No. 7. 



DEPARTMENT OF AGRICULTUK1^J. 



485 



ROTATION VS. CONTINUOUS CULTURE 



(For this portion of his address Mr. Wallace displayed a number 

 of charts showing in detail the results of the experiments dis- 

 cussed.) 



At the Ohio Station we have two series of tests which have now 

 been in progress for seventeen years, that present some interesting 

 facts as to the value of rotation as compared with continuous crop- 

 ping both with and without the use of fertilizers and manure. 



In one test we have established a five-year rotation of corn, oats, 

 wheat, clover and timothy, and in the other corn, oats and wheat, 

 each having been grown continuously on the same ground for the en- 

 tire period of the test. 



Under rotative cropping the average unfertilized yield of corn has 

 remained practically unchanged for the entire period. The average 

 annual yield at the end of the first five-year period was 31.89 bushels 

 per acre ; at the end of the third period the yield was 31.04 bushels 

 per acre^less than a bushel difference between the first and the last 

 period — a difference so small as to make it unsafe to attach to it any 

 particular significance. In the continuous culture plots, however, 

 both the unfertilized yield of corn and wheat show a rapid decrease 

 in yield, the average for the third period being only about half that of 

 the first. 



On the fertilized plots the nitrogen is applied at the same rate per 

 acre as Plot 11 in the rotative cropping, and on Plot 2 in the con- 

 tinuous culture, but the corn and oats grown continuously receive 

 more phosphorus and potassium than the same crops in the rotation. 

 At the end of the first five years the corn had yielded slightly more, 

 on an average, in the continuous than in the rotative cropping and the 

 oats and wheat nearly as much. During the second and third 

 period, however, all the crops in the rotation have made steady and 

 constant gains while the yields on the continuous culture plots have, 

 with the exception of oats, been gradually going down, notwith- 

 standing the heavier application of fertilizer. In the following table 

 are given the yields for each of the three five-year periods both for 

 Plot 2 of the continuous cropping and Plot 11 of the rotation : 



Corn, 

 Oats. . 

 Wiieat, 



bus. 

 64.13 

 53.49 

 33.10 



In the case of plots receiving barnyard manure comparison is 

 made between Plot 20 in the rotatiou work, which receives a total of 

 eight tons of manure every five years — four tons each on corn and 

 wheat — and Plot of the continuous culture which gets five tons of 



