John A. Stuedemann

The relationship of land use practices to surface water quality in the Upper Oconee Watershed of Georgia

On a watershed scale, geospatial information can be used to identify water resources that are least buffered from contamination. Implementing conservation practices at these locations may accelerate the process of increasing a watersheds ability to support its designated uses. The Upper Oconee Watershed of Georgia contains land areas devoted to poultry, dairy, and beef production. Within these historically agricultural lands, urbanization is proceeding rapidly around existing cities. Agricultural production practices are concentrated in the watershed with poultry in the headwaters area and dairy near a major lake (Lake Oconee). The objective of this research was to relate data sets representing surface water quality at selected sites throughout the watershed to the predominant land use in that portion of the watershed. The location of 550 poultry operations in the headwaters of the Upper Oconee Watershed, away from the city of Athens GA, has minimized conflicts between agricultural and urban interests. Phosphorus, nitrogen, and fecal coliform bacteria were high near the poultry production area, but were reduced within the watershed prior to reaching the intake for the municipal water supply. Athens had a large impact on surface water quality and approximately doubled the amount of phosphorus and nitrogen in the Oconee River. The Oconee River contributed approximately 70% of the water flowing to Lake Oconee. The residents of Lake Oconee have noted the 30 dairies located west of the lake impacting two relatively minor creeks flowing to the lake. These two creeks make up approximately 2.5% of the flow to the lake, but the proximity of the dairies to the lake makes losses of phosphorus, nitrogen, and fecal bacteria apparent in water samples. Fecal coliform numbers were elevated in some creeks with little agricultural or urban development. To test alternative microbial assays, surface water from a grazed watershed was compared to water from a wooded watershed. Assays for enterococci and E. coli may provide a better test for fecal contamination and allow differentiation between natural areas and areas impacted by grazing animals. Analysis of the Upper Oconee Watershed identified agricultural impacts and areas that should be priorities for natural resource management to reduce agricultural non-point source pollution. Focusing conservation efforts at these locations may prevent agricultural-urban conflict. However, the data also indicate that municipal sources of nutrients and fecal bacteria must be reduced to make significant progress in the watershed.

Pathophysiology of fescue toxicosis

Abstract The pathophysiology of fescue toxicosis is discussed relative to observed symptoms and the inhibition of animal production (average daily gain and decreased reproductive efficiency). Hyperthermia, vasoconstriction and perhaps increased activity of hepatic mixed-function oxidases are important effects. Perhaps secondarily intake is reduced by the above mechanisms and possibly by unpalatability factors. The decreased milk yield is considered a function of decreased intake and suppressed prolactin secretion. Evidence is discussed that corpora lutea in cattle are morphologically altered and consequently may not support a pregnancy. The effect of endophyte presence upon the outcome of pregnancy in the mare is considered a function of an alteration in placental function as a result of vasoconstriction.

Bermudagrass Management in the Southern Piedmont USA

al., 1994). Summed to 1-m depth, SOC content was not different between cropland and conservation reserve. Estimates of potential soil organic C (SOC) and total N (TN) In a shortgrass-steppe with 56 yr of grazing in Colorado, sequestration at depths below the traditional plow layer (i.e., 0–0.3 m) in agricultural systems are needed to improve our understanding of SOC was not different between unharvested and lightly management influences on nutrient cycling and potential greenhouse grazed rangeland at any soil depth increment to 0.9-m gas mitigation. We evaluated the factorial combination of nutrient depth(Reederetal.,2004).Incontrast,SOCwasgreater source (inorganic, inorganic cover crop, and broiler litter) and in four of seven depth increments to 0.9-m depth under forage utilization (unharvested, hayed monthly, and low and high heavily grazed compared with unharvested rangeland. grazing pressure) on profile distribution of and changes in SOC and At the end of 12 yr of grazing on a previously ungrazed TN during the first 5 yr of ‘Coastal’ bermudagrass [Cynodon dactylon mixed-grass rangeland in Wyoming, SOC and TN were (L.) Pers.] management. Nutrient source did not affect SOC and TN greater with light and heavy stocking than an ungrazed in the soil profile. Contents of SOC and TN under haying were lower exclosure at a depth of 0 to 0.3 m, but statistically similar than under other management systems throughout the soil profile. between treatments at a depth of 0 to 0.6 m (Schuman et

Crop and cattle responses to tillage systems for integrated crop-livestock production in the Southern Piedmont, USA

Integration of crops and livestock has the potential to provide a multitude of benefits to soil and water conservation and nutrient cycling efficiency, while reducing economic risk and increasing profitability. We conducted a field study from May 2002 to October 2005 to determine crop and cattle responses to three management factors on a Typic Kanhapludult in Georgia, USA. Summer grain/winter cover [sorghum (Sorghum bicolor L. Moench) or corn (Zea mays L.)/rye (Secale cereale L.)] and winter grain/summer cover [wheat (Triticum aestivum L.)/pearl millet (Pennisetum glaucum L. R. Br.)] were managed with either conventional tillage (CT) or no tillage (NT) and with or without cattle grazing of cover crops. All crops were successfully established, irrespective of tillage and cover crop management. Although pearl millet was often lower in the plant stand with NT than with CT, plants compensated with greater biomass on an area basis. Across years, grain yield of sorghum (1.9 Mg ha -1 during three seasons) and corn (7.3 Mg ha -1 in one season) was 25% greater under NT than under CT when the cover crop was not grazed. Wheat grain yield (2.7 Mg ha -1 during three seasons) was unaffected by tillage and cover crop management. Unharvested stover production of summer grain crops was greater with NT than with CT (6.5 versus 4.1 Mg ha -1 ; P < 0.001). Grazing rye rather than allowing it to accumulate as surface residue reduced summer grain yield 23% and reduced standing grain-crop dry matter 26% under NT, but had no effect under CT. In contrast, grazing pearl millet rather than allowing it to accumulate as surface residue increased wheat standing dry matter yield by 25 – 14% (mean – standard deviation among 3 years and two tillage systems). Ungrazed cover crop production was greater under NT than under CT for rye (7.0 versus 6.0 Mg ha -1 ; P = 0.03) and pearl millet (10.2 versus 7.6 Mg ha -1 ; P = 0.01). Calf daily gain was either greater or tended to be greater under NT than under CT on rye (2.27 versus 2.09 kg head -1 d -1 ; P = 0.15) and pearl millet (2.05 versus 1.81 kg head -1 d -1 ; P = 0.05). Total cattle gain per grazing season was either greater or tended to be greater with NT than with CT on rye (350 versus 204 kg ha -1 ; P = 0.01) and pearl millet (324 versus 277 kg ha -1 ; P = 0.15). Net return over variable costs was greater with grazing than without grazing of cover crops (US

Simulating the influence of stocking rate, sward height and density on steer productivity and grazing behavior

302 versus - US

Water infiltration and surface-soil structural properties as influenced by animal traffic in the Southern Piedmont USA

63 ha -1 ; P < 0.001). Livestock grazing of cover crops had variable effects on subsequent crop production, but increased economic return and diversity overall. Therefore, an integrated crop‐livestock production system with conservation tillage is recommended as a viable option for producers to diversify farming operations to avoid risk, improve ecological production of crops, and potentially avoid environmental damage from soil erosion and nutrient loss.

Stocker performance and production in mixed tall fescue-bermudagrass pastures of the Southern Piedmont USA

Abstract A simulation model was written to study how sward characteristics affect steer performance and the grazing behavior of steers. This model, called INTERFACE, simulates grazing behaviour as affected by both horizontal and vertical distribution of forage quality throughout simulated swards. Simulated steers grazed small, rectangular pastures containing a tall fescue monoculture. Horizontally, the pasture was divided into 12 equally-sized sites with the water and mineral source both located in one site. Steers randomly selected a site for grazing. Vertically, the sward was divided into five layers, each of which varied in quality, i.e. proportion of cell wall, nitrogen, minerals or lignin. Results of trial simulations indicated that steers spent more time grazing sites near the water source and progressively less as distance from the water source increased. Grazing time increased as the sward became shorter and more inferior in quality. Although this model simulates diet selection simply as a random process, grazing time comparisons with actual grazing data suggest that this assumption may be adequate. This model can be used to test hypotheses about grazing behavior as influenced by forage quality and sward height.

Bermudagrass Management in the Southern Piedmont U.S. IV. Soil Surface Nitrogen Pools

Surface-soil structural condition in perennial pastures is expected to be modified by how forage is (a) harvested through haying or grazing and (b) stimulated through source of nutrients applied, as well as by compactive forces, e.g., grazing cattle or hay harvest machinery. Changes in surface-soil condition can affect hydrologic processes that have important implications for plant growth, greenhouse gas emissions and off-site water quality. We determined the effects of harvest management and nutrient source on the rate of ponded water infiltration and penetration resistance in a bermudagrass [Cynodon dactylon (L.) Pers.]/tall fescue (Lolium arundinaceum Schreb. S.J. Darbyshire) pasture on a Typic Kanhapludult in Georgia. During a period when soil was wet (61% water-filled pore space), the rate of water infiltration was 2.8 – 1.5 times greater when forage was left unharvested as when hayed or grazed (mean – standard deviation among nine nutrient sourcerharvest management comparisons). During a subsequent period, when soil was dry (28% water-filled pore space), the rate of water infiltration followed the same treatment pattern, but was not statistically different among harvestmanagement practices (1.5 – 0.4 times greater between unharvested and other systems). Penetration resistance of the surface at 10 cm depth followed the order: unharvested (62 J) < hayed (100 J) < low grazing pressure (119 J) < high grazing pressure (137 J). Water infiltration during the wet period was negatively related (PO0.01) to soil-water content (r =- 0.57), penetration resistance at 0‐10 cm depth (r =- 0.50) and bulk density at 3‐6 cm depth (r =- 0.53), but was positively related to surface residue C (r = 0.47) and soil organic C concentration at 12‐20 cm depth (r = 0.42). These results suggest that complex soil physical (i.e., aggregation, penetration resistance and infiltration) and biological (i.e., plant growth, surface residues and soil organic matter) interactions occur in pastures. We conclude that well-managed grazing systems with excellent ground cover should have adequate hydrologic condition to promote pasture productivity and limit environmental contamination from runoff. Further work is needed to understand the linkages between field- and watershed-scale hydrology in perennial pastures and their implications on water quality.

Adapting the SPUR animal submodel for use on fescue pastures by including rumen and heat stress logic

Stocker performance and production from mixed cool- and warm-season perennial pastures are important determinants of agricultural sustainability that can be influenced by management. We evaluated the factorial combination of three sources of nutrient application (inorganic only, organic+inorganic combination, and organic only) and two forage utilization regimes [low grazing pressure (LGP) and high grazing pressure (HGP)] on steer stocking density and rate, performance and production during 7 years of pasture management {tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] overseeded into existing Coastal bermudagrass [Cynodon dactylon(L.) Pers.] sod} on a Typic Kanhapludult in Georgia, USA. Nutrient source had few major impacts on responses, except for lower animal performance with organic fertilization (broiler litter) than with organic+inorganic and inorganic only fertilization, especially with LGP. Seasonal changesin stockingweightand rateoccurred,notonlyas expected dueto environmental conditions and dominant forage species present, but that also counteracted expected differences imposed by grazing pressure; signaling negative feedback of HGP on forage productivity. Steer performance was greatest in spring and summer under both grazing pressures, but wassignificantly reducedwithincreasinggrazingpressureinthe autumnandwinterduetolowforageavailability.Across years, steer gainha �1 (863kgha �1 ) was not different between grazing pressures, but gainha �1 declined with time under HGP and was stable with time under LGP. Reducing grazing pressure to a moderate level can lead to equivalent steer production as HGP, and would likely contribute to a more sustainable balance among production, socio-economic and environmental goals. These multi-year results will help cattle producers in warm, moist climates design and implement more sustainable grazing systems.

Early Response of Soil Organic Fractions to Tillage and Integrated Crop-Livestock Production

The fate of nitrogen (N) applied in forage-based agricultural systems is important for understanding the long-term production and environmental impacts of a particular management strategy. We evaluated the factorial combination of three types of N fertilization (inorganic, crimson clover [Trifolium incarnatum L.] cover crop plus inorganic, and chicken [Gallus gallus] broiler litter pressure and four types of harvest strategy (unharvested forage, low and high cattle [Bos Taurus] grazing pressure, and monthly haying in summer) on surface residue and soil N pools during the first 5 years of ‘Coastal’ bermudagrass (Cynodon dactylon [L.] Pers.) management. The type of N fertilization used resulted in small changes in soil N pools, except at a depth of 0 to 2 cm, where total soil N was sequestered at a rate 0.2 g ‧ kg‧ year1 greater with inorganic fertilization than with other fertilization strategies. We could account for more of the applied N under grazed systems (76–82%) than under ungrazed systems (35–71%). As a percentage of applied N, 32 and 48% were sequestered as total soil N at a depth of 0 to 6 cm when averaged across fertilization strategies under low and high grazing pressures, respectively, which was equivalent to 6.8 and 10.3 g ‧ m ‧ year. Sequestration rates of total soil N under the unharvested-forage and haying strategies were negligible. Most of the increase in total soil N was at a depth of 0 to 2 cm and was due to changes in the particulate organic N (PON) pool. The greater cycling of applied N into the soil organic N pool with grazed compared with ungrazed systems suggests an increase in the long-term fertility of soil.