II. B. HrTCiiTNSox AM) K. ;MaoLkxxax 



1»," 



aninionia and nitrate production (as an indication of increased bacterial 

 activity) and the amount of plant growtli in tlrese soils. 



Full details have already been given elsewhere (37), but the following 

 table will serve to bring out this relation more clearly. 



Table Vll. The Relation bettveeii Soil Acidity, the. Prodndion of 

 Ammonia and Nitrates, and Plant Growth in certain Soils. 



* The authors desire to express theii' indebtedness to Dr .J. A. Voeloker, Director of 

 the Station, who very kindly placed this and other samjjies of soil at their disposal, 

 t From other experiments, first croji only. 



The two soils, Rothanisted and Chelsea, contained initially an 

 abundance of carbonate (2-6 and 0-8 per cent. resp(;ctively) and the 

 further addition of chalk gives returns varying only slightly from those 

 of the control soils; Millbrook soil, which is almost neutral, gives a 

 slight increase in nitrates and a depression in ]jlant growth. The two 

 acid soils, Woburn and Oraibstone, respond readily to chalk applica- 

 tions as indicated by increased iiitrate production and plant growth in 

 the first four crops after treatment. 



In another e-xj^eriment the addition of calcium carbonate to a soil 

 showing a lime requirement of 0-1 17 per cent, resulted in an increase 

 of the following barley crop of 30 per cent. 



Having shown that the method suggested provides a good indication 

 of preceding treatment of the soil in the laboratory, some further deter- 

 minations with field soils may be of interest. The samples used in 

 these experiments were obtained from the permanent wheat and barley 

 plots of the Woburn Experimental Station, already well known on 

 account of their pronounced acid character as a result of continued 

 applications of sulphate of ammonia. Up to 1897 the crops on some of 

 these plots had already begun to fail, while a preliminary application of 



