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Submitted to: Society for Range Management Oklahoma Section Newsletter
Publication Type: Trade Journal Publication Acceptance Date: 10/15/2001 Publication Date: 12/30/2001 Citation: NORTHUP, B.K. 2001. HOW SEASON AND SOIL MOISTURE AFFECT FORAGE PRODUCTION BY TALLGRASS PRAIRIE. SOCIETY FOR RANGE MANAGEMENT OKLAHOMA SECTION NEWSLETTER. v. 10(4). p. 3-4. Interpretive Summary: Tallgrass prairie is an important source of low-input forage for livestock production in central Oklahoma and can produce large amounts of plant material, if properly managed. An understanding of how different environmental factors and maturation of plants can affect amount and quality of forage is important to proper management. A study ws undertaken to examine relationships between growing condition (length of season, soil moisture), maturity of grass plants (tillers), and community production in a southern tallgrass prairie dominated (65% of vegetation) by the warm-season grasses big bluestem, little bluestem, indian grass and switch grass, during the 2000 growing season. Most forage was produced by the plant community during May-July, when tillers of the dominant grasses were rapidly increasing in live weight and maurity, and soil moisture exceeded plant growth requirements. After mid-July, the amount of dead material increased rapidly as tillers became more mature (reproductive); live weigh produced by the community and tillers began declining in early August. Quality of forage (crude protein content) declined with length of growing season, and fell below maintenance requirements (7.5%) for mature cattle by early July. The best time to harvest forage (by grazing or haying) for this site during the 2000 growing season appeared to be in late June when the combination ofamount and quality of forage, and tiller maturation, were optimum. Technical Abstract: Conditions during the growing season and maturatin of grass tillers impact quality and production of herbage by grasslands. A study was undertaken to examine how time of growing season, soil moisture, and tiller development of key grass species affected the productivity of a southern tallgrass prairie in central Oklahoma. Data were collected at 14-day intervals from 16 replicate plots of a loamy prairie site on a Norge silt loam (Udic Paleustoll) soil during April-September 2000. Aboveground biomass was collected from 0,5 m-2 quadrats at each date, divided into green and standing dead fractions, and dry weights determined. Additionally, 75 tillers of both Andropogon gerardii and Schizachyrium scoparium per plot (key species producing up to 65% of total herbage) were collected, maturity determined by the Nebraska growth staging system, and mean dry weights defined. Gravimetric soil mositure was determined for the top 50cm of the soil profile. The majority of forage produced by the plant community occurred during May-July, when tillers of the dominant grasses were rapidly increasing in live weight and maturity, and soil moisture exceeded plant growth requirements (wilt point). After mid-July, dead material increased rapidly as tillers became more mature (reproductive); live weight produced by the community and tillers began declining in early August. Quality of forage (crude protein content) declined with length of growing season, and fell below maintenance requirements (7.5%) for mature cattle by early July. The best time to harvest forage for this site during the 2000 growing season was late June when the combination of amount and quality of forage, and tiller maturation were optimum. |
