408 Decoinposition of Organic Matter in Soil 



The richness in organic matter is reflected in the numbers of bacteria 

 which during the winter season remain at some 22 milhons, about three 

 times as high as the unmanured plot. There is no rise in April or May 

 when the temperature rises, but a very pronounced fall to 13 millions 

 in June, then a quick rise in July, followed again by a drop throughout 

 August and September with only one break : then comes a rapid rise 

 in October to 34 millions, the highest point reached, and finally a quick 

 drop to the winter level. 



The amount of COg in the soil air starts from its winter level of about 

 0-1 % and rises gradually to 0-36 % in May, but there is no rapid rise 

 as is recorded for the nitrate dviring April. There is a kink in the curve 

 in May when the land was ploughed, and afterwards a slow rise to a 

 maximum (0-63 %) in July, the land was then again ploughed and 

 there was a continuous drop ; nothing was obtained to resemble the 

 continuous rise in the nitrate curve; the ploughing, however, greatly 

 facilitated the escape of CO2. This apparent cessation of activity in 

 July is very remarkable, and is not easily explained as a mere tempera- 

 ture or moisture effect ; the soil is moist and warm, yet both bacterial 

 numbers and CO2 remain low. Nitrate is steadily accumulating, howeverw 



The CO2 differs but little from that on the unmanured plot. This 

 unexpected result is due in part to the great difference in physical 

 texture, the unmanured soil being close and compact and not readily 

 favouring diffusion, while the dunged soil is much more porous. 



The nitric nitrogen begins at 80 lbs. per acre in top 18 inches in 

 April and rises rapidly to over 100, then it drops till May, when a steady 

 rise begins which, with only one break in July, is continued to Septem- 

 ber, when the extraordinarily high quantity of 170 lbs. of nitric nitrogen 

 per acre is present. Beyond this point there comes a rapid drop to the 

 winter level. During this fall more than 100 lbs. of nitrogen are lost. 

 Yet through the whole period of loss the drains only ran on one day. 

 The result suggests that something besides leaching is involved (Fig. 9). 



Excepting during June the fluctuations in bacterial numbers are 

 reflected in those of the COg quantities ; the high rise in October, how- 

 ever, does not lead to a corresponding rise in CO2. The nitrate curve 

 falls out of hne, only till June does it resemble the COg, its further rise 

 till September being shown neither by the bacterial numbers nor by 

 the CO,. 



