Effects of shade, water and species mix on perennial ryegrass and red clover competition : a simulated silvopasture system
Abstract: A silvopasture system is an agroforestry system specifically designed for the production of trees, tree products, forage for grazing and livestock. Research has shown that silvopasture systems can be an environmentally and economically feasible alternative to traditional land uses. Two potential silvopasture forage species, perennial ryegrass (Lolium perenne L.) and red clover (Trifolium pretense L.), were exposed to shade, low water levels and varying species mixes. They were grown in a greenhouse for 14 weeks and were harvested at two occasions. The light treatments were full light, 50% shade or 80% shade. The water levels were either a well watered treatment or a water level where the plants were exposed to water stress. There were three different species mixes; 75% grass / 25% clover, 50% grass / 50% clover or 25% grass / 75% clover. After harvest the biomass was measured, development stage determined, and protein content and neutral-detergent fiber (NDF) content analyzed. The objectives of the study were to investigate how a grass species and a legume species in different mixes are affected by different levels of shade and water. The biomass increased with increased light and water. The grass dominated mix gave a higher biomass than the clover dominated mix for both species. Only the clover showed differences in development stages between the treatments. The maturity of the plants was increased by increased exposure to water and light. In the second harvest both the grass and the clover increased their protein concentration when the shade levels increased. The grass had a higher protein concentration when grown in a low water treatment while the clover had a higher protein concentration when grown in a high water treatment. The grass dominated mix increased the protein concentration for the grass while the clover dominated mix increased the protein concentration for the clover. The actual amount of protein in the plants followed the variations of the biomass; a larger plant had a higher protein content and vice versa. The NDF levels varied between treatments, crops and harvests. The second harvest generally showed larger effects of the treatments than the first harvest. The reason was that the plants started to grow in an untreated condition until they were well established for the first harvest, while they had to start regrowing in the treated environment for the second harvest.
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