Under Stressful Conditions, High Cattle Density Maintains White Clover Abundance

Abstract

Core Ideas Clover richness depends on the grazing management and available water in the topsoil. Clover recovery is not related to the pre‐drought spatial distribution. Tiller density, within a patch, is related to the previous presence of white clover. The steer density adjusts tall fescue and white clover populations in the pasture. ABSTRACTThe aim of the present study was to evaluate the abundance and dynamics of white clover (WC) (Trifolium repens L.) under cattle grazing, in a stressful environment. To this end, we performed a 5‐yr experiment in Buenos Aires province, Argentina, where treatments were low and high forage offers (LFO and HFO) of a tall fescue (TF) [Lolium arundinaceum Schreb. (Darbysh.)]–WC mixture and two sites regarding the initial existence of WC in the pasture (with and without white clover, WC+ and WC–). Climatic conditions determined periods of deficiency or abundance of plant available water in the topsoil, which interacted with the grazing management, leading to either the absence or richness of WC in the pasture. Before a drought, the basal cover of WC was 31.0 and 11.2% with LFO and HFO treatments, respectively (P < 0.001); whereas, during recovery after drought, the corresponding values were 44.0 and 2.7% (P < 0.001), respectively. Re‐establishment of WC at the pasture level was poorly related to the pre‐drought spatial distribution. At the beginning of the experiment, the TF tiller density was greater in WC– sites; whereas, at the end of the experiment, the opposite was observed. The N derived from biological fixation was 85.5% and differences among treatments were of small magnitude. We concluded that, at the pasture level, the abundance of WC in an environment with hot and often dry summers is favored when the competition by TF is controlled and the availability of water in the soil is not limiting.