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Cool-season perennial grass growth is suppressed during hot, dry summers. This "summer slump" reduces the availability of grazable forage. Tall-growing perennial warm-season grasses that produce 65 to 75% of their yield in midsummer may provide needed herbage during this period of reduced cool-season forage production. However, establishment of perennial warm-season species is slow and inconsistent when compared to cool-season species. Before these warm-season species can be relied on for summer forage production, a successful establishment methodology must be developed. A study was conducted to evaluate the influence of atrazine [2-chloro·4(ethylarnino)-s-triazine] and carbofuran on establishment of switchgrass (Panicum virgatum L.) and Caucasian bluestem [Boyhtiochloa caucasica (Trin.) C. E. Hubbard]. Treatments of carbofuran at 0 and 1.1 atrazine/ha placed in the row with the seed and of atrazine broadcast at 0, 1.1, and 2.2 kg/ha were imposed in all possible combinations. Another study investigated the influence of limestone, P, and carbofuran on the establishment of switchgrass. Treatments included carbofuran at 0 and 1.1 kg/ha, limestone at 0 and 4.48 Mg/ha, and P at 0 and 22 kg/ha in all possible combinations. Seedling growth rate, leaf appearance rate, plant height, and leaf elongation rate (LER) of seedlings were recorded. Seedling weight and populations were determined at the sixth leaf stage of development. Yields of forage and botanical compositions were also measured in the establishment year. Establishment was further evaluated with yield measurements the year after seeding. Carbofuran application increased first year yield, seedling weight, population, leaf appearance rate, and seedling growth rate. Atrazine reduced seedling population, weight, leaf appearance rate, LER, and yield. Carbofuran partially moderated atrazine influence. The 2.2 kg rate of atrazine tended to injure the switchgrass more than the Caucasian bluestem. In the study investigating limestone and P, carbofuran increased yield, seedling weight, seedling population, LER, seedling growth rate, and leaf appearance rate. The greatest yield, leaf appearance rate, and LER occurred with applications ofP and carbofuran. Even though initial soil pH was 5.1, limestone broadcast prior to planting did not influence seedling measurements and yields in either year. These plantings were made during 1985 and 1986, which were the driest summers in recent years. In spite of the moisture stress, acceptable stands of perennial warm·season grasses were established in both experiments in both years. Including 1.1 kg granular carbofuran/ha in the row, and broadcast application of 1.1 kg atrazine/ha at planting will improve establishment of perennial warm·season grasses. Where the P levels in the soil are low, a broadcast application of 22 kg P/ha improves chances for successful establishment. / Ph. D.

Experiments were conducted to determine: 1) the fermentation characteristics and in vitro dry matter digestibility (IVDMD) of corn (<i>Zea mays</i>) stover treated with different sources of N; 2) digestibility, N utilization and palatabi1ity in sheep fed corn stover treated with different N sources; and 3) fermentation characteristics and nutrient utilization by sheep of sorghum (<i>Sorghum bicolor</i> L., Moench) forage treated with urea an poultry litter. In a small silo study, corn stover was ensiled untreated or after treatment with 3% aqueous NH₃, 50% and 75% poultry litter, 5.8% urea alone or with 10% cattle waste, 1.5% urease powder or 5% soybeans (<i>Glycine max</i>), DM basis. All treatments resulted in substantial increases (P < .01) in CP of corn stover. Lactic acid was detected in substantial levels only in the stover which was untreated and treated with 50% poultry litter. Ammonia and urea treatments decreased NDF content of stover by 4 to 7 percentage units. Increases (P < .01) of IVDMD of 9 to 14 percentage units resulted from treatment with NH₃ or urea. Use of urease sources did not enhance IVDMD. / Ph. D.

A series of experiments were conducted to compare nine new sainfoin populations developed to persist in mixtures with alfalfa under a multiple-cut management. In trials at Lethbridge under rain-fed and irrigated conditions, new sainfoin populations produced higher (P<0.05) dry matter yields as compared to Nova sainfoin. New cultivars persisted for three production years in mixed stands with alfalfa accounting for >20% DM at each harvest. Condensed tannin concentrations in sainfoin were highest at the bud stage. One new sainfoin population, LRC-3519 seeded in alternate rows with alfalfa caused a reduction (p<0.001) in bloat incidence by 98% as compared to Nova-alfalfa stands. Average daily gains (>1.0 kg d-1) of steers on alfalfa-sainfoin mixed pastures were similar (p>0.05). Seeding of these new sainfoin populations in mixed stands with alfalfa could prove to be a means of taking advantage of the productivity of mixed forage legume pastures while preventing bloat in grazing ruminants.