Agriculture Reference
In-Depth Information
4.2.5 S patIal p atternS r elated to a nImal b ehavIor
Cattle tend to congregate around shade and water sources, and therefore, can affect
the distribution of manure and carbon inputs in pastures. At the end of 12 years of
management, SOC was greater nearest shade and water sources at 0-3-, 3-6-, and
6-12-cm depths (Franzluebbers and Stuedemann 2010). The total SOC plus residue
was 2-5 Mg ha −1 greater near shade compared with farther away in systems where
the stock of SOC was 42 Mg ha −1 throughout the pasture under low grazing pressure
and 39 Mg ha −1 under high grazing pressure.
In tall fescue pastures grazed by cattle for 8-15 years, SOC was greatest near
shade and water sources, and declined logarithmically with increasing distance. To a
depth of 30 cm, SOC was 46.0 Mg ha −1 at 1 m from shade, 43.2 Mg ha −1 at 10 m from
shade, 39.9 Mg ha −1 at 30 m from shade, 40.5 Mg ha −1 at 50 m from shade, and 39.4
Mg ha −1 at 80 m from shade (Franzluebbers et al. 2000a). The zone within a 10-m
radius of shade and water sources became enriched in SOC, most likely owing to the
high frequency of organic deposition from cattle defecation and urination. To mini-
mize the probability of nitrogen contamination of surface and groundwater supplies
(since total nitrogen also increased with increase in SOC), shade/water sources are
recommended to be moved periodically, positioned on the landscape to minimize
flow of percolate or runoff directly from these areas to water supplies, or avoided
during routine fertilization. In livestock congregation sites, such as mineral feeders,
water troughs, and shaded areas, Sigua and Coleman (2009) reported soil penetrom-
eter resistance decreased linearly with increase in distance away from the center of
mineral feeders and water trough, but that it increased slightly with distance from
the center of shade.
Stream channel instability is often attributed to the effects of livestock grazing.
Miller et al. (2010) found that cattle exclusion significantly reduced the surface run-
off depth of water and nitrogen loads compared with the grazed pasture, suggesting
that this fenced pasture may act as a buffer for certain runoff variables. However, in
the 3-year study, turbidity, electrical conductivity, pH, concentrations and loads of
total suspended solids, and certain nitrogen and phosphorus fractions in the cattle-
excluded pasture were generally not improved by stream bank fencing.
Verdoodt et al. (2009) evaluated soil and vegetation properties in communally
managed and privately managed enclosures for controlled grazing, compared with
uncontrolled extensive grazing in Kenya. The communal enclosures with higher lev-
els of management than the private enclosures exhibited biomass production fully
recovered up to its optimal level relative to neighboring nature reserves, while the
private enclosures exhibited restricted biomass production. In the communal enclo-
sures, improvements in topsoil bulk density, SOC, total soil nitrogen, and microbial
biomass carbon and nitrogen were observed compared with the open rangeland. In
private enclosures, only topsoil bulk density and the microbial biomass carbon stock
were significantly higher than open rangeland.
Smet and Ward (2006) reported significant negative effects of management type
on soil parameters (i.e., soil pH, nitrogen, and SOC) within 0-100 m from the water
point of three production systems in South Africa. Commercial livestock ranch-
ing had the greatest negative effect on the immediate area around the water point
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