Aim more shelter to stem erosion

Press, Volume CXIII, Issue 33384, 16 November 1973, Page 6

Aim more shelter to stem erosion

There was a sequel this week to the dust storms that occurred in the Waipara district last autumn when the North Canterbury Catchment Board held a field afternoon to inspect shelter belts and discuss shelter belt planting, as one of the means of preventing wind erosion, with farmers in the district.

In a “hand-out” prepared for the occasion Mr R. D. Dick, chief soil conservator of the board, and Mr D. I. Robertson, a soil conservator, said that the severe wind erosion had even blown the top soil from grazed stands of lucerne and bared the taproots down to an inch below the crown of the plants. The erosion, they said, had not been confined to the plains land, but had also occurred on land that had been cultivated and sown to pasture on neighbouring hill and downland. . . . Winds from the north-west had caused the most serious erosion. . . . The main method of preventing this erosion was to maintain a dense cover of vegetation on the soil. In dry weather irrigation assisted in the production and maintenance of the vegetative cover. However, reduction of the velocity of the wind at ground level also reduced the risk of wind erosion, and this could be achieved by wind breaks of trees across the direction of the dry, high velocity winds. Mr J. M. Pickering, chairman of the board’s soil conservation committee. said that the principal purpose of the day was to try to have shelter belts planted over the whole of the affected district, with the help of the board and the subsidy available for this purpose through the Soil Conservation and Rivers Control Council. He envisaged the trees on one farm acting with trees on other farms to protect the whole area and to transform the countryside.

Up to a year ago he said that the subsidy available for this purpose had beefc $1 for $l, but a year ago after much argument the council had decided to increase it to $2 for $1 (on the cost of the trees and all labour and the fence on one side of the belt). Generally speaking he said he thought the subsidy would apply in most circumstances in this district — certainly where plantings were made across the north-west to save the land. Mr Dick said that subsidised belts normally had a minimum of two rows and up to four rows, though in odd cases such as on Marshland market garden country a single row might be eligible for a subsidy. When it was suggested that it was required that a slower growing species, such as Cedrus deodara, be planted on the windward side of the faster growing Pinus radiata, Mr Dick said that this was to shelter the pines when they reached 20 years, or even less, and became susceptible to wind damage. On the question of the area of land that might be taken up by such shelter belts and the subsequent lateral growth of trees, Mr Dick said that in his experience of being associated with 180 miles of tree planting, the vast majority of farmers felt such land occupied by trees well used in the benefit it conferred in preventing wind erosion and also in increasing production in the lee of belts.

In the Rakaia gorge area, he said that the contrast in growth on an area in the lee of shelter and on an adjoining area not so protected was so great that it looked as though the sheltered area had been top-dressed with a hundredweight of sulphate of ammonia.

This was also confirmed by farmers with experience of shelter. Mr R. G. Forbes, whose property was visited and a fine pinus stand more than 40 years old viewed, said he had noticed that as the trees grew the area from which extra production was derived extended outwards, and in such situations he said that hay cuts were twice those from areas not sheltered. Mr Dick said that to be eligible for subsidy belts had normally to be at about 20 chains apart. Any trees could qualify so long as they were suitable for the area in which they were being grown.

The trees in a subsidised belt belonged to the farmer and to carry out the terms of the agreement under which he obtained the subsidy he had to look after and maintain the trees and not cut them down until they had reached reasonable maturity. In the event of the sale of a property he said that the vendor would require the new owner to accept these conditions or else the subsidy would have to be repaid, but in some 25 years of experience with such planting he had not known of the new owner not accepting the transfer of responsibility.

On the Marlow property of Mr R. D. Gould at Glasnevin attention was drawn to the success Mr Gould has had in establishing trees at the height of the drought in the district. When a stop was made at a point on Mr Gould’s property where two rows of cedars and two rows of

pines had been planted 18 months ago, Mr Dick noted that here 80 to 90 per cent of the trees were alive when in other areas he had seen there was a comparable incidence of dead trees.

Mr Gould said he felt that the secret of his success had been in giving the ground a good fallow before the trees were planted. He said he did his plantings in paddocks which he had up for winter feed—these were up for two years. He said they subsoiled the rows prior to planting and made a trench with a grader blade. It was observed that the little trees were still sheltered in this trench and any rain falling would also drain into the trench to the benefit of the trees. Mr Dick noted that ripping of the planting lines prior to planting to a depth of 18 inches was resulting in success with planting, including contract planting.

Mr R. A. Milne, senior advisory officer of the Ministry of Agriculture and Fisheries at Rangiora, said that a farmer in a similar dry area ploughed country about Christmas time and then left it open to the stock before planting. Noting that a large part of the capital cost of planting was in fencing, Mr Dick also drew attention to a fence on Mr Gould’s property, which he said might be used elsewhere for fencing shelter belts, with possibly slight modification. It contained 10 12| gauge steel wires with" wooden posts every 15ft and permanent strainers. The materials for this fence would cost some $7 to $8 per chain. The cost of two 12J gauge wires was equivalent to the cost of one No. 8 galvanised wire, he said, and where no barbed wire was used this saving would cover the cost of three 12| gauge wires. During the discussions, some concern was expressed lest farmers wishing to plant in the coming season might not be able to do so because of a shortage of trees. Mr Pickering said that the board would be prepared to take this up with the Forest Service arid nurserymen so long as they had a good idea in advance as to what numbers of trees would be required.

At the end of the day, in thanking the board for holding the afternoon, Mr F. J. Bain said that if the board could help local farmers to obtain good tree stocks they (the farmers) should then make a real effort in the way of planting. They could not afford to lose much more soil, he said. The farmers were given information about a reconnaisance survey of shelter belt planting in the area done by Mr Robertson. It showed that on some 25,000 acres of flat arable land north and south of the Waipara, including about 69 properties, there were about 39 miles of belts to prevent soil erosion by northwest winds and about 28| miles of belts to protect stock against cold southwest winds. Mr Dick said that one of the most striking features of the survey was that

north of the Waipara some 40 per cent of the breaks planted to prevent wind erosion were more than 40 years of age, and it had to be remembered that pine trees did not last for ever, while in the southern area some 40 to 50 per cent had been planted in the last 20 years. If in the next 10 years another 40 miles of belts could be planted to provide protection from the northwest, then he suggested that conditions in the district would be greatly improved, including pasture growth. Whereas in earlier days the gum (Eucalyptus globulus) and Cupressus macrocarpa had been planted with the pines, in the last 15 years the hardy Cedrus deodara and Cupressus arizonica had been used with the fast growing pines, Messrs Dick and Robertson said.