VALUE OF STUBBLE AND ROOTS
When in his system of rotation the farmer is ready to plow up his alfalfa, he has another inestimable contribution to the land’s fertility in the stubble and roots. It is not recommended to plow under any considerable growth as a green manure, as the hay crop is too valuable. Its market value would buy more fertilizers than the same growth is worth for humus. After a field has stood for five or six years, the roots have added largely to the humus content. Prof. W. P. Headden of Colorado, estimated that the fertilizing value of the stubble and 61⁄2 inches of roots plowed under is about $20 per acre, while the value of the stubble and entire root system is not less than $35 per acre.
The New Jersey station estimated that the amounts of plant food gathered by an acre of alfalfa in two years were equivalent in nitrogen to that contained in 3500 pounds of nitrate of soda; in phosphoric acid to that contained in 600 pounds of boneblack superphosphate, and in potash to the amount contained in 1200 pounds of muriate of potash, or equal to what would have cost $124.