56 



BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 



organic matter, which would aid in rendering the less soluble phos- 

 j)hate more effective. The conditions, therefore, were much more 

 fa\'orable to the water soluble phosphates than to raw ground rock. 



The results of the other long-time experiment published in this 

 same report^ cover a period of seven years. This second experi- 

 ment was conducted on a larger scale than that just described and 

 had two objects in view: First, to determine the possibility of main- 

 taining soil fertility by the use of commercial fertilizers, and second, 

 to determine the comparative value of raw rock phosphate and acid 

 phosphate. 



A 10-acre field, the soil of which was a clay loam and excellent 

 grafe.-, land, was selected for this experiment, and divided into four 

 plots of 2^ acres each. For two years (1888 and 1889) no fertilizers 

 whata^er were applied to any of the plots, grass being grown in 

 order to determine their relative natural fertility. Fertilizers were 

 {.pplied only once during the seven years of the experiment (in 

 1890), so the results after that year show in a measure the residual 

 effects of the various fertilizer treatments. 



The re&ults of this experiment are given below in Table XXX. 



Table XXX,. — Results obtained on plots of two and one-half acres each, in the 

 growing of various crops (1888-1894). 



Fertilizer. 



Stable Doiimire- 



Ground South Carolina rock. 



Nitrate of soda 



Ammonium sulphate 



Potassium chloride 



Acid phosphate 



Nitrate of soda 



Ammonium sulphate 



Potassium chloride , 



No manure 



Appli- 

 cation 

 per 

 acre. 



Loads. 

 20 



Pounds. 



1,000 



66 



16 



100 



600 



66 



16 



100 



Hay.i 



Pounds. 

 2,542 



2,416 



2,082 

 2,510 



18901 



Barley 

 and 

 peas. 



Pounds. 

 2,208 



1,712 



1,422 

 1,118 



Oats, 



Total. 



Pounds. 

 3,818 



2,981 



2,972 

 2,480 



Barley, 

 hay. 



Pounds. 

 3,444 



2,324 



1,930 

 1,161 



Sum- 

 mer 

 tilled. 



Pounds. 



1894 



Oats, 



dry 



matter.* 



Pounds. 

 1,894 



2,453 



1,734 



957 



1 Fertilizer applied in 1890 only. 



2 Oats were cut before maturing and used for silage. 



The indications are that the plot which was afterwards treated 

 with acid phosphate was naturally less fertile than the other plots 

 of the experiment field. Contrary to what one would expect the raw 

 rock phosphate was apparently as effective as acid phosphate during 

 the first year of its application, yet the following year (if the ap- 

 parent relative natural fertility of the two plots be taken into con- 

 sideration) the acid-phosphate plot appeared to greater advantage 



1 Idem., p. 28-32. 



