Autumn yield of caucasian and white clover pastures under irrigated and drought conditions : a dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Agricultural Science with Honours at Lincoln University

The autumn performance of Caucasian clover, white clover and five grass species: perennial ryegrass, cocksfoot, phalaris, tall fescue and grazing brome were examined at Lincoln University during autumn 1998, after a summer drought. The effects of irrigation, clover and grass species on yield, botanical composition and water use of pasture swards were measured. Total dry matter production from irrigated plots was (3,470kg DM/ha) , more than 10 times that of unirrigated plots (320kg DM/ha). While there were differences in total production between species, the order depended on irrigation. With irrigation, cocksfoot, phalaris, and grazing brome yields were about the same (4050- 4,330kg DM/ha) , while under unirrigated conditions, grazing brome, cocksfoot and ryegrass pastures had the greatest yields, at 530, 420 and 330kgDM/ha, respectively. Dry matter production over time showed similar trends to total yields. Growth rates under irrigation ranged from 32kg DM/ha/d for pure white clover, to 110kg DM/ha/d for cocksfoot and phalaris pastures. Sward composition changed significantly over time, with total clover producing a larger percentage of pasture yield in Caucasian clover pastures, than white clover pastures from 8 February to 20 March. Both clovers formed less than 6% of the biomass of grass/clover pastures on 21st June, 1998. Dry-land white clover pastures had not recovered by the 9th of September, although dry-land Caucasian clover and both clovers under irrigation had. Water use of swards increased by 47% with irrigation. Under irrigation, pure clover swards used less water than grass species. Caucasian clover may be beneficial as an additive to mixed grass/white clover pastures, increasing total autumn clover contents, as well as increasing summer yields under moisture deficit conditions. Cocksfoot, phalaris and grazing brome pastures provide the greatest pasture production under non soil moisture limiting conditions in autumn, after summer drought