BOOKS AND CURRENT LITERATURE 



Higher Plants and Nitrate Formation. — This mpmoir^ contains 

 the result of investigations conducted during the past six years upon 

 th(^ rehitions of certain crops to the nitrate content of the soil. The 

 authors had previously advanced the hypothesis that certain non-legumi- 

 nous plants exert a stimulating or a depressing influence on the process 

 of nitrate formation, depending on the stage of growth. In the present 

 paper the data substantiating this contention are assembled. It was 

 found that during the most active growing period of maize, nitrates are 

 frequently higher under this crop than in cultivated soils bearing no 

 crop, a result contrary to the general teaching and belief. This phe- 

 nomenon is accounted for on the assumption that nitrate formation is 

 stimulated by some processes connected with the active growth and ab- 

 sorbing function of the plant, although there are indications that maize 

 obtains a large part of its nitrogen in some other form than as nitrates. 

 The combination of these conditions may account for the very high 

 nitrate content of the soil under maize. Under a mixture of maize and 

 millet, when both crops were most actively growing, the nitrates are 

 higher than under millet alone. 



It was also found with oats as well as with maize that the nitrate 

 content was higher at the time when the crop was making its greatest 

 draft on the soil nitrogen, than in the later stages of growth, in spite of 

 the fact that the nitrates in the uncropped soil were increasing while those 

 on the cropped soil were disappearing. When, late in the season, nitro- 

 gen absorption had practically ceased under both oats and maize there 

 was no increase in nitrates, although there was a very marked increase 

 in nitrates in uncropped soil. These facts indicate that during the later 

 period of their growth, oats and maize exert in some manner a depressing 

 influence on nitrate formation. 



A characteristic relation of the several plants to the nitrate content of 

 the soil in the year following that in which the plants had been grown was 

 also noted. Central plats were planted to maize, oats, and potatoes, 



' Lyon. T. Lyttleton and Bizzell, J. A., Some relations of certain higher 

 plants to the formation of nitrates in soils. Cornell Agr. Exp. Sta. Memoir 

 No. 1: 1-111, 1913. 



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