141 



Crop yields in bushels jxr acre of Blootniiujton soil e.rperinieiit fuUU eonilucted 

 hy the T'nirersity of Illinois. 



[Prairie soil: Brown silt lo:im, Early Wisconsin (Jlaciat ion.l 



Plant food applied. 



None -- 



Nitrogen 



Phosphorus 



Potaasium - 



Nitrogen, phosphorus 



Nitrogen, potassium - 



Phosphorus, potassium - - 



Nitroi^i'ii, i)li(>splu)rus. potassium -- 



Averaije t;ain for nitrotjen --- 



Average gain for ])hosi)horus - 



Average gain for jjotassium 



Average gain for phosphorus when added to nitrogen 

 Value of this inoreasje 



1905, 

 wheat. 



29 

 31 

 39 

 33 

 51 

 30 

 38 

 52 



6 

 14 



1 



21 

 $14.70 



" Steamed bone meal used on this field. 

 Approximate cost of 2o pounds of phosphorus. 



lu rock phosphate $0.80 



In steamed hone meal <» , 2.50 



In acid ])hosphate 3.20 



In complete fertilizer 8.00 



I ask your attention to this tahular statement, which gives the actual crop 

 yields ohtained during the tirst four years on one of our regular soil-experiment 

 fields in central Illinois on typical corn-helt soil. 



Each plat is L' liy l(j rods, and contains exactly one-fifth acre. The results are 

 given in hushels per acre. The idant-food elements applied per acre per aniunn 

 are as follows : 



Nitrogen, KU) pounds, at a cost of .$1<;, in 700 pounds of dried blood, which is 

 sufficient for less than a 7()-lmshel crop of corn. 



Phosphorus. 2.". pounds, at a cost of ."f;J..")0, in 200 pounds of steamed bone meal, 

 which is sufficient for more than a 100-bushel crop of corn. 



Potassium, 4(t pounds, at a cost of .$2.ri(>. in 1(M» pounds of potassium sulphate, 

 which is sufficient for less than a CO-bushel crop of corn. 



As an average of all tests during the last three years, an investment of $16 m 

 dried blood has yielded a gross return of .$2.78; an investment of $2.50 in 

 steamed bone meal has returned $G.G2 ; and $2.50 invested in potassium sulphate 

 lias returned 2?. cents. 



During these three years we have applied 300 pounds of nitrogen. \\ e have 

 actually removed 287 pounds of nitrogen from our best-yielding plat — 120 pounds 

 in the corn, 83 pounds in the oats, and 84 pounds in the wheat— so that if there 

 has been no loss of nitrogen from the soil by leaching, our account shows a 

 gain of 13 pounds of nitrogen in the soil and a loss of .$39.05 in money. Meas- 

 ured by the increase in crop yields on this soil, the actual value of the nitrogen, 

 which "costs 10 cents a pound, is less than 3 cents. 



In the account with potassium we have applied 40 pounds a year, or 120 

 pounds in three vears. From our best-yielding plat we removed 58 pounds in 

 the corn, 59 pounds in the oats, and 59 pounds in the wheat, making a total of 

 176 pounds removed. In balancing this account we find two net losses, one 

 amounting to 56 pounds of potassium from the soil, and the other $6.80 in money. 

 Measured by the increase in crop yields, the potassium applied has been worth 

 0.6 cent a pound, or one-tenth of its cost, which was 61 cents. 



In our phosphorus account we have applied 25 pounds a year, or 75 pounds m 

 the three years. We have removed 19 pounds in the corn, 13 pounds in the oats, 

 and 13 pounds in the wheat, and our balance shows two net gains— 30 pounds of 

 phosphorus in the soil and $12.35 in' money. The phosphorus, which costs 10 

 cents a pound in steamed bone meal, has already returned 26* cents a pound in 

 increased crop yields, and 40 per cent of the phosphorus applied still remains in 

 the soil. 



a Potassium is applied as a soluble corrosive salt which, like common salt, 

 may sometimes act as a temporary stimulant and liberate some phosphorus or 

 nitrogen from the soil. 



