Recent Research Work

New Zealand Journal of Agriculture, Volume 101, Issue 1, 15 July 1960, Page 93

Recent Research Work

IMPROVEMENT OF HILL COUNTRY PASTURES

A HILL country pasture improvement trial on a field scale was begun in July 1957 at Fordell, 12 miles from Wanganui. The normal improvement technique •of topdressing and oversowing was compared with spraying with dalapon, topdressing, and oversowing. The merit of applying nitrogen was also investigated.

■npHE area selected for the experiment was a moderately -*■ steep, southerly face with a browntop dominant pasture containing sweet vernal, dogstail, a little cocksfoot, and annual clovers. The trial area was part of a .fairly large paddock and because of being a southerly face it had been to a large degree neglected by stock. The paddock had no previous topdressing and was in an unimproved state with manuka invading the sward.

At the beginning of the trial the southerly face on which the plots were situated was fenced off from the rest of the paddock to permit good grazing management and to facilitate mob stocking during the trial. Soil tests taken in October 1957 gave a pH of 5.7, a calcium level of 7, a medium to high potash level (8), and a low phosphate level (1). The hill face was pegged off into three one-acre plots which were given the following treatments: PLOT 1 Sprayed with 5 lb of dalapon and sown with 30 lb of grass and clover seed 13 weeks after spraying. Topdressed with (a) 1 cwt of sulphate of ammonia 15 weeks after spraying and (b) 3 cwt of superphosphate 17 weeks after spraying. PLOT 2 ' ' • Sprayed with 5 lb of dalapon and sown with 30 lb of grass and clover seed 13 weeks after spraying. Topdressed with 3 cwt of superphosphate 17 weeks after spraying. PLOT 3 Oversown with 30 lb of grass and clover seed and topdressed with 3 cwt of superphosphate. No dalapon or nitrogen was used on this plot. The seeds mixture used was 20 lb of perennial ryegrass, 4 lb of cocksfoot, 2 lb of crested dogstail, and 4 lb of white clover, giving a total of 30 lb per acre.

The 5 lb of dalapon per acre in the first two plots was applied as a spray in 13 gallons of water by a helicopter using a 23 ft boom with 42 tee jets. The helicopter flew

at 27 miles per hour and covered the trial area in three runs. The spray coverage was not particularly good; three strips across the plots received very little spray. Weather was ideal at the time of spraying, but the condition of the pasture was not particularly suitable because rank browntop occupied a considerable portion of the plots. The remainder of the area was closely grazed.

EFFECT OF SPRAYING

There was a limited amount of cocksfoot in the pasture and this was the first grass to die off after spray treatment. It was three to four weeks before the rank brown-

top began to die off and six to eight weeks before the pasture was open enough for oversowing. The area was not oversown, however, until 13 weeks after spraying, partly because of the unavailability of the helicopter and partly because of possible germination injury from a heavy population of slugs in the decaying vegetation. The pasture on the trial area was point

analysed in October 1958 to measure any changes in pasture composition that had taken place as

a result of the treatments. A previous point analysis had been taken at the beginning of August 1957.

PLOT 1 Dalapon -|- sulphate of ammonia -j- superphosphate and oversowing: There was a reduction in the amount of browntop in the sward and individual browntop plants were less matted. White clover entered the sward strongly and became one of the major components. Ryegrass and sweet vernal increased and there was a slight increase in cocksfoot and crested dogstail. PLOT 2 Dalapon -|- superphosphate and oversowing: More ryegrass entered the sward than in plot 1. White clover again established strongly. There was an increase in the amount of sweet vernal and a small increase in danthonia and crested dogstail. The amount of cocksfoot recorded was slightly less than in the original sward. PLOT 3 Superphosphate and oversowing: White clover established at least as well as in the first two plots. There was only a small increase in the amount of ryegrass and no increase in crested dogstail or cocksfoot. There was a considerable increase in sweet vernal . and a small increase in danthonia. . . : The pasture on the three plots appeared . very similar on visual observation and all plots were better than the surrounding pasture. The biggest factors in . improving the pasture in this particular case were topdressing with superphosphate and oversowing with 4 lb of white clover, which was included in the general seed mixture. The fencing off of the southerly face permitted good pasture management and allowed the full benefit from the topdressing and oversowing to show up. There was no benefit from topdressing with 1 cwt of sulphate of ammonia. Unfortunately, there was too great a lapse of time between spraying and oversowing and this allowed the partially killed weed grasses to reinfest the pasture. The rate of dalapon (5 lb per acre) was not sufficient to give a complete kill of the existing turf on either the closely grazed or rank portions of the pasture. The kill of turf was, however, relatively better on the close grazed areas.

—A. A. DUNCAN,

Farm Advisory Officer,

Department of Agriculture,

Wanganui