FERTILIZERS. 579 



when used alone or in combination with each other, but without phos- 

 phoric acid, seem to have reduced the yiekl, but when either or both 

 of these were added to .snperi)hosi)hate the yield was generally increased 

 beyond that from the superphosphate alone."' 



The superphosphate appeared to increase the proportion of straw in 

 the case of wheat. 



The general results of these experiments are summarized as follows: 



"The experiments herein reported, which have now extended over 8 seasons on 2 

 separate tracts of land, and over 2 seasons on 2 other tracts, all widely diverse in 

 location and character of soil, indicate that the highest efficiency of a fertilizer for 

 cereal crops or potatoes is only attained Avhen it contains all three of the chief 

 constitnents of fertility, nitrogen as well as i)hosphoric acid and potash. 



"In the absence of clover or other legnniinons crops, the niaximnna increase has 

 been produced when the quantity of nitrogen applied was eqvial to or greater than 

 that of phosphoric acid. 



"The Avork has not yet gone far enough to give definite information concerning the 

 effect of clover or other leguminous crops in the rotation, but at the present stage 

 of the work it seems doubtful whether clover can be relied upon to furnish sufficient 

 nitrogen for maximum crops, grown in rotations of 5 years or more. 



"It appears that corn, and jjossibly potatoes, have a far greater capacity for 

 obtaining plant food than wheat or oats, the statistics of crop production showing 

 that an average crop of corn may obtain nearly twice as large a total quantity of 

 nitrogen, jihosphoric acid, and potash as an average crop of wheat or oats, grown 

 under the same conditions of soil and climate. 



"Where the cereal crops have been grown in continuous culture for 7 or 8 years in 

 succession, the total recovery of plant food, applied in chemical fertilizers, by the 

 crops to which they were applied, has been about one-third the nitrogen and one- 

 eighth the phosphoric acid and potash. Where they have been grown in rotation 

 with clover, 50 per cent more nitrogen was recovered in the increase than was 

 applied in the fertilizer, but only one-sixth as much jihosphoric acid and half as 

 much potash. 



"The immediate increase from barnyard manure has been much smaller in propor- 

 tion to its chemical constituents than from the chemical fertilizers used in these 

 tests; but the residual eftect of manure is shown to be much greater than that from 

 chemicals. 



"Nitrate of soda has been the most effective carrier of nitrogen in these experi- 

 ments, with sulphate of ammonia, dried blood, and linseed-oil meal but little inferior. 

 Of the various carriers of phosphoric acid, dissolved boneblack, acid ])hosphate, and 

 basic slag seem to produce jiractically equal results, ])ound for pound of phosphoric 

 acid contained. . . . 



"With fertilizers rated at the prices which Ohio farmers have been paying for 

 them, and with the increase valued at the average market prices of recent years, the 

 cost of the fertilizer has never been recovered in the direct increase, when used on 

 cereal crops, except in a i'ew instances which have not been rejieated in subsequent 

 crops. 



"When the cereals have lieen grown in rotation with clover tlicre has been a 

 larger increase, from one-third to one-half tlie total recovery of plant food being 

 found in the hay crops, and when fertilizers have been used on potatoes there has 

 been a gooil profit, with ordinary yields and average prices of potatoes.'' 



On the substitution of soda for and its value in connection 

 with potash, H. J. Wheeler and G. M. Tucker {Uliode Island Sta. 

 Rpt. isOo^xip. 21~j-;j:il). — Investigations in this line commenced in 1894 

 (E. S. E., 7, p, 840) were continued in 18U5. 



