Response of Crimson Clover to Different Defoliation Intensities 1

CRIMSON clover, Trifolium incarnatum L., is regarded as the most important winter annual legume for the South and is extensively used also in the west coitst section of the United States. Before World War II, all crimson clover was of the common type. Although reseeding varieties were not developed until the late 1930’s, more than half of the domestic seed produced is of the reseeding type. It has been generally recognized that grazing or clipping during late winter or early spring may slightly reduce seed yields, if spring growing conditions are unfavorable. On the other hand, if some growth is not grazed off and if spring growing conditions are favorable growth may become so rank that it will lodge and low seed yield or failure will result. Additional information is needed conceming management of crimson clover to assure maximum utilization of the forage and to assure production of an adequate supply of seed for a reseeding or volunteer stand. The experiment reported in this paper was initiated in 1954 to determine the effect of defoliation and time of last forage harvest on forage production and on the quantity and quality of seed produced. Many .experiments have been conducted on a wide range of crops to determine the effects of time and frequency of grazing or clipping on forage production, seed production, and persistency. There is general agreement that frequent defoliation of perennial crops has a deleterious effect on total forage production as well as on stand longevity (1, 6, 12). Lower yields and weakened stands under frequent defoliation have been attributed to reduced food reserves and low light interception. Crowder et al. (2) determined the effect of clipping intensity on a mixture of Arlington Oats, ryegrass, and crimson clover for 3 years at Experiment, Georgia. Dry matter yields were greatest with an 8-week interval between clippings when compared to yields with 2and 4-week intervals. Evans and Thatcher (3) found that maturity of timothy strains influenced forage production. A late selection of timothy produced less than a medium strain at early harvest dates with the late strain producing higher yields at the late dates. An early selection produced a higher total yield than the medium or late strain. Gardner and Wiggans (4) found that delayed repeated clipping of spring oats beyond the 4-leaf stage increased forage yield. Single clippings at the 4-, 5-, and 7-leaf stages reduced grain yield by 9, 28, and 98%, respectively. Hubbard and Harper (5) studied the effect clipping on 24 small grain varieties or mixtures of varieties and concluded that grain yields generally were not reduced by moderate clipping in the fall, in the late winter, or before about jointing time in the spring. In most instances yields were increased by moderat.e clipping, whereas severe clipping through February or later always caused a reduction in grain yield. Voorhees (13) analysed squarefoot samples of crimson clover and found that the tops increased from 2/3 of the total plant food on April 24 to 9/10 on May 24.