160 SOIL PHYSICS AND MANAGEMENT 



At Fairfield, in southern Illinois, on gray silt loam on tight clay, 

 Marion silt loam, the gain for phosphorus, limestone and manure 

 ovei manure alone was 2.65 tons per acre of good clover hay. All 

 know that the growing of large legume crops aid the production of 

 large crops of grain (Fig. 80). 



3. By Accumulations in Pastures. The livestock farmer has 

 one decided advantage over the grain farmer in that some of his 

 land must be in pasture and accumulations of organic material 

 are taking place during this period of "rest." A large amount of 

 the organic matter that grows in the pasture will be eaten and de- 

 stroyed by stock in the process of digestion, but the total result 

 will be beneficial to the soil. From the table on page 162 it will 

 be seen that oftly 580 pounds of organic matter are recovered in 

 the manure for each ton of pasture grass eaten by -stock. For red 

 clover pasture, the amount is 680 pounds, while for alfalfa it is 660 

 pounds. Pasture grasses develop systems of roots which add quite 

 largely to the organic supply in the soil. If legumes can be grown 

 in connection with these pasture grasses much better results will be 

 secured than from the grass alone. In the case of sweet clover 

 growing with blue grass, it is found that the amount of blue grass 

 will be larger than if grown alone. In pastures there is very little 

 organic matter lost by oxidation, since this process is not very act- 

 ive in sod, there being no more nitrates formed than are used by 

 the grass. In old compacted pastures, nitrification is not sufficiently 

 rapid to maintain a good growth of grass. Farmers speak of such 

 pastures as being " sod bound/' Plowing and reseeding or at 

 least a thorough disking may be necessary to completely aerate 

 the soil and bring about larger growth. 



Pasture grasses are frequently eaten so closely by stock that 

 very little benefit is derived by the soil. Clover is often pastured 

 so that at the end of the season there is nothing left on the ground 

 to turn under for soil improvement. 



4. Green Manures. One of the very important ways of in- 

 creasing the organic matter is by the use of green manures. Almost 

 any crop may be used for this purpose, but legumes are much better 

 because of the greater value of the material for soil improvement. 

 The crop selected should depend upon the time of planting, the 

 period available for growth, the character of the soil to be im- 

 proved, and the system of farming practiced. The legumes best 

 adapted to single summer growth are cowpeas, soybeans, common 

 vetch, field peas, and velvet beans. Red, sweet and mammoth 



