Effects of Sulfur Fertilization on Productivity and Botanical Composition of California Annual Grassland

Abstract

Changes in botanical composition and productivity of total herbage and 14 categories of annual range plants caused by elemental sulfur fertilization, range site, and precipitation were studied. Total herbage production on the wetter and more fertile swale sites was not affected by sulfur fertilization, but production on adjacent open upland and rocky, brushy upland sites usually increased with added S. Herbage production increased 28% or 1,400 kg/ha on fertilized open upland sites and 51% or 1,800 kg/ha on fertilized rocky, brushy upland sites during the wettest year sampled. Over the 3 years sampled, the most desirable grass, soft chess, averaged 68, 22, and 66% higher production (438, 287, and 388 kg/ha increases, respectively) on fertilized versus control range units for swale, open upland, and rocky, brushy upland range sites, respectively. Likewise, the less desirable but important earlyforage species, ripgut brome, increased 164% or 544 kg/ha on swales and 205% or 437 kg/ha on rocky, brushy uplands with fertilization; only a 16% increase or 98 kg/ha occurred on open upland sites. Grass responses were offset by decreased forb production, while the proportion of legumes remained nearly the same. Upland sites benefited from sulfur fertilization by exhibiting both increased clover and other legume production in the wettest year. Filaree was unaffected by sulfur fertilization. Sulfur is recognized as an important macro-nutrient on California's unimproved and improved annual-type rangeland. Martin (1958) noted a sulfur deficiency on sites in 34 of the 58 California counties representing 60 soil series. Conrad (1950) found that The authors are post-graduate researcher and associate professor, Department of Agronomy and Range Science, University of California, Davis 95616, and range scientist (retired), Pacific Southwest Forest and Range Experiment Station, Forestry Sciences Laboratory, Fresno, Calif. 93710. Data were collected by a number of scientists in the U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station, Fresno, Calif. Our data analysis and manuscript preparation were supported under Cooperative Aid Agreement PSW-69. Manuscript accepted June 25, 1984. elemental sulfur significantly increased hay production on 4 widely separated sites in California. Yield of dryland pasture species increased significantly when sulfur was applied as gypsum at the Hopland Field Station (Jones 1964), and substantial increases in herbage productivity occurred during the first year on plots sulfurfertilized with gypsum or elemental sulfur (Jones and Ruckman 1966). In the second year elemental S was more effective than gypsum. Winter forage was optimized with 67 kg S/ ha yearly with elemental S or 25 kg S/ ha as gypsum yearly on subterranean clover (Trifolium subterraneum L.) seeded rangeland at Hopland (Center and Jones 1983). Studies of sulfur fertilization with gypsum showed that herbage yield and grazing capacity on upland range sites increased (Bentley et al. 1958). Conrad et al. (1966) reported only slight increases in herbage production on pastures fertilized with gypsum but found an increase in grazing capacity on the fertilized pastures, although individual cattle gains were unaffected. Wagnon et al. (1958) observed that steers exhibited increased weight gain during the summer dry-forage season on pastures fertilized with gypsum and Green et al. (1958) showed that summer forage had higher crude protein, phosphorous, and calcium levels when fertilized with gypsum. McKell et al. (1960) also reported higher protein levels in forage on range fertilized with gypsum. Increased production and improved quality of forage due to legume enhancement may extend the amount of time cattle graze without supplementation. Plants take up sulfur as sulfate, while elemental sulfur must be oxidized by soil bacteria before plants can use it. Plants respond more quickly to sulfate forms of sulfur during low-rainfall years (McKell and Williams 1960, Williams et al. 1964). With higher rainfall sulfate fertilizers are susceptible to leaching and runoff during the application year (Williams et al. 1964) and sulfate fertilizers have lower residual value than elemental sulfur (Jones et al. 1968, Jones et al. 1970, Jones and Ruckman 1966). In high rainfall areas elemental sulfur elicits longer lasting results. 108 JOURNAL OF RANGE MANAGEMENT 38(2), March 1985 This content downloaded from 40.77.167.32 on Sun, 31 Jul 2016 05:28:19 UTC All use subject to http://about.jstor.org/terms Table 1. Average total herbage production on control and sulfur fertilized range sites. Swale Open-upland Rocky, brushy upland Control Fertilized Control Fertilized Control Fertilized Year Fertilizer effect kg/ ha kg/ ha kg/ ha kg/ ha kg/ ha kg/ ha I Ist year 220