Plant Biomass and Elemental Changes in Shrubland Forages following Biosolids Application

Abstract

AbstractLand application of biosolids is a viable management practice for agriculture, but minimal information exists on beneficial uses for native rangeland. This study was conducted to determine the effect of surface‐applied biosolids on the canopy cover, aboveground biomass, and nutrient status of native plant species in a sagebrush (Artemisia spp.) community in western Colorado. Biosolids were applied once in 1991 at nine rates consisting of 0, 5, 10, 15, 20, 25, 30, 35, and 40 Mg ha−1 to plots measuring 3320 m2. Biosolids application increased the biomass of perennial grasses up to 300% at 25 Mg ha−1 treatment rates in 1993. We also found 60 to 70% increases in plant tissue N concentrations in western wheatgrass (Agropyron smithii Rydb.), bluebunch wheatgrass [A. spicatum (Pursch) Scribn. & Smith], and Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker]. The quality of grass forage was also improved through a change in the Cu/Mo ratios. Before biosolids application, the three grasses noted above had Cu/Mo ratios below 1.2/1, which is known to cause Mo‐induced Cu deficiencies in cattle (Bovis abortus), sheep (Ovis aries), and some wild ruminants. Biosolids treatment increased the Cu/Mo ratio above 2/1 for western wheatgrass and bluebunch wheatgrass 1 yr after application at low rates and 2 yr after amendment at intermediate application rates. The Cu/Mo ratio of Indian ricegrass also increased above 2/1 2 yr after surface application at intermediate biosolids application rates. Forage quantity and nutritional value of some native grasses was improved for livestock and wildlife consumption with biosolids application.