THE EFFECT OF SWARD HEIGHT ON RESPONSES OF MINI-SWARDS OF PERENNIAL RYEGRASS WHITE CLOVER TO SLURRY APPLICATION

The influence of sward height at the time of slurry application on swa rd responses to slurry was investigated using perennial ryegrass (Loli um perenne)/white clover (Trifolium repens) mini-swards under greenhou se conditions. Pig slurry, cattle slurry and a fertilizer control were applied either to: swards cut 1 d before slurry application to height s of 2, 4 or 8 cm (CH2, CH4 or CH8); or to swards cut to 4 cm with reg rowth intervals of 1, 4 or 8 d before slurry application (RI1, RI4 and RI8). Scorch, smother and growth of marked clover stolons and grass t illers were monitored after slurry application. Dry-matter yields of b oth species were recorded over two harvests. Electrolyte leakage from leaves was used to assess leaf damage. Both slurries increased leakage , which was greatest from clover leaves, with biggest increases caused by pig slurry. Yield responses to slurry application varied with plan t species and sward height. Reduced grass growth after slurry applicat ion to long swards (CH8, RI4, RI8) was probably caused by greater smot her. In short swards (CH2), grass leaf growth was not depressed follow ing slurry application but grass yields were reduced. Ammonia volatili zation losses may have been greater in both long and short swards, con tributing to yield reductions. Yield responses to slurry were greatest in swards cut to 4 cm, 1 d before application.