Project Number: 6619-13210-001-00
Project Type: Appropriated

Start Date: Sep 18, 2002
End Date: Sep 17, 2007

Objective:
Objective 1: Develop grass and legume resources with improved productivity and nutritive value for the subtropical United States [evaluate Paspalum for frost tolerance, persistence, photoperiod sensitivity, and nutritive value; determine the impact of lignin bonds in tropical grasses (Paspalum and Cynodon) on forage quality; introduce and evaluate new lines of perennial Arachis for forage and conservation uses; and develop new tropical legume germplasm (Lotononis and Leucaena) for use in the subtropics.] Objective 2: Assess the impact of spatial and temporal distribution of grazing cattle on soil nutrients and water quality in the subtropical United States [quantify the roles of edaphic characteristics and varying levels of grazing intensity in regulating belowground nitrogen cycling processes, phosphorus availability, and carbon dynamics of grass-legume mixtures as a basis for improving pasture productivity in the subtropics; assess changes in soil and water quality around and beneath cattle congregation sites; and assess spatial and temporal nutrient dynamics, nutrient loadings, and plant uptake in grazed pastures and surrounding landscapes in subtropical beef cattle agro-ecosystems.] Objective 3: Enhance the economic and environmental sustainability of grazing systems in the subtropical United States [determine the impact of functional groups (grass, legume, forbs, and browse) on total and seasonal nutrient availability of pastures in the subtropics; and determine the effect of stocking rate and grazing behavior on spatial utilization of grazed ecosystems by beef cattle in the subtropics.]

Approach:
Objective 1: Four populations of P. notatum will be screened for insensitivity to extended light (14 hr) vs. natural daylength at 31o Lat. and nutritive value (digestibility and crude protein) using both conventional and NIRS. Bahiagrass and bermudagrass selections with a range of IVOMD will be planted in 2002, staged in the spring and summer of 2003-2004, and young leaves from the top of the plants will be sampled for lignin bonds after 30 days of regrowth. Germplasm will be collected from Paraguay in 2002 as outlined in the 2002 Plant Exploration Proposal, "Plant Exploration in Paraguay to Collect Arachis Germplasm for Forage Crop Improvement." All germplasm will be deposited at the National Plant Germplasm System (NPGS) and will be increased until sufficient material exists for replicated field plantings in 2004. In 2002, seedlings (n=200-500) of F2 Lotononis bainesii seed will be evaluated for physiological, morphological, and agronomic characteristics. In 2002, accessions of Leucaena leucocephala (n=10-15) will be transplanted at Brooksville and Ona, and survival, DM yield, flowering time, and seed production will be determined. Objective 2: Using bahiagrass as link for all locations, N, P and C dynamics of pasture at Brooksville, Ona, Gainesville, and Marianna will be determined. Composite soil samples (0-10 cm and 10-20 cm) and soil cores (up to 80 cm depths with 20 cm increments) will be taken from each pasture from July 2002 to January 2006. Baseline soil samples and water samples at congregations sites in established subtropical beef cattle pastures will be collected from July 2002 through January 2005. Soil samples will be collected at two depths (0-15 cm and 15-30 cm) at different locations around the congregation sites following a radial (every 45 degrees, n = 8 transects) sampling scheme at 10, 20, 40, 80, and 160 m from the approximate center of the sites. Soil bulk density, soil compaction, volumetric soil moisture content, soil chemical properties (pH, total C, total N, NOx, NH4, total P, soluble P, Na, K, Ca, Mg, Al, and Fe) will be determined for each location. Permanent transects (approx. 500 m) will be established in pastures to assess the temporal and spatial nutrient dynamics in beef cattle pastures and surrounding landscapes. Soil samples (0-30 cm in 15-cm increments) will be collected seasonally (July and January) every 10 m along the transects to establish pool sizes and storage of soil total C, total N, and total P to account for the temporal changes of nutrient dynamics in the landscapes. Objective 3: Plant species surveys of grazinglands will be conducted in Florida to construct a database of pasture plant diversity in the eastern United States. As part of an ongoing USDA-NRI Grant, "Agro-Ecosystem Indicators of Sustainability as Affected by Cattle Density in Ranch Management Systems," four cows in each pasture (n=3) per replicate (n=2) will be fitted with GPS collars. To determine diet selection and quality, in February, May, July, and October 2001-2003, four cows per pasture will be dosed with a bolus containing C32 and C36 alkanes.

Project Team

Williams, Mary - Mimi Coleman, Samuel - Sam Sigua, Gilbert

Project Annual Reports

FY 2003

Related National Programs

Food Animal Production (101)   Rangeland, Pasture, and Forages (205)

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