﻿10 BULLETIN 16, U. S. DEPAETMENT OF AGKICULTUEE. 



a leguminous crop, but since both the vines and the roots are re- 

 moved in harvesting (unless used for grazing hogs) they -may be 

 considered an exhaustive rather than an improving crop. Sweet 

 potatoes, however, leave practically everything on the field except 

 the potatoes themselves, which are principally starch, and this crop, 

 therefore, tends to improve the soil. The vines decay very rapidly 

 and their plant-food content, although rather small, soon becomes 

 again available. Here again the rotations mentioned are to be con- 

 sidered only as suggestive, and any number of variations will readily 

 suggest themselves to the thoughtful farmer; but the importance of 

 maintaining a bountiful supply of vegetable matter of a kind not 

 too rich in nitrogen at the time the field comes in tobacco should 

 always be kept clearly in mind when planning the rotation. 



FERTILIZERS FOR FLUE-CURED TOBACCO. 



Bright-tobacco soils as a class are naturally rather infertile; but 

 they are light and friable and of a character to respond readily to 

 fertilizers, particularly in producing a crop of high money value 

 like tobacco. Fertilizers increase the chances of profit from growing 

 bright tobacco in two ways. They greatly increase the yield, some- 

 times by 100 per cent or more, and if properly balanced they generally 

 improve the quality. Because of the natural deficiencies of bright- 

 tobacco soils and because of the special adaptability of commercial 

 fertilizers to bright tobacco, there are no other types of tobacco pro- 

 duced in this country on which fertilizers are so freely used, except 

 on some of the high-priced cigar-wrapper types in New England 

 and Florida. 



A so-called complete fertilizer — that is, one containing each of the 

 three materials, ammonia (nitrogen), phosphoric acid, and potash — is 

 generally needed, and the maximum yield can not be secured unless 

 each is supplied in sufficient quantity. No general rule as to the 

 proper proportion or balance between these materials can be given, 

 and the farmer must exercise judgment in the matter. The best 

 proportion for the three elements is likely to vary considerably 

 on different fields, according to the soil and its state of improve- 

 ment. As stated, each of these elements has its effect in limiting 

 the yield; but, aside from this, there is, broadly speaking, a special 

 effect on the quality of the leaf that may be attributed to each 

 element. Too much ammonia, especially if unsupported by a suffi- 

 ciency of the other fertilizing compounds, particularly phosphoric 

 acid, will make the tobacco coarse, dark, and late in maturing, with 

 a tendency to damage by "red fire" or dead spots here and there 

 on the leaves. Without a sufficient supply of ammonia, however, the 

 tobacco will be small, thin, and poor, although the color may be good. 



