Studies on Competition Between Grass and Legume in Mixed Sward : I. The growth of two species in orchard grass and ladino clover mixed sward

The balance between grass and clover in mixed sward is highly susceptible to environmental change. Many studies have shown that a sward can become grass-dominant or clover-dominant according to the nutrient status or grazing management imposed on it. In this paper seasonal and yearly changes of botanical composition in mixed sward of orchard grass and ladino clover grown under different treatments in cutting height and amount of nitrogen application, are presented. 1. In all results so far obtained by the author, the percentages of grass are tend to decrease as time passes. It is found that the kind of treatment affects on decreasing rate of grass percentage. Low cut treatment accelerates decreasing rate and high cut treatment makes it slow. Seasonal maximum in grass percentage is found in spring, and then it decreases rapidly through summer to autumn. 2. Yield decrease in grass and yield increase in clover in progress of year are due in part at least to decrease of stem number density in grass and increase of stolon number density in clover progress of year. 3. Spring high yield in grass is due to its high stem number density and plant height. Summer low yield is due to sudden decreasing in stem number density and autumn low yield is due to low stem number density and plant height. 4. Spring high yield in clover is due to its high stolon number density, and summer decrease of yield is in parallel with decrease of stolon number density. It is likely that autumn increase of yield is due to increase of new developed stolon number. 5. By cutting at a high level, yield of grass increases but that of clover decreases. Those are attributed to increase of grass stem number density and the consequent shading of clover, i.e. to decrease of stolon number density. 6. Application of nitrogen gives increased yields of grass and decreased yields of clover especially in spring. In any seasons, much more yields of clover are found in the plots without nitrogen. 7. The responses of clover in pure stand to treatment in height of cutting and nitrogen application are quite different from those in mixed sward. On the other hand, in case of grass, differences to treatment between pure stand and mixed sward are not so much, however the decreasing rates of hill number density in mixed sward are rather faster than those in pure stand. It is likely to be concluded that various aspects of responses found in pure stand are not applicable to phenomena which take place in mixed sward.