Department of Agriculture, Sigatoka, Fiji
Mission grass (Pennisetum polystachyon) pastures on steep hill land were oversown with legumes, fertilised with superphosphate at three levels, and grazed continuously for eight years at a series of 6, 6 and 12 stocking rates between 0.9 and 3.5 steers ha-1.
Superphosphate increased total presentation yields of herbage, especially at low stocking rates.
Heavier stocking decreased the contribution from mission grass and increased that from the native legume, hetero (Desmodium heterophyllum) and a weed legume, Mimosa pudica, irrespective of fertiliser level. Siratro (Macroptilium atropurpureum) dominated Schofield stylo (Stylosanthes guianensis) in the early years only when heavily fertilised, but both declined with increasing stocking rate and with time. Total legume (siratro, stylo and hetero) contribution was nearly constant, at about 25%, over the range of stocking rates for the oversown pastures after 8 years.
The grasses, Chrysopogon aciculatus and Axonopus spp., became more prevalent at high stocking rates with nil or low fertiliser, while a herbaceous creeper (Mikania micrantha) increased greatly following three years of vigorous growth of siratro at low stocking rates and high fertiliser.
Changes in the composition of major species were continuing in the eighth year of grazing.
Improved grasses oversown at the beginning of the experiment failed to establish but creeping Nadi blue grass (Dichanthium caricosum), oversown later, had spread to contribute up to 14% of the herbage after 4 years and was suppressing weed growth. It combined with hetero to form a stable permanent pasture at the higher stocking rates needed to justify fertiliser application.