96 



Lliiic J^ajidnnaiifs t/j L'citain Soils 



lime sufficed to bring crop productiou to its uornial level. Since 1898 

 various other dressings with lime have been made, in each case with 

 marked benefit (38), and the effect of these dressings is reflected in the 

 reaction of the samples at the present date. For purposes of com- 

 parison we have iiiclnded in the following table the carbonate content 

 of the soils and the yields of barley for the 1913 crop. Full details of 

 the manuring, etc., are to be found in the official reports of the Woburn 

 Station. 



Table VIII. The TAme Requirements of Cerlain Field Soih. 

 (Permanent Barley Plots, Woburn Experimental Station.) 



Without necessarily indicating that tiie controlling factor in crop 

 production of these plots is one of physiological resistance to soil 

 acidity, there is still a very close agreement between yields and soil 

 reaction. In all cases where the soil is neutral in reaction, high letunis 

 are obtained; where the requirement is more than 0-18 per cent, the 

 crop shows almost if not complete failure. In addition to an improve- 

 ment in conditions for plant growth, bacterial ])rocesses are sj)eeded up 

 so that, while in our experiments the amount of ammonia and nitrate 

 formed in the untreated soil within the first fifty tlays was only 7 parts 

 per milhou, that in soil with only 0-2 per cent, calcium oxide reached 



