Haby, Vincent A.

Kerby, Joel L.

Nimr, Gary H.

Rouquette, F. M., Jr.

Silveira, M. L.

English

Texas A&M University

Changes in Soil Phosphorus in Common and Coastal Bermudagrass Pastures During 35 Years of Various Stocking and Fertility Regimens

Texas A&amp;M Repository

    PUBLICATIONS 2006 CHANGES IN SOIL PHOSPHORUS IN COMMON AND COASTAL BERMUDAGRASSPASTURES DURING 35 YEARS OF VARIOUS STOCKING AND FERTILITYREGIMENSM.L. Silveira, F.M. Rouquette, Jr., J.L. Kerby, G.H. Nimr, V.A. Haby, and G.R. SmithBackground. A detailed description of stocking rates and fertility regimens from 1969through 2005 are presented in a companion 2006 Field Day Report by Rouquette et al. Theobjective of this experiment was to evaluate changes in soil phosphorus (P) concentrations incontinuous stocked bermudagrass pastures under different stocking rates.Research Findings. Initial soil P concentrations in 1969 were very low « 3 ppm). Thisis consistent with non-fertilized, P-deficient sandy Coastal Plain soils. Soil P concentrations in the0-6 inch depth significantly increased (up to 10-fold) from 1975 to 1985 as result of P fertilizerapplication (~100 Ibs P20s/ac year) (Figure I). Sixteen years (1969-1985) ofP application (total Pload of 1,500 Ibs P20s/ac) shifted soil P status from very low (0-5 pm) to high (21-40 ppm). Thisincreased soil P level enhanced forage growth, especially ryegrass and clover.During 1985 to 1996, bermudagrass pastures received no inorganic P fertilizer; thus, themajor P contributions to the soil occurred via nutrient recycling as animal excreta. Average soil Pconcentrations in 1985 were approximately 33 ppm for common and 27 ppm for Coastalbermudagrass. In 1996, soil P concentrations were comparable to those in 1985 (31 ppm forcommon and 24 for Coastal), suggesting that P was not depleted during II years of continuousstocking with no P-fertilizer applied. Nutrient cycling through animal residues and prior historyof P application sustained relatively constant P concentrations in the 0-6 inch depth of soils.In general, soil P concentrations were similar in common and Coastal bermudagrasspastures with different fertility regimens (Figure 1). From 1985 to 1996 there was a slightdecrease in soil P concentrations at low stocking rates (I pair/ac) for both common and Coastalbermudagrass pastures. This suggested that animal excreta was playing an important role in Precycling. Relatively small increases in soil P concentrations were observed in commonbermudagrass fertilized with N under high stocking rates (2 to 3 cow-calf pair/ac) from 1985 to1996; however, this difference was not statistically significant.From 1999 to 2004, P fertilizer was applied at 100 Ibs/ac P20 S. Soil P concentrationsincreased across all treatments, except for common bermudagrass pastures under high andmedium stocking rates (Figure I). Increases in soil P due to fertilization during this 5-year periodwere more evident in pastures under low and medium stocking rates.39Application. Nutrient cycling through animal excreta can sustain adequate soil Pconcentrations for optimum bermudagrass production. Overseeded ryegrass and clover growthare especially favored by adequate soil P levels. Coastal plain soils previously fertilized with Psustained relatively constant soil P concentrations during 11 years of no-P fertilizer. Phosphorusfertilization, however, can considerably affect soil P concentrations, and, thus, adequatefertilization rates and intervals of application should be carefully managed to minimize potentialenvironmental concerns associated with accumulation of P in soils and subsequent edge-of-field Plosses.20041996b. No N +Clover19851975o706050E 40CoCo~ 30201020041996Common Bermudagrassa. Nitrogen +Ryegrass1985197510o706050E 40CoCo~ 3020Coastal Bermudagrassb. No N +Clover70 a. Nitrogen +Ryegrass 7060 6050 50E 40 E40Co CoCo Co~ 30 ~3020 2010 100 01975 1985 1996 2004 1975 1985 1996 2004• High Stocking Rate • Medium Stocking Rate [J Low Stocking RateFigure 1. Changes in soil P concentrations (0-6" soil depth) in common and Coastalbermudagrass pastures after 29 years of continuous grazing at different stocking rates and fertilityregimens.40

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Changes in Soil Phosphorus in Common and Coastal Bermudagrass Pastures During 35 Years of Various Stocking and Fertility Regimens

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Texas A&M University

Texas A&M Repository

Changes in Soil Phosphorus in Common and Coastal Bermudagrass Pastures During 35 Years of Various Stocking and Fertility Regimens

Abstract

Similar works

Full text

Available Versions

Texas A&M University

Texas A&amp;M Repository

Texas A&M Repository