Haby, Vincent A.

Kerby, Joel L.

Nimr, Gary H.

Rouquette, F. M., Jr.

Silveira, M. L.

English

Texas A&amp;M Repository

    PUBLICATIONS 2006 SOIL DEPTH DISTRIBUTION OF PHOSPHORUS IN COASTAL BERMUDAGRASSPASTURES SUBJECTED TO LONG-TERM STOCKING RATES AND FERTILITYREGIMENSM.L. Silveira, F.M. Rouquette, Jr., J.L. Kerby, G.H, Nimr, VA. 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 study was to investigate phosphorus (P) distribution within the soil profile inCoastal bermudagrass pastures continuously stocked for 35 years at various stocking rates.Research Findings. With continuous stocking, soil P concentrations were nearly two-times greater at high stocking rates (2-3 cow-calf/ac) than at the low stocking rates (1 cow-calf/ac) (Figure 1). Differences in soil P concentrations due to stocking rates were mainlyobserved in the top 48-in soil depth. In contrast, deeper soil depths showed no evidence ofstocking rates affecting P concentrations. Across all treatments, P concentrations decreasedsignificantly with soil depth. This trend was expected, since P has slow mobility in the soil profileand tends to preferentially accumulate in the surface horizons in grazed pastures due to aboveground contributions from fertilizer, animal wastes, and nutrient recycling.After II years of no-P fertilization (1985-1996), soil P concentrations dramaticallydecreased, but were still rated either as high (21-40 ppm) or medium (11-20 ppm) within the top36-in soil depth. Soil P depletion due to plant uptake was more evident in the 0- 48 in. soil depth.During this II-year period of no P fertilizer, soil P concentrations were reduced by as much as60% at low stocking rates, and from 20-30% at high stocking rates. From 1998 to 2004, cloverand ryegrass pastures received P fertilizer (~ 100 Ibs P20 S/ ac), and soil P concentrationssignificantly increased in 2004. Stocking rate effects on soil P concentrations were less evident,probably because P fertilizer application played a major role controlling residual soil P.There were no significant differences in soil P concentrations between non Nand N-fertilized pastures, except in 1989, when non N- clover pastures showed greater P concentrations(at both low and high stocking rates) compared to nitrogen-ryegrass pastures. This may be due tothe high fertilizer N rates applied, which ultimately may have favored P uptake.Application. Coastal bermudagrass pastures with prior history of P fertilization canmaintain adequate soil P concentrations for several years under continuous stocking. Under lowstocking rates, soil P will deplete faster than at high stocking rates. Animal manure can recyclesubstantial amounts ofP and sustain adequate bermudagrass growth in Coastal Plain soils. Over4535 years of grazing, there was no evidence that P was accumulating in soils at levels that maypotentially become an environmental hazard.Nitrogen +Ryegrass -1989 No N +Clover -1989-+-High SR~LowSRP (ppm)0 20 40 60 80 06 618 --_ .._--- ------ 18g 30 -+-High SR g 30.c 42 .c 42Q. ~LowSR ...54 Co 54Gl Glc 66 c 66'0 78 '0 78l/) l/)90 90102 10220P (ppm)40 60 80Nitrogen +Ryegrass -1996 No N +Clover - 1996-+-High SR~LowSR-+-High SR~LowSR8060P (ppm)40200618g 30.c 42...Co 54Glc 66'0 78l/)901028060P(ppm)40200618g 30.c 42Q. 54Glc 66'0 78l/)90102No N +Clover - 2004-+-High SR~LowSRNitrogen +Ryegrass - 2004P(ppm)0 20 40 60 80 06 618 18;g 30 g 30.c 42 -+-High SR .c 42... ...Co 54 Co 54CII~LowSRGlc 66 c 66'0 78'078l/) l/)90 90102 10220P(ppm)40 60 80Figure 1. Phosphorus distribution in the Coastal bermudagrass soil profile as a function ofdifferent stocking rates (SR) and nitrogen fertilization.46

Soil Depth Distribution of Phosphorus in Coastal Bermudagrass Pastures Subjected to Long-term Stocking Rates and Fertility Regimens

Texas A&M University

https://oaktrust.library.tamu.edu/bitstream/1969.1/189689/1/article28.pdf

Soil Depth Distribution of Phosphorus in Coastal Bermudagrass Pastures Subjected to Long-term Stocking Rates and Fertility Regimens

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Soil Depth Distribution of Phosphorus in Coastal Bermudagrass Pastures Subjected to Long-term Stocking Rates and Fertility Regimens

Abstract

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Texas A&amp;M Repository

Texas A&M University

Texas A&M Repository