500 



Journal of Agricultural Research 



Vol. VI, No. 13 



Under greenhouse conditions it was extremely difficult to secure a seed 

 crop of oats during the winter months; hence, the differences of produc- 

 tive power of the various phosphates must be measured by the yields of 

 straw. In a general way the results obtained in this manner are in har- 

 mony with those reported for clover. The brown rock excelled the other 

 phosphates in the production of hay; blue phosphate ranks second; and 

 where apatite was applied it will be observed that the plants made very 

 little growth. Plate LXXVI indicates greater difference in the growth 

 of clover than the dry weight of the top. 



The above data indicate that there was an increase in yield as the 

 quantity of phosphorus was increased. The question naturally arises 

 as to the point at which larger applications of rock phosphate failed to 

 produce greater returns. In order to answer this query, the following 

 results are inserted (Table VIII) : The lowest treatment in the table is 

 about the same as the highest application in series two. This set of pot 

 cultures was planted on August 27, 1914, and harvested on December 

 4, 1914. 



By referring to the clover in Table VIII, a comparison of the yields 

 shows nothing particularly in favor of excessive quantities of rock phos- 

 phate. One point, however, is of interest, and that is that the oats pro- 

 duced a seed crop on the land with the heavy application of brown rock. 

 The hay on the other pots was scarcely more than could be produced by 

 the phosphorus in the seeds planted. 



Table IX. — Dry matter produced by various kinds of mineral phosphates in cowpeas, 



series j 



Kind of phosphate 

 added. 



None 



Do 



Tennessee 

 brovvn rock . . 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Canadian apa- 

 tite 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Utah rock 



Do 



Do 



Pot 

 No. 



19 

 20 



Phos- 

 phate. 



Gm. 



O 



O 



II 



22 

 22 



66 



66 



220 



220 



II 



II 



22 



22 



66 



66 

 220 

 220 



10. II 

 10. II 



20. 22 



Yield of 

 hay. 



Gm. 



0,9 



I. 

 4- 

 4- 



II. 



10. 



17- 



13- 



Kind of phosphate 

 added. 



Utah rock 



Do 



Do 



Do 



Do 



South Carolina 

 land rock . . . 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Tennessee blue 



rock 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Pot 

 No. 



22 



23 

 24 



25 

 26 



27 

 28 

 29 

 30 

 31 

 32 



33 



34 



35 

 36 

 37 

 38 

 39 

 40 



41 



42 



Phos- 

 phate. 



Gm. 



20. 22 



60.66 



60.66 



202. 20 



202. 20 



10. 16 

 10. 16 

 20.32 

 20.32 

 60. 96 

 60. 96 

 203. 20 

 203. 20 



ID. 42 

 10. 42 

 20. 84 

 20. 84 

 62. 52 

 62.52 

 208. 40 

 208. 40 



Yield of 

 hay. 



Gm. 

 2. 2 

 1.4 

 1.4 



•9 

 •9 



4.0 

 3-5 

 4-7 

 S-o 

 3-9 

 4.2 

 1.9 

 2. I 



