No. 6. DEPARTMENT OF AGRICULTURE. 355 



The losses of nitrate in a wheat field, or on fallow ground are there- 

 fore greater during the fall and winter months; and least during the 

 summer months. 



The increased loss of nitrates in a wheat field during the fall and 

 winter months is due to a combination of causes: 



1. Diminished evaporation and increased drainage. 



2. The accumulation of nitrates in the soil during the summer 

 months beyond the needs of the plants, which are washed out of the 

 same during the fall and winter, and 



3. The inability of wheat at this season to utilize the soil water 

 and prevent excessive percolation. 



These considerations teach a most important principle, i. e,, that 

 ground should be kept in some crop as much of the time as possible 

 especially during the fall and winter. The growth of wheat as one 

 crop in a system of rotation is of course necessary, notwithstanding 

 the inevitable losses of nitrates which follow its seeding. 



There are, however, certain violations of the above rule which 

 need correction. 



Corn land should never be left fallow through the winter. The 

 same is equally true of tomato and trucking land. Either these 

 crops should be followed by wheat or some winter cover crop put in 

 to conserve nitrates. In a loose sandy soil in which it is more diflB- 

 cult to accumulate available nitrogen it would be inadvisable to fol- 

 low a cultivated crop like tomatoes, or potatoes by wheat, but rather 

 to use crimson clover or rye to hold the nitrogen. 



(/.) Increasmg the Supply of Available Nitrogen in the Soil. 



Soils may become too rich in humus and available nitrogen. The 

 use of crimson clover has in some cases in Delaware been carried so 

 far as to work actual injury to the land, especially if the latter has a 

 tendency to become heavy and retentive of nitrates. The majority 

 of farm lands, however, are not open to the charge of being too rich; 

 on the contrary, the improvement of land and the growth of larger 

 crops is the great desideratum. 



I have already pointed out that most soils contain large supplies 

 of organic nitrogen, which, by the aid of nitrification, can be made 

 available to crops. The question of utilizing these stores of organic 

 nitrogen already in the soil becomes mainly one of underdraining, 

 deep plowing and more frequent cultivation. 



Every cultivation of a corn or potato crop is equivalent to a dress- 

 ing of nitrate of soda in its cheapest possible form. Hence if we 

 could cultivate twice to each once by our present system we would 



