THE EFFECT OF IRRIGATION INTERVAL AND SOIL TYPE ON PASTURE AND LUCERNE PRODUCTION

The responses of pasture and lucerne to irrigation were compared in 2 series of trials (1976-1981 and 1980-1984) on 8 different Canterbury soils. Pasture responses were also measured on a further 4 soils. With unrestricted irrigation, pasture yields were similar (about 11 t DM/ha/yr) on 8 of the 12 soils. These soils ranged from stone free Wakanui clay loams to a very stony Balmoral silt loam. Two soils yielded at a higher level, and two very stony soils significantly less. Non-irrigated lucerne yielded more than pasture in "average" Canterbury seasons, but less in two exceptionally dry years. With irrigation, lucerne yielded more than pasture for the first 2 or 3 years but tended to decline thereafter. The paper discusses irrigation strategies for border strip irrigated pastoral farms in times of water restrictions. It concludes that maximum DM production is likely to be obtained by spreading the available water over all irrigated pasture untii the irrigation interval reaches 23 to 28 days on shallow stony soils and 34 to 38 days on higher water holding capacity soils. Keywords: pasture production, lucerne production, irrigation, irrigation interval, Canterbury.