Caucasian clover establishment in the high country and grazing responses in ryegrass/white clover lowland pasture

Abstract

A trial to measure the effects of establishment techniques and fertiliser application on seedling establishment and early root and rhizome development of Caucasian clover (Trifolium ambiguum) was sown in early October 1992, on a low-fertility, depleted, short tussock grassland site at Mesopotamia Station, South Canterbury. Three sowing techniques, broadcasting, sod seeding and strip seeding, each with two rates of fertiliser, 150 or 300 kg/ha molybdic sulphur superphosphate (8% P, 20% S), were used. By mid December, 48% and 38% establishment had occurred in the strip and sod seeding treatments respectively, but only 10% in the broadcast.

Strip seeding resulted in the earliest taproot and rhizome development of Caucasian clover and the greatest lateral spread of rhizomes. However, all plants strip and sod seeding developed rhizomes after nine months. Plants established by broadcasting were small with few rhizomes in the first season. The higher fertiliser rate improved establishment and growth, particularly in the strip seeding treatment. Strip seeded Caucasian clover established as rapidly as white clover and plants were similar in size after five months. However, Caucasian clover had a larger underground mass which could lead to greater persistence.

A grazing trial was established to observe how two cultivars of Caucasian clover and two seed lines of zig zag clover responded to four diverse grazing treatments. The experiment was located at Lincoln University, latitude 43º 39S and longitude 172º 28E on a medium to free-draining soil of medium fertility with an annual rainfall of 651mm. In March 1989 a seed production experiment was established and consisted of Caucasian clover cultivars Alpine and Monaro and zig zag clover seed lines Porters Pass and Kentucky. In spring of 1992 high endophyte ryegrass was direct drilled into this experiment. The first grazing to establish main plot treatments occurred in early October 1993. The experiment design was a randomised block design with two replicates of four treatments. The treatments included two grazing frequencies; rotational grazing and set stocking; and two grazing intensities; hard and lax. Point analysis was used to measure the botanical composition of the pastures.

Only the hexaploid Monaro Caucasian clover was agronomically suitable as a companion for high endophyte ryegrass and white clover under the range of grazing managements. The zig zag clovers showed a classic hay type species inability to persist and contribute to dry matter production under grazing. The diploid Alpine Caucasian clover persisted undergrazing but had a low cover percentage. Monaro Caucasian clover had a mean seasonal cover of between 14% and 21% in the grazing treatments, contributing more to pasture cover in the rotationally grazed treatments. White clover, in contrast was more suited to the set stock hard grazed treatment and to a lesser extent the set stock lax grazed treatment.