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United States Department of Agriculture

Agricultural Research Service

Title: Levels and changes of soil phosphorus in the subtropical beef cattle pastures

Authors
item Sigua, Gilbert
item Williams, Mary
item Coleman, Samuel

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2004
Publication Date: February 1, 2004
Citation: Sigua, G.C., Williams, M.J., Coleman, S.W. 2004. Levels and changes of soil phosphorus in the subtropical beef cattle pastures. Communications in Soil Science and Plant Analysis. 35(7&8):975-990.

Interpretive Summary: Florida's grazinglands have considerable variability in soils, climate, and growing season, which not only affect the types of forage that can be grown, but also the overall environmental and biodiversity management. The role of how pasture management (stocking rate, grazing system, etc.) and fertilizer application affect nutrient dynamics and water quality in flatwood and ridge soils are issues of increasing importance to environmentalists, ranchers, and public officials in the state. Nutrient dynamics in various agro-animal-ecosystems are continually evolving in response to changing management practices. The objective of this study was to investigate the effects of grazing and haying on soil phosphorus dynamics (levels and changes) in subtropical beef cattle pastures with bahiagrass (Paspalum notatum) and rhizoma peanut (Arachis glabrata) with or without phosphorus fertilization in Brooksville, FL from 1988 to 2000. Grazing animals have a dominant effect on the movement and utilization of nutrients through the soil and plant system, and thus on the fertility of pasture soils. Grazing has been documented to modify both the magnitude and distribution of soil phosphorus. Environmentally, soil P levels in STARS are declining. During the past 12 years, there was no P build up despite of the annual application of P-containing fertilizers. The average soil test values for P in STARS had declined by about 28.3%. The soil test values of P in BG-GZ was about 23% higher than that of BG-GZ+HY, suggesting that GZ followed by HY could have lowered levels of soil P. Soil testing program in the station should continue to measure the amount of soil P that is proportional to what is available to BG and RP, and also continue looking at alternative soil P tests that are better predictors of the loss and/or build up of total and dissolved P to soil and water systems. Maintaining a balance between the amount of nutrients added to the soil as manure and fertilizer and the amount of nutrients removed as forages, hay, or livestock is critical for productive crop growth and water quality protection. If more nutrients are added that can be used for productive forage growth, nutrients will build up in the soil, creating high risk for runoff and water contamination.

Technical Abstract: Long-term pasture management is believed to change soil chemical properties, but little is known about whether pasture management, such as fertilizer application, grazing, or haying can initiate such change in sandy and well-drained subtropical beef pastures. The objective of this study was to investigate the long term effect of pasture management (grazing + haying, GZ + HY) on soil phosphorus (P) dynamics (levels and changes) in subtropical beef cattle pastures with bahiagrass (BG, Paspalum notatum) and rhizoma peanut (RP, Arachis glabrata) with (WP) or without (WNP) P fertilization in Brooksville, FL from 1988 to 2000. Soil P dynamics in Subtropical Agricultural Research Station (STARS) was significantly affected by P fertilization (p ' 0.001) and pasture management (p ' 0.0001). The soil P levels across years from the fertilized fields of 119.0 + 4.9 mg kg-1 was significantly higher than those pasture fields with no P fertilization (62.8 + 7.8 mg kg-1). However, during the past 12 years, there was no P build up despite of the annual application of P-containing fertilizers in addition to the daily in-field loading of animal waste bi-products like fecals and urine. The average soil test values for P in STARS had declined by about 28.3%. The soil test values of P in BG-GZ was about 23% higher than that of BG-GZ+HY, suggesting that GZ followed by HY could have lowered levels of soil P. Soil testing program in the station should continue to measure the amount of soil P that is proportional to what is available to BG and RP, and also continue looking at alternative soil P tests that are better predictors of the loss and/or build up of total and dissolved P to soil and water systems.

Last Modified: 10/23/2014
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