AN OLD PRACTICE 



191 



southern California it was found that it required from 270 to 1080 

 pounds of nitrate of soda 2 together with a green manuring crop of 

 barley to produce as good a yield of corn as when a legume was 

 plowed under. In either case the same amount of organic matter 

 was added. 



In a test made in Canada, increases of twenty-eight per cent 

 in potatoes and forty per cent in corn resulted in growing these 

 crops following clover. 



In Alabama the plowing under 

 of a legume (cowpeas) gave a clear 

 gain of 696 pounds of seed cotton 

 per acre (Fig. 127). 



A legume crop (crimson clover) 

 plowed under in Maryland gave an 

 increase of twenty-seven bushels in 

 potatoes and seven bushels in corn 

 (Fig. 128). 



At the Virginia Truck Station, 

 Norfolk, " cowpeas plowed under 

 green in the fall gave as large a 

 yield of cabbage per acre as twenty 

 tons of stable manure." 



On the better soils where good 

 clover or alfalfa can be grown 

 often, the need of a special green 

 manuring crop is seldom felt. 



It is Necessary to Maintain 

 Organic Matter. Many farmers 

 fail to appreciate the necessity of 

 replenishing the organic matter in 

 soils, and too often clover is left out of the cropping plans. 

 On many farms clover does not grow so well as it used to, or fails 

 entirely. This should be taken as a warning that something is 

 wrong with the soil or the system of farming. When clover is 

 left out of the cropping system, and the organic matter of the soil 

 is allowed to become depleted, it is only a question of a few years 

 when the other crops will cease to give paying returns. 



An Old Practice. Green manuring to add organic matter and 

 nitrogen is not a new farm practice. Its value has long been known. 

 Twenty centuries ago Varro told the Roman farmers the following: 



2 A soluble nitrogen fertilizer. 



Fio. 127. Cowpea. (U. 8. D. A.) 



