146 TROPICAL AGRICULTURE 



the form of ammonia or inorganic nitrogen which may be 

 ammonified and not in the form of nitrate. These experiments 

 were continued on seven successive crops of rice in the field 

 and were repeated in soil and sand cultures in pots. It was 

 clearly demonstrated not only that rice requires its nitrogen 

 in the form of ammonia rather than nitrate but that rice cannot 

 be grown to maturity in the soil or cultures where nitrogen 

 occurs only in the form of nitrates. In these experiments the 

 addition of nitrate of soda depressed tlie yield of rice below 

 that obtained on check plats without any fertilizer, while the 

 application of sulphate of ammonia to the extent of 150 to 

 300 pounds per acre doubled the yield over that of unfertilized 

 plats. These results are readily understood when it is remem- 

 bered that rice is grown as an aquatic crop, being submerged 

 under water 3 to 6 inches deep and that therefore nitrification 

 cannot take place in the puddled soil. Organic nitrogen in 

 leguminous green manuring crops, however, can be readily 

 ammonified under these submerged conditions and from the 

 ammonia the rice plant derives the nitrogen necessary for its 

 development. It has also been demonstrated that practically 

 all of the nitrogen of the rice plant is taken up from the soil 

 by the time the plant is two-thirds grown. 



Rice is too starchy a food for use as an exclusive ration by 

 man. The organic phosphorus and the proteid in rice are 

 largely deposited in the outer portion of the grain, which is 

 unfortunately removed in the complete milling of rice. It is 

 in many ways to be regretted that so strong a demand has been 

 developed for highly polished rice and for white wheat flour, 

 for in milling these grains to meet the market demands some 

 of the most important food elements are removed. The general 

 reader is doubtless familiar with the numerous scientific in- 

 vestigations which have connected the eating of a too exclusive 

 diet of highly milled rice with the development of the disease 

 of malnutrition known as beri-beri. While there may be doubt 

 as to the universal connection of an exclusive milled rice diet 



