ORCHARD HEATING

Hawke's Bay Herald-Tribune, Issue 10, 27 January 1937, Page 15

ORCHARD HEATING

Frost Control Methods In England FUEL BURNERS BEST Orchard heating as a rneans of combating frosts was mentioned by Mr Ealph Paynter, in an address- to Hawke's Bay orchardists recently. Mr Paynter was returning to New Zealand from England when the disastrous frost occurred which wiped out so much of the Hawke's Bay fruit crop, and otherwiae, he explained, he would have gone more closely into studying frost combating methods as adopted at Home. Durinfg his address Mr Paynter read extracts from a bulletiiS issued by the British Ministry of Agriculture and Fisheries ,and, for the benefit of Hawke's Bay orchardists, the "HeraldTribune" reproduces the article in full: ORCHARD HEATING Many investigations ,nave been carried out in recent years both in Eutopean countries and in America with thb object of discovering an economical and satisfactory method of protecting fruit trees from damage by frosts after the trees have reached the blossom stage. Unseasonable frosts are fortunately not a conmion occurrence in this countfy, but when they do happen as in midMay, 1935, widespread damage, amounting in many instances to total loss, usually results. It rnust be borne m mind that one night's damaging frost may not onjy ruin or greatly reduce the crop and so destroy the value of the 'whole year's work and expenditure, but highly manured trees carrying a crop suffer a disturbance in balance, and the crops of the following, and subsequent, years. are apt to be aifected. Briefly, the methods of protection against frost damage which have been investigated are as followa:— * (1) Coyering the crops with cloth or gaper. (2) Circulatihg the air. (3) Humidifying the air. (4) Blanketing the orchard with a smoke cloud. (5) Heaitng the air. , Investigators have found that neither of the methods (2) and (3) has proved effective, while methods (i) and (4), although effeetive with some types of frost, failed witk othera, and, qioreover, were impracticable and too expensive when conducted on a large scale. Method (5), heating teh air, has given encouraging results. Thd object of heating the air is of course to prevent .the temperature of the orchard falling below freezing point, i.e,, 32 degrees F. Many devices including coke braziers, generating heaters, distilling heaters and oil burners, have been employed for this purpose, but from the point of view of cheapness, simplicity and effeotiveness the last-named has given the best results. i Mr A. G. Harrington, of the Putnoe orchard, Bedford, has devised a Jiquid fuel burner to maintain their temperature of orchards above the danger point. This heater is of simple construction and consists of a aietal canister having a flame hole, covered by a lid, in the top, and two air holes in the side separated .by a quarter of the circumference. The wicks are made. of asbestos rope so that they can be used throughout the season without renewal simply by resoaking them in the fuel oil when the latter is renewed. The heaters are designed to burn crude oil. I The minimum number of these heat-. ers to the acre should be 40, and if properly distributed they are capable of raising the temperature of the orchard by 5-6 degrees. They have been used by some growers at the rate of 60 to the acre and at this concentratjon have seeured a rise of 10-12 degrees in the temperature. The heaters are designed to burn for a period. of eight hours. The fuel capacity is two gallons; the first gallon is burnt of£ in three hours and the second, when the heater is burning less ilercely, is- consumed in five hours. If the frost is a prolonged one covering a longer period in one night than" eight hours the heaters have to be refilled. The carrying round of the oil in the dark is a difticult task and fortunately is seldom likely to occur. The designer of these heaters is of the opinion that it is better to install two heaters in one spot than to attempt refilling. The two heaters are theii set going in sequence. The uso of orchard heaters necessarily involves the adoption of a frost alarm system undess a night watchman can be employed to give the warning. Mr Harrington 's alarm system consists of a Negretti and Zambra maximum and minimum thermometer with one wire on the left-hand side set at 33 degrees F. and the other in the mercury at the bottom. When the temperature falls to 33 decrees the circuit is closed and a bell is set ringing in the proprietor's bedroom. This gives time for the light force to be mustered and en-. ablcs all the heaters to be started before the temperature falls to freezing point. The heaters can usually be lighted in a half to thTee-quarters m£ an hour with a properly trained lighting force. One man can light the heaters for two to three acres in that period. The fionclusions to be drawn after the tests of the system provided by the severe frosts of 1935 are that orchard heating is practieable provided the organisation is good, the number of heaters to the acre is not below the | minimum laid down and that there is f litlo or no wind. The heaters must be | refilled in the morning after a frost [ even if they have only burned for au ! hour, and at least three days ' supply of fuel oil should always te on hand. Some growers employ their small-power spraying machines . for refilling, the oil being pumped direct from 40-gallon (Juims.