Defoliation Impacts on Quality and Quantity of Forage Harvested from Big Sacaton (Sporobolus wrightii Munro)

Abstract

Forage quality and quantity and stand vigor of big sacaton were evaluated for seven defoliation systems during 1977 and 1978. Big sacaton plants were either shredded monthly, shredded in spring/midsummer, spring/early summer, spring, spring/late summer/fall, midsummer/fall, or late winter. Forage quality of big sacaton was improved by defoliation during both years. With few exceptions, crude protein content was highest in plants defoliated the previous month. IVDOM contents were also improved by defoliation. Digestibility decreased to below 50% in early summer in nonshredded plants and in mid summer in all plants regardless of prior defoliation treatment. IVDOM increased to above 50% in late summer and fall in plots defoliated the previous month. Forage harvests during the growing season were greatest from plots that were defoliated three or more times and were defoliated in the fall. The least amounts of forage were harvested from the plots defoliated in spring, spring/early summer and spring/midsummer. In the fall and winter the nonshredded and spring defoliated plots supported relatively large amounts of forage, and the spring/early summer and spring/midsummer plots supported intermediate amounts of forage for winter grazing. Stand vigor was maintained best by brief periods of defoliation in the spring or spring/early summer, followed by defoliation of old forage in late winter. Vigor appeared to be decreased by early fall defoliations to a 7.5 cm stubble height. The spring/early-summer system provided large amounts of high quality forage and maintained stand vigor. This system defoliated plants when soil moisture was usually adequate for plant regrowth, provided nutritious forage during the growing season and provided adequate standing forage for fall and winter grazing and protection against damage due to low temperature.