Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 1997
Publication Date: N/A
Interpretive Summary: Drought is a common occurrence during the summer in the southeastern USA. Periods of drought are particularly detrimental to temperate forage legumes such as white clover because plants have shallow roots and often compete for moisture with tropical pasture grasses. The ability to tolerate drought would contribute to the persistence of this nutritional forage in the region. Our objective was to test the drought tolerance of commercial varieties and experimental germplasm in a pasture environment. Using a water-supply gradient, we were able to determine that few differences in drought tolerance exist among the most widely-available white clover varieties and improved germplasm. Our results suggest that tolerance to grazing and heat should be considered when efforts to improve the drought tolerance of white clover are made by plant breeders.
Technical Abstract: Periods of drought common during the summer and fall in the southeastern USA can be detrimental to growth of the shallow-rooted, temperate forage legume white clover (Trifolium repens L.). Our objective was to determine white clover response to a water-supply gradient on a Catalpa silty clay (fine, montmorillonitic, thermic Fluvaquentic Hapludoll) during the summer and fall. From May to October, a line-source irrigation system produced regimes of high, medium, low, and zero water supply across parallel 1.0-m rows of three cultivars and three germplasms transplanted (10 plants row-1) into a common bermudagrass (Cynodon dactylon (L.) Pers.) sod the previous fall. Plots were continuously-stocked (5-cm stubble) with cattle (Bos taurus). Each month, differences in lateral plant spread among entries were similar regardless of water-supply regime. Within each regime, spread declined sharply after June and remained near a minimum (< 0.20m2 row-1) from August until October. Yield and morphology differences among entries in July were similar in each of the water-supply regimes as well. By October, however, there were differences in herbage yield, stolon length, and stolon apex density among entries at the high water-supply regime, but not at the zero, low, and medium regimes. The results suggest that either there is no difference in drought tolerance among these cultivars and germplasms or that white clover response to drought is influenced by other stresses, such as grazing or competition from an associated grass.