560 Protection of Orchards from Spring Frosts, [oct., 



with about 90 oil heaters to the acre, with the result that a 

 full crop of fruit, valued at ^5,000, was obtained, while in 

 the rest of the valley the apple crop was almost a complete 

 failure. 



Smudge Fires. — Here the object is to create a thick smoke 

 which will lie over the orchard like a cloud. It is stated that 

 the fires should be started early in the evening, as, if radia- 

 tion is permitted to go on during the early part of the night, 

 it cannot afterwards be checked by smoke. The method is 

 economical and well adapted for use when the night is not 

 windy and the temperature is not expected to fall much 

 below 27 0 F. Manure with a little oil poured on it makes a 

 good smudge fire, or mixtures of tar or oil with damp straw, 

 hay, or sawdust. The use of moist fuel has several advantages. 

 The water is evaporated and the vapour added to the air, 

 the subsequent condensation of which, as it moves away 

 from the fire, will liberate much latent heat ; in addition the 

 smoke is heavy and thick. 



Oil, creosote, and other materials are also burnt in iron 

 pots, which can be placed in suitable positions in the 

 orchard. A full description of this method as employed in 

 some orchards in Gloucestershire was given in this Journal, 

 April, 1907, p. 23, and some preliminary experiments with 

 the same system were conducted at Wye College in 1908 

 (Journal, March, 19 10, p. 1024). 



Experiments in Oregon. — Farmers' Bulletin 401 gives an 

 account of experiments conducted in 1909 in Southern 

 Oregon, chiefly with fires for heating the air. It is pointed 

 out that considerable preparation is necessary in order that 

 fires may be started immediately frost appears likely 

 to occur. A sufficient quantity of the material to be used 

 must be placed in position in the orchard early in the season, 

 and everything got ready for immediate use. As regards 

 fuel, wood was principally used in these experiments, but 

 this would depend on local conditions. Crude oil was used 

 to a limited extent, but the particular kind of oil which was 

 available, being of low quality, was not successful, as it 

 was difficult to ignite and failed to burn well. It was, how- 

 ever, found useful for saturating shavings and other materials 

 for starting fires. Stable manure, straw, and rubbish were 



