Progress Of Wind Studies

Press, Volume CVIII, Issue 31653, 13 April 1968, Page 9

Progress Of Wind Studies

Just what effects does wind have on crops in New Zealand? What kinds of shelter belt give the best protection? Can crop plants themselves be made less vulnerable to wind by treating them with chemicals? Answers to these questions are being sought by the Crop Research Division of the Department of Scientific and Industrial Research.

Dr J. W. Sturrock, leader of the division's agronomy section, is studying the performance of various crops in both windy and sheltered conditions, and is Investigating methods by which the adverse effects of wind can be reduced. His current projects include aerodynamic studies of existing shelter belts of different types in Mid-Canter-bury. Using anemometers and wind direction recorders, he is finding out how much each belt reduces the speed of the wind; the distance from the belt at which the maximum reduction occurs; and the distance required for the wind to recover speed. At the same time, he is trying to develop practical techniques for measurement of the permeability of shelter belts, and the air turbulence that occurs in the lee of some belts. His ultimate aim is to determine which tree species, in what planting patterns and orientations, will give the best shelter in various situations, and the extent to which shelter can be combined with saleable timber production. Dr Sturrock is also experimenting with growth retardant chemicals which may give plants a sturdier, more compact form without reducing their harvestable yield. Plants so changed should be more resistant to mechanical damage by wind, such as lodging in cereal crops. In glasshouse experiments at Lincoln, chemical treatment has given height reductions of up to 27 J per cent in wheat without loss of yield. Wind is an important problem of the cropping industries in New Zealand. Over most of the country it persists almost the whole year round. At Lincoln, the total wind-run over an experimental crop during its five-month growing season was 24,000 miles—and even higher airflow figures are common in some districts.

Wind can affect crops in many ways, mostly adverse. It batters plants and dries out their moisture. It may reduce the palatability and nutritional value of green crops by causing the plants

to develop a higher proportion of strengthening tissue. Dry winds cause leaf pores to close against moisture loss, and this reduces intake of carbon dioxide, which is essential for the plant's healthy growth. The effect on yield can be considerable. Overseas research has shown that some crops produce from two to four times as much when sheltered as they do when exposed to wind. The lack of precise information on this in New Zealand is one of the gaps Dr Sturrock’s studies are designed to fill. In experiments at Lincoln, using artificial wind barriers, he found that reduction of wind speed to an average of 2} miles an hour throughout the growing period resulted in a 40 per cent increase in the dry matter yield of turnip roots, and a 5 per cent increase in the dry matter yield of rape. The reactions of the plants to wind varied according to their phase of growth. Turnips reacted least while they were still in the rosette stage, but rapidly became more vulnerable as they got beyond it. Rape, on the other hand, was most susceptible in its early and middle stages of growth. Dr Sturrock thinks it probable that plant height, form, spacing and degree of mutual protection, as well as the relative susceptibility of different growth phases, are all factors which affect the reaction of plant species. “It is obvious, too, that work on the effects of shelter must be long-term in order to discover the reaction of crops to variations in seasonal weather,” he says. Dr Sturrock is continuing experiments with various crop species at Lincoln. He

hopes also, with the co-oper-ation of farmers, to lay down field trials to assess the actual effect of various shelter belts on the yields of a number of crops.