A Conservation Farming System for New Zealand Hill Country

New Zealand Journal of Agriculture, Volume 95, Issue 2, 15 August 1957, Page 161

A Conservation Farming System for New Zealand Hill Country

By

D. A. CAMPBELL,

Superintendent of Soil Conservation, Department of Agriculture, Wellington NEW ZEALAND'S soil erosion and flooding problems have their origin on the hill country pastoral lands, especially where farming has forced grass to take over the protective functions of vigorous native forest, scrub, fern, and swamp vegetation. Experiments by Soil Conservation officers of the Department of Agriculture on several typical hill country farms acquired by the Soil Conservation and Rivers Control Council have provided the basis for a conservation farming system for hill country which could reduce costly erosion and flooding. The system is based on topdressing and oversowing to rebuild fertility, spelling to strengthen pastures and promote reseeding, fencing to control grazing by cattle and sheep, tree planting of eroded land, gully control, contouring of ploughable land, the construction of water control dams, and fire and pest control.

SOME 70 per cent, of the occupied agricultural land of New Zealand is unploughable pastoral land and much of this demands special conservation farming methods because of the hitherto serious deterioration, soil erosion, and weed invasion problems which beset it.

Investigation of catchment problems has revealed in general that the drastic changes in the vegetation brought about by developing farming resources have been reflected in equally drastic changes in the soil on the hill country and that soil erosion and. flooding have their origin on hill country.

The protective, stabilising, and water-controlling combination of vigorous native vegetation, litter, and spongy soil, has given way to a shal-low-rooted, less protective, in fact threadbare carpet of grass on compacted, impervious, and often exhausted soils. The problem is one of restoring an erosion-resistant and water-absorbent combination of soil and vegetation with a satisfactory capacity to control water, which causes most soil erosion.

Farms Acquired To develop practical soil conservation methods for this problem hill country eight typical, deteriorated, and eroded farms were acquired as soil conservation reserves. Being typical of hill country, these farms provided little scope for applying the array of well-known soil conservation practices developed in the United States for ploughable land. However, they provided ample opportunity to investigate various adaptations of the limited range of management practices available on unploughable hill country. Experimental Work Experimental work was undertaken to find out what combinations of suitably adapted farm management and special conservation practices were necessary to combat soil erosion and provide practical methods of conservation farming. Because this experimental work had to produce practical answers, the units of land acquired were typical of the size of the average farm in the area.

The changes in land use and modifications required in a conservation farming programme had to fit into the economic unity of the farm. Additional experimental work was undertaken on private farms where gully, slip, sheet, stream, and wind erosion problems were tackled directly by subsidising farmers through Catchment Boards to do the work to specified standards. By 1947, the early work on the experimental and demonstration farms together with the soil conservation works undertaken by Catchment Boards had yielded the following information and results:—

Spelling or retirement from grazing for variable periods, especially during flowering and seeding, revived both native and sown pastures remarkably, and generally produced a much more erosion-resistant and water-controlling cover on eroded lands. Surface sowing of clovers, and evei. grasses under certain circumstances, resulted in surprisingly good establishment on deteriorated sown and native grasslands, particularly wher. grazing was strictly controlled during and after establishment. Topdressing with phosphate and trace elements proved to be the biggest

factor in promoting the introduction of clovers and the strengthening of the grasses on deteriorated and exhausted hill country soils in both the main islands of New Zealand. Rotational grazing of cattle was more effective than sheep grazing in regenerating poor pastures, and cattle obviated the need to burn native pastures periodically. The rapid recovery of native pastures where burning and rabbits were eliminated and cattle grazing was controlled was most promising. The value of planted trees in healing unstable eroded land, particularly in gullies, was confirmed in all districts, as was the effectiveness of native cover regenerated by complete spelling in the higher rainfall areas. The worth of pasture furrows in conserving water and reducing scour of soil and flooding of streams was enhanced by their beneficial effect on pastures in the lower rainfall areas. Graded banks and broad base terraces were strikingly effective in stopping the loss of soil from cultivated slopes by sheet and rill erosion, and in reducing greatly the amount of uncontrolled run-off, in all the initial trials. Early trials proved that wide, shallow, grassed waterways could effectively dispose of excess run-off in this country, where good swards of grass were readily obtainable. The merits of water control dams capable of storing temporarily flood waters and regulating their discharge through a pipe were also demonstrated. Gully control works soon revealed that structures such as the various kinds of debris dams, drops, and plantings in the gully had to be supported by radical changes in the grazing management of the catchment, and by topdressing, terracing, and the diversion of the water where possible.

All these single practices were of limited value unless they were used to support each other and were backed up by constructive farm management. As they had to be used mainly on unploughable hill country, they were of limited use until the fertility of the land was built up by topdressing and oversowing. This not only increased the protective capacity of the pasture, but also increased carrying capacity and provided revenue for other improvements and supporting practices. Thus, the only practical challenge to the almost insuperable problem of the general deterioration of hill and high country, and the foundations of con-

servation farming, depended basically on replenishing fertility by topdressing and oversowing with clovers. Because of the scarcity of labour and impractical hand topdressing methods the key to conservation on the hill country was aerial mechanisation of topdressing and seeding. Pioneering Aerial Farming Restoring fertility and the protective cover on pastoral lands was of sufficient urgency for the Soil Conservation Council to organise and finance aerial topdressing and seeding trials, plans for which were proposed by the author and approved in July 1947. The prospect of obtaining direct benefit to the farmer and indirect benefit to the catchment was sufficient justification to overcome what was then regarded as impossiblethe economic barrier to the use of aircraft in topdressing. Though aircraft had been used for many years overseas for spraying and seeding work and their . capacity for this work had been demonstrated in New Zealand, no one was prepared to gamble on the pioneering of aerial topdressing. In November 1947 the Soil Conservation Council called a meeting ’ of the following Departments and organisations, which became its Advisory Committee on Agricultural Aviation — the Departments of Agriculture and Scientific and Industrial Research, the Lands and Survey Department, the Public Works Department, the Royal New Zealand Air Force, the Civil Aviation Administration, the Soil Conser-

vation Council, Federated Farmers, and fertiliser manufacturers. Topdressing Trials The initial trial flights at Ohakea in September 1948 were followed by a hill country trial at Te Mata and two trials for further adjustment to the equipment at Ohakea by the R.N.Z.A.F., which adapted an Avenger aircraft and ground control equipment for the trials. A final evaluation and demonstration of an aerial, topdressing service was made at a 1000-acre trial in the Wairarapa. This trial, on 10 properties at varying distances up to 30 miles from the aerodrome, was financed through the Wairarapa Catchment Board •by the Council and was carried out by the R.N.Z.A.F. The technical aspects, including distribution, were measured and assessed by staff of the R.N.Z.A.F., the Soil Conservation Council, and the Department of Agriculture. This trial created a big demand among farmers (over 100 farmers in Wairarapa alone asked for the topdressing of upward of 20,000 acres) and successfully demonstrated the capacity of aircraft to topdress and oversow hill country. A Soil Conservation Council report to the Government that an aerial topdressing service should be organised and operated by the R.N.Z.A.F. was not approved. However, just before the Wairarapa trials a small aerial topdressing contract carried out by Airwork, Christchurch, proved conclusively that small aircraft (Tiger Moths) could be used

efficiently within the farm for topdressing and seeding. This trial resulted in several private operators establishing aerial topdressing on a contract basis with farmers and out of it has developed the vigorous aviation industry of today. The Council’s Advisory Committee on Agricultural Aviation adopted the plans and specifications prepared by Civil Aviation Administration for a special, safe, rugged, medium-sized aircraft for topdressing, and these ideas were incorporated in a recently manufactured aircraft. It undertook, with the Council’s finance, the development of packaging, flying, and drop-

ping techniques needed for the aerial delivery of fencing materials, and publicly demonstrated these successfully in May 1955. Growth of Industry In a little over 7 years the agricultural aviation industry has grown phenomenally to 60 companies using over 300 aircraft and employing over 500 personnel. Its performance is startling; with over 5 million flights to its credit it has contributed the equivalent of upward of 3 million man-days of work in improving hill country. The If- million tons of fertiliser distributed on the equivalent of 12 million acres of hill country have contributed considerably to the 20 per cent, increase in sheep and cattle numbers over the period. Over 1000 tons of clover seed have been introduced into hill country pastures. The 14,000 tons of rabbit poison dropped on deteriorated and rabbit stricken country have reduced the pest to a stage where follow-up methods to eliminate it are now possible. Three thousand tons of weed spray distributed on pastoral hill country have contributed greatly to improved pastures by controlling thistles in particular. The dropping of fencing supplies is only in its infancy, but it has a great future, as the subdivision fencing required by hill country (approximately 1 chain per acre of improved hill country) lags behind and requires, it is estimated, some 100,000 tons of fencing material a year. Conservation Farming System The results of the early experimental work on the Council’s Soil Conservation reserves have been combined to support each other in comprehensive practical farming programmes on each of the Council’s 8 properties. This has resulted in the formulation of a conservation farming system that can be adapted to the needs of various districts. This programme is based on suitable combinations of the follow- . ing:—

1. Restoring fertility and improving hill country pastures by aerial topdressing, seeding, weed spraying, and rabbit poisoning. The effects of this programme are evident in greener and more productive hill country pastures. These operations must be supported by other equally important conservation measures and be restricted to relatively stable land suited to farming if increased soil erosion and run-off are to be avoided. 2. Grazing is the most powerful factor affecting hill country farming. Complete spelling for various periods, including the seeding period, has increased soil protection, control of water, and subsequent production on both North Island and South Island hill country. Predominantly cattle grazing has been most helpful in the initial improvement of deteriorated native and sown pastures, in controlling roughage, and in strengthening clovers and the better grasses. The judicious combination of cattle and sheep grazing on hill country on a rotational, or deferred grazing and spelling . system, or mob stocking basis over portions of the year is highly desirable in the promotion of conservation. It reduces trampling and consolidation and consequently increases the ground’s capacity to absorb rainfall, while the greater bulk of vegetative cover protects the soil from drying out and from erosion. 3. Trees to protect and stabilise land are essential in a conservation farming system. Grass alone is incapable of stabilising the steeper and more actively eroding farmed slopes; trees planted singly and in groups restore the stability of many grassed slopes. Various combinations of grasses and deciduous trees (willows, poplars, and false acacias), used according to the severity of erosion, promise to increase the utilisation of marginal land where the spacing varies from open, scattered planting on the more stable land to the close planting of unstable land. In the higher rainfall districts natural regeneration of shrubs and later forest trees is so effective that fire control and fencing to protect such land from livestock are fully justified. .4. Probably the most outstanding conservation practice is contouring, which consists of the construction of furrows, banks, or terraces on the true contour or on a slight grade to control the movement of soil and water and to conserve both. It also includes cultivation along the contour, which reduces the rate of movement of soil and water downhill.

5. The dams necessary in many cases to control gully erosion and to retard the flow of flood water from small catchments are an example of the importance of combining soil conservation and engineering techniques in any comprehensive soil erosion and flood control programme. Good progress has been made in hundreds of gully control projects, in co-operation with farmers, using a combination of pasture improvement, contouring, grazing management, tree planting, and debris damming practices, and the best results have been achieved where these have been used to support each other. This work is now being supported by the construction of dams in the head waters of gullies to regulate flow and minimise scour as much as possible during floods. In suitable catchments storage dams are becoming popular for extra stock water, and they can also be used to

supplement irrigation and fire fighting supplies. 6. Fire and pest controls are important conservation practices in many parts of the hill country, though a great deal has been achieved by bylaws restricting burning of native grass to spring when the soil is wet. Much remains to be done in some places in developing effective alternatives to burning, with the greater use of cattle, topdressing, and seed sowing.

The remarkably successful killer campaign waged by the Rabbit Destruction Council through Rabbit Boards promises to lead to the elimination of a most damaging pest. Other pests such as deer, wallabies, goats, opossums, and wild pigs still challenge the farmer’s ingenuity and industry, though progress is being made toward organised control.

Promotion of Subsidies Subsidies are normally available for approved conservation works on a £1 for £1 basis on farm lands for the following: Conservation Fencing Grazing control is so fundamental in recuperating and maintaining protective swards that the cost of materials is subsidised where it can be established that soil erosion and run-off will be reduced progressively by increased fencing and consequent improved management. Tree Planting Trees play such an important role in protecting land from wind erosion

and in anchoring and stabilising steep lands that the cost of suitable trees and the fencing required to protect them from livestock is subsidised. Subsidy can also be claimed for the cost of fencing bush and scrub covered land to promote regeneration if the farmer is prepared to retire unstable and eroding lands from grazing. Contouring Pasture furrows, graded banks, broad base terraces, diversion terraces, and grassed waterways are so effective in reducing flood-producing run-off and soil erosion, conserving water, and increasing pasture and crop production that the cost of the work is subsidised.

Dams Dams are subsidised according to the service they perform in flood control, ranging from a 3 to 1 subsidy when the dams are used exclusively for flood control to a 1 to 1 subsidy when they are used for stock water and irrigation as well. Gully Erosion Control A 2 to 1 subsidy is available for comprehensive planned treatment of gullies and their catchments. Farm Conservation Schemes Farm conservation schemes are further encouraged in special cases by assistance with the initial sowing and fertilising of badly depleted lands. A

land capability survey is made and a conservation farming programme, geared to the resources of the farmer, is prepared for a 5-year period, while the various practices are subsidised on the basis given in the foregoing. Catchment Control Schemes The adverse effects of floods on more heavily populated and more productive lowlands have led to the urgent treatment of some particular trouble spots, but long-term soil erosion and flooding programmes must work from the hill and mountain tops down the catchments to the rivers and to the sea. The goal of soil conservation is the application of conservation schemes on every farm in a catchment. Greater protection and control can be obtained in closely integrated schemes where gullying and flooding often affect several farms. Farmers can do only a limited amount of effective control individually, but collectively they can restore completely balanced control and full use of the soil and water resources. Such a scheme applied to several farms is working admirably in the Glenmark Catchment in Canterbury by minimising soil erosion and flooding as well as doubling pasture production on most of the land. The Council and the Department of Agriculture promote the widespread adoption of conservation farming by giving technical assistance to farmers who undertake soil conservation, and by . means of subsidies through Catchment Boards. Further information on conservation work and the assistance available can be obtained from officers of the Department of Agriculture and from Catchment Boards.