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Improved forage management impacts on soil organic C and S depth distribution and surface residue accumulation could be large, but detailed temporal data are not available. We evaluated the factorial combination of three levels of N fertilization [inorganic, crimson clover (Trifolium incarnatum L.) cover crop plus inorganic, and broiler litter] and four levels of harvest strategy (unharvested, low grazing pressure, high grazing pressure, and hayed monthly) on soil bulk density, soil organic C, and total S, and surface residue C and S during the first 5 yr of `Coastal' bermudagrass [Cynodon dactylon (L.) Pers.] management. Soil bulk density of the 0- to 6-cm depth responded very little to management, but across treatments it decreased 0.06 Mg [m.sup.-3] [yr.sup.-1] due to increasing soil organic matter with time. Soil organic C did not respond significantly to fertilization strategy during the 5 yr, but total S of the 0- to 6-cm depth was greater under broiler litter than under other fertilization strategies at the end of 3, 4, and 5 yr. Low and high grazing pressure were similar in their effect on soil organic C accumulation, averaging 140 g [m.sup.-2] [yr.sup.-1]. Most of the net change in soil organic C occurred in the 0- to 2-cm depth. Soil under unharvested and hayed management accumulated organic C at rates less than one-half of those observed under cattle grazing. Cattle grazing shunted C more directly from forage to the soil, which contributed to greater sequestration of soil organic C than with haying or unharvested management.

Ergot alkaloids cause fescue toxicosis when livestock graze endophyte-infected tall fescue. It is generally accepted that ergovaline is the toxic component of endophyte-infected tall fescue, but there is no direct evidence to support this hypothesis. The objective of this study was to examine relative and potential transport of ergoline and ergopeptine alkaloids across isolated gastric tissues in vitro. Sheep ruminal and omasal tissues were surgically removed and placed in parabiotic chambers. Equimolar concentrations of lysergic acid, lysergol, ergonovine, ergotamine, and ergocryptine were added to a Kreb's Ringer phosphate (KRP) solution on the mucosal side of the tissue. Tissue was incubated in near-physiological conditions for 240 min. Samples were taken from KRP on the serosal side of the chambers at times 0, 30, 60, 120, 180, and 240 min and analyzed for ergot alkaloids by competitive ELISA. The serosal KRP remaining after incubation was freeze-dried and the alkaloid species quantified by HPLC. The area of ruminal and omasal tissues was measured and the potential transportable alkaloids calculated by multiplying the moles of transported alkaloids per square centimeter of each tissue type by the surface area of the tissue. Studies were conducted to compare alkaloid transport in reticular, ruminal, and omasal tissues and to determine whether transport was active or passive. Ruminal tissue had greater ergot alkaloid transport potential than omasal tissue (85 vs 60 mmol) because of a larger surface area. The ruminal posterior dorsal sac had the greatest potential for alkaloid transport, but the other ruminal tissues were not different from one another. Alkaloid transport was less among reticular tissues than among ruminal tissues. Transport of alkaloids seemed to be an active process. The alkaloids with greatest transport potential were lysergic acid and lysergol. Ergopeptine alkaloids tended to pass across omasal tissues in greater quantities than across ruminal tissues, but their transport was minimal compared to lysergic acid and lysergol. Key Words: Ergot Alkaloids, Festuca, Rumen Mucosa, Toxicity

Soil aggregation is important for maintaining soil surface integrity and allowing water to infiltrate, rather than runoff and cause erosion. The effect of grazing animals on soil aggregation compared with other conservation management strategies in the Southern Piedmont USA is not well known. We tested a hypothesis that grazing animals might negatively affect soil aggregation characteristics. Water-stable macroaggregates ([is greater than] 0.25 mm), mean-weight diameter, and their stabilities were (i) similar between conservation-tillage cropping and tall fescue (Festuca arundinacea Schreb.)-common bermudagrass (Cynodon dactylon L.) pasture; (ii) similar between 15- to 19-yr-old grazed and hayed hybrid bermudagrass; (iii) 7 to 14% greater in 30-yr-old than in 10-yr-old grazed tall fescue and hybrid bermudagrass pastures; (iv) similar among long-term grazingland, hayland, and forestland; and (v) 5 to 11% lower under cattle grazing than under monthly haying or unharvested management during the first 4 yr following conversion of cultivated cropland to pastureland. Water-stable aggregate distribution at a depth of 0 to 50 mm was 0.30 [+ or -] 0.07 g [g.sup.-1] in the 1.0- to 4.75-mm class, 0.46 [+ or -] 0.07 g [g.sup.-1] in the 0.25- to 1.0-mm class, 0.15 [+ or -] 0.02 g [g.sup.-1] in the 0.05- to 0.25-mm class, and 0.07 [+ or -] 0.01 g [g.sup.-1] in the [is less than] 0.05-mm class, averaged across management systems and replications (n = 56). Total glomalin of the 1.0- to 4.75-mm dry-stable aggregate class was highly related to whole soil organic C content, but neither of these properties was particularly well related with water-stable macroaggregation, mean-weight diameter, or their stabilities. We conclude, overall, that grazing of pastures in the Southern Piedmont USA has little detrimental effect on soil aggregate distribution and stability and is comparable in soil conservation with other land conservation strategies.

Cattle (Bos taurus) behavior may be an important variable controlling the spatial distribution of soil C and N pools in long-term, grazed pastures. Shade and water sources are more frequented areas of a pasture that can also serve as camping areas where excreta are deposited. We sampled a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludult) under tall fescue (Festuca arundinacea Schreb.) at distances of 1, 10, 30, 50, and 80 m from permanent shade or water sources at the end of 8 and 15 yr of grazing. To a depth of 75 mm, soil bulk density was 1.15 Mg [m.sup.-3] at 1 m and averaged 1.00 Mg [m.sup.-3] at other distances from shade or water. To a depth of 300 mm, soil organic C was 4.6 kg [m.sup.-2] at 1 m, 4.3 kg [m.sup.-2] at 10 m, and [approximately equals] 4.0 kg [m.sup.-2] at distances of 30, 50, and 80 m from shade or water. Particulate organic C averaged 1.53 kg [m.sup.-2] at distances of 1, 10, and 30 m and 1.30 kg [m.sup.-2] at distances of 50 and 80 m from shade or water. Soil microbial biomass C, basal soil respiration, and net potential N mineralization were also greater nearer shade or water than farther away. Although lateral distribution effects were most dramatic at a depth of 0 to 25 mm, similar effects were observed even at a depth of 150 to 300 mm. Long-term cattle grazing in relatively small paddocks (0.7-0.8 ha) with permanent shade and water sources resulted in significant lateral and vertical changes in soil organic C and N pools.

Tall fescue (Festuca arundinacea Schreb.) is an important cool-season perennial forage for cattle production in the humid regions of the USA and throughout the world. While endophyte (Neotyphodium coenophialum Glenn, Bacon, & Hanlin) infection of tall fescue has many benefits, it also results in accumulation of toxic alkaloids in leaf tissue known to cause animal health disorders when ingested. We hypothesized that pastures containing these alkaloids may alter soil organic matter dynamics. A set of three grazed field experiments representing low (0-29%) and high (65-94%) endophyte infection of tall fescue was evaluated at the end of either 8 or 15 yr. Soil samples from 12 paddocks (0.7-0.8 ha) were collected at depths of 0 to 25, 25 to 75, 75 to 150, and 150 to 300 mm. Soil under tall fescue with high endophyte infection had 13 [+ or -] 8% greater concentrations of soil organic C and N and particulate organic N to a depth of 150 mm than with low endophyte infection. However, with high endophyte infection, microbial biomass and basal soil respiration per unit of soil organic C or particulate organic C were 86 [+ or -] 5% of those with low endophyte infection. Only small differences in soil microbial community structure, estimated via fatty acid methyl ester profiles, were observed between soils under rescue with 0 and 100% endophyte infection. Endophyte infection of tall fescue may perform an important ecological function, allowing more soil organic C and N to accumulate, perhaps because of reduced soil microbial activity on plant residues containing endophyte byproducts.

Naturalized populations, or ecotypes, of white clover (Trifolium repens L.) are found in many southeastern U.S. pastures, often persisting despite adverse environmental and cultural conditions. Our objective was to compare the growth, morphology, and vegetative persistence of white clover ecotypes (small- to medium-leaf) with selected cultivars (large-leaf) and improved germplasm under grazing in four southeastern states. Seed or stolons of white clover ecotypes were collected primarily from grazed pastures in spring 1994 in Louisiana, Mississippi, Alabama, and Georgia, and increased by intercrossing. Plots of seven ecotype collections, `Osceola', `Regal', `Louisiana S-I', `Grasslands Huia', `Grasslands Prestige', Brown Loam Synthetic No. 2 germplasm, and Southern Regional Virus Resistant germplasm were established in October 1995 in each state. Plots were stocked continuously with cattle (Bos taurus) (5-cm stubble) from January 1996 to January 1998. Stolon length and axillary bud viability, and number of stolon apices, rooted nodes, and seedlings were measured every 3 mo. Stolon length of the ecotypes usually exceeded that of the cultivars and germplasm at all locations, particularly in the winter and spring. By the end of the experiment, the ecotypes also exhibited greater stolon branching than the cultivars and germplasm (1580 vs. 320 branches [m.sup.-2]). Superior vegetative growth of the ecotypes was attributed to a greater proportion of the stolon nodes being both branched and rooted, particularly during the summer. White clover ecotypes represent a valuable source of germplasm to incorporate into breeding programs or to develop directly into more persistent cultivars., WHITE CLOVER is a vital component of permanent pasture systems in New Zealand and Great Britain, contributing to greater animal performance and reduced reliance on N fertilizer. In both these [...]

A reliable, efficient, and accurate detection method for presence of the endophytic fungus Neotyphodium coenophialum (Morgan-Jones and Gains) Glenn, Bacon, and Hanlin comb. nov. in tall fescue (Festuca arundinacea Schreb.) seed and plant tissue would be beneficial for tall fescue breeding and seed lot analysis. This experiment was conducted to determine the accuracy, reliability, and reproducibility of the Phytoscreen Neotyphodium immunoblot detection kit (Agrinostics Ltd. Co., Watkinsville, GA). Tissue immunoblot was compared with histological staining followed by microscopic analysis on tall rescue tillers from a greenhouse grow-out test, field grown spaced plants, established field paddocks, and different tall fescue seed lots. Endophyte-infected and endophyte-free tall fescue populations were evaluated by both methods. Results obtained by both methods were similar regardless of the infection level of the population, type of tissue assayed, or the technician that conducted the assay. The immunoblot detection kit was accurate and reliable and readily accommodated large numbers of samples., The presence of ergot alkaloid-producing endophyte (N. coenophialum) in tall fescue may be viewed as a positive or negative attribute, depending upon whether the fescue is used for turf or [...]