132 COBN CROPS 



supplemented by plowing under organic matter, especially 

 green crops, containing enough legume crops to maintain 

 the nitrogen supply. 



Perhaps the best comparative idea of the value of farm- 

 yard manure and fertilizers can be obtained by examining 

 certain data secured at the Pennsylvania station in a 

 twenty-five-year test, two experiments at the Ohio station 



— one for sixteen years and the other for thirteen years 



— a nine-year test at the Indiana station, a thirteen-year 

 record at the Illinois station, and a single corn crop after 

 timothy at the Cornell station. 



The foregoing table is a summary of the data secured at 



. the Pennsylvania and Ohio stations. These are the best 



continuous records that we have in the older portion of 



the United States, where the use of manure and fertilizers 



is now becoming a matter of importance. 



The summary shows that land yielding, under a good 

 rotation, an average of 35.4 bushels of corn per acre has 

 been maintained at an average of 48.4 bushels for the corn 

 crop by an average expenditure of $15.20 for commercial 

 fertilizers (where a complete fertilizer was used) for each 

 course of the rotation (average of four years). These 

 complete fertilizers were fairly well mixed to meet the 

 needs of the soils in each case. An average application of 

 11 tons of manure every four years has maintained the 

 yield of corn at 51.82 bushels. 



The second part of the table shows the average financial 

 returns for all crops grown during the course of rotation. 

 Eleven tons of manure shows a better average return than 

 $15.20 worth of commercial fertilizer, and an average 

 return of $2.46 per ton for the manure. The Illinois 

 station received a return of $1.60 per ton and the Indiana 

 station $1.50 per ton for manure. Both the latter stations 



