C. P. West

Soil Quality Differences Under Native Tallgrass Prairie Across a Climosequence in Arkansas

Abstract Climate, specifically moisture and temperature, influences plant growth and nutrient cycling; thus, climate also influences prairie development. Relatively little research has been conducted in the ecological transition zone between the Great Plains and the more humid forests. Since moisture and temperature affect many ecosystem processes, the wetter climate of the southern forest region should influence soil biogeochemical cycling quite differently from that in grassland soils. The objective of this study was to evaluate soil quality and the relationships between selected soil properties across a climosequence in a transition zone between tallgrass prairie in humid-temperate (Ozark Highlands) and humid-subtropical (Grand Prairie) climate regimes in Arkansas. Soil physical, chemical and biological properties of the upper 10 cm differed significantly between physiographic regions. Linear relationships between total soil nitrogen (N) and carbon (C), extractable phosphorus and manganese, electrical conductivity and soil organic matter concentration differed significantly between physiographic regions. Total soil N and C decreased with increasing soil bulk density in both physiographic regions. The relationship between total C and bulk density differed by physiographic region, while the relationship between total N and bulk density did not. Soil organic matter concentration, C:N ratio, and many extractable nutrients, were higher and relationships between selected soil properties differed under native tallgrass prairie in a relatively warm and wet climate than that in a relatively cooler and drier climate. The results of this study suggest that prairie preservation, restoration and management practices should differ depending on climate regimes.

Performance by spring and fall-calving cows grazing with full, limited, or no access to toxic Neotyphodium coenophialum-infected tall fescue1

Replacing toxic, wild-type Neotyphodium coenophialum-infected tall fescue (E+) with nontoxic, N. coenophialum-infected tall fescue (NE+) has improved cow performance, but producer acceptance of NE+ has been slow. The objective was to compare performance by spring- and fall-calving cows grazing either E+ or NE+ at different percentages of the total pasture area. Gelbvieh×Angus crossbred cows (n=178) were stratified by BW and age within calving season and allocated randomly to 1 of 14 groups representing 5 treatments for a 3-yr study: i) Fall-calving on 100% E+ (F100); ii) Spring-calving on 100% E+ (S100); iii) Fall-calving on 75% E+ and 25% NE+ (F75); iv) Spring-calving on 75% E+ and 25% NE+ (S75); and v) Spring-calving on 100% NE+ (SNE100). Groups allocated to F75 and S75 grazed E+ until approximately 28 d before breeding and weaning, then were then moved to their respective NE+ pasture area for 4 to 6 wk; those allocated to F100, S100, and SNE100 grazed their pastures throughout the entire year. Samples of tall fescue were gathered from specific cells within each pasture at the time cows were moved into that particular cell (∼1 sample/mo). Blood samples were collected from the cows at the start and end of the breeding season. Stocking rate for each treatment was 1 cow/ha. Forage IVDMD, CP, and total ergot alkaloid concentrations were affected (P<0.05) by the treatment×sampling date interaction. Hay offered, cow BW, and BCS at breeding, end of breeding, and at weaning were greater (P<0.05) from fall-calving vs. spring-calving. Cow BW at weaning was greater (P<0.05) from F75 and S75 vs. F100 and S100. The calving season×NE+ % interaction affected (P<0.05) calving rates. Preweaning calf BW gain, actual and adjusted weaning BW, ADG, sale price, and calf value at weaning were greater (P<0.05) from fall-calving vs. spring-calving and from SNE100 vs. S75 except for sale price which was greater (P<0.05) from S75 vs. SNE100. Cow concentrations of serum prolactin at breeding and serum NEFA at the end of breeding were affected (P<0.05) by the calving season×NE+ % interaction. Serum Zn and Cu concentrations from cows were affected (P<0.05) by calving season. A fall-calving season may be more desirable for cows grazing E+, resulting in greater calving rates, cow performance, and calf BW at weaning, whereas limited access to NE+ may increase calving rates, serum prolactin, and NEFA concentrations during certain times in the production cycle, particularly in spring-calving cows.

Five-year change in soil profile chemical properties as affected by broiler litter application rate.

The broiler (Gallus gallus domesticus) industry generates large quantities of nutrient- and trace metal-enriched litter. Broiler litter (BL) is typically land applied as a nutrient source for forages. Continual annual BL applications can increase nutrient and trace metal concentrations in soil over time, creating the potential for negative environmental impacts. The objective of this study was to determine the long-term effects of BL application rate on soil profile chemical properties in a Captina silt loam (fine-silty, siliceous, active, mesic, Typic Fragiudult) with a history of BL applications. Broiler litter was applied annually at 0, 5.6, and 11.2 Mg of dry weight-based litter ha−1 during a 5-year period. Soil was sampled in 10-cm increments to 90 cm and characterized for pH, electrical conductivity, organic matter, dissolved organic C, P saturation, and acid-recoverable (P, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, Al, As, Cd, Cr, and Se), Mehlich-3-extractable (P, K, Ca, Mg, Na, Fe, Mn, Zn, and Cu), and water-soluble (P, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, Al, As, Cd, Cr, and Se) soil nutrient and trace metals. Soil nutrient and trace metal contents generally increased with continued BL application for 5 years in the Mehlich-3-extractable and water-soluble pools. Soil properties affected by litter treatment generally increased over time in the top 20 cm as litter rate increased. It seems that continued annual application of BL to soil with a history of BL application will continue to accumulate Mehlich-3-extractable and water-soluble soil nutrient and trace metals near the soil surface. A decrease in soil nutrient and trace metal contents when BL applications ceased generally did not occur. Therefore, it seems that decreases in most soil chemical property magnitudes caused by the cessation of BL applications will require more than 5 years and could continue to pose potential negative environmental consequences.

Policosanol, α-tocopherol, and moisture content as a function of timing of harvest of switchgrass (Panicum virgatum L.).

Using switchgrass ( Panicum virgatum L.) as a cellulosic feedstock for the production of ethanol could lead to the extraction of co-products prior to the pretreatment step, thereby adding value to the ethanol conversion process. Policosanols, registered as 142583-61-7, are present in Poaceae and are a mixture of long-chained primary alcohols. Policosanols are composed mainly of docosanol (C(22)), tetracosanol (C(24)), hexacosanol (C(26)), octacosanol (C(28)), triacontanol (C(30)), and dotriacontanol (C(32)). This study determined changes in moisture, policosanol, and alpha-tocopherol concentrations of Cave-in-Rock and Blackwell switchgrass cultivars during maturation from July to December in Arkansas and Oklahoma. Moisture content on a dry weight basis declined from 150 to 50% with progressive harvests. The total policosanol concentration ranged between 89 mg/kg for July harvested Cave-in-Rock switchgrass from Arkansas and 182 mg/kg for August harvested Cave-in-Rock switchgrass for Oklahoma, and these values remained relatively constant throughout the season. This is the first report on the presence of policosanols in switchgrass. Total switchgrass policosanol concentrations were lower than those typically reported for sorghum grains; however, switchgrass-extracted policosanols contained different policosanol ratios, wherein C(30) and C(32) alcohol ranges were 36-41 and 43-50%, respectively. alpha-Tocopherol extracted from both switchgrass cultivars varied between 320 and 400 mg/kg but decreased in the October harvest after frost.

Endophyte Effects on Growth and Water Relations of Tall Fescue

The endophyte Neotyphodium coenophialum enhances drought survival of its host tall fescue (Festuca arundinacea Schreb.) in field populations. Detailed studies on growth and water relations are needed during the onset of drought stress to identify mechanisms associated with drought survival. We conducted field studies of the growth, water relations and carbohydrate profiles of 3 tall fescue associations with (E+) and without (E−) their native endophytes to identify physiological traits associated with endophyte-enhanced drought tolerance.

Economic and Greenhouse Gas Emission Response to Pasture Species Composition, Stocking Rate, and Weaning Age by Calving Season, Farm Size, and Pasture Fertility

Since cow-calf operations are large contributors of agricultural greenhouse gas (GHG) emissions in North America, consequences of pasture species composition, weaning age, and stocking rate decisions were examined by operation size, calving season, and pasture fertility. Fixed resource use and seasonal prices affected the mix of forage and beef production. Overall, adding fertilizer to pasture was unprofitable, resulting in increased stocking rates and greater emissions. Calving season and attendant breeding failure rates influenced the relative profitability of the analyzed beef-production strategies, which in turn affected farm GHG emissions. More-efficient practices led to greater amounts of beef sold per bred cow.