116 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



as clover or alfalfa or cow peas for gathering this nitrogenn 

 from the air. This is no hardship, for every well regulated 

 dairy farm should have a good supply of either clover or al- 

 falfa or cow peas on hand. It is therefore safe to state that the 

 farmer who practices the system of rotation and feeds legume 

 hay, need pay no attention to the nitrogen supply of his farm. 



Dr. Hopkins says that there is enough potash in the soil to 

 last for many years and at the present time we need give it no 

 consideration. In our caluculation of the amount of fertility 

 used, it will be noted that there are 43 pounds of phosphorus 

 lost which can be obtained in the form of raw rock phosphate 

 for the sum of 4 cents per pound or making the 43 pounds 

 worth $1.72, the cost of fertility that should be purchased for 

 every cow kept in the herd. This calculation may be a little 

 high for the average cow but it comes very close to what Dr. 

 Hopkins advocates in retaining and building a permanent sys- 

 tem of agriculture. He states that a farmer who is raising 

 maximum yields of corn, clover, oats and wheat should apply 

 250 pounds of the raw rock phosphate annually or 1,000 pounds 

 every four years. If we calculate that the raw rock phosphate 

 furnishes phosphorus at 4 cents a pound, this amounts to $1.25 

 per year per acre. It should be remembered that in my calcula- 

 tion, assuming that the cow consumed a certain amount of feed, 

 it would require $1.72 worth of phosphorus which is not very 

 far from the figures advocated by Dr. Hopkins and based upon 

 actual field tests. I feel, therefore, reasonably safe in stating 

 that every dairyman should make it a point to purchase from 

 $1.00 to $1.50 worth of raw rock phosphate for each cow that 

 he keeps in order to keep his soil up and supply plant food for 

 the production of maximum yields of crops. 



I realize that many of the farmers in this community pur- 

 chase a considerable portion of their feed; in view of this it is 

 not necessary to purchase nearly as much of the rock phosphate 

 as where no feed is brought to the farm. In the following table 

 is shown the amount of fertility contained in 1,000 pounds of 

 bran and 300 pounds of oil meal: 



