242 EXPEEDIENTS ON THE CULTURE OF TUENIPS. 



comparable. The value of the results of these . two sets of 

 expermients can scarcely be overestimated as general guides to 

 the manuring of the turnip crop ; but with variety of soils and 

 climates, under different conditions of cropping and previous 

 manuring, considerable variation, both of quantity and propor- 

 tion of the constituents of an artificial manure, are necessarv 

 to grow full crops. Therefore, the results of the experiments to 

 wdiich I have alluded, are only a2:)plicable in their entirety 

 to the immediate districts in which they have been carried out, 

 or to similar soils under similar conditions, and are only useful 

 otherwise, in a creneral wav, as scientific facts. So far as I 

 understand these experiments, their great aim has been to 

 arrive at the facts to which I have referred, and to enable them 

 to do so, the soil experimented on must necessarily be in as 

 poor a condition as possible, in order to show the exact increase 

 of crop grown by the various applications, thereby enabling the 

 experimenter to estimate them at their proper manurial value. 



This sort of work, wdiile very necessary, is also very expen- 

 sive ; its performance, therefore, naturally falls into the hands of 

 wealthy associations, being, properly speaking, scientific work 

 which ought to be carried out by them. 



It is pretty generally admitted, that any farmer who wishes 

 to grow full crops and make profit from his holding does his best 

 to keep his farm in a good state of cultivation. It necessarily 

 follow^s that soils in a fair state of cultivation do not require 

 quite the same manurial treatment as those poor soils to which 

 I have referred. This class generally possesses, to some extent, 

 every plant-food constituent necessary for the growth of the 

 ordinary crops of the rotation ; but some of the most necessary 

 constituents may be present in very small proportion, whilst 

 others may be in superabundance; and, as most practical farmers 

 are aware, the bulk of a crop does not depend on the presence 

 in the soil of a single constituent of plant-food, but in all the 

 necessary constituents being there in proper proportion. In 

 fact, whilst the bulk of a crop depends on all the essential 

 ingredients being present in the right proportion, an excess of 

 any one of them may, and very often does, prove injurious 

 instead of beneficial to the plant. The manure applied ought to 

 aim at supplying any deficiency of these constituents, and the 

 one most suitable for doing so will most undoubtedly give the 

 best and most economical results. Analyses, to a certain extent, 

 may help the agriculturist to form an idea of the deficiencies of 

 his soil ; but they cannot ahvays be relied on as a correct guide, 

 and may often be misleading, as it very frequently occurs that 

 plant-food is present in considerable quantity in the soil, and 

 yet not in a condition to be available for being absorbed by the 

 plant. 



Thoroughly reliable results can only be got by practical tests 



