On the Agriculture of the Netherlands. 



51 



its fertility by judiciously stirring-, pulverising^, and mixing to- 

 gether the different earths of which it may be composed ; adding 

 those which are deficient — where it can be done without too great 

 expense of labour or capital — and, above all, impregnating it 

 throughout with portions of humus, that is, organic matter in a 

 state of decomposition. 



The mechanical texture of the soil is of the first importance ; 

 for on this depends the proper retention of moisture, without 

 superabundance or stagnation, which implies that the subsoil is 

 naturally porous, or made so artificially ; especially in northern 

 climates, where the evaporation is slow, and much rain falls 

 throughout the year. 



The roots of plants, in their tender state, must find pores in 

 which they can shoot and increase in bulk, for which the air 

 and water are indispensable. They must also find substances 

 which can yield them carbon, in a soluble state, as carbonic 

 acid, which is produced in all vegetable fermentation. In water 

 and air are contained all the other elements of vegetables, and 

 even carbon in a small proportion. If the pores are so large 

 as to let the moisture through, or allow it to evaporate readily, 

 the vegetation ceases, and the plant soon dies : if they are filled 

 with water, so as to exclude air, the same result follows. Hence it 

 is evident that by altering the mechanical texture of a soil, with- 

 out any chemical change in its component parts, it may be made 

 much more capable of supporting vegetation than it was before. 

 The quantity of organic matter, or humus, which will sustain 

 vegetable life is extremely small, when other circumstances are 

 favourable. Hence in the improvement of barren soils the most 

 essential process is to alter the mechanical texture. In clays this 

 is effected by repeated tillage, when the situation allows the 

 superfluous moisture to run off. This is the reason why good 

 clays are in all countries looked upon as the best soils, and sands 

 as comparatively inferior. A soil which contains but little argil- 

 laceous or calcareous earth in its composition was long consi- 

 dered as irreclaimably barren: but when the alternative pre- 

 sents itself of starving, or making poor sands productive, means 

 are soon found to correct their barrenness. 



As pure siliceous sand is too porous, the first thing is to add 

 substances which will readily fill up some of the pores. Fine 

 clay diffused through water does so most effectually ; and it is 

 astonishing how small a portion of pure alumina will consolidate 

 a loose sand, and convert it into a good loam, the parts of which, 

 when moistened, will adhere and form a clod in drying. When- 

 ever this is the case, the soil can no longer be considered as bar- 

 ren ; but it may not yet be fertile, however its porosity may be 

 corrected ; for this purpose it requires organic matter already so 



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