CLA 



CLA 



customary to value soils by the pro- 

 portion of tills earth. 



Chemically, the alumina is a feeble 

 base, uniting with acids, and is found 

 as a phosphate and sulphate, as well 

 as silicate. Clay can hardly be said 

 to furnish food to plants directly, but 

 is of consequence in giving texture 

 and absorbency to soils. 



CLAY, BURNED. See Clay Soils 

 and Turf. 



CLAYING LANDS. This is the 

 spreading of clay over soils which are 

 too sandy. It is an important remedy 

 for loose lands ; but the expense is 

 too heavy to justify the practice, ex- 

 cept in garden culture. The clay 

 should be carried on in the fall, to 

 mellow during winter; 100 or more 

 loads to the acre will be necessary 

 for a good result : the addition is per- 

 manent. If marl can be obtained, it 

 is very preferable. 



CLAY SOILS. A clay soil con- 

 sists of a large proportioit of alumina 

 united to silica of various degrees of 

 fineness. ^Vhen the sand is very 

 line, and intimately mixed with the 

 alumina, the clay, although stiff in 

 appearance, is fertile in proportion to 

 the humus which it contains, or which 

 is artificially added to it. It then 

 forms that class of rich wheat soils 

 which produce many successive abun- 

 dant crops without change or manure. 

 It has a strong affinity for water, 

 which prevents the plants that grow 

 in it being injured by drought ; and 

 it has a sufficient degree of porous- 

 ness to allow superfluous moisture to 

 percolate without making it too soft. 

 All that is required for such a soil is 

 a porous substratum of rock or grav- 

 el ; and where this is not the case, 

 sufficient under-drains must be made 

 to produce the same effect. Clay 

 soils are of a compact nature, which 

 retains the water ; hence they require 

 expensive draining and manuring to 

 render them productive. This has 

 made lighter soils, which are more 

 easily worked, to be generally pre- 

 ferred, although naturally less adapt- 

 ed to the growth of wheat ; and the 

 mode of cultivation of the light soils 

 has advanced more rapidly towards 

 O 2 



perfection than that of the clays ; yet 

 the latter will undoubtedly repay the 

 outlay best when once they are 

 brought to a certain state of improve- 

 ment. When clay soils are well 

 drained, and when the effi'ct of no.x- 

 ious salts has been removed by liming, 

 burning, and frequent stirring, it will 

 be found that a much smaller (juantity 

 of manure will produce a more cer- 

 tain return in grass or corn than on 

 any light soil. The great difficulty is 

 to choose the time when stiff clays 

 are to be worked ; and here it may 

 be observed that ploughing some- 

 times does more harm than good. 

 When clay is wet, especially in the 

 beginning of summer, and it is plough- 

 ed in the regular process of fallow- 

 ing, the tough, moist slice cut out by 

 the plough is set on edge, and the 

 sun bakes it into a hard mass like 

 brick. In this state it is not im- 

 proved by exposure to the air, which 

 cannot penetrate this hard substance. 

 It would be much better to plough 

 out deep water-furrows with a plough 

 made on purpose, and wait until tlie 

 moisture is reduced by gradual per- 

 colation and evaporation, so that the 

 plough should raise a slice ready to 

 break and crumble as it is turned 

 over. This should be done imme- 

 diately before winter, and then the 

 frost will so divide and mellow the 

 soil that, provided it he kept free 

 from superfluous water by under- 

 drains and water-furrows, it will have 

 the appearance of the finest mould 

 when worked with the harrows in 

 spring. To plough it again would be 

 to spoil all. It should have received 

 the necessary manuring in autumn, 

 and be ready for the seed to be sown 

 on this pulverized surface. The 

 horses which draw the harrows or 

 the sowing machines should be made 

 to walk in the furrows, wliich should 

 afterward be deepened out with a 

 plough constructed for tbe purpose. 

 A free course and outlet should be 

 formed for all surface water ; for no 

 maxim is more true than this, that 

 stiff clays are never injured by a con- 

 tinuance of dry weather, unless they 

 were in a wet state mrmedialely be- 



161 



