Impact of spatial heterogeneity of plant species on herbage productivity, herbage quality and ewe and lamb performance of continuously stocked, perennial ryegrass–white clover swards

Abstract

AbstractThe benefits of white clover (Trifolium repens L.) in pastures are widely recognized. However, white clover is perceived as being unreliable due to its typically low content and spatial and temporal variability in mixed (grass‐legume) pastures. One solution to increase the clover proportion and quality of herbage available to grazing animals may be to spatially separate clover from grass within the same field. In a field experiment, perennial ryegrass (Lolium perenne L.) and white clover were sown as a mixture and compared with alternating strips of ryegrass and clover (at 1·5 and 3 m widths), or in adjacent monocultures (strips of 18 m width within a 36‐m‐wide field). Pastures were stocked by ewes and lambs for three 10‐month grazing periods. Over the 3 years of the experiment, spatial separation of grass and clover, compared with a grass–clover mixture, increased clover herbage production, although its proportion in the sward declined through time (0·49–0·54 vs 0·34 in the mixture in the first year, 0·28–0·33 vs 0·15 in the second year and 0·03–0·18 vs 0·01 in the third year). Total herbage production in the growing season in the spatially separated treatments decreased from 11384 kg DM ha−1 in the first year to 8150 kg DM ha−1 in the third year. Crude protein concentration of clover and grass components in the 18‐m adjacent monoculture treatment was greater than the mixture treatment for both clover (310 vs 280 g kg−1 DM) and grass (200 vs 180 g kg−1 DM). There was no clear benefit in liveweight gain beyond the first year in response to spatially separating grass and clover into monocultures within the same field.