49° 



NA TURE 



[September 15, 1904 



ment of the country was, comparatively speaking, in its 

 infancy, the estimate of our timber requirements was, in 

 the light of present experience, amusing in its modesty. 

 Captain Cook estimated that " 100,000 acres of waste taken 

 from the Grampian Hills for the growth of larch would in 

 two generations not only supply the ordinary wants of the 

 country, but enable us to export timber."' Assuming a 

 rotation of eighty years, this estimate postulates that the 

 produce of some 1200 acres, of a value of about I20,oooi., 

 was sufficient to make us independent of foreign supplies. 

 Such is the estimate of 1838 ; now let us turn to the estimate 

 of 1904. Dr. Schlich, in his volume on " Forestry in the 

 United Kingdom,"" passes in review Britain's timber re- 

 quirements, and, after making allowance for woods like 

 mahogany, teak, &c., which cannot be grown here, he comes 

 to the conclusion that " if all these items are added up we 

 find that we now pay for imports in timber . . . the sum 

 of 27,000,000/., all of which could be produced in this 

 country." Assuming as before that the value of an acre 

 of mature forest is 100/., it means that our imports are 

 drawn from 270,000 acres, and to maintain our supplies 

 merely at their present level a forest area of more than 

 20,000,000 acres, worked on an eighty years' rotation, is 

 necessary. 



.■\lthough it has been reserved for the Cambridge Meeting 

 of 1904 to witness the delivery of an Address from the Chair 

 of an Agricultural Subsection, this is by no means the first 

 occasion on which an agricultural subject has furnished 

 the theme for a Presidential Address. In 1880 the then 

 Dr. Gilbert presided over Section B, and chose for his 

 subject Agricultural Chemistry ; in 1S94 Prof. Bayley 

 Balfour inaugurated the work of the Biological Section 

 with an Address on Forestry ; while in i8g8 the President 

 of the Association focussed the vision of all thinking men 

 on the greatest agricultural problem of all — the World's 

 Supply of Wheat. 



German Investigations on tlie Action of Consefvation 

 Agents on Farmyard Manure. 



Those who have followed the progress of Agricultural 

 Science in Germany must have noticed how much attention 

 has been given during the past ten years to investigating 

 the changes that take place in farmyard manure during 

 storage under varying conditions. The stimulus and funds 

 for this work have for the most part been supplied by the 

 German Agricultural Society, which in 1892 resolved to 

 carry through an exhaustive inquiry. For this purpose it 

 enlisted the cooperation of several of the most fully equipped 

 stations in the Empire, and the reports that have appeared 

 bear testimony to the industry and analytical ingenuity that 

 have been brought to bear on this important subject. 



The experiments were originally designed to extend over 

 four years, the first, 1892-3, being devoted to preliminary, 

 chiefly laboratory, experiments ; the others, to work on a 

 scale more in accordance with (arm practice. But although 

 the period originally contemplated is now long past, the 

 problem is by no means solved, and the Society has recently 

 been making a fresh grant for additional experiments of a 

 similar character. In point of fact, the subject has been 

 found to bristle with difficulties, and the results obtained 

 with small quantities of manure, or in summer, have not 

 always been confirmed with large quantities of manure, or 

 in winter. 



In 1897 I published an account' of the more important 

 results obtained up to that time, confining myself chiefly 

 to questions of temperature and the loss of organic matter, 

 and the conclusion arrived at was that " none of the con- 

 servation agents usually employed appears to have any very 

 important influence on the decomposition of farmyard 

 manure." 



Since then several important reports ■* have appeared, and 

 I propose shortly to refer to their contents. 



1 Cook, " On the Genera Pinus and Abies." 



- Bradbury, Agnew and Co., 1904. 



■^ Journal Board of Agricuttu7X. September, 1897. 



■* Hansen and Giinlher, ' ' Versuche iiber Stallmist-Behandlung," A rhcHcn 

 der Dent. Laud. Gcsell. Heft 30, 189S. Pfeiffer, " Stallmist-Konserv 

 irung," /^/(/. Heft 73, 1902. Immendorff, " Ueber Slallmist-Bewahrung," 

 Mitt, dcr Dent. Land. Gcsell. Heft 21, 1903. Schneidewind, " Funfter 

 Bericht uber die Versuchswirtschaft," Lanchstddt, Land. Jahrb. .\xxiii. 



While the experiments have in almost all cases dealt 

 with the fate of nitrogen, phosphoric acid, and potash, the 

 chief interest centres round the nitrogen, for, given reason- 

 ably satisfactory conditions of storage, it is only this con- 

 stituent of farmyard manure that is likely to suffer loss. 

 But much importance, from the experimental point of view, 

 attaches to the analytical results obtained with the other 

 two substances, for the reason that the quantities of these 

 found are the surest test of the accuracy of the work. The 

 general method of procedure has been to employ a fairly 

 simple but sufficiently nutritious food-mixture, and to allow 

 a definite quantity of this and of litter for a certain number 

 of selected cows. The weight of nitrogen, phosphoric acid, 

 and potash in the food is accurately determined, all of which 

 ultimately reaches the manure, less what goes into the 

 milk, and into the live-weight increase, if any. If the 

 account of what the animals receive as food and litter, and 

 what they furnish as liquid and solid faces, milk, and 

 animal increase, approximately balances as regards mineral 

 matter, it may be assumed that the sampling and analysis 

 have been sufficiently accurate to justify definite conclusions 

 being based on any deficiency in nitrogen that may be 

 found. 



The work of Hansen and Giinther, Pfeiffer, and Immen- 

 dorff was carried out at consecutive periods from 1893 to 

 1902, at the experimental station of Zwatzen, near Jena, 

 where stalls and dung-pits had been constructed for the 

 purposes of this research. Schneidewind's experiments were 

 conducted at the station of Lauchstadt, near Halle. 



Effects of Kainit. — This was used by Hansen and Giinther 

 at the rate of 0-75 kg. per 1000 kg. live weight of stock, 

 per day, vfhile Pfeiffer and Immendorff used twice as much. 

 The kainit was in no case spread on the litter in the stall, 

 as this would have caused inflammation of the skin of the 

 udder, legs, and abdomen of the cows, but was sprinkled 

 on the manure as spread and pressed into the pits. In 

 certain series of the experiments the manure was removed 

 from the stalls daily, in others it was only removed once 

 a vi'eek. Two weeks was the usual time necessary to collect 

 a sufficient quantity of manure, which, with the liquids, 

 usually amounted to about 8000 kg. at Zwatzen, and about 

 one-fifth of this weight at Lauchstadt. The period of 

 storage was generally about four months. 



Hansen and Gunther found that in pits the untreated 

 manure lost 11-5 per cent, of nitrogen; while the manure 

 treated with kainit lost 144 per cent. 



Pfeiffer found that the loss of nitrogen in untreated manure 

 was 17 2 per cent., which compares with a loss of 195 per 

 cent, in the presence of kainit. The loss of nitrogen when 

 kainit was used by Immendorff was 21-3 per cent., the 

 loss in the untreated manure not being given in his 

 tentative report so far available. Schneidewind did not ex- 

 periment with kainit. The results of these experiments are 

 in complete relative agreement, and show that the loss of 

 nitrogen is greater when kainit is used than when it is 

 withheld. 



Effects of Superphosphate. — This substance was spread 

 twice daily over the litter in the stall at the rate of 0-75 kg. 

 per 1000 kg. live weight. The results obtained were as 

 follows ; — 



Hansen and Gunther 



Pfeiffer 



ImmendorfT 



; Loss of Total Nitrogei 



In untreated dung 

 I0'25 

 1 7 '20 



When super, used 

 16-25 

 20 80 

 19-80 



NO. 1820, VOL. 70] 



With superphosphate, as with kainit, the loss of nitrogen 

 during the storage of dung has been increased. It may, 

 however, be mentioned that Hansen and Gunther and 

 Immendorff found that superphosphate conserved nitrogen 

 to an appreciable extent so long as the dung lay in the stall, 

 but that its effects disappeared whenever its acid phosphate 

 and fi-ee sulphuric acid had been neutralised by ainmonia, 

 and this rapidly occurred in the pit. 



Effects of Precipitated Phosphatic Gypsum. — This at the 



