Productivity and survival of defoliated wheatgrasses in the rolling plains of Texas
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In the Texas Rolling Plains, cool-season perennial grasses may complement limited forage availability in March-May and October-December. In two experiments conducted at Vernon, TX, on a sandy loam soil (fine-loamy, mixed, thermic Udic Paleustalfs), we evaluated productivity and persistence of crested [Agropyron cristatum (L.) Gaertn. x A. desertorum (Fisch. ex Link) J.A. Schultes], hybrid [Elytrigia repens (L.) Nevski x Pseudoroegneria spicata (Pursh) L've], intermediate [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey], pubescent [T. intermedium ssp. barbulatum (Schur) Barkw. & D.R. Dewey], and tall wheatgrass [T. ponticum (Podp.) Barkworth & D.R. Dewey] under combinations of 3- or 6-wk defoliation frequency at 7.5- or 15-cm. About 64% more herbage yield was harvested from all species at the 7.5- vs. 15-cm defoliation height in the first, but only from crested, hybrid, and pubescent wheatgrass in the second growing season. Frequent defoliation increased herbage by 22% in Experiment A or 37% in Experiment B only in the first growing season. Tiller survival increased with frequent defoliation in intermediate wheatgrass by 33% in Experiment A and up to 70% in Experiment B, but decreased by 52% in hybrid and by 33% in pubescent wheatgrass in Experiment A, and up to 50% in Experiment B. Lower nighttime soil temperatures increased tiller survival during summer in swards defoliated at the 7.5- vs. 15-cm height. Wheatgrass productivity increased under intensive or frequent defoliation in the first, but declined in several species in the subsequent growing season, making their potential to complement forage base limited.
