Roger Wittie

Goat weight gains, forage selectivity and forage quality dynamics in three cultivated warm season pastures in north-central Texas

Cultivated warm-season pastures are needed to compliment range-based goat production in south central USA. Boer×Spanish does averaging 25 kg were evaluated to determine average daily gain (ADG) and selectivity for six legumes, redroot pigweed, and crabgrass grown in full-sun grass-only, full-sun mixed, and pecan grove shaded mixed paddocks during two warm seasons. Goats in the mixed pasture obtained the highest (100 g per day) and the grass-only pasture goats the lowest ADG (27 g per day) during the low rainfall year (year×pasture interaction P=0.05). The animals in both the shaded mixed and grass-only paddocks had greater ADG whereas mixed pasture animals were unchanged the second, higher rainfall year, indicating that there was competition for moisture between the herbaceous forages and the pecan trees when rainfall was low and that crabgrass monocultures require more soil moisture to maintain animal gains. Grass percentage composition increased over time for all treatments in both years. Legume percentage composition decreased over time for both mixed pasture treatments in both years, indicating goat selection for this component. Forbs tended to survive longer in mixed pasture than in the shaded mixed pasture while the grass component tended to increase in both paddocks with time. Herbage analyses indicated that crude protein (CP) tended to decrease over time while acid detergent fiber (ADF) and lignin increased, at least partially due to animal selection.

Efficacy of Soil Extracting Solutions for Assessing Potential Phosphorus Loss from a Dairy Waste Application Field Soil in North Central Texas

Elevated phosphorus (P) from manure application field (MAF) soils transported to surface waters is a concern throughout the world because of Ps role in eutrophication. Our goal was to determine why the common labile extractants alkaline-buffered sodium bicarbonate (Olsen), ammonium bicarbonate–diethylenetriaminepentaacetic acid (DTPA), and dilute acid–fluoride (Mehlich III) produce different values given the same soil sample. Ten sites within a dairy MAF were sampled by genetic horizons from fine, mixed, Thermic, Udic Paleustalf (Windthorst) map units. In addition to determining plant labile P, soluble and total P were determined. All P pools decreased with depth, but concentrations between the labile P were variable. Mehlich III extracted more plant labile P at neutral and slightly alkaline pH values. Mehlich III also dissolved more carbonates. The fraction of labile P that Mehlich III extracts in excess of Olsen and DTPA warrants further characterization of carbonate associated P to assess its role in plant nutrition and environmental quality regulation.

Vegetative Covers to Control Sediment and Phosphorus (P) in Runoff from Dairy Waste Application Fields

Excessive Phosphorus (P) in runoff contributes to eutrophication of fresh water bodies. Studies have shown that manure and effluent from animal feeding operations (AFOs) applied to waste application fields (WAFs) have contributed to excess P in segments of the North Bosque River in east central Texas. There is a growing need for environmentally sound, economically viable, and easy to establish best management practices (BMPs) to control such pollution. Vegetative buffer strips offer a potential solution for reducing runoff P from WAF by extracting it from soil and by reducing sediment P delivery to streams by decreasing runoff and soil erosion. In a field study, eight plots (5m × 5m), were assigned to four replicated treatments namely control (bare, plant cover) cool season grass, warm season forb, warm season grass, and warm season legume to assess their efficacy of runoff sediment control and P sequestration potential from soil. These plots were established on a coastal Bermuda grass WAF that received dairy lagoon effluent. A runoff collection system; a 1m × 1m sub-plot with a runoff conveyance and collection apparatus, was established on the upstream and downstream margins of each plot. Natural rainfall runoff samples were collected and analyzed for total P, soluble P, and total suspended solids (TSS). Additionally, the total mass of runoff collected from each sub-plot was estimated. Results show that the warm season forb (perennial sunflower), and warm season grass (switchgrass) were the most effective treatments for reduction of runoff P, followed by coastal Bermuda, and cool season grass.