Treatment of Sick Soils 



29 



changes the calcium carbonate into calcium bicar- 

 bonate, which is very soluble, and readily leaches 

 out with the drainage water. 



Soils which are heavily manured are apt to be- 

 come more acid. The decomposition of the organic 

 matter yields large quantities of carbon dioxide 

 which act on the carbonate in the manner above in- 

 dicated. In addition to these causes, poor drain- 

 age has a tendency to increase the soil acidity. The 

 application of ammonium sulphate as a fertilizer 

 leads to a development of acidity by the production 

 of sulphuric acid. The same is true when other 

 acid fertilizers are used. In the process of nitrifi- 

 cation, in which nitrogen is made more available for 

 plants, acids are produced. Acidity in a soil is 

 usually characterized by a languid condition of the 

 growing crop. This may be due directly to the 

 effect of the acid on the plants, or to the inhibiting 

 effect of the acid on the soil flora. In the latter case 

 the plant food in the soil, although very plentiful, 

 may not be in a form available for plants. 



Not all crops are equally sensitive to soil acidity. 

 Hartwell and Damon* have determined the degree 

 in which truck crops are benefited by the application 

 of lime to an acid soil. Those which are very sen- 

 sitive to soil acidity are followed by the number 

 (3), while a lesser degree of sensitiveness is indi- 

 cated by the numbers (2) and (1). Crops which 

 tolerate a moderate amount of acidity are followed 



*Hartwell, B. L., and Damon, S. C, Rhode Island Agr. Expt 

 Sta. Bui. 160: 408-446, 1914. 



