78 



Elementary Principles of Agriculture 



cleaned and partly filled with distilled water (water cul- 

 tures), or with pure sand (sand cultures), to which are 

 added solutions containing the different substances 

 supposed to be necessary for plants. These solutions are 

 made similar in every respect to the solutions as they 

 occur naturally in the soil. Plants have been grown to 

 maturity in these artificial solutions side by side with 

 ones just like them planted in the ground, 

 and with equally satisfactory results. Where 

 it was desired to determine if, say, potas- 

 sium was really necessary, a solution was 

 prepared having all the ingredients found 

 in the soil waters except potassium, and in 

 this the plants would be grown. Fig. 42 

 shows the results of growing buckwheat in 

 a complete or normal nutrient solution and 

 also when certain important elements are 

 withheld. It should be remembered that 

 some potash, calcium, etc., was in the seed 

 so that not all the mineral nutrients 

 are kept from the plantlet. Sodium, 

 while quite simi- 

 lar to potassium, 

 can not replace 

 potassium as a 

 nutrient. 



110. Effect of 

 Fertilizers. An- 

 other way of 

 testing the effect 



Fig. 42. Buckwheat grown in artificial solutions of <>f a Substance 



mineral nutrients A, complete solution; B, potas- - Q + n rrrn\v fViA 



sium withheld; C, nitrogen withheld; D, calcium 1S IO g r W tnt 



(lime) withheld; J?, without potassium, but so- i-vlarie in enma 



dium added. Drawn from photograph by Nobbe. P^ntS in SOme 



