Views On Farm Shelter Belt Planting

Press, Volume CVI, Issue 31167, 17 September 1966, Page 9

Views On Farm Shelter Belt Planting

The recent late winter storms with heavystock losses on some farms—there have been reports this week of losses of as many as 1000 and 1500 lambs on individual farms—have again focused attention on the need for shelter.

I Farm foresters believe that ' well-planned shelter belts, designed according to the best knowledge available, may not only provide useful shelter for stock but may also have a marked effect on production of crops and grass, but they are at a loss to understand why, to a country like New Zealand subject to wind, so little investigation has been made into shelter as it affects agricultural production. Writing of this year’s annual conference of the New Zealand Farm Forestry Association held in Invercargill in the most recent issue of the journal of the association Mr N. A. Barr, one of the country’s leading farm foresters, says: “Some of our members worked fairly hard on the { Director-General of Agricul- | ture, Mr D. N. R. Webb, who opened the conference, to have some trial work done on the effects of shelter on grass and crop growth. It is inconceivable that in a country as exposed to wind as New Zealand no experimentation has been done to see if grass growth can be stimulated by shelter, both on the score of a warmer microclimate in colder months and that of increased moisture retention in the periods of hot, drying winds. As an insurance against lamb losses from exposure and mis-mothering, surely several well-placed shelter belts would be worth many hundreds of lambs lost over a lifetime.” Discussing farm shelter belts this week, Mr A. C. Meyer, of Hook, South Canterbury, who is South Island vice-president of the association, said he could not see that provision of shelter just for ewes and lambs was warranted on an economic basis, but if through research the value of shelter to crops was also demonstrated in New Zealand then they would have something worthwhile. Mr Meyer’s opposite number in the North Island, Mr N. Alexander, has also had something to say on this issue. He has said that in Denmark, where there are similarities in conditions to New Zealand, the Jutland plant breeding station’s records over the years show an increase of 34 per cent in grass growth and 27 per cent in lucerne growth in sheltered compared with unsheltered areas. The increase in grass growth, he says, was found to be four and a half times the loss of growth under and alongside shelter belts. The lesson from overseas experience was that wind could and did reduce pasture and crop production, and that scientifically designed and spaced shelter belts provided an effective counter.

Mr Alexander, incidentally, emphasises the value of shade as far as milk, butterfat and beef production in cattle is concerned. While he suggests that the cattle beast is well equipped naturally to with-

stand wind, it is not so equipped against heat and its production declines in the face of rising temperatures.

Trials done in Missouri have demonstrated the economic value of shade in hot climates. A mob of steers was divided into two lots. For 50J days in each of two successive summers the two lots had the same grazing but one lot was provided with shelter—possibly moveable “sun shades”—and the other was not. The average daily weight gain for the unshaded cattle was 1.041 b while that for the shaded cattle was 1.491 b—a 43 per cent improvement

Benefits And at this year’s farm forestry conference Mr G. Chevasse, of the Forest Service in Invercargill, after quoting some figures for increases in production attributable to shelter in several countries in the course of a panel discussion, observed that the general order of additional production in the dry and windy areas from which his figures were obtained was about 20 per cent, and this could easily be the general level for the drier parts of New Zealand east of the Southern Alps. “We do not know because no-one has been interested to find out,” he added. “Some cases have come to my notice, one to do with increased milk yields in a dairy herd and several to do with stock losses during lambing and immediately following shearing. Surely this too is a subject over-ripe for research.”

Mr Chevasse also stated, in the same context, that if wind breaks were established at about 20 height intervals (20 times the height of the trees) the reduction of evaporation would be about 20 per cent over the whole property. This could be worth several inches of rain and in the driest areas the saving could be critical, for example, in Maniototo. The control of evaporation loss could mean a marked increase in production. Now for the type of shelter belt that should be planted on a farm. Here Mr Meyer says that there is need for research in New Zealand into the types of trees most suitable for this purpose, their siting and the costs involved.

But from investigations overseas and practical experience in New Zealand some sort of picture of the best course to be followed has been built up. The sort of shelter that will best fill the bill in Canterbury is not the trimmed straight hedge-type of shelter belt, Mr Meyer says. This may have a limited place for shelter at lambing or after shearing, but as Dr. D. S. Jackson, in an address to the farm forestry association conference in 1963, noted, else-

I where, whether it be for the (general shelter of crops, of {pastures or of grazing animals, it is the maximum extent of effective shelter that is required, and this is provided, not by the dense impenetrable belt but by the screen of medium density throughout its height. Mr Meyer has prepared a diagram which shows this point well. With the permeable shelter belt—the fairly open sort of belt—there is a 50 per cent reduction in wind velocity from a distance equivalent to the height of the trees in the belt to 13 times their height out, and then a 25 per cent reduction from 13 heights to 20 heights. On the other hand while there is a 75 per cent reduction in wind velocity in the lee of the dense type of belt for two heights out, there is a 50 per cent reduction only from two heights to Six and a half and a 25 per cent reduction from six and a half heights to 15 heights. One of the important advantages of the more permeable belt is that stock do not congregate close to the belt, with the attendant problems of fouling and disease, and are able to be well distributed over the paddock and grass can grow right up to the fence line. Mr Meyer says that if there is fouling and a blood poisoning problem because of stock congregating near a belt, then it only indicates that the particular shelter belt is not adequate for the area it is intended to shelter.

In general, he said, in farm forestry circles the dense, trimmed hedge-type belt was not looked on with much favour, in that the attention that this sort of belt needed was a further burden on the farmer from the labour point of view and over-all it was not so effective.

Unhappy Mr Meyer says that frequently in the past farmers have got sick of shelter belts, having trimmed and topped them and then found that when they had reached the end of their usefulness they could hardly give them away as firewood.

Of the topping angle, Dr. Jackson says that ultimately topped shelter belts open up just as much below as those which have not been given this treatment, and that much more permanent effects on the density can be achieved by structural alterations of the belt.

The only benefit of topping, he says, comes from the temporary retention (lasting about 15 years) of density in the zone below the height at which tops are removed, but against this are the diminished extent of leeward shelter; the costs in wages and/or manpower diverted to topping, cleaning up and maintenance; the consequences of diverting the tree’s potential growth from terminal to lateral extension —encroachment on pasture with subsequent stock disease, weed infestation and increased transfer of fertility —and the virtual elimination of any potential sawlog value and the cost of ultimate shelter belt replacement and

clean-up without any offsetting monetary returns, except perhaps from posts and strainers.

Dr. Jackson also emphasises to relation to topping that the most important single factor for shelter belt effectiveness is maximum •height, so that to achieve maximum shelter it is obvious that the height of the belt should be the greatest which the site is capable of sustaining without the risk of wind damage in normal storms. From here Dr. Jackson passes on to the idea of a dominant species providing the framework of the belt, to grow to the maximum height compatible with the stability of the site concerned, and a complementary species to improve density to the zone from ground level to the base of dominant crowns, and to reduce lateral development and spread of toe dominant species below a height of about 20ft—above this level branches will never reach such a length that at the latitudinal range of New Zealand they will exclude sunlight from the base Of the belt.

This idea of attempting to improve bottom density by the use of a species complementary to the dominant one is not a new one, says Dr. Jackson.

Mr Meyer says that the idea is to have both a tall growing species and also a smaller shrub type of tree. They could be confined to one row being iirterplanted, thus being economical of ground use. Dr. Jackson had suggested planting Pinus radiata at 12 to 15 feet intervals in single rows to allow adequate space for root development with an eye on stability in later life. Actually in single rows Mr Meyer said that trees were more with a better balance of root development.

The shrub-type species would grow to 12 or 14ft and above that there would be the high permeable shelter.

It was believed that the new improved strains of radiata that were now available and being generally used could be grown in such single row plantings. They were taller, had finer branching and considerably less side branching and a narrower crown.

As the dominant species, Mr Meyer said, other possibilities were other species of pine, the new strains of poplars, and eucalypts There could be others subject to further research. The number of possibilities for the low growing species were too numerous to mention. There needed to be a certain amount of compatability between the two species and here the nurseryman should be able to advise. Some of those which might be suitable were the Pittosporum species and Cedrus speciesin Southland he said he had recently seen Lombardy poplars and lawsonianas. The lawsonianas would be 15ft high and they intertwined beautifully with the boles of the poplars rising to about 80ft high, but he doubted whether this combination would be suitable for the Canterbury plains, though there would be combinations to suit all conditions.

A belt might also comprise

all eucalypts, with every second tree being cut back periodically to keep it down and provide the denser lower shelter.

Where pines were grown In association with cedars he said that when the pines were cleared out after 30 or 40 years the former species could be allowed to take over. Where the tall species were pruned up to the height of the low growing species the result would be relatively clean saleable logs. According to Dr. Jackson, where a farmer is not prepared to prune then prevention of the wide-spreading lateral branches of the dominant species becomes an essential function of the complementary species. Another possibility in Mr Meyer’s view is to grow single or double rows of radiata pine and allow these trees to grow for up to 15 years without trimming. They would then be all felled for the post trade. This would be a system of providing quick, low shelter on a short rotation system. It had been customary to plant shelter belts In an eastwest direction, but they need not do that and belts in a more north-south direction would be just as effective and would get over the problem of having a cold south side, Mr Meyer said.