122 CHEMISTRY OF FARM PRACTICE 



sugar beets, and truck, it is necessary to make additional 

 use of nitrogen derived from a commercial source. How- 

 ever, it is recommended that the annual legumes be used 

 as catch crops and cover crops to supplement the arti- 

 ficial supply. 



It is an interesting fact, established experimentally by 

 Lipman of New Jersey, that a non-leguminous crop grown 

 as a companion crop with a legume may derive nitrogen 

 from the supply of atmospheric nitrogen fixed by th3 

 legume. The experiment was conducted as follows: A 

 small glazed pot was placed in a large pot to serve as a 

 check, while a small non-glazed pot was placed in another 

 pot for the determination. All pots were filled with earth 

 and a legume was planted in the outer pot in each case, 

 and the non-legume in the inner pots. Where the non- 

 porous inner pot was used, the non-legume made much 

 poorer growth than where the porous inner pot was used, 

 because the soluble nitrogen could go through the walls 

 of the porous inner pot to serve to nourish the non-legume. 



90. Commercial Nitrogen Profitable. After supplying 

 all nitrogen that it is practicable to secure by means of 

 leguminous crops, it is still generally advisable to apply 

 nitrogen in the commercial form to specialized, high-priced 

 crops. The grower of early truck can afford to purchase 

 a large amount of high-priced fertilizer if it will improve 

 the quality, yield, and early maturity of his product. The 

 same will hold true to a less extent with tobacco, sugar 

 cane, sugar beets, .and cotton. 



91. Selection of Source of Nitrogen. In purchasing 

 nitrogen in its various forms, great care must be taken in 

 the selection of the source to assure high agricultural value. 

 As nitrogen is the highest priced element of commercial 

 fertilizers, there are more attempts to palm off an inferior 

 kind of nitrogenous fertilizer than in the cases of phos- 

 phorus or potassium. It is usually unwise to buy low- 

 grade fertilizers at any price; the best are cheapest in 



