Managing Intermountain Rangelands

This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. TREATMENT OF INLAND SALTGRASS AND GREASEWOOD SITES TO IMPROVE FORAGE PRODUCTION Bruce A. Roundy, Greg J. Cluff, James A. Young, and R. A. Evans ABSTRACT: Greasewood and saltgrass sites that Greasewood and saltgrass dominated plant once supported basin wildrye can be highly communities generally occur in these lowland productive after chemical brush control and floodplains and basins below the upper and forage restoration by proper management or by higher precipitation sagebrush zone that seeding. Application of 2,4-D in June, once or Billings (1945) considered edaphic climates for 2 consecutive years, effectively controls within the drier shadscale zone. These sites greasewood and salt rabbitbrush. Associated are characterized by low precipitation of 5 to saline soils can be successfully seeded to 10 inches (12 to 25 em) annually, saline and salt-tolerant grasses such as basin wildrye and fine textured soils, a shallow wa~er table and tall wheatgrass by using irrigation or on sites in some areas, seasonal flooding. Plant growth where salinity is low and in years when spring and distribution are affected by total soil precipitation is high. salinity, concentrations of specific ions, and depth of soil salts, soil areation, and depth SITE DESCRIPTION AND POTENTIAL of the watertable and salinity of ground water, total soil water potential as affected by salts The decisions of how to manage or treat a (soil osmotic potential) and water content specific site to increase forage production are (soil matric potential) and the seasonal most dependent upon the site potential and variability of these factors. associated limiting factors to plant establishment and growth. A brief discussion of Great variability in these factors may occur the ecological setting of greasewood and over short distances due to location of beach saltgrass sites will aid in understanding the ridges, drainages, and springs and may result potential of these sites. Basin and range in highly variable plant communities and site faulting began in the Miocene in the Great Basin potentials. In these soils Na, Cl, and so 4 and created many closed basins (Papke 1976). are the major ions (Kelly 1951) and Ca and Mg During the Pleistocene, reoccurring periods of are minor. B concentrations may also be high. cold, moist climatic conditions resulted in the Excessive Na concentrations result in poor creation of two large pluvial lakes, Lake aerations, slow infiltration and slow Lahontan in Nevada and Lake Bonneville in Utah, permeability of these soils (Naphan 1966). and numerous smaller lakes in many different basins (Morrison 1964; Papke 1976). The variable Despite all these limiting factors, range level of these Pleistocene lakes over the years improvements are of interest because these resulted in a series of terraces superimposed on ranges are extensive and convenient to many the alluvial fans of the adjacent mountains (Hunt ranch base properties and because some sites 1967). historically produced tremendous amounts of forage before they were misused. The As the climate became more arid, most of these subsurface and overland drainage water these lakes evaporated completely leaving salts and areas receive may help highest condition basin fine sediments in the lake beds which are now wildrye stands produce up to 7,136 lb/acre known as playas (Papke 1976). Since the lakes (8000 kg/ha) (Lesperance and others 1978) and became more saline as they shrunk, concentric the wettest and most dense saltgrass meadows zones of increasing salinity occur from the upper produce 2,319 lb/acre (2600 kg/ha). More terraces to the valley bottoms (Flowers and Evans commonly, good condition wildrye and saltgrass 1966). Further salinization of these basins and stands could be expected to produce about 892 salinization of other basins and floodplains lb/acre (1000 kg/ha). Winter and fall which never had a pluvial lake has occurred due grazing of standing wildrye would protect this to restricted drainage. As salt-bearing waters grass which is sensitive to spring-grazing, and drain from upland areas, ground water may be save ranchers tons of alfalfa hay. Saltgrass raised to the soil surface of lower lands. is resistant to heavy grazing and its meadows Subsequent evaporation of moisture on the soil stay green into the summer after upland surface results in the accumulation of salts bunchgrasses have gone dormant. which are not leached out due to low precipitation and drainage (Richards 1954). Although greasewood is estimated to cover 12.6 million acres (5.1 million ha) (USDA 1936), the site potential and associated species may vary greatly. Both greasewood and saltgrass occur Bruce A. Roundy, James A. Young and R. A. Evans over wide ranges in soil moisture, salinity and are Range Scientists at the Renewable Resource drainage. The plants they are associated with Center, USDA Agricultural Research Service, Reno, Nev. Greg J. Cluff is a Range Agronomist at the University of Nevada, Reno. Roundy, B. A. and G. J. Cluff, Reno, NV: Data on file with USDA/ARS; 1977-1980. 54 may be more indicative of limiting factors and Control of greasewood and rabbitbrush by site potential. Many descriptive and some soil-applied herbicides including karbutilate quantitative studies have been conducted in the (tandex), tebuthuiron (spike), buthidazole basins of the arid west, some of which had the (ravage) and picloram was generally intent of using plant species to indicate soil unsuccessful possibly due to the low conditions (Kearney and others 1914; Shantz and permeability of the associated saline-sadie Piemeisel 1924, 1940; Flowers 1934; Billings soils. Highest mortality was only 40 percent 1945; Gates and others 1956). In table 1 some of from 10 percent picloram pellets while other the most common associates of greasewood and herbicides averaged less than 30 percent saltgrass are listed with plant tolerances and mortality. site conditions with which they are generally associated as summarized from the literature and A variety of foliar-applied herbicides our own experience at the Gund Research and including 2,4-D plus picloram, triclopyr, Demonstration Ranch in central Nevada (see Young 2,4,5-T, silvex and dicamba were more and Evans 1980). successful than soil herbicides in controlling rabbitbrush and greasewood (Cluff and others Soil salinity, soil moisture and understory cover 1983). None of these herbicides were more should be considered in deciding on brush control effective than 2,4-D applied duting the period and seeding treatments to improve forage. Sites of optimum susceptibility. Mortality from that have little understory and are too dry or foliar herbicides varied among years and sites too saline to seed should be avoided. and was correlated with soil moisture potential Greasewood/shadscale and greasewood/kochia areas and greasewood and rabbitbrush growth phenology generally fall into this category. Sites where (Cluff and others 1983). Rabbitbrush grows greasewood and saltgrass are associated with slowly from March until late May when it begins white-flowered rabbitbrush, pickleweed, a period of rapid growth that generally ends in salicornia, alkali grass or nitrophila generally early August (Roundy and others 1981, fig. 1). have soils of high salinity and a high Greasewood generally begins rapid growth watertable. Only where a good grass understory similar to rabbitbrush in late May, but has a already exists should these communities be lower rate and shorter period of rapid growth treated to control brush. Sites that should be that generally ends in late June. Greasewood considered for brush control are those that have and salt rabbitbrush were most susceptible to a good understory of basin wildrye, saltgrass, 1.9 lb/acre (2.2 kg/ha) 2,4-D applied during alkali sacaton or other forage grasses or that mid-June when both shrubs were rapidly growing may be lacking in understory but have soils of with mortality averaging 72 and 87 percent, low to moderate salinity. Greasewood and respectively. An average leader length of 1.6 saltgrass in these situations are generally inches (4 em) indicates that rapid growth of associated with big sagebrush and/or salt salt rabbitbrush is under way while the first rabbitbrush. opening of flower buds is correlated with rapid growth cessation (Roundy and others 1981). BRUSH CONTROL Appearance of staminate spikes is correlated with beginning of greasewood rapid growth and the The effects of rotobeating and soil and foliar appearance of dried spikes indicates rapid growth applied herbicides on control of big sagebrush, has ceased. salt rabbitbrush, white-flowered rabbitbrush and greasewood were studied over a 6 year period in On a xeric site dominate by big sagebrush, central Nevada. The foliar herbicide trials were greasewood and salt rabbitbrush, sagebrush was conducted on small plots using a back-pack most susceptible to 2;4-D in mid-May while sprayer and on large plots using a rangeland greasewood and rabbitbrush were more susceptible ground sprayer (Young and others 1979). Trials in June (table 2). On this xeric site, were conducted on the following brush greasewood had a much lower growth rate and much communities: Greasewood/salt rabbitbrush, lower mortality (table 2) than greasewood on a greasewood/salt rabbitbrush/ white-flowered mesic site. Greasewood that has been sprayed and rabbitbrush and big sagebrush/salt resprouts

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