“JACK FROST”

Hawke's Bay Tribune, Volume XVII, 30 November 1927, Page 3

“JACK FROST”

HOW TO FIGHT HIM PROSPECTS OF ORCHARDS HEATING. OUTLINED BY DR. KIDSON. “Jack Frost” is perhaps the principal enemy of the fruitgrowers, and naturally any means of vanquishing him will be of interest. To this end the Hawke’s Bay Fruitgrowers’ Association invited Dr. E. Kidson, Government Meteorologist, to address the members of the association in Hastings, and last evening quite a large number hoard Dr. Hudson’s views on the matter. The lecture was quite appropriate as within the last few days two frosts have been experienced, and no doubt the Doctor’s suggestions will be carried out as quickly as possible. After minutely describing the formation of frost, Dr. Kidson stated that it might seem possible to stir up the air sufficiently to prevent the formation of frost but investigations had shown that this scheme w-as not a sound one. To be successful it would be necessay to generate a moderate wind all over the orchard and that would be far too costly. MACHINES TO GENERATE WIND. The leecturer showed lantern slides depicting various machines to generate winds in America. The principle of the machines was for a high vertical pipe to suck down the air some 35 or so feet above the ground. The air is heated and then discharged either along the ground or just over the tops of the trees. The results obtained from these machines were interesting though the experiments were a failure in that it was not possible to force out the air stream more than a few feet against the natural drift in the orchard. The lecturer then showed a picture of two heaters made to burn one or two gallons of oil. A device called tho “spider” was placed across the top of the heater, which resembled a big milk can, and this produced a more uniform burning and reduced the rate. The larger type of pail heater cost about 2s and burnt crude oil, which the speaker was given to understand cost 9d to lOd in New Zealand as compared with 3d in U.S.A. The oil was lit from a torch from the spout of which a burning mixture of kerosene and petrol was allowed to drip into the pail of crude oiL FUEL FOR ORCHARD HEATING “There is no doubt that crude oil is the most convenient fuel for orchard heating” continued Dr. Kidson. In New Zealand, however, it is expensive. Other fuels have been used, including coal in various forms. It has generally been found rather troublesome owing to difficulties of lighting and maintaining a good burn. Its relative cheapness as compared with oil in New Zealand makes it almost imperative to find some way in which it can be used satisfactorily. Your president, Mr Paynter, already appears to have been successful in this. It is not necessary for me to describe his methods. Should cheap briquets become vailable in the near future they would almost certainly be found to be the most convenient form of coal to use. One gallon of oil is equivalent in heating power to about 11 or 12 pounds of coal. A good deal of experimenting will be required before standard methods are developed. Before undertaking heating a grower should work out the cost and see if it is going to be worth while. ORGANISATION ‘ ‘ About 100 pails per acre should bo provided. They should be evenly spaced in parallel rows throughout the area to be protected. The positions should alternate, a pail in one row being opposite a gap in the next. It is well to double the number of heaters on the outside rows to windward. On any particular night it may bo necessary to light only a quarter or a half of the heaters. The most dangerous period is the two hours centred about sunrise and the whole labour and cost of heating will be wasted unless it can be prolonged over the danger period. “The temperature of the orchard must be accurately known. This means that accurate and properly exposed thermometers must bo distributed throughout the orchard. The taking of the temperature of the air is not an easy l problem and care must be exercised. If the thermometer be exposed to the sky it will radiate out neat into space just as the earth does, become colder than the air and and read too low. The thermometer must, therefore, be protected from radiation by a suitable shelter. For night work, quite a simple one wlh do. Ono may bo made from two board* set at right angles to each other. Ono is nailed at a height of 4 feet 6 inches or 5 feet to a post fixed vertically in tne ground.

“The other projects as a horizontal «nelf above it. The thermometer in hung from screws on the vertical board and is sheltered by the horl zontal one. The shelter should face south, away from the sun. Tho noards should be about 10 inches wide and three or four inches longer than the thermometers. It is convenient when setting the thermometer if the upper board is hinged. The thermometer recommended is the horizontal, alcohol minimum thermometer. Thu existing temperature at any time can be'ascertained by reading the portion of the surface of the alcohol nearest the bulb. At the same time the end of the glass index furthest from tho bulb gives the lowest temperature that has 'Occurred since the thermo meter was last set. TAKING THE TEMPERATURE. “Sometimes It will be found that the index is inclined to stick. This can be overcome by tilting tho bulb down slightly. The tilt snoul.d not be too great, however, or the index may be shaken down into the btllb during a (trong wind. The thermo motor is <et by tilting up the bulb until the index slides into contact with the alcohol surface. It should be read quickly or the observer’s body and the reading lamp may raise the temperature. An electric torch is by far tho best means of reading at night. Occasionally, the spirit column wi 1 be broken by bubbles or the index may break through the sur-

face. The column should then be rejoined by holding the thermometer in tho hand with the bulb downwards and tapping the hand on the knee or some soft object. “To prevent this kind of trouble, the thermometer should be taken indoors during the day and kept vertical with the bulb downwards. The accuracy of the thermometers should be tested occasionally. This can be done by immersing the bulb in a mixture of ice and wafer which is kept stirred. The thermometer should be kept in for 2 or 3 minutes without letting it touch the bottom. To read it the stem should be withdrawn just sufficiently far from the water toi enable a reading to be taken. The reading should be at freezing point. NEED OF CARE. “There should be a least two thermometers in the area protected, one of them near the windward edge and the other near the centre. If the area is above three acres an additional themometer must be added for eacn additional thhee acres. This applies to flat country; if there are variations of level the number of thermometers would need to be increased. One or more check thermometers should be placed outside and to windward of the protected area. These will indicate tho amount of heating and when heo.ting can be discontinued. It must be remembered that the difference between a temperature that will cause heavy damage and one that is safe is a matter of a degree or two only. Consequently, to be forewarned of a dangerous frost and to be able tn heat correctly a fruitgrower must have accurate and properly exposed thermometers. ”n SUMMARY OF ADVICE. Dr. Kidson concluded by giving the following summary of hints to growers: “Each grower should study his own problem, and estimate how frequently and to what extent he m liable to suffer loss from frost. “If his losses are serious he should study his location; note what are the probable sources of cold air; test its flow on cold night by means of the smoke from small flres; note the direction and rate of drift and whether it rises or clings to the ground. The slower the drift and the lower the smoke hangs, the easier will the frost be combated.

“With the information so gained he may find that considerable protection may be provided by means of a high wall or a tree Break on the windward side of the drift.

“Or ho may find that certain portions only of his land are likely to be affected. It may bo advisable to abandon these portions, or grow only the hardier crops, or the more -frost resisting varieties thereon. “It may prove that fruit growing is unlikely 7 to be profitable on the area, and the sooner tho attempt is abandoned the better.

“Seek the best expert advice vailable as to equipment and methods. “The cost of heating can thus be worked out in detail and a final decision taken as to whether heating is likely to pay. Possibly some other form of insurance would bo more satisfactory. “The question as to whether heating will bp successful and economical cannot be decided in one year. It will certainly take several years.” Dr. Kidson was heartily applauaeU for his address.