I98 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



developed to fit in with our present rotation it may be confidently 

 expected to play a considerable part in helping the farmer to struggle 

 against bad weather. 



Table showing the Effect of Wet and Dry Winters respectively on 

 the Yield of Corn at Rothamsted. 









Yield of grain, bushels to the acre. 







Rainfall 



LUUCl — .'IdlLll. 



Ammonium Salts applied. 



Difference in favour 









In Autumn. 



In Spring. 



of Spring dressing. 



1 Dry winter 





«*73 



3 i'8 



32-5 



07 



1 Wet „ 





16-73 



27-5 



32-5 



50 









Total prod uce (grain and 



straw), lb. to the acre. 



Dry winter 





«*73 



5.631 



5.829 



196 



Wet „ 





16-73 



4.932 



6,004 



1,072 



1 The dry winters were those preceding the harvests of 18S9, '90, '91, '93, '98, 

 1901, '02, '03, '05, '06, '09, for which the results are averaged here; the wet 

 winters were those preceding the harvest of 1892, '94, '95, '96, '97, 1900, '07, '08, 

 'io, 'it. 



We must now leave these interesting weather problems, and turn 

 to the other factors affecting the activity of the soil bacteria. 



Calcium carbonate is absolutely essential to the activities of soil 

 bacteria, and the soil is not a good medium for bacterial activity until 

 it has adsorbed or combined with as much as it can. It is impossible 

 to say why : one can only state the fact, and in the expressive language 

 of the practised man say that the soil is " sour." Either calcium 

 carbonate or calcium oxide (quicklime) may be used, and for long 

 it was supposed that both acted in substantially the same manner. 

 Dr. Hutchinson has recently shown, however, that there is a funda- 

 mental distinction between the two, in that quicklime is a partial 

 sterilizing agent having the same effect on soil as any other partial 

 sterilizing agent, causing first a depression and then an increase in 

 bacterial numbers and in ammonia production, while chalk has no 

 such effect. 



It is often said that the value of calcium carbonate is to neutralize 

 acids which would otherwise form in the soil, and there is some 

 probability, although little evidence, for the supposition. Organic acids 

 may be formed in the decomposition processes, and we know that 

 practically all calcium salts of organic acids decompose without 

 difficulty with re-formation of calcium carbonate. It is possible, there- 

 fore, that the carbonate plays as it were the part of a lubricant coming 

 into the cycle to help over a difficult stage. 



It has also been asserted that toxins are present in the soil which 

 after a time stop the further action of the organisms. There 

 is no evidence of this, excepting that most dangerous argument of 



