ChileanJAR

The effect of P, K and S application to white clover/perennial ryegrass (Trifolium repens/Lolium perenne) sward on thetotal, clover and ryegrass DM yield and on the changes of N, P and Kavailability in soil were measured. The sward was established in 1983 on avolcanic soil (Typic dystrandept), Mañil series, located at the Quilamapu Regional Research Center. An experiment with four levels of each element was conducted during two growing seasons (1984/85 and 1985/86). Phosphorus application significantly increased (P < 0.05) the total D. M. yield in 25 and 30% over the control without P when 66 and 132 kg of P/ha/year were applied, respectively. The extra D.M. production, when the level of Pwas 66 kg/ha/year, was 7.0 and 6.0 kg per kg oftriple superphosphate applied, in the first and the second growing sea son, respectively. There was no effect of K application in 1984/85; but in 1985-86 the D. M. production increased in 20% when the level of K applied was 42 kg/halyear compared with the control. Both elements, particularly P, affected only the clover growth. Sulphur did not affect the D.M. production. Nitrogen and K availability in soil were not affected by P or K application and P availability in soil only increased with the highest rate of P applied (132 kg/ha/year).