The effect of cutting frequency and root segregation on the yield from perennial ryegrass-white clover associations

Dry-matter and nitrogen yields were recorded from perennial ryegrass-white clover associations which were defoliated 2, 4 or 6 times a year during the period 1963 to 1965. 2. The average yearly output of dry matter was approximately 4000, 7000 and 6000 lb/acre for 1963, 1964 and 1965 respectively. Nitrogen harvested amounted to 132, 184 and 179 lb N/acre. 3. The mean annual dry-matter yields from 2, 4 and 6 defoliations were 5300, 6100 and 6000 lb/acre and the corresponding figures for nitrogen yields were 112, 166 and 217 lb N/acre. 4. Both segregation of the species below ground and increasing the defoliation frequency were responsible for higher contributions towards drymatter and nitrogen yield from the clover component. 5. A comparison of the nitrogen yields between the plots with species segregated rather than integrated below ground suggests that the effects of underground nitrogen transference from 30–31 lb N/acre could first be demonstrated in the spring of the third year.