Simulated grazing of lucerne

Abstract

Over recent years, there has been a considerable increase in the area of lucerne grown in New Zealand, particularly that used for grazing. The total for conservation and grazing increased from 19,000 ha in 1947 to about 145,000 ha in 1968 (White, 1968) and it is expected that the figure will reach 200,000 ha by 1973. In the same manner, the proportion used for grazing rose from less than 10% in 1947 to more than 40% in 1966 and it is anticipated that this trend will continue into the foreseeable future. More recently, the importance of pure lucerne, especially in early spring, has become greater following the general trend of intensifying animal production through early weaning of lambs (Jagusch et al., 1970; Jagusch et al., 1971; Joyce et al., 1972; McConnell, 1972).

One of the main aims of the trials reported in this thesis is to verify Professor K.F. O'Connor's theory that removing the apices of immature lucerne plants stimulates the growth of crown buds and at the same time enhances the growth of axillary shoots on the upper portions of the stubble. Results of such findings could prove to be valuable in future in view of the reported increase in the number of young lambs weaned on to lucerne pastures and noting also that the grazing behaviour of these animals differs markedly from that of the older stock. Further, it has been shown that leafy tops (stem apices) and immature lucerne or cool season growth are high in feed quality (Bailey et al., 1970; Jagusch et al., 1970; Smith, 1970; Jagusch et al., 1971).

Although a few workers (O'Connor, 1970; Peart, 1970; McKinney et al., 1972) have attempted to provide balanced data on the performance of both animals and pastures in a grazing system, little is known about the individual plant responses to varying grazing behaviour, particularly its reactions to different periods of grazing and spelling. Lack of information on the above aspects prompted the cutting treatments described in this thesis to be designed and the experiments carried out. It is hoped that the principle of optimal growth and production or other relevant information discovered from the cutting trials could gain useful applications to a real grazing situation.