June 26. 1916 Mineral Phosphates and Plant Nutrition 495 



Probably the most striking point shown by Tables II to VI is the gradual 

 increase in the yield of both grain and straw from wheat, oats, and barley 

 and in the hay from rye and timothy. In all cases larger applications of 

 phosphorus gave higher returns, though not always in the same degree. 



The grain yield of wheat is especially interesting. Eleven gm. of 

 Tennessee brown rock phosphate produced 1.2 gm. of grain, while double 

 this application produced 4.05 gm., or almost four times the yields from 

 the light-application pots. Pots 7 and 8, which received 6 times as 

 much phosQ^orus as pots 3 and 4, produced approximately 1 1 times as 

 much wheat. Pots 9 and 10 received 20 times as much phosphorus as 

 pots 3 and 4, but gave in return only about 14 times as much grain. 

 Scarcely more evidence is necessary to show that wheat is able to take 

 its phosphorus supply from Tennessee brown rock phosphate. It is also 

 evident that the rate of yield is to a certain degree dependent upon the 

 rate of application of the fertilizer. In the case of the heavy application, 

 there were indications that the size of the pot was a limiting factor. 



Oats responded more uniformly to the phosphate application than did 

 wheat. The average yield of grain for pots 13 and 14 was 4.6 gm.; pots 

 15 and 16, which received double the quantity of phosphorus supplied 

 to pots 13 and 14, yielded less than twice the amount of grain. For the 

 highest application there is still a larger difference in the phosphorus 

 applied and the crop produced, due, no doubt, to the limited size of the 

 pot. The yield of straw followed about the same rate of increase as the 

 grain. 



Spring rye was not able to endure the heat of the summer days, and 

 at the time of harvest growth had almost ceased without producing a 

 single grain. The hay yield shows a gradual increase in dry matter 

 as the application of phosphate rock was increased. 



The yields from barley are not so consistent as those reported for 

 wheat and oats. However, in all probability the same uniformity 

 would have resulted had the crop not been attacked by smut. Although 

 pots 34, 35, 37, 38, and 39 were badly affected, there was a gradual 

 increase in grain and straw as the application of phosphorus increased. 

 A yield of even 18 bushels for barley is not altogether unsatisfactory. 



The data on timothy are no less interesting than .those on the growth 

 of the cereals, because of the opportunity to study the yields of the 

 various cuttings. Timothy displays the same tendency to produce 

 larger returns for greater quantities of phosphorus applied to the sand. 

 For each pot there was a gradual decrease from the first to the last 

 cutting, although the drop was less abrupt between the first and second 

 than between the third and fourth cuttings. 



Contrary to what might be expected the legumes respond to phosphate 

 treatment no better than do the cereals. Perhaps on the whole this 

 latter group produced larger gains than the former. 



