EXPEEIMENTAL WORK WITH RAW ROCK PHOSPHATE. 



Ill 



Table LXVI. — Yields of oats obtained in four pot experiments with various 



types of soil. 



Fertilizer. 



Application 

 per acre 



Yields of oats, average of four pots. 



CJoastal 

 Plata SOD. 



Piedmont, 



Red Lands 



soil. 



Piedmont, 



chocolate 



soil. 



Piedmont, 

 gray soil. 



Acid phosphate , 



Floats 



No fertilizer , 



Nitrate of soda 



Potassium sulphate. . 



Nitrate of soda 



Potassium sulphate . 



Nitrate of soda 



Acid phosphate 



Nitrate of soda 



Potassium sulphate . 



Acid phosphate 



Lime • 



Pounds. 

 200 

 120 



100 

 100 

 100 

 100 

 100 

 200 

 100 

 100 

 200 



Orams. 

 37.9 

 30.9 

 33.9 

 34.1 

 32.3 



34.5 

 45.5 



25.8 



Grams. 

 42.9 

 43.2 

 46.5 

 646 

 44.0 



50.0 

 60.1 



65.0 



Grams. 

 37.5 

 28.6 

 32.8 

 45.2 

 45.5 



47.4 

 57.0 



51.0 



Grams. 

 38.1 

 35.7 

 34.4 

 39.1 

 37.8 



51.5 

 51.5 



53.0 



With the exception of the Coastal Plain soil, the various types 

 seemed to respond more readily to nitrogen than to phosphoric acid 

 applications. On the basis of equal applications of phosphoric acid, 

 however, the acid phosphate pots gave considerably better yields 

 than those treated with raw rock phosphate, the latter material ap- 

 parently producing no effect whatever. The rate of application, 

 however, was so low,^ and the duration of the experiments so brief, 

 that appreciable increases in yield could hardly be expected. 



In 1913 Johnson,^ of the Virginia Truck Station, published the 

 results of a fertilizer experiment in the growing of kale. This ex- 

 periment was the outgrowth of one begun in 1908, the object of which 

 was to determine the relative value of various fertilizer materials 

 and the best quantities to apply, and also to determine the relative 

 value of stable manure and clover as sources of humus both with 

 and without lime. 



The fertilizer treatment was continued over a period of five years, 

 but the results of only one year (1913) are recorded. The ground 

 raw rock phosphate plots compared very favorably with the acid 

 phosphate plots, but the best yields were obtained from the use 

 of bone products, owing probably to the nitrogen contained in the 

 latter. However, the limited data recorded render the results of this 

 experiment inconclusive. 



The work of the Virginia station has not as yet been extensive 

 enough to justify a comparison of acid phosphate with ground raw 

 rock phosphate, particularly as in every experiment the applications 

 of the latter material have been too light to get the full benefit from 

 such an insoluble substance. 



1 The amount of phosphoric acid applied was sufficient to add about 0.0014 per cent of 

 PzOb to the first 9 inches of a soil of medium texture. 

 »Va. Truck Expt. Sta., Bui. No. 9 (1913). 



