B. P. I— 536. 



SEASONAL NITRIFICATION AS INFLUENCED 

 BY CROPS AND TILLAGE. 



INTRODUCTION. 



The attempt to bring the vast areas of prairie lands of the Great 

 Plains under a profitable system of agriculture has been undertaken 

 with renewed vigor during the last few years, both by the older settlers 

 and by many new ones entering the Plains. These new settlers come 

 mainly from the Middle West, where the climatic and soil conditions 

 are very different from those in the newer areas where they settle. 

 On the Great Plains the rainfall is likely to be too little rather than 

 too much for good crop returns and, moreover, it does not always 

 come at the time most convenient for the farmer; besides, the wind 

 movement, especially in the spring, when the crops are being planted 

 and when the surface of the soil is usually exposed in a rough con- 

 dition, saps the soil of its moisture very rapidly. 



Under such conditions it becomes necessary to control the quantity 

 and the movement of the soil moisture, and as this moisture consti- 

 tutes the plant nutritive solution it is -obvious that not alone the 

 absolute amounts of soil moisture present but the nutritive character 

 of this solution become of importance, so that any cultural system 

 inaugurated for the purposes of moisture conservation should be such 

 that the quality as well as the quantity of the nutritive solution can 

 be controlled. 



It has often been observed that of two contiguous plats on the 

 same type of soil one may yield considerably higher than the other, 

 although the amount of soil moisture may be the same in both. In 

 such cases it is often found that the properties of the nutritive solu- 

 tions from the two plats are markedly different in their behavior 

 toward plant growth, and often the history of the plats will show that 

 the cultural methods have been different and that these may explain 

 the differences found in the character of the soil moisture constituting 

 the plant nutritive solution. The mere storing up, then, of soil mois- 

 ture is not always sufficient for the purposes of good crop returns. 



During the last few years a number of substations have been estab- 

 lished by the Bureau of Plant Industry throughout the Great Plains 

 173 7 



