Pasture irrigation in the Mackenzie Basin

Abstract

Yields of 25 species and cultivars were compared under irrigated and dryland management on a soil of the Grampians set. Species were grown as pure standards at 3 fertiliser levels (0, 250, or 800 kg per ha per a superphosphate for legumes plus 0, 115, or 345 kg per ha per a of nitrogen for grasses) with basal sulphur and molybdenum added for all species. Depending on species, herbage was cut and removed under either a 6-week or 4-week cutting interval for 2 or 3 years. Yields from 5 legume treatments exceeded 15 tDM per ha per a under irrigation and 9 exceeded 5 tDM per ha per a under dryland conditions. The legumes were generally the highest yielding, grasses only equalling legume production at high N levels. The productivity rating of the legumes was in the following approximate order: Wairau lucerne (best), Hamua, Pawera and Turoa red clover, alsike clover, Huia and Pitau white clover, and then hybrid, Maku, and G4703 lotus. The yield of a Huia white clover/Ruanui ryegrass mixture was similar to that of white clover alone. Within the grasses, with both superphosphate and N fertiliser added, the ranking was: Kahu timothy (under 6-week cutting cycle as compared with 4-weeks for others), Apanui cocksfoot, Roa tall fescue, Matua and Butts prairie grasses, Ariki ryegrass, Nui, Ruanui, and Manawa ryegrasses, Massey Basyn Yorkshire fog, phalaris, dogstail browntop, and Poa pratensis. The yield ratio of irrigated:dryland averaged 3.4 for legumes,and 2.0 for grasses. In a subsequent experiment several species showed up to 50% increase in annual yield under 6 weeks as compared with a 4 week cutting

Pasture irrigation in the Mackenzie Basin 3. Hay mixtures

“…This was larger than had been reported earlier for the same Streamlands soil under trickle and spray lITIgation (Scott & Maunsell 1981). Soils show greater leaching of sulphur than of phosphorus, and we suspect that high rates of fertiliser were needed to counter the leaching of sulphur under borderdyke irrigation.…”

“…They occur in the zone of low rainfall, which has limited their agricultural development in the past. However, the advent of irrigation makes them potentially the most productive soils in the high country, as demonstrated by yields of pure species stands (Scott & Maunsell 1981). Similarly, the present work with species mixtures has shown that high hay yields can be obtained.…”

Irrigation of a High Country Mackenzie Soil

“…Pasture herbage production in excess of 15 t DM/ha/yr under irrigation and 2 -5 t DM/ha/yr without irrigation was measured on a deep Streamland soil by Scott & Maunsell (1981). At the other extreme irrigation of very shallow, stony Labreck soils yielded only 3.7 -5.7 t DM/ha/yr (Scott et a/ 1982). At Tara Hills High Country Research Station near Omarama, an irrigated shallow, stony Mackenzie soil, typically produces 9.5 t DM/ha/yr from established pasture (Greenwood unpub.…”

“…Pasture establishment on the stony soils in the Upper Waitakl Basin is slow and, under irrigation, pastures can remain clover dominant for many years (Scott et al 1982). It Is important that this phase of pasture development be taken into account in the economic planning of irrigation schemes.…”

Sustainability of New Zealand high‐country pastures under contrasting development inputs. 4. Organic matter components

“…Although N fixation rates were not measured, they would be expected to be high (c. 400-600 kg N ha-'yr" 1 ) during the early pasture development stage (Hoglund et al 1979). In a study in the same region on a brown-grey earth soil, the N fixation rate was estimated to be in this range from the difference in pasture growth and N content of legume versus grass swards (Scott & Maunsell 1981).…”