80 REPORT OF THE AGRICULTURAL RESEARCH 



Indian soils. It has been found that important differences 

 exist between the biological changes taking place in the 

 latter and those which have been observed in the soils of 

 Europe; these differences appear to be due to the high 

 average temperatures of Indian soils and their consequently 

 high relative rate of bacterial action. In soil at tempera- 

 tures between 15° C. and 18° C. the process of ammonifica- 

 tion, which is the natural and necessary predecessor of 

 nitrification, takes place at such a rate as to allow the latter 

 to proceed pari passu; in many Indian soils, however, it has 

 been found that at the higher temperatures 25° C. to 30° C. 

 which obtain in them for many months in the year, ammoni- 

 fication may proceed w4th such rapidity as to produce a 

 concentration of ammonia in the soil water sufficiently high 

 to interfere with nitrification or even to inhibit it alto- 

 gether. Where large quantities of nitrogenous organic 

 matter are turned into the soil and put under intensive 

 cultivation much nitrogen may be lost in the form of 

 ammonia, and experiments have shown that the biolysis of 

 organic nitrogenous material requires very careful investi- 

 gation from this point of view. 



It is evident that these facts must be taken into account 

 in selecting the time of year for applying organic manures, 

 along with other considerations depending on local meteo- 

 rological conditions and the optimum moisture content of 

 the soil. 



Further experiments have demonstrated another source 

 of loss of nitrate nitrogen. It has been shewn that where 

 intense bacterial action is taking place in soil any nitrates 

 present will be reduced without the occurrence of anaerobic 

 conditions; it appears probable that the nitrate is utilized 

 as a source of nitrogen by the bacteria. It was found, for 

 instance, that in Pusa soil the optimum moisture content 

 for nitrification is 16 per cent, whereas general bacterial 

 action is intense up to 25 per cent, and at the latter figure 

 rapid reversion of nitrate to the protein form takes place. 

 This would help to explain observations made in field prac- 

 tice both at Pusa and in the Punjab, that excess of soil 



