694 



Manurial Value of Sewage Sludge. [dec, 



the co-operation of the Board of Agriculture and Fisheries these 

 experiments were carried out at several collegiate centres as 

 follows : — 



Series i. — Experiments with mangolds and swedes at five 

 -collegiate centres, under the supervision of Dr. W. Somerville. 



Series 2. — Experiments with grass at eight collegiate centres 

 under the direction of Professor Middleton, and at Woburn by 

 Dr. J. A. Voelcker. 



Series 3. — Pot-culture experiments at Woburn by Dr. J. A. 

 Voelcker. 



In all three series of experiments the same sewage sludges 

 were used, and in each case the sludge was artificially dried 

 before being sent to the experimental stations. 



Full details as to the experiments are given in Appendix VIII 

 to the Fifth Report of the Commissioners, and only the general 

 •conclusions will be given here. As regards Series 1, Dr. Somer- 

 ville states : — 



" So far as these experiments go, they show that in the season of 1905 

 none of the sludges experimented with produced any consistent manurial 

 •effect on the growth of turnips, swedes, or mangolds. Although the season 

 was not a good one for the growth of the root crops, it permitted artificial 

 manures to exert considerable influence on the yield of this crop. We 

 would, therefore, appear to be justified in drawing the conclusion that the 

 nitrogen and phosphoric acid of sludge are in a much less available form 

 .than the same substances in sulphate of ammonia, superphosphate, and fish 

 meal." 



As regards the second series of experiments, which were similar 

 *to Series 1, except that hay was the crop to be grown, the broad 

 results showed that at the northern stations, where the wet 

 summer was favourable to slow-acting manures, the application 

 of sludge seems to have been useful. In the South of England, 

 where the hay is cut much earlier, the sludges produced no 

 results whatever, and, speaking generally, the two sludges 

 containing the most lime gave the best results among the sludge 

 .grown crops. 



In a general survey of these experiments and the experi- 

 ments of Series 1, Mr. Middleton says : — 



" The figures obtained in this experiment and in the corresponding 

 experiments made last year are not of a satisfactory character, and do not 

 permit of any conclusions as to the relative money values of sludge and 

 .artificial manures. 



" The only definite conclusion which may be stated is that, for root crops 

 .and .grass, the action of the nitrogenous and phosphatic constituents of 



