1. Plant Soil Science Dep.Texas Tech Univ. Box 42122 Lubbock TX 79409 USA
2. Current address, Sustainable Water Management Research UnitUSDA‐ARS 4006 Old Leland Rd. Leland MS 38776 USA
3. Natural Resources Management Dep.Texas Tech Univ. Box 42125 Lubbock TX 79409 USA
4. Animal Food Science Dep.Texas Tech Univ. Box 42141 Lubbock TX 79409 USA