AVERAGE PRODUCE PER ACRE. 117 



draw from an acre of land. This is really the direct information 

 which the farmer requires. An attempt to do this is made in 

 the subjoined tables. We have included in them only those 

 elementary constituents of plants which are commonly added, 

 or may require to be added, to the soil as manures, or fertilisers, 

 as they are sometimes called. For the sake of brevity, and on 

 other considerations, lime is not included. Of the importance of 

 lime, not only as a constituent of the ash of plants, but as 

 having special functions in the soil, there can be no doubt. But 

 in this country, at least, we do not usually apply a modicum of 

 it^?e?' se in ordinary manuring. We endeavour to ensure a fair 

 amount of it in the soil at all times by giving a considerable dose 

 of it when necessary, amounting, in Scotland, to from two to 

 three tons of dry caustic lime per acre. It has been long recog- 

 nised as a rule over the greater part, if not the whole, of Scotland, 

 that the first thing to be done on newly reclaimed land, is to 

 give it a limimj — greater or less in amount, according as the soil 

 is heavy or light. The cost of lime is also much less tlian that 

 of the other principal constituents of plants; abundant supplies 

 of it can be obtained with comparative ease at about £1 per ton, 

 whereas potash costs at least twelve times, and phosphoric acid 

 twenty times as much. 



But it is at least of as much importance that we should 

 know and have distinctly before us the amount of combined 

 Nitrogen which the produce of an acre of our ordinary crops 

 requires, as that we should know the amount of mineral matter 

 required by the same. We have therefore added a column con- 

 taining the avcrcuje amount, in pounds, of nitrogen which the 

 several crops in their normal condition require. 



It is needless to say that no precise or absolute accuracy in 

 figures is possible in this matter. An approximation, more or 

 less close, to fair averages is all that is aimed at. A large 

 number of carefully executed analyses of some crops is now 

 available for comparison. In the cases of some other cro[>s, the 

 data at our disposal are less ample or less satisfactory. In some 

 cases, results which are manifestly exceptional have to be left 

 out of consideration. Our plodding and persevering brethren 

 in Germany have of late years done a good deal towards the 

 buildin-' up of the structure of whicli their distinguished 



Of o 



countryman, Liebig, may, in some respects, be said to have laid 

 the foundation forty years ago. Our authorities in ash analy- 

 sis are mainly Professor Eniil Wolll" of Wurtemberg, Way and 

 Ogston, Lawes and Gilbert, I)r. Voelcker, and the late Dr. 

 Anderson, together with a few others who have devoted special 

 attention to particular plants or to particular points either in 

 this department or in organic analysis. The authorities for 

 nitrogen or "albuminoids" are partly the same, but with a 



