COVER CROPS AND THEIR EFFECT ON THE SOIL. 



Dr. Lipman. 



In discussing cover crops this morning I shall attempt to answer 

 four general questions. In the first place, what are cover crops? 

 Second, what advantages may result from the use of cover crops? 

 Third, what disadvantages may result from the use of cover 

 crops? Fourth, how may cover crops be used for the improvement 

 of the soil and the crop? 



As to the first of these questions, there is more or less mis- 

 understanding or confusion as to the meaning of the term or terms 

 "cover crops", "green manure crops" and "catch crops". Logically, 

 a cover crop is any crop that will prevent leaching or erosion. 

 That was the main purpose in the growing of cover crops. It 

 was intended to have a crop on the soil during a certain portion of 

 the year to prevent the washing out of soluble plant food or the 

 erosion of the surface soil if the topography be rolling. A green 

 manure crop, most of us understand, is a crop that will take the 

 place of animal manure to some extent. It will increase the con- 

 tent of vegetable matter, and also it might add to the plant food 

 content of the soil. Green manure crops will, in other words, 

 increase the content of vegetable matter out of which humus is 

 made. And finally, a catch crop is a crop that may be used as a 

 cover crop. The catch crop may be harvested or plowed under. 

 The green manure crop is intended to be turned under, so that 

 there are really important differences in the character of each crop. 

 Recently we have come to understand cover crops to mean green 

 manure crops, sown not merely to protect the soil but to add some- 

 thing to the soil. 



As to the next question: what advantages might result from 

 the use of cover crops? In studying the history of cultivated land 

 we find that there is a tendency for such cultivated land to deter- 

 iorate in quality. Stating it briefly, any soil that is placed under 

 cultivation, produces, in its new state, large crops which gradually 

 decline. Then after a time if the markets, population and other 

 conditions justify it, that land will be improved again and will 

 be made to produce more than the virgin soil ever produced. 



Some of you may have read a little book, "The Farmers of 

 Forty Centuries," that was published by the late Prof. King, of 

 the University of Wisconsin, regarding his travels in China and 

 Japan. It shows in a very striking way what the soils which have 

 been cultivated for thousands of years have done in supporting a 

 very large population. We know that our soils must deteriorate 

 under prevailing practices, and it must come to pass in the develop- 



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