18 



half of the nitrogen expected. The loss was traced to the broken 

 straw and solid excreta which always finds its way into the liquid ; 

 these bring- about an absorption of nitrogen compounds which 

 deprives the liquid of much of its value. 



Further investigation of this absorption is going on : it may be 

 avoidable, in which case the value of the liquid manure, already 

 marked, could be enhanced still further. In case it seems to be 

 unavoidable, however, a second method of procedure is being 

 studied. 



(b) The solid is collected as before, but the liquid is allowed 

 to run through straw under conditions which encourage the 

 absorption of nitrogen compounds. By suitable arrangement the 

 straw increases in fertiliser value while the liquid loses part of its 

 valuable constituents, and can more easily be sacrificed. 



This method is still in the initial stages, but may prove cf 

 considerable value. Mr. Richards is carrying out the laboratorv 

 experiments at Rothamsted and the large scale experiments ;.t 

 Woking on Viscount Elveden's Home Farm: he has applied it 

 also to the treatment of sewage from small installations. 



2 — Artificial jarmyard manure made without animals. — Few 

 farmers are able to make sufficient farmyard manure for their needs 

 and some difficulty arises about the best method for utilising stra^^ . 

 Direct experiment shows that straw is not a useful fertiliser; indeed 

 in many cases it depresses the crop. Once it is decomposed, how- 

 ever, it is of great value both for its physical and chemical 

 properties. 



Laboratory work by Dr. Hutchinson and Mr. Clayton had 

 shown that the breaking down of the material of straw — the so- 

 called cellulose — is effected by organisms. One of these had 

 eluded all previous investigators, but the Rothamsted workers 

 succeeded in obtaining it in pure culture and in studying 

 it freely (see p. 42). In order that it may decompose straw it re- 

 quires two conditions — air and soluble nitrogen compounds as 

 food. If either of these is missing it ceases to act. Moreover, it 

 will only attack cellulose ; it is unable to feed on sugar, starch, 

 alcohol or any organic acid yet tried. Given, however, the neces- 

 sary nitrogen compounds and a sufficiency of air, the micro-organ- 

 isms quickly decompose straw, breaking it down to form a black, 

 sticky material, looking very much like farmyard manure. This 

 has been investigated in conjunction with Mr. Richards (p. 57) ; 

 further quantities are now being prepared for fertiliser tests. 



3 — The clover crop is very valuable, not only on account of the 

 hay, but also for the effect of its root residues on the next succeed- 

 ing crops. It is, however, one of the most difficult of the farm 

 crops to grow and few farmers would claim that they could grow it 

 as frequently as they wished. The difficulty arises from the fact 

 that the plant depends for success on the activity of certain bacteria 

 in its roots, and the conditions, therefore, have to be favourable 

 both to the plant and the organisms. 



Experiment shows that the clover crop is improved in four 

 uavs : — 



