REGRASSING EXPERIMENTS ON CANTERBURY BACK-COUNTRY.

New Zealand Journal of Agriculture, Volume XXVI, Issue 6, 20 June 1923, Page 358

REGRASSING EXPERIMENTS ON CANTERBURY BACK-COUNTRY.

F. E. WARD,

Instructor in Agriculture, Christchurch

Several factors have no doubt played a part in bringing about the condition of denudation which extends over thousands of acres of good sheep-country in the Mackenzie district. Among the chief causes of depletion are severe climatic conditionshot north-west winds in summer with heavy and continuous frosts in winter ; ' overstocking with sheep and rabbits; and conditions of tenure which have not encouraged the occupiers to improve their holdings.

In the spring of 1921 the Agricultural Instruction Branch of the Department, in co-operation with Canterbury College, undertook experimental' sowings to ascertain whether or not these areas could be regrassed by surface-sowing, or with the aid ■ of such agricultural operations as could be applied in’ a practical manner over large areas. The Department already had two wire-netted areas on which experimental sowings of grass had been made a number of years previously. Numerous species had been tried, and the plots gave a useful guide as to what grasses were likely to establish if sowings were made on selected areas not protected by wire netting.

In planning the sowings now dealt with, three aspects were taken into consideration : (1) Flat ground exposed to wind, (2) ’ sunny faces, and (3) dark faces. The sowings were. made in the spring of 1921, autumn of 1922, and spring of 1922. The grasses used in the spring of 1921 were cocksfoot, .. heath mixture. (Yorkshire fog, white * clover, and rye-grass), yarrow, tall fescue, white clover, sheep's burnet, Grimm lucerne, tall oat-grass, Poa pratensis, and florin. The sowings made on the flat ground exposed to wind germinated and dried off, and resulted in no take of grass. Those made on sunny faces were also very poor and practically useless, except where soil conditions were favourable enough to support a weak strike.

The results on the dark faces were most encouraging. The first sowings (6th September, 1921) were inspected in March, 1922, when a satisfactory strike was noticed, but all plants were small and tender, and it was problematical whether or not they would be lifted out by frost during the advancing winter. . When again inspected on 7th September, 1922, it was found that practically all the plants had wintered well, and quite a green tinge was noticeable on what had hitherto been a dark-brown face. The portion here referred to was Gallows Hill, on Haldon Station, the altitude of the latter being about 1,200 ft. The top of the hill, some 300 ft. above the surrounding flat country, is rocky, but it was . among the rocks that the grass appeared to be doing particularly well. The hill was stocked with sheep from time to time, but not heavily in the early stages.

A further inspection was made. on 23rd February, 1923, when it was found that the hill had been heavily stocked with both sheep and

rabbits. The grass showed evidence of having been closely eaten, but not to any extent pulled out. Yorkshire fog had established strongly, and though despised in low-country pastures it x is quite accepted in the country under notice. Cocksfoot, which had wintered well, was now showing signs of depreciation under the dry summer weather, and many plants secured at this time by a weak roothold were in grave danger of being pulled out by sheep. With due consideration to the amount of seed sown, the grasses present in order of abundance were : Very numerousYorkshire fog, cocksfoot, yarrow, rye-grass ; Rarer — clover, sheep’s burnet, goose-grass, and Poa pratensis ; lucerne, tall -grass ; practically noneflorin and tall fescue. A few plants of fog, cocksfoot, rye-grass, and goose-grass in sheltered positions had seed-heads.

In a wire-netted area having a northerly aspect eight one-acre plots were sown, each plot having a different predominating constituent.’ There were two main objects in view with these sowings—firstly to ascertain if a quantitative sowing of the various constituents played any important ' part in regrassing such country, and secondly to note whether chain-harrowing had an advantage over surface-sowing without artificial means of covering the seed.

At date of writing one cannot see any appreciable advantage in quantitative sowings. 'Owing to the very dry local conditions plants require a good deal of soil-space/ and when the seed is thickly sown the death-rate is great and' a thin strike results. It cannot yet be stated that any one plot excels the others, but the grasses most in evidence are the same species as those already mentioned as doing well on Gallows Hill; The same grasses were sown in the area as outside, with,the addition of Chewings fescue and chicory. Owing to there being no stock in the netted area, the .grasses when inspected in March, 1923 (sown 6th September, 1921), were tall and straight in habit of growth, but very little evidence was present of their seeding. Here cocksfoot, yarrow, tall fescue, and chicory were very noticeable, the

last-named having seeded fairly freely. The chain-harrowing to give cover to the seed seemed quite unnecessaryin fact, appeared to cover the seed too deeply in many places. The frost-cracked ground, with a shower of rain after spring sowing, gave the most satisfactory results. Somewhat similar sowings were made on Mount Possession Station, Ashburton County, where the rainfall is somewhat heavier than ' at Haldon, but the land probably of poorer quality. Here flat and undulating country was selected (altitude approximately. 2,000 ft.), and sowings made both in autumn and spring. The autumn sowings confirmed the Mackenzie country experience, and were quite useless. The spring-sown seed gave a fairly good strike' particularly on the southerly aspects or where protected from the north-west wind. As far as present observations go, • bare ground proved a more acceptable seed-bed than that covered - with’ vegetative growth, such as scabweeds, Triodia australis, Strathmore weed, a yellow composite, New

Zealand bluebell, native willow-weed, &c. On the flat ground the tussocks (Poa caespitosa and Festuca novae-zelandiae) afforded shelter, and the seedlings were better and stronger than those, in the open. The general conclusions drawn so far are, — (i.) Spring is the best time to sow. (2.) Frost-cracked • bare ground with a southerly aspect affords the best chance of a strike. |G; (3.) The regrassing of these positions should be attempted before the sunny faces or those positions exposed to the north-west winds. (4.) The grass species mentioned are suitable for the purpose. The introduction of grasses from other countries having similar climatic conditions should have useful results. -

Four grasses have been introduced from South Africa and four from Queensland, and these will be sown next spring. The South African species are Ischaemum glauchtachigum, Pennisetum cinroides, Panicum maximum, and Panicum laevifolium. ■ The Queensland grasses are Eriochloa annulata, Setaria glauca, and two samples of Panicum tussock-grasses. Australian spiked blue-grass (Agropyron pectinatum) was evidently introduced into the Mackenzie country by the wool of rams imported from Australia, and it is spreading rather rapidly, even on the sunny faces. Thanks are due to Messrs. James Inness (Haldon Station) and James Grant (Gray’s Hill Station) for their valuable assistance, which facilitated the carrying-out of this work. The co-operation and assistance of Mr. M. Dalziel, supervisor of the Canterbury College reserves, is also cordially acknowledged.