AGRICULTURE AND RURAL ECONOMY. 553 



Harris devotes ten pages to fertilizers for corn. He says 

 that we know less about the requirements of this crop than 

 any other we raise. The great question is its power to gath- 

 er its nitrogen from soil and air, whether it is, like wheat, an 

 exhausting or, like clover, a "renovating" crop. Mr. Lawes 

 has lately written several letters on this same subject to 

 prominent agriculturists in this country. He is inclined to 

 class corn with the cereals, where it belongs botanically, but 

 urges the need of experiments to decide the question. Ville 

 classes corn with sugar-cane, turnips, and rutabagas. A con- 

 siderable light is thrown upon the subject by the series of 

 co-operative experiments with fertilizers made by farmers in 

 various parts of the country, and described elsewhere.* Corn 

 grown in ordinary soils was most benefited by phosphoric acid, 

 next by potash, and least by nitrogen. Concerning the ques- 

 tion of the nitrogen supply, the experiments bear quite unit- 

 ed, though not complete, testimony. They imply that corn 

 can get a great deal of nitrogen from natural sources, and is 

 in this respect more nearly allied to the legumes than to the 

 cereals. 



COMPOSITION OF PLANTS. 



Of the late investigations into the composition of plants, 

 some of the most interesting in their practical bearings are 

 those upon the nitrogen compounds. It has become custom- 

 ary to base the valuations of foods and the proportions for 

 mixing them upon their percentages of albuminoids, carbo- 

 hydrates, and fats. It is likewise the custom to estimate the 

 albuminoids by multiplying the amount of nitrogen by the 

 factor 6^,it having been found that the albuminoids, albumen, 

 fibrin, casein, and the like, are essentially similar in compo- 

 sition, and contain nitrogen in about the proportion named. 

 The small variations from this proportion of nitrogen are 

 commonly overlooked for the sake of uniformity. One source 

 of error here, however, is the assumption that all the nitrogen 

 exists as albuminoids. In the light of later research this er- 

 ror is becoming more and more apparent and important. Be- 

 sides ammonia and nitric acid Avhich occur in plants, there 

 are numerous compounds classed as amides, aspargin, betain, 



* See "Farm Experiments with Fertilizers," p. 560. 



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