The yield and quality of plant species grown in mixed organic swards

摘要

Mineral availability is a critical factor in the maintenance of the health and fertility of livestock in organic systems that are based on the production of grass and white clover swards and the feeding of high-forage diets. Extra minerals are required in the diets of ruminants to replace those exported from the farm as meat or milk. A number of plant species have been found to have significantly higher mineral concentrations than either grass or clover plants. However, little information is available on the total mineral supply from these plants to animals when they are grown in mixed swards or their effect on either the yield or quality of the sward. A study was conducted to investigate the yield, quality and mineral concentration of plant speciesgrown in mixed swards. Plots were established with perennial ryegrass (Lolium perenne), timothy (Phleum pratense) or a mixture of the two grass species. Due to the differences in seed size the grasses were sown at rates of 10, 20 or 30 kg/ha (perennialryegrass) and 6.6, 13.2 and 20 kg/ha (timothy) to establish similar plant populations. In addition to the grass seed 4, 2 and 2 kg/ha of white clover (Trifolium repens), chicory (Cichorium intybus) and plantain (Plantago lanceolata) seed was also sown oneach plot. No significant differences were recorded between the total yields from plots sown with either perennial ryegrass or timothy, however, differences in mineral concentrations were recorded between the grass species. Reducing the grass seed rateled to significant changes in both the proportion of the individual plant species and the yield of minerals. Large variations were recorded between species in mineral, energy and protein values and these have implications in relation to animal health andproduction.