Surface application vs. incorporation of limestone for no-till alfalfa production
DiPaola, Louis George
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No-till alfalfa (Medicago sativa L.) establishment is the only environmentally sound procedure for alfalfa production on erodable land. Surface limestone application is the only reasonable method of placement in no-til1 systems with pH below 6.5. The purpose of this research was to evaluate surface limestone application vs. incorporation throughout the plow layer for alfalfa production in acidic soils. In this study limestone placement included: 1. incorporation during tillage operations, 2. surface application after tillage and preparation of seedbed, and 3. surface application without tillage. Limestone was applied at 0, 1.25, 2.50, and 5.00 tons per acre with each placement method. Limestone treatments were imposed on 30 Sept. 1986 in Montgomery County, VA (37Â° 1lâ N, 80Â° 25â W and 1950 ft. elevation) on a Groseclose silt loam (clayey, mixed, mesic Typic Hapludult) having a pH of 5.6 in the top 9 inches. Limestone treatments were imposed at a second site on 25 Nov. 1986 in Orange County, VA (38Â° l3â N, 70Â° 7â W and 515 ft. elevation) on a Davidson clay loam (clayey, oxidic, thermic Rhodic Paleudult) having a pH of 5.7 in the top 9 inches. 'Cimmeronâ alfalfa was planted using no-till procedures on 23 March 1987 in Montgomery County and on 26 Aug. 1987 in Orange County. Soil samples were taken about 2 years after limestone application at depths of 0 to 1, 1 to 2, 2 to 3, and 3 to 6 inches for surface applied treatments and 0 to 3, 3 to 6, and 6 to 9 inches for incorporated treatments. Soil samples w0ere also taken at a depath of 18 to 24 inches whenre limestone was incorpdorated during tillage at 5 tons per acre. Four harvests were made in 1988. At both locations, limestone application increased yields by 114 to 300% as compared with the check where no limestone was applied. Yields from plots receiving surface limestone application were equal to plots with incorporation at both locations. Tillage did not increase yields as compared with no tillage except in Orange County on plots where no limestone was applied. Soil pH increased from 5.6 to 6.8 at the 1- to 2-inch depths and from 5.6 to 6.3 at the 2- to 3-inch depths where 5 tons per acre of limestone were surface applied in Montgomery County. In Orange County, soil pH increased from 5.5 to 6.5 at the 1- to 2-inch depths and from 5.6 to 6.1 at the 2- to 3-inch depths where 5 tons per acre limestone were surface applied. Above pH 5.5, Al saturation was below 2.7% in Montgomery County and 0.7% in Orange County. Aluminum saturation averaged 9.0% and 4.6% where pH was between 5.0 and 5.5 in Montgomery and Orange Counties, respectively. At both locations, in the 18- to 24-inch depths a pH of 4.8 was not influenced by limestone incorporated at 5 tons per acre. Aluminum saturation at 18- to 24-inch depths was 51% and 62% in Montgomery and Orange Counties, respectively. These data indicate that surface applied limestone can produce first year alfalfa yields similar to yields obtained with incorporated limestone.
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