16 The Bulletin. 



USE OF SASH. 



Glazed sash may also be used in winter lettuce culture, but they 

 have never come into common use. This is doubtless due to their 

 increased cost over cotton covers and their being fragile and also cum- 

 bersome to handle. It is also more difficult to irrigate glass-covered 

 frames than those on which the cotton covers may" be quickly and 

 easily reefed. Sash-covered frames, however, maintain a higher and 

 more even temperature in cool weather than cotton-covered frames 

 and bring the crop more quickly to maturity. They also require con- 

 stant attention regarding ventilation during bright weather. It may 

 be, considering the earliness gained by the use of sash and their 

 greater durability in comparison with canvas, that glass is in the 

 long run the most economical and profitable. This point will be 

 tested in future experiments at the State Truck Test Farm. 



Sash for forcing purposes are made in the regulation size, 3 by 6 

 feet, and cost about $3 apiece glazed. The frames would be 11 

 feet wide and had best run north and south, to get the sun on both 

 slopes of the sash. Single-sash beds are best facing the south. 



HEATING. 



For winter lettuce-growing in the mild climate of eastern North 

 Carolina a heating plant is not an absolute necessity, as there are 

 few days when the temperature falls below freezing, but it pays to 

 have a heating system ready to guard against cold snaps and freezes. 

 The supplementing of the natural daily sun's rays with accessory 

 heat makes winter lettuce-growing a very sure thing. The additional 

 heat also helps to keep the lettuce growing in cool weather and brings 

 it in for the higher prices of the early market. The history of let- 

 tuce-growing in North Carolina has proven that steam lettuce-grow- 

 ing has been the surest and most profitable method. The steam 

 capacity required per acre for heating and also for irrigating is about 

 8 to 10 horse-power. 



Piping.— The main heating-pipes will vary in size from 4 inches 

 down, according to the acreage to be covered. Lateral heating-pipes 

 should be 1 inch in diameter. The method of piping lettuce frames 

 is simple. It is usually a straight main, with a 1-inch lateral run- 

 ning off it at right-angles into each bed. It is not necessary to have 

 a circulation, but simply a straight push of steam with an exhaust 

 at the end. We find, however, that with an exhaust for each frame 

 it is very expensive of steam, and that it is better to couple the rear 

 ends of the pipes in every five or six frames into a common pipe and 

 make one exhaust for the whole. This is found to be sufficient ex- 

 haust to allow for condensation and to keep the system working and 

 the temperature fairly uniform throughout. Just a slight exhaust of 

 steam is found to be all that is necessary to keep the steam moving 



