -----bu/acre---123 a 59 a 107 b 58 a 103 b 56 a 115 a 55 a 123 a 54 a 108 a 56 a 110 a 56 a 123 a 51 b 114 a 50 b † Within a tillage system, yields followed by the same letter were non-significant at 0.05 level. Table 2. Effect of lime material and tillage on soybeans and corn at the MU Delta Center Lee Farm in 2003 and 2004 on Sharkey clay with initial soil pHsalt of 4.6. Tillage Lime No tillage Dolomitic Calcitic Check Dolomitic Calcitic Check Dolomitic Calcitic Check Strip tillage Conventional Grain yield † Corn Soybean -----bu/acre---96 a 38 a 82 a 41 a 78 a 43 a 105 a 41 ab 78 ab 43 a 67 b 37 b 79 ab 37 a 101 a 37 a 70 b 32 a † Within a tillage system, yields followed by the same letter were non-significant at 0.05 level. Tiptonville Silt Loam Extractable Mn, lb/acre Soil pH (salt) 4.0 5.0 6.0 0 7.0 0 10 15 20 25 Calcitic Dolomitic Check Dolomitic Calcitic Soil Depth (inches) Soil Depth (inches) 5 0 2 4 Check 2 4 6 6 Figure 1. Conventional tillage soil pHsalt and Mn levels in the surface 0 to 6-inch soil layer in 2004. Extractable Mn, lb/acre Soil pH (salt) 4.0 5.0 6.0 0 7.0 4 6 Dolomitic Calcitic Calcitic 10 15 20 25 Dolomitic Check Soil Depth (inches) Soil Depth (inches) Check 2 5 0 0 2 4 6 Figure 2. No-tillage soil pHsalt and Mn levels in the surface 0 to 6-inch soil layer in 2004.