220 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



On the other hand, it will be seen that the nitrate of soda and 

 sulphate of ammonia plots benefit greatly by the addition of dung, 

 as it supplies the important ingredient, humus, that was otherwise 

 lacking. 



Table IV. shows the relative yield of various crops from the use 

 of superphosphate, basic slag, and bone meal as sources of phos- 

 phate. It will be seen that the longer the crop is on the land the 

 better is the yield from bone meal, as in the case of wheat and swedes, 

 whereas with the shorter crops, barley and mangolds, it is not as 

 good as that obtained from the mineral phosphates. This is due to 

 the slower solubility of bone meal, and had a more soluble form of 

 organic phosphate been used the superiority would undoubtedly have 

 been more marked. 



Table IV. — Relative Yield from various Phosphates. 

 (Rothamsted) Unmanured = 100. 



Crop. 



Superphosphate. 



Basic slag. 



Bone meal. 



Swedes 



120 



Il6 



126 



Barley 



119 



121 



no 



Mangolds . 



II 4 



I05 



III 



Wheat 



IOO 



IOS 



117 



Swedes 



132 



IO9 



131 



Means 



11S 



112 



119 



The experiments of the Highland Society have also shown bone 

 flour to be more successful than any other phosphatic manure for 

 turnips. 



It will therefore be seen from these experiments that organics 

 fully hold their own against the corresponding mineral unit. Fur- 

 ther, they are not all exhausted in one year, but leave behind 

 valuable residues for following years. This has been clearly proved 

 at Rothamsted, where the effect of dung has actually been detected 

 forty years after its application. This is not so with mineral 

 ammoniacal manures, which both the Rothamsted and YVcburn 

 experiments show are practically exhausted in one year. 



It is clear, therefore, that we cannot dismiss the question on 

 solubility only, for, as we have seen, organic manures even supplied 

 in the raw state not only give better results but leave the soil richer 

 instead of poorer, and had the soluble organic manures that are now 

 obtainaDle been used in the experiments doubtless their superiority 

 would have been even more marked. 



This conclusion, of course, will not surprise practical men. 

 We all know the value of dung, crushed hoof, meat and bone stuffs, 

 &c, and that we cannot get good crops by the use of minerals alone, or 

 put heart into a poor soil by the application of superphosphate and 

 nitrate. The point is, why cannot we ? Wherein lies the undoubted 

 superiority of the organic manures for these purposes ? 



I think we can best answer these questions by considering the 



