Browsing Journal of Range Management, Volume 42, Number 2 (March 1989) by Title
Now showing items 17-19 of 19
Seeded wheatgrass yield and nutritive quality on New Mexico big sagebrush rangeEstablishment, yield, and nutritional quality of 'Nordan' crested wheatgrass (Agropyron desertorum [Fischer ex Link] Schultes), 'Fairway' crested wheatgrass (Agropyron cristatum [L.] Gaertner), 'Arriba' western wheatgrass (Pascopyrum smithii [Rydb.] A. Love), 'Luna' pubescent wheatgrass (Thinopyrum intermedium subsp. barbulatum [Schur.] Barkw. and D.R. Dewey), and 'Largo' tall wheatgrass (T. ponticum [Pod] Barkw. and D.R. Dewey) were evaluated on big sagebrush range (Artemisia tridentata Nutt. tridentata) in northcentral New Mexico during a 5-year study. All the above wheatgrasses showed high initial densities and long-term persistence. Wheatgrass yields across years and seasons during the last 2 years of study averaged 760 kg/ha compared to forage yields of 355 kg/ha on surrounding ungrazed native rangeland. There were no differences (P > .05) among wheatgrasses in standing crop of current year's growth during spring, summer, or fall. Crude protein concentrations did not differ (P > .05) among wheatgrasses with seasonal advance. However, all the wheatgrasses showed a consistent decline in nutritional quality from spring to summer to fall. All the wheatgrasses we studied will provide high-quality, spring (mid-April to mid-June) forage for livestock. During summer, use of native range is advantageous because it contains a high component of warm season grasses and forbs. Interseeding shrubs in wheatgrass seedings could reduce protein supplementation costs in winter.
Silicon in C-3 grasses: effects on forage quality and sheep preferenceSilicon in forage reduces dry matter digestibility and may reduce grazing preference. Two studies were conducted with the following objectives: (1) to evaluate a method of determining grazing preference, and (2) to characterize the distribution and solubility of silicon in 31 accessions of C-3 grasses and relate these traits to grazing preference and estimated forage digestibility. Forage samples were clipped at the beginning of each 7 to 10-day grazing period corresponding to 6 phenological stages of the Agropyron sp. Samples were washed and analyzed for acid detergent fiber (ADF), neutral detergent fiber (NDF), and silicon in ADF and NDF residues. Leaf silicon concentrations increased from the vegetative to seed-ripe stage. Genera were aligned into 3 groups based on the increase in leaf silicon concentration with advancing phenological age. Silicon concentrations in leaves of Agropyron, Pseudoroegneria, and Thinopyrum increased at nearly twice the rate of those in Critesion, Hordeum, Leymus and Psathyrostachys. Elymus leaves contained higher concentrations of silicon at the vegetative stage than the other groups, but the accumulation rate was intermediate. About 32% of total leaf silicon remained in NDF and 76% in ADF residues at the vegetative stage. These insoluble portions of silicon increased with aging. Preference was positively related to estimated dry matter digestibility at boot and anthesis, but was not related to fiber or silicon measurements. Leaf harshness was negatively related to preference at seed-ripe stage. Further progress in characterizing the role of silicon in C-3 forage grasses should be possible by studying a representative species from each group.
Some effects of a rotational grazing treatment on cattle preference for plant communitiesRotational grazing is commonly assumed to improve livestock distribution compared to continuous grazing, but little evidence supports this contention. Research was conducted on the effects of rotational grazing (RG) compared to continuous grazing (CG) on the preference of cattle for plant communities. Different livestock densities in the RG treatments were created by varying the size of paddocks in a 465-ha, 16-paddock, cell designed RG treatment stocked at a rate of 3.6 ha/cow/yr. Paddock sizes of 30 and 10-ha were used to simulate RG with 14 (RG-14) and 42-paddocks (RG-42), respectively. The CG treatment consisted of a 248-ha pasture stocked at 5.9 ha/cow/yr. Data consisted of hourly daylight observations of cattle location and activity during 8 seasonal trials lasting 6-15 days. These data were expressed as a percent of the time cattle were observed in each of 4 plant communities and the area surrounding permanent water. Relative electivity (RE), a preference index, and a selectivity index (SI) that measures departures from random distribution were calculated from these data. Relative electivity (i.e., preference) for plant communities was not affected by grazing treatment. However, cattle were less selective for plant communities as livestock density decreased from the RG-42 to the CG treatment. In the RG-14 treatment, the cattle were either unaffected or less selective on the last day than on the first day in a paddock. We hypothesize that grazing systems influence cattle preference for plant communities by affecting the availability of forage biomass per unit land area rather than by their effect on grazing pressure.