MAINTAINING THE ORGANIC MATTER OF SOILS 171 



duced only about iy 2 pounds, so that the burning of corn stalks 

 results in a loss of 14 y 2 pounds of nitrogen per ton, which at 15 

 cents a pound would amount to $2.17. There is little doubt but 

 that the value of the corn stalks for improving the tilth would be 

 equal to one-half of the value of the nitrogen, so that for turning 

 back into the soil the corn stalks are worth fully $3 per ton. The 

 value of residues is shown in the yields secured where they have 

 been returned to the soil for a number of years. 



One of the most valuable crop residues is that from legumes, 

 which are frequently grown for the seed and the straw returned 

 to the soil. It furnishes organic matter in its most active form, 

 rich in nitrogen, and its rapid decomposition makes it one of the 

 best amendments for soils in bad physical condition. 



On the experiment field at Bloommgton, Illinois, where crop 

 residues had been turned under for five years, the yield of wheat 

 for 1911 was increased 4.4 bushels over that where the crop residue? 

 had been removed, and in 1912 the yield of corn was increased 7.9 

 bushels and in 1913, 5.9 bushels. At the experiment field at Du Bois, 

 Illinois, crop residues turned under gave an increase of $19.28 * 

 for twelve crops, or $1.61 per acre annually, while with phos- 

 phorus applied the increase for residues was $40 for the twelve 

 crops, or $3.33 per acre. 



The turning under of crop residues on the grain farm in the 

 corn belt is very essential, since it is the only means the grain 

 farmer has of maintaining the organic matter. If he makes use of 

 residues and an occasional crop of clover he has even a better 

 chance of maintaining the organic matter than the stock farmer 

 who loses so much organic matter during the process of feeding. 

 (See the table page 1(>2.) 



9. Growing Non-Tilled Crops. Tillage increases oxidation of 

 organic matter by bringing about favorable conditions of moisture 

 and aeration. The compact condition of the soil where non-tilled 

 crops are grown retards decomposition of organic matter, hence 

 the benefit of such crops as wheat, oats, rye, barley and grasses. 



10. Rotation of Crops. dotation permits the growing of tilled, 

 non-tilled and soil-renovating crops. Farmers should plan their 

 rotations with the thought of soil maintenance. This is funda- 

 mental. The length of the rotation and crops selected should be 

 adapted to the soil and to the system of farming. On soils well 



'The price of porn wa<* figured at 35 rents per bushel, oats at 30 eents, 

 wheat at 70 cent's, eloverseed at $! and soyl>eans at $1 per hnshel. 



