460 



[December, 1912. 



SEWAGE-SICK SOILS. 



2 he Gardeners' Chronicle for November states that an investigation by 

 Messrs. Russell and Golding (Journal of Agricultural Science, October, 

 1912) into the sickness of the sewage soils has led the authors to the 

 conclusion that the causes which produce this state are, in the main, 

 identical with those which bring about sickness in ordinary soils. 



As the result of previous investigations by Russell and Hutchinson it 

 is suggested that even in an ordinary soil the community of soil micro- 

 organisms is not working at its maximum efficiency as measured by the 

 rate at which plant food is being produced. 



If such imperfectly efficient soils be partially sterilised, the crops 

 taken on them are larger than those obtained from untreated soil. Hence 

 the agent which is lowering the fertility of the soil is a vital agent. 

 Various considerations point to the unicellular animals (protozoa) of the 

 soil a? the cause of reduced fertility and it is suggested that in ordinary 

 soils these animals prey upon soil bacteria, reduce their numbers, and 

 hence their activity in producing nitrogenous plant food. 



By partial sterilisation, the protozoa are killed, but certain of the 

 bacteria are not. Free from their hereditary foes the surviving bacteria 

 increase, multiply and manufacture more vigorously than in either 

 normal or sick soils. 



The essential conclusion reached by Russell and Golding with respect 

 to sewage-sick soils is similar to that just outlined. Such soils will stand 

 no more sewage. If further additions be made the material fails to perco- 

 late through the soil, crops are injured and even killed. Partial sterili- 

 sation of the soil restores its "health." 



Hence, if a practical method can be devised whereby sick soil may be 

 sterilised partially and cheaply, a definite advance will have been made in 

 the problem of sewage treatment ; for the sewage farm may then serve 

 for an indefinite period for the successful cultivation of crops. 



POTATO-DRYING IN GERMANY. 



Germany's total potato crop in 1908 amounted to 915,000,000 cwt-, of 

 these 256,000,000 cwt. were used tor human consumption, 79,000,000 cwt. 

 for starch and alcohol production, 108,000,000 cwt. for seed, and 374,000,000 

 cwt. foi feeding animals, leaving a surplus of 98,000,000 cwt., valued at 

 £6,000,000. This surplus is largely converted into dried potatoes. Accord- 

 ing to the Journal of the Board of Agriculture, U.K. (1912, 18, 1C48) there 

 were 257 potato-drying factories in Germany in 1910 producing either dried 

 slices or dried flakes, la eight factories peeled potatoes form the raw 

 material, in the remainder the unskinned potato is employed. The 

 production for the year amounted to 1,723,000 cwt. of dried material. 

 Feeding trials have shown that dried potatoes form an excellent feeding- 

 stuff for all kinds of stock. The price of potato flakes is stated to be 

 §ibout 7s. to 8s. per cwt.— Imperial Institute Bulletin. 



