C. Crowther and a. G. Ruston 213 



The proportions of nitrogen (total) in the soils are much what one 

 would expect from the manuring, the dung plots ("2-6) having accumu- 

 lated considerable reserves. 



The ammonia results can be explained by assuming that the 

 conditions for nitrification were much more unfavourable than in the 

 soils examined by Russell. This is highly probable in view of the low 

 proportions of calcium carbonate in the soils. The case of Plot 12 

 (ammonium salts alone) is specially interesting, the relatively low 

 proportion of ammonia in this soil as compared with Plots 8 and 10 

 indicating that on this plot the conditions are becoming unfavourable 

 even for production of ammonia (see later). 



The nitrates present in the soils at the time of analysis were in no 

 case high, and indeed on the ammonia plots were hardly measurable. 



Further evidence of the low bacterial activity on some of the plots 

 is furnished by the presence (cf. p. 204) round the bases of the grasses 

 of a decided mat of undecayed vegetable matter, this being notably 

 the case on Plots 8, 10, and 12. That this acts as a handicap to the 

 grasses by withholding water from their roots was illustrated by samples 

 of some of the soils taken to a depth of 9 inches on September 17. 1912. 

 The determinations of moisture gave the following results: 



Plot Moisture 



12 16-7 per cent. 



10 178 



8 19-2 



7 21-7 



3 24-7 



2 28-0 



The difference of 12 per cent, between Plots 2 and 12 will represent 

 roughly a difierence of 120 tons of water in the supply per acre, equiva- 

 lent to a rainfall of IJ inch. Similar observations in a neighbouring 

 pasture with Umed and unlimed plots — the unlimed plot having a 

 thick "mat" — lead to the same conclusions and indicate further the 

 beneficial effect of the liming upon bacterial activity. These results 

 are summarised below : 



Plot Date of test Moisture in soil 



jUnlimed Nov. 9, 1911 8-1 per cent, 



i Limed „ „ 21-5 



fUnUmed Oet. 30, 1913 111 



(Limed „ „ 18-7 



