Abstract 173

Winter,-WH

Trop. Ecosystems Res. Cent., Div. Trop. Crops and Pastures, CSIRO, Winnellie, NT 5789, Australia.

Tropical-Grasslands. 1987, 21: 2, 71-81; 25 ref.

Productivity of cattle grazing the native perennial tall grasses Themeda triandra, Sehima nervosum, Sorghum plumosum and Chrysopogon fallax in the monsoonal tropics is low because of the poor fodder quality for most of the year. In typical pastures at Katherine, combinations of 3 management options for improving livestock production were studied. In the late dry (LD) and early wet (EW) seasons cattle liveweight changes were better in treatments where half of the paddock had been burnt early in the dry season. The EW response was dependent upon the supplementary feeding of NaCl. In the late wet (LW) season the steers responded positively to NaCl alone. Steers fed a complete supplement of urea and minerals, in conjuction with pasture burning and NaCl, had the highest gains in the EW, LW and early dry (ED) seasons and the smallest losses in the LD season. Annual gains for the 5 treatments were: control 21 kg, salt 47 kg, fire 46 kg, salt + fire 66 kg, salt + fire + supplement 134 kg. These responses were attributed to the supplements overcoming seasonal dietary deficiencies of Na, N, P and possibly S. Burning the pasture reduced pasture yield in the subsequent wet season by about 40% but the quality and accessibility of the forage in the EW season, in particular, was better. These factors contributed to better growth in cattle grazing the previously burnt pastures at this time.