57 o VARIOUS FERTILITY FACTORS 



In case the soil contains limestone, that application could be 

 omitted, and perhaps two forms of phosphorus tried, such as 

 steamed bone meal and an equal value of raw rock phosphate. 

 The use of acid phosphate is not advised for such experiments be- 

 cause of its indirect effect, due in part to its marked acidity, and 

 in part to its soluble salt content, including much calcium sulfate. 



As a rule, the applications are made but once for the rotation, 

 2 tons of limestone, 2000 pounds of raw phosphate, 800 pounds of 

 steamed bone meal, and 1000 pounds of kainit, per acre, being 

 recommended for a four-year rotation. For each ton of produce 

 hauled off from any plot during the rotation, one ton of manure 

 can be returned, even though the wheat and some part of the other 

 grain should be sold, and by exercising great care and making large 

 use of bedding, it is possible to return 1 J tons of average fresh ma- 

 nure for each ton of produce used for feed and bedding. Of course, 

 the crop residues in the grain system will be returned in accordance 

 with the amounts produced on the respective plots, excepting on 

 plots i, 5, and 10, from which all crops are removed and nothing 

 returned. 



Another system which is especially designed to furnish informa- 

 tion concerning the needs of the soil, rather than to demonstrate 

 how those needs should be supplied, is as follows : 



PLAN FOR PLOT EXPERIMENTS WITH FERTILIZERS 



The applications should be at the rate of 1000 pounds of dried 

 blood, 200 pounds of steamed bone meal, and 200 pounds of potas- 



