FIELD CROPS. 897 



Clover and beans under all conditions of manuring took up much 

 more jiliosplioric acid in rotation than in continuous culture. Without 

 fertilizers clover utilized but little more of this ingredient than beans; 

 with superphosphate more than twice as much; and with a complete 

 fertilizer still more. The draft of phosphoric acid was less with the 

 leguminous crops than with the cereals. 



Wheat, like barley, took up more phosphoric acid in rotation than in 

 continuous culture. Without fertilizers and also with superphosphates 

 about four fifths of this ingreilient was stored in the grain. However, 

 with a complete fertilizer, inducing luxuriant growth, the grain con- 

 tained only about half the phosphoric acid, the rest being stored in the 

 straw. 



Amounts of potash in the crops. — The authors have shown elsewhere 

 that root crops are essentially sugar crops, and that the presence of 

 considerable jjotash is an important condition in the formation within 

 plants of carbohydrates and especially of sugar. Most of the potash 

 of the turnip crop was found in the roots and this proportion increased 

 with the yield of the crop, the bulk of the potash and sugar being 

 stored in the same part of the plant. 



In turnip roots and leaves on the rotation plats, unfertilized, the 

 amount of potash per acre was 4 to 6 lbs.; on the superphosphate plat 

 25 to 28 lbs., due to the increased feeding capacity resulting from phos- 

 phatic fertilizer; and on the area receiving a complete fertilizer 80 lbs. 

 Less potash was utilized in continuous culture than in rotation. 



In barley the greater i^ortion of the potash was found in the straw. 

 The amount of potash in the straw was subject to great fluctuations, 

 depending on the supply in the soil and fertilizer, while that in the 

 grain bore a fairly uniform relation to the dry matter. 



Without fertilizers and with superphosphate the amounts of potash 

 in the barley croi) were not widely different, but with a complete fer- 

 tilizer the quantity was largely increased. With a complete fertilizer 

 and on a rotation plat from which the root crop had not been removed, 

 the potash in rotation and in continuous culture crops was practically 

 identical. 



Beans took up about twice as much potash in rotation as in continu- 

 ous culture. Without fertilizer and with superphosphate alone the 

 quantaties of potash were practically the same, but with a complete 

 fertilizer these amounts were doubled. Comjiared with beans grown 

 under parallel conditions clover utilized much more potash; without 

 fertilization, 3 times as much (30 lbs. per acre) ; with superphosphate 

 alone, more than 5 times as much (57.6 to 65.5 lbs. per acre); and with 

 a complete fertilizer, also more than 5 times as much (123.1 to 132.Glbs. 

 per acre). 



The beneficial effect on clover of superphosphate used alone appeared 

 to be closely connected with the increased capacity thereby conferred 

 on clover of taking up larger quantities of the potash of the soil. In 

 beans more than two thirds of the total potash was found in the seed. 



