Assessment of summer forage crops for sheep by the put-and-take grazing technique

Abstract

During three summers a sorghum-Sudan grass hybrid (Sorghum bicolor x S. sudanense) and S. almum were grown at three levels of nitrogen fertilizer (0, 84, or 168 kg N/ha) in a cool temperate environment at Armidale, N.S.W. A pearl millet (Pennisetum typhoides) was included in the experiment during one summer and Japanese millet (Echinochloa crus-galli var. frumentacea) in two summers.

Differences in dry matter production were non-significant except in one summer when Japanese millet produced almost twice as much as the sorghums.

The forages were grazed by young sheep on the put-and-take method. Carrying capacity as judged by this technique was high on all crops except pearl millet but average daily gains were low, the performance on S. almum being generally the poorest. Total production (expressed as metabolizable energy intake) was significantly higher for S. almum than for the hybrid or pearl millet in the first year but there were no significant differences thereafter.

Pre-sowing application of anhydrous ammonia did not increase the dry matter available at the first grazing and tended to depress animal performance. Liveweight gain per hectare was significantly reduced by nitrogen in one of the three summers. Residual soil nitrogen subsequently assessed by an oat crop was substantial on plots that had received ammonia.

Crop performance measures were computed in various ways and differences between them are discussed. It is tentatively concluded that, of the four crops, Japanese millet has the most potential for use by sheep in this environment.