Herbicide Treatment and Vegetation Response to Treatment of Mesquites in Southern New Mexico

Abstract

Mesquite (Prosopk juliifrora) is a major unwanted plant in the Southwest This study evaluated the herbage responses obtained from various aerial applications of 2,4,5-T on mesquites in southem New Mexico. The dead plants on the various areas ranged from 7-64% of the mesquite. Yields of perennial grasses ranged from 3-1931 kg/ha on the untreated controls and 11-2696 kg/ha on the areas sprayed with 2,4,5-T. In dense stands of mesquite, about 30% of the mesquites must be kIIled before grass yields are significantly increased. There are an estimated 38 million ha of land infested with mesquite [Prosopis julifroru (Swartz) DC.] in the United States (Platt 1959). An estimated 4 million ha occur in New Mexico (Sampson and Schultz 1956). Although mesquite is an indigenous plant, it has invaded large areas and has become dominant on some of these in the last 100 years (Norris 1950, Wright 1960, Paulsen and Ares 1962, Buffington and Herbel 1965, York and DickPeddie 1969). The invasion and increase of mesquites have resulted in a decrease in cover and production of the perennial grass plants that once dominated these areas. As mesquites become established, an area devoid of herbaceous vegetation develops around the maturing mesquite plants. As the herbaceous cover is depleted wind erosion becomes more severe, particularly on sandy rangelands of the Southwest. Eventually, the “A” horizon and part of the “B” horizon is deposited around the mesquite or removed from the area entirely, resulting in a further decrease of the desirable perennial herbaceous plants and a build-up of sand dunes. Because of the competition for soil water by mesquite, few herbaceous plants become established on the eroded soils unless the mesquite is controlled. associations, the Upton-Simona association (shallower soils) and the Kermit-Maljamar-Berino association (Maker et al. 1970). The soils of the Jomada site are in the Simona-Harrisburg association (Bulloch and Neher 1980). These soils have a sandy surface that are quite susceptible to wind erosion. The surface relief is undulating or duned. The vegetation on the deeper sands in southeastern New Mexico is dominantly tall and mid-grasses, mesquite, sand shinnery oak [Quercus havurdi Rydb.)] and sand sagebrush [ArtemisiuJilifolia (Torr.)]. The more shallow soils support short and mid-grasses, mesquite, broom snakeweed [Xunthocephulum surothe (Pursh) Shinners] and some creosotebush [Lurreu tridentutu (DC.) Cov.]. The average annual precipitation varies from 258 mm at the Ochoa Weather Station in the southeast portion of the study area to 3 13 mm at Roswell. The study site on the Jornada Experimental Range is dominated by mesquite, broom snakeweed, and short and mid-grasses. The average precipitation is 225 mm.