492 



Journal of Agricultural Research 



Vol. VI, No. 13 



AVAILABILITY OF THE PHOSPHORUS IN TENNESSEE BROWN ROCK 



PHOSPHATE 



This series comprises a study of the ability of different crops to secure 

 phosphorus for growth from Tennessee brown rock phosphate without 

 the aid of decaying organic matter. The literature indicates rather 

 clearly that crops differ widely in this respect, but there is but very little 

 direct information from trials conducted under controlled conditions 

 where sand was used as a substitute for soil. The suggestion has been 

 made, also, that there is slight increase in the yield with large applica- 

 tion of phosphate. The object of the series reported in Tables II to VI 

 is to present new information on these two important points. 



The pots used were the large, glazed 4-gallon jars into which could be 

 placed 22,000 gm. of sand (PI. LXXIII, LXXIV, LXXV). In this case 

 the sand was not leached with dilute acid, but was washed for several 

 days with distilled water. The rock phosphate was ground sufficiently 

 finetopass through a sieve of 100 meshes to the inch. On March 20, 191 4, 

 the pots were seeded; and after the plants had made satisfactory growth, 

 they were thinned to 15 to each jar. 



Table II. — Dry matter and phosphorus content of plant products from wheat and oats 

 SERIES ia; spring wheat harvested on JUNE 29, 1914a 



SERIES IB; SIXTY-DAY OATS HARVESTED ON JUNE 7, I914& 



o Seed planted in each pot in series lA contained 0.46 per cent of phosphorus. Fifteen seeds contained 

 1.7 mgm. of phosphorus. 



Seed planted in each pot in series iB contained 0.35 per cent of phosphorus. Fifteen seeds contained 

 1.29 mgm. of phosphorus. 



