Preliminary Study On The Mechanism Of Interspecific Competition Between White Clover And Perennial Ryegrass

Having observed man-built lawn of white clover and perennial ryegrass for years, we found that, once white clover intruded into the population of perennial ryegrass it would rapidly occupy econiche and then became the dominant species. Mechanism of interspecific competition between white clover and perennial ryegrass was studied preliminarily, the results showed as following:1. Relationship of interspecific competition between white clover and perennial ryegrassIn the first year when the lawn of white clover and perennial ryegrass was built, the competition ratio of perennial ryegrass was higher than that of white clover; but in the man-built lawn, once white clover intruded into the population of perennial ryegrass it would rapidly occupy econiche and then became the dominant species. In three random plots where white clover intruded into the population of perennial ryegrass, area of white clover increased from 17875.50 cm2, 5838.46 cm2 and 10277.32 cm2 in November in 2005 to 30655.38 cm2, 13802.20 cm2 and 31819.30 cm2 in July in 2006 respectively.2. Relationship between allelopathy and interspecific competition of white clover and perennial ryegrassAt the stage of branching, the aqueous extracts of roots from white clover inhibited seed germination and seeding length of pinnacle significantly, the inhibited ratio were 90.72% and 48.61% respectively; at the stage of flowering, the aqueous extracts of roots from white clover significantly inhibited the seed germination of pinnacle and inspire, the root length of inspire and the root dry weight of pinnacle, the inhibited ratio were 35.14%,36.17%,69.18% and 68.34% respectively, and it inhibited the root dry weight of inspire with the inhibited ratio of 49.52%; at the stage of maturing, the aqueous extracts of roots from white clover accelerated seed germination and root growth of all three receptor plants, it increased 67.09%,54.21%,69.21% and 93.08%,93.14%,93.04% respectively. The allelopathic effect of pinnacle and inspire was higher than the self-destructive effect of the two. At the stages of tillering and booting, aqueous extracts of roots from different varieties of ryegrass significantly inhibited dry matter weight of white clover.3. Influence of soil nutrients on the interspecific competition between white clover and perennial ryegrass There was significantly negative relationship between the height of white clover and the available potassium (K), and there existed significantly positive relationship between the tiller number of white clover and the available phosphorus, the correlated coefficients were 0.755 and 0.626 respectively;Both the height and the tiller number of the mixed grass with pinnacle and inspire were significantly correlated to available phosphorus negatively, the correlated coefficients were 0.864 and 0.871 respectively, but the tiller number was significantly correlated to the value of soil pH positively and the correlated coefficient was 0.891;The tiller number of inspire was significantly correlated to available phosphorus negatively, the correlated coefficient was 0.902;There was no significant relationship between the height of white clover and perennial ryegrass with the available nitrogen and the value of soil pH, and there was no significant relationship between the tiller number and the available nitrogen,available potassium (K). In the whole phenological stage and under all treatments, available nitrogen and available potassium (K) had no influence on the growth of both white clover and perennial ryegrass, but available phosphorus had some influence on them. And value of pH was high which was not good for the growth of white clover and perennial ryegrass.4. Influence of soil enzyme activity on the interspecific competition between white clover and perennial ryegrassThe height of both pinnacle and inspire was significantly correlated to phosphatase activity positively, the correlated coefficients were 0.837 and 0.883 respectively; The tiller number of pinnacle,inspire and the mixed grass of pinnacle and inspire was significantly correlated to phosphatase activity positively, the correlated coefficients were 0.853,0.858 and 0.814 respectively;There was no significant relationship between the height and the tiller number of white clover and perennial ryegrass with the catalase activity and urease activity. Increase of catalase activity accelerated transformation of nitrogen, phosphorus and potassium (K) which could be absorbed by white clover and perennial ryegrass effectively, increase of urease activity promoted circulation and transformation of soil nitrogen which could supplement need of perennial ryegrass for nitrogen, and in the middle and later stages, increase of phosphatase activity supplied available phosphorus for white clover and perennial ryegrass.5. Influence of shade on the height of perennial ryegrassThere was no significant influence of shade on the height of perennial ryegrass at the beginning, but gradually the height of perennial ryegrass reached the highest under the treatment with 1 window shade and under the treatment with 2 window shades the height of perennial ryegrass reduced a little. Proper shade was good for the height growth of perennial ryegrass, but when the light reduced fewer than 25%, it is not good for the growth of perennial ryegrass.6. Influence of cutting on the height of white clover and perennial ryegrassThe height of white clover and perennial ryegrass was significantly different with different cutting methods. Some cutting method would be partial to accelerate one kind of grass in the mixed lawn. So the higher grass would bring shade to the lower grass, therefore it brought about competitive inhibition, and furtherly influenced the proportion and the productive struction of the lawn.