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United States Department of Agriculture

Agricultural Research Service

Research Project: OPTIMIZING FORAGE-BASED COW-CALF OPERATIONS TO IMPROVE SUSTAINABILITY OF BEEF CATTLE AGRICULTURE AND WATER QUALITY PROTECTION AND MANAGEMENT Title: Quantifying soil organic carbon in forage-based cow-calf congregation-grazing zone interface

Authors
item Sigua, Gilbert
item Coleman, Samuel
item Albano, Joseph

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 2009
Publication Date: April 7, 2009
Citation: Sigua, G.C., Coleman, S.W., Albano, J.P. 2009. Quantifying soil organic carbon in forage-based cow-calf congregation-grazing zone interface. Nutrient Cycling in Agroecosystems Journal. 85:215-223.

Interpretive Summary: Recent concerns about global warming due to accumulation of atmospheric carbon dioxide have encouraged the achievement of a better understanding of the role of animal agriculture in mitigating carbon dioxide emissions. Beef cattle pastures may represent a potential sink for reducing atmospheric carbon dioxide concentrations. The way pasture management and landscape interact to affect soil carbon dynamics is an issue of increasing importance to environmentalists, ranchers and public officials. The rate at which soil organic carbon is accumulating in terrestrial beef agro-ecosystem is uncertain because the mechanisms responsible for the carbon sink are not understood. Baseline soil samples around the cattle congregation sites in established (>10 yr), grazed cow-calf pastures were collected in the fall and spring of 2003, 2004, and 2005, respectively. Soil samples were collected from two soil depths (0-20 and 20-40 cm) at different locations around the CCS following a radial (every 90 degrees: North, South, East, and West direction) sampling pattern at 0.9, 1.7, 3.3, 6.7, 13.3, 26.7, and 53.3 m away from the approximate center of MF, WT, and SA. On the average, the potential soil organic carbon sequestered within the grazing zone was higher than that of the animal congregation zones. Of the cattle congregation sites, shades sites had the greatest soil organic carbon followed by water troughs and mineral feeders. Results of our study did not support our hypothesis that cattle congregation sites typical on most ranches may have higher concentration of soil organic carbon. The levels of soil organic carbon within the congregation zone (3.42 g kg-1) were not significantly different from the concentration of soil organic carbon at the grazing zone (3.16 g kg-1). Based on the average concentration of soil organic carbon, the congregation zone of bahiagrass-based pasture may have had sequestered 6,840 kg ha-1 (684 g m-2) of soil organic carbon while potential soil organic carbon sequestration at the grazing zone was about 6,320 kg ha-1 or 632 g m-2.

Technical Abstract: Recent concerns about global warming due to accumulation of atmospheric CO2 have encouraged the achievement of a better understanding of the role of animal agriculture in mitigating CO2 emissions. Grazing can accelerate and alter the timing of nutrient transfers, and increase the amount of nutrients cycled from plant to soil. Our reason for conducting this study is to test whether cattle congregation sites (CCS) typical on most Florida ranches, such as mineral feeders (MF), water troughs (WT), and shade areas (SA) have higher soil organic carbon (SOC) than in other locations of pasture. Baseline soil samples around the congregations zones (MF, WT, and SA) and grazing zones in established (>10 yr) bahiagrass pastures, grazed by cow-calf pairs were collected in the fall and spring of 2003, 2004, and 2005, respectively. Soil samples were collected from two soil depths (0-20 and 20-40 cm) at different locations around the CCS following a radial (every 90 degrees: N, S, E, and W) sampling pattern at 0.9, 1.7, 3.3, 6.7, 13.3, 26.7, and 53.3 m away from the approximate center of MF, WT, and SA. The levels of SOC varied significantly with CCS (p=0.001), distance away from the center of the CCS (p=0.05), sampling depth (p=0.001), sampling year ((p=0.001) and the interaction of CCS and soil depth (p=0.001). Sampling orientations did not significantly affect the levels of SOC. The levels of SOC (averaged across CCS) within the congregation zone (3.42 g kg-1) was not significantly different from the concentration of SOC at the grazing zone (3.16 g kg-1). The SA sites had the highest level of SOC of 3.58 g kg-1, followed by WT sites (3.47 g kg-1) and MF sites (2.98 g kg-1). Results of our study did not support our hypothesis that cattle congregation sites typical on most ranches, such as MF, WT and SA, may have higher concentration of SOC.

Last Modified: 10/1/2014
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