112 MISSOURI AGRICULTURAL REPORT. 



with that from acid phosphate and muriate of potash ; or that from 

 acid phosphate and nitrate of soda, with that from the complete fertihzer,. 

 wc find that in both cases the cost of he muriate of potash has been more 

 than recovered in the additional increase from the fertilizer, but the 

 margin of profit has been small. We have as yet no data from which 

 to determine definitely whether a smaller application of potassium would 

 have been more economical, but the results of the experiment would 

 encourage the endeavor to find a cheaper source of potassium, rather 

 than to reduce the quantity used, and this is equally true of nitrogen. 

 Taking the combination of fertilizers which has produced the greatest 

 net gain, we note that it consists of 320 pounds of acid phosphate, cost- 

 ing $2.40, 260 pounds of muriate of potash, costing $6.50, and 4.8;) 

 pounds of nitrate of soda, costing $12.00, or $18.50 for potassium and 

 nitrogen, against $2.40 for phosphorus. The total value of the increase 

 from this combination has been 42.47, leaving a net value of $21.57 ^^ter 

 paying for the expensive fertilizer used ; but if only the phosphorous had 

 been bought, the nitrogen and potassium being secured on the farm 

 without cost — as they may be — the net profit would have been $40 i)er 

 acre for the 5-year period, instead of $21. 



IV. 



THE FARM SUPPLY OF NITROGEN AND POTASSIUM. 



Since 1897 there has been in progress on the same farm on whicli 

 the experiments above described are located, a 3-year rotation of corn, 

 wheat and clover, each crop in this case, as in the other, being grown 

 every season after the first. The average unfertilized yields in this test 

 have been as wollows : 



XI. -AVERAGE UNFERTILIZED YIELDS IN 3 YEAR ROTATION OF CORN, WHEAT 

 AND CLOVER FOR THE 9 YEARS. J897-1905. 



Oorn (9 years)... 

 Wheat {i years). 

 Oiover* .. 



I 



37.4 bus. Rralu, 2.198 lbs. stover. 

 8.9 " •' L02-J " 

 l,96:i lbs. Iiiy. 



•For the 5 years, 1901-199). Sjy beans were grown Instead of clover during the first 3 

 years and these were plowed under. 



It will be observed that, the unfertilized \ itld of corn in this experi- 

 ment has been several bushels larger than in the rotation first described, 

 the corn in the shorter rotation being grown on clover sod, in the longer 

 one on timothy sod. The wlieat yields are practically the same in the 

 two tests, if we compare on the basis of the entire 1 2-year period of the 



