1921.] Artificial Farmvarp Manure. 899" 



(1) Air suppli/. — It lias been found invariably that charac- 

 teristic breakdown changes in straw remain suspended when a 

 free supply of air is excluded either by intense consolidation or 

 by immersion of the straw in liquid. The fermentation appears, 

 therefore, to be an essentially aerobic one, at least in its early 

 stages, and the typical disintegration of the straw with the 

 production of dark-coloured plastic material does not take place 

 in the absence of air. Moreover, the colour of aerobically pro- 

 duced manure is rapidly reduced when oxygen is excluded. The 

 great importance of air supply is shown by the following 

 experiment, in which four lots of straw were fermented under 

 aerobic and anaerobic conditions for three months at 37° C. 



(^9° F. ) . Loss of Dry Matter. 



Straw loithout Nitrogen. Strav: vnth Nitrogen. 



Without Air Supply ... 16-3 per cent. 17*1 per cent. 



With Air Supply " ... 40-1 59-8 



The data explain what may be seen in the ordinary 

 heap of farmyard manure, viz., that straw submerged in liquid 

 urine, and therefore protected from air, remains in an 

 unchanged state for long periods. On the other hand, the 

 practice of carting manure from the yards and boxes and 

 storing it in heaps in the field, although carried out for other 

 reasons, provides better conditions for rotting than are likely 

 to prevail where the dung is consolidated by trampling and 

 saturated with urine. 



(2) Suitable Temperature. — Except in those cases where 3tra\v 

 is being fermented under otherwise unfavourable conditions, 

 special measures to maintain a favourable temperature for 

 fermentation are not called for. In common with other fresh 

 fermentable materials, moist straw rapidly undergoes a 

 preliminary fermentation during which the temperature may 

 rise to upv/ards of fi5° C. ^149^ F.). It is, however, in the 

 subsequent stages that the effect of treatment becomes most 

 evident in maintaining the temperature. Experience has shown 

 that a supply of nitrogen, by increasing the energy of fermen- 

 tuition, leads to an increase of 15 -20'^ C. (59—08° F.) in 

 favour of straw which has received a sufficient supply^of 

 nitrogen, as compared with untreated straw. 



(3) A Supply of Soluble Nitrogeu Comjwutuls in suifnhlc Con- 

 centration, and poasessinfi a iieutral or sliqhfhf aJlialinc reaction. 

 — Repeated experiments have shown that the most rapid break- 

 down of straw occurs when some source of nitrogen in an avail- 

 able or indirectly available foini was supplied, arid then only in 

 those cases where the re-action of the so]iiti(^n was neutral or 



