Control in South Otago

New Zealand Journal of Agriculture, Volume 73, Issue 6, 16 December 1946, Page 549

Control in South Otago

By

J. G. RICHARDS,

Instructor in Agriculture,

Balclutha.

IN many regions of New Zealand the vegetative cover today differs greatly from that which existed when the pioneers arrived. In the broadest of classifications this vegetative cover was of two distinct types, and chief among the factors governing their distribution was rainfall. Where rainfall was high an association of native trees and shrubs thrived, forming the famed New Zealand bush; where the rainfall was low the plants forming the ground cover were tussocks and other xerophytes. With the growth of New Zealand’s farming industry several million acres of each type have given way to pasture land, and the species dominant in the pastures are English and other introduced grasses and clovers. In many cases these introduced species have thrived so well under present farming methods that they have even ousted native species from their natural areas. On the other hand many of the native plants are con-

stantly trying to regain their former place, and as the introduced species have a much higher productive capacity the New Zealand farmer is ever on the alert to maintain his production and check the reversion of his pasture land. ‘ INVADING native species cause the greatest concern under high rainfall conditions— more than 40in. a year—and particularly where.. pasture has been established on unploughable land. This problem. of pasture land reverting to secondary growth constantly confronts settlers in the.Catlins district of South Otago, and in 1939 the. Government introduced a scrub-cutting scheme to assist those farmers in their efforts to retain their unploughable pasture lands. The plant species which cause the most trouble are wineberry (Aristotelia racemosa) , fuchsia (Fuchsia exorticata'), boxwood (Cassinia iulvida), manuka, and bracken fern. In a survey carried out in 1938 it was estimated that about 20 per cent, of the area of each farm and 45 per cent, of the area of surface-sown bush land had reverted and was clothed with these species.

Review of Areas Cut

Under the scrub-cutting scheme areas were cut on SI properties and .the total area of secondary, growth felled

was: 988 acres. Work was begun in February, 1939, and continued until the following September, during which time up to 43 men were employed. A typical cross-section of the areas cut was recently inspected and salient points were noted in the control of this secondary growth on unploughable land.

With few exceptions the majority of the areas were reverting- to an association of fuchsia and wineberry (Fig. 1). From the tall and profuse growth on some blocks it was apparent that reversion had begun within two years of the scrub being cut and burned.

Apart from supplying meals to the workmen, no costs were borne by the farmer,' the State paying all wages, but the farmer had to agree to treat his area as recommended by the committee in charge of the . scheme. For instance, he had to produce written evidence that he would sow .out the area with' an approved seeds mixture, and. fence ' and stock to the best of his ability. In practically all cases farmers honoured their obligations, but. where they did not do so the reversion was most rapid. ■ .

For the successful maintenance of pasture on this unploughable land the settler must consider many factors of prime import, and these factors are very closely linked. They are:—1. The size of the area to be felled. 2. The time at which the scrub is felled. 3. The necessity for first-class burns. 4. The availability of stock to crush the growth. . 5. The logging-up of unburnt debris. 6. Pasture species to be included in the seeds mixture. 7. Manurial treatment. . . - 8. Pests such as rabbits. Size ,of Area to be Cut Men who are efficient at cutting secondary growth are almost invari-

ably at a. premium, and when a farmer obtains the services of scrub-cutters he usually- wants'to use their services to the fullest and tries to fell as much scrub as possible. The felling of large areas of scrub on any property is quite in order if the farmer is able to handle the regrassing of the area, but in many cases where large blocks are cut and burnt that is the only treatment they receive, and . they rapidly revert to scrub.

It is imperative, therefore, that the area of scrub cut each year be of such size that, with the aids of management he has available, the farmer is able to sow out and properly control it. Too often areas have been felled and not even burnt, solely because the farmer is too occupied in other directions to undertake the work.

Time to Fell Scrub In the Catlins work many poor burns were obtained, and ’ the chief reason was not the' lack of a good fanning wind but the absence of sufficient foliage to carry the fire. The quantity of foliage available-to carry the fire— . particularly, in the "case of deciduous trees, such as fuchsia— governed by the time of the year at which the scrub is felled. The best time to fell this type of secondary growth is in September and October, ■ when the sap is on the rise and leaf production is at a maximum. .It is freely admitted that most of the Catlins scrub was felled much too early in the year, but in that case the availability : of labourgoverned the time of cutting. . . . When scrub is cut in. September- , October it is- usually ready to fire in

December, and sowing out at. this period of the year on the ash of - the burn should allow sufficient time for the young pasture to become well established before the winter, •< . Necessity for Good Burns L . '. J . Unless a good clean burn is obtained, the successful establishment of grass on this unploughable ■ country is most difficult. The essentials for a . good burn are adequate foliage and . a good fanning, but not too vigorous, wind, Under a poor burn reversion is taking place most rapidly from old . fuchsia stumps and roots which are not Killed oy he fire and from heaps of unburnt logs and sticks which become a nuisery for fern and other undesirables, Fig. ,1 . shows regeneration from unburnt fuchsia stumps and Fig. 2 shows a typical fern nursery among logs and sticks. In Fig. 3 the righthand , side shows little reversion after a good burn, whereas the left-hand side shows complete reversion to fern after' a poor burn.

Stock Management It is imperative that adequate stock be available to crush and graze the growth. Cattle are the . most efficient, and areas were seen that had reverted because insufficient cattle beasts were present at the required time.

Logging-up of Debris On areas where major success has been obtained the farmers’ management. practice has included the logging-up of burnt and sown blocks. ■Logs and stumps are removed by gelignite, or by horses or tractor,: and

piled into heaps, for - burning; it is customary to form these heaps about regenerating fuchsia so that the heat will kill the : plan Logging-up of an area should be done "as soon as possible after the sward has become established, and the size of the area to be coped with is important. If too large an area be felled, it may be some years before the farmer can log up the whole block and much of it may revert in the meantime. By the. use of bulldozers logging-up . can . be greatly facilitated, and good use has been made of these machines. .. > .

Seeds- Mixtures

, In': some cases blocks of scrub were felled and burnt but were not sown out. That practice is very wasteful, for the scrub immediately comes in and again occupies the area. : ; On, blocks cut under the scrub-fell-ing ' scheme . and sown out cocksfoot was predominant as a pasture species in the seeds mixture, and where it is growing in association with legumes such as white clover and Lotus major this grass is giving excellent results in providing feed. Cocksfoot was included in mixtures in quantities ranging from 8 to 141 b. It cannot be too strongly emphasised that only the best strains of grasses and clovers should be used as the components of a seeds mixture for sowing out on scrub burns, and . the • following might be recommended; : ’ ; lb. per acre Certified perennial ryegrass 12 . ' Certified cocksfoot .. 10 to 14 Certified white clover .. 11 Lotus major .. , . . . . 1 Browntop .. .. . . 2 Crested dogstail .. .. ,4

301 to 341

Value of Liming - An encouraging feature to be noted in the Catlins district is the farmers’ awareness of the benefits to be derived from the use of lime. The amount ‘of lime delivered into this district is increasing yearly, and on properties where lime has. been used for some years the results are most evident. The soils in the Catlins district have developed under bush, and their lime requirement varies with the type of forest trees which formed the cover. ' The continued use of lime and phosphates on grassland in this area is certainly warranted. * ' Control of Rabbits ' i The ravages of the rabbit are too ( well. known to need elaboration, but it may be emphasised that full effort should be made to check them during all' seasons. Too often the life of a pasture is seriously , reduced by their depredations in . its ' establishment stages.

MAIZE GROWING FOR GRAIN

The demand for maize for stock food is so important that every endeavour should be made to have the acreage of this crop increased. In certain parts of -.the North Island maize can be grown successfully and is quite a payable crop whether the grain is fed to stock on the farm where it is produced or : marketed. -Full instructions for sowing, cultivating, manuring, harvesting,, and storing, the maize crop are given, in Bulletin No. 269, "Maize Growing for. Grain,” which contains diagrams and descriptions of "various types of cribs for maize storage. Diseases and insect pests affecting the crop and methods of feeding the grain to stock are also described. This bulletin is available free from the Department -fit Agriculture at Auckland, Palmerston North, Christchurch, and Dunedin.