Effect of Excreta on Stolon Development of White Clover Under Continuous Cattle Grazing

The effects of cattle excreta on white clover growth in perennial ryegrass-white clover pastures were studied under continuous grazing. During 2 6-week periods in June-July and September-October. Caltle selectively grazed the sward where urine had been recently voided and subsequently grazed these areas more fequently than other areas, while grazing the sward adjacent to the dung pats less intensively than other areas. Despite differences in of herbage mass and light interception resulting from altered grazing patterns, dung did not affect the density of white clover (Trifolium repens L,) growing points or the number of branches per stolo1i in the surrounding areas. Urine consistently reduced the number of growing points of clover and the number of branches per stolon

Identifying causes of low persistence of perennial ryegrass (Lolium perenne) dairy pasture using the Basic Grassland model (BASGRA)

Recent years have seen a decline in herbage production and tiller populations in New Zealand's perennial ryegrass (Lolium perenne) dairy pastures. One hypothesis is that modern genotypes are less suited to the warmer, drier weather experienced under changing climate patterns. In this study, a combination of long‐term trial data (2011–2017) and a process‐based pasture model (BASGRA) was used to explore the causes and possible mitigation of the observed production and population loss at three sites (dryland sites in Northland and Waikato and an irrigated site in Canterbury). Bayesian calibration was used to identify the model parameter sets that were consistent with the trial data and to identify differences in plant morphology and responses between sites. The model successfully simulated the observed differences in tiller numbers between the dryland sites, where populations and production declined rapidly after the second year and the irrigated site where populations and production were maintained. Analysis of the model calibrations along with preliminary scenario simulations suggests that increased tiller mortality associated with drought was the main cause of persistence failure at the dryland sites and that decreasing grazing pressure or breeding for tolerance to higher temperatures may not be successful in preventing this