26 



removed from the soil, the leaves and stalks, contain 58.9 pounds of 

 nitrogen, 7.72 pounds of phosphoric acid, and 77.86 pounds of potash/' 



This shows that the larger part of the fertilizing constituents is 

 found in the leaves and stalks, and emphasizes the exacting charac- 

 ter of the demands of the tobacco plant on the soil and the importance 

 of returning to the soil all of the stalks and roots. 



In several places it was noticed that planters in preparing tobacco 

 ground for a future crop had thrown out of the field all of the roots 

 and stalks of the tobacco, a practice that would not have been per- 

 mitted had the planters appreciated their value. It was also noticed 

 that beans were harvested by cutting and removing the whole plants 

 from the field. As this crop belongs to the leguminous family, and 

 through the agency of the tubercles on its roots has the power to utilize 

 free nitrogen from the air, thus becoming itself rich in this element, 

 the vines and all unused parts of the plants should be returned to the 

 soil. 



Manure in the form of well decomposed compost is excellent for 

 tobacco and one which can easily be supplied in considerable quantity 

 in Porto Rico. Any plant debris, such as banana stalks, weeds, and 

 grass may be used, and should be supplemented as far as possible 

 by animal manures and animal debris. Horse manure is the most 

 valuable and cattle manure ranks next. It is said that goat and pig- 

 manure gives the tobacco a bad taste, while sheep manure produces a 

 heavy leaf. These should therefore be avoided. It is important that 

 the compost be well decomposed ; if not, its application may become 

 harmful. An application may consist of 5 to 20 tons per acre, accord- 

 ing to the requirements of the soil and the concentration of the 

 compost. 



Green manures, i. e., the plowing under of leguminous crops, such 

 as cowpeas or velvet beans, often give good results and increase the 

 thinness and elasticity of the tobacco leaves. 



Guano, which occurs in many caves in Porto Rico, is also a valuable 

 manure. Its composition varies greatly, and the requisite amount to 

 use can only be determined by experiment. 



Commercial fertilizers should be used with great care. The use of 

 potash improves the combustibility of tobacco, but it should be used 

 only in the form of a sulphate, carbonate, or nitrate. Muriate of pot- 

 ash should never be used, as the chlorin is considered very harmful. 

 Cotton-seed-hull ashes is also a most valuable source of potash. Phos- 

 phoric acid should not be used in excess, for, according to ISTessler, 

 the more there is in the soil the more the plant takes up, and too 

 much affects the color of the ash. Acid phosphate and phosphatic 

 slag are used in preference to bone phosphate, on account of being 

 immediately available. Nitrogenous manures should be used with 

 moderation. According to Schloesing, they increase the vigor of the 



"Virginia Sta. Buls. 14 and 50. 



