Enhancing Germination of Indian Ricegrass Seeds with Sulfuric Acid 1

Indian ricegrass [ Oryzopsis hymenoides (R. & S.) Ricker] is the dominant forage species on millions of hectares of rangeland in the western United States. Revegetation of degraded rangeland by seeding Indian ricegrass has been generally unsuccessful because of low seed germination. Our purpose was to evaluate the influence of acid seed scarification on germination of Indian ricegrass seeds. Seeds of ‘Paloma’ and ‘NezPar’ Indian ricegrass were scarified in sulfuric acid (H 2 SO 4 ) from 0 through 45 min at 5‐min intervals. Without scarification, germination of the seeds of these two cultivars was less than 10%. Seedlots from 1 to 11 years old were treated. Germination data were used to develop regression equations for the relationship between duration of acid seed scarification and germination for each cultivar. Seeds of Paloma Indian ricegrass required 25 to 35 min of scarification, whereas seeds of NezPar required 15 to 25 min scarification. The relative composition and morphological forms of the seed may explain the difference in duration of required scarification. The scarified seeds were incubated at 55 constant and alternating temperatures to obtain data with which to construct quadratic response surfaces for temperature‐germination profiles. Even with scarification, the seeds of the two cultivars produced mean germination for the profiles of only 9 to 31%. The dormancy of Indian ricegrass seeds is controlled by complex interacting factors. Acid scarification is a very imprecise tool for enhancing the germination of dormant seeds of Indian ricegrass.