258 SYSTEMS OF PERMANENT AGRICULTURE 



phate, even though twice as much phosphorus is applied in the raw 

 phosphate as in the acid phosphate. If more clover were plowed 

 under or if more manure were returned, so as to remove the nitro- 

 gen limit, the comparative value of the two forms of phosphorus 

 could, perhaps, be more definitely determined. Such additional 

 supplies of decaying organic matter would tend to make avail- 

 able still larger supplies of potassium, magnesium, etc., and thus 

 to avoid their becoming limiting factors. It is possible that the 

 use of acid phosphate tends to prevent loss of ammonia from the 

 manure during the few weeks that elapse between the mixing of 

 the phosphate with manure and the application to the land. 



Two important facts are well established by these Ohio experi- 

 ments: First, that fine-ground natural rock phosphate is a material 

 that can be employed with very large profit as a phosphorus 

 fertilizer, when used in connection with liberal amounts of decaying 

 organic matter; and, second, that, under the conditions of these 

 experiments, the raw phosphate gave practically the same profit 

 per acre, and twice as much profit for the money invested, as the 

 acid phosphate. (For later averages, see page 299.) 



In the Ohio Farmer for August 22, 1908, Director Thome re- 

 ports some interesting and valuable results showing the effect of 

 raw phosphate on clover grown in 1908 on the Strongsville Experi- 

 ment Farm, located between Wooster and Cleveland, on a heavier 

 type of soil of nearly level topography. The author has also been 

 given the figures for the 1908 oat crop. 



Director Thorne states that lime and raw phosphate were ap- 

 plied across the plots in the five-year rotation, " dividing the sec- 

 tion of plots into 4 divisions, using one ton of lime per acre on the 

 first, two tons of lime on the second, one ton of floats on the third, 

 and two tons of floats on the fourth, applying the lime and floats 

 across all the plots, fertilized and unfertilized alike." 



The crops grown in the five-year rotation experiments at Strongs- 

 ville are corn, oats, wheat, clover, and timothy, and the fertilizers 

 applied are similar to those in the older five-year rotation at Woos- 

 ter as reported in Table 82, with ten additional plots in each series. 

 It is understood that during the course of five years all of the series 

 have received (or will receive) the treatment with lime and raw 

 phosphate, as above described. 



