26 FERTII^ITY AND FERTILIZER HINTS 



and turning them under in time for the summer crops, erosion 

 will be stopped considerably during the winter and much organic 

 matter will be supplied which will make clay soils more porous 

 and spongy. Underdrainage prevents erosion by carrj'ing the 

 excess of water away gently. 



Many farmers terrace their soil to prevent it from washing 

 away. This custom is not as beneficial as deep plowing, plow- 

 ing under of green crops, or putting the land in pasture. Many 

 of the most successful farmers keep their rows level so when 

 it rains the water remains in the furrows instead of washing 

 down hill. These furrows will not be straight but answer the 

 purpose of saving fertility. 



Drainage, — The loss of fertility by drainage is chiefly concerned 

 in the loss of nitrogen. This element to be favorable for most 

 plants to assimilate must be in the form of nitrates which are 

 readily soluble in water. Phosphoric acid and potash are fixed 

 in the soil so that they are insoluble in water and hence very 

 inappreciable amounts are lost by drainage.* 



Experiments have shown that the loss of nitrogen by drain- 

 age is greater on soils that are idle than on cultivated soils. At 

 first thought one would suppose that the loss would be greater 

 on the cultivated soils as they are more open and porous, and 

 hence permit of a more free passage of water through the soil. 



The excess of nitrates in cultivated soils is carried down in 

 the soil but after a rain the capillary water carries it up again 

 to the plant roots. Again, the plants are continually using up 

 the available supply of nitrogen as fast as it is formed so that 

 there is no appreciable excess to be carried away. 



It has been found that about 37 pounds of nitrogen per acre 

 are lost from average idle land during a year. This loss of ni- 

 trogen is quite large when we consider that 20 bushels of wheat, 

 not counting the straw, remove 25 pounds of nitrogen ; 50 bush- 

 els of oats, 35 pounds ; and 65 bushels of corn, 40 pounds.* 



Fallowing. — In the arid sections of this country where dry 

 farming is followed it is often necessary to let the land remain 

 idle for a season to conserve enough moisture to produce profit- 



