16 



five times our present agricultural consumption. Under present 

 conditions most of this is wasted, only a small portion finding its 

 way on to the farms. A new method of dealing with sewage has, 

 however, been devised by Dr. Fowler and his assistants at Man- 

 chester, and has been carefully tested at Rothamsted by Messrs. 

 Richards and Sawyer. It yields an " activated " sludge, contain- 

 ing 6 or 7 per cent, of nitrogen and 4 per cent, of phosphoric acid, 

 much richer than any of the older sewage sludge, and of very 

 distinct promise as a fertiliser (p. 56). Moreover, no less than 

 15% of the nitrogen present in the sewage w^as recovered. Assum- 

 ing, as seems permissible, the same percentage recovery elsewhere, 

 the general adoption of this method would add considerably to the 

 supplies of organic manures. 



An entirely new method of treating sewage has been evolved, 

 suitable for country houses, villages, etc., in which straw is used 

 and a manure akin to farmyard manure is produced. 



The phosphatic manures are of almost equal importance with 

 the nitrogenous fertilisers. Considerable attention has been 

 devoted to Basic Slag, which during the War changed considerably 

 in character, and is not likely to go back to the old pre-war 

 standard. A grazing experiment with sheep, and a set of hay 

 experiments on permanent and on temporary grass land, have been 

 started to ascertain the value of modern slags and of mineral phos- 

 phates. In addition an elaborate series of pot experiments is in 

 hand to find out whether any constituent besides the phosphate is 

 of value and whether the ordinary solubility test is sufficiently 

 reliable to justify its retention. This work involves co-operation 

 with the steel makers, and in order to develop it fully a Committee 

 has been set up by the Ministry, composed of steel makers and 

 agriculturists, under the Chairmanship of the Director. 



Manures not only increase the crops ; they bring about other 

 changes. Phosphates improve root development, not only of 

 swedes and turnips, but of cereals also. The Botanical Staff under 

 Dr. W. E. Brenchley have shown that phosphates, nitrogenous and 

 potassic inanures, all cause marked increases of root development of 

 barley, sodium nitrate whether alone or in conjunction with super- 

 phosphate being particularly effective. The root system of wheat, 

 however, is less affected by nitrates or phosphates. Nitrogenous 

 compounds in reasonable amount encourage early growth and help 

 the plant in case of insect attack, while the combination of a small 

 dressing of nitrogenous manure \\ ith a large amount of phosphates 

 has been shown to help cereal crops, particularly oats, to mature 

 more early in cold, wet districts. Potash increases the resistance cf 

 the mangold crop to disease and improves the sugar content of the 

 root. Further, manures very considerably affect the composition of 

 the herbage in grass land. Potash and phosphates encourage 

 leguminous herbage and greatly improve the feeding quality of thr 

 herbage ; nitrogen compounds encourage the grasses and largely 

 increase tlie bulk of hay (p. 70 et scq.). 



The effects of manures and cultivations on crop yields are by 

 no means simple and straightforward. Every farmer knows the 

 variations due to season and weather conditions. And although 

 weather mny nc\er be c()ntn)]laV)le forekn<^wledge of its proba))le 



