TILLAGE. 87 



to set free or unlock these elements suited to plant-growth. But these agencies are slow in 

 their work of preparing these elements, and do not generally supply them with sufficient rapidity 

 for the use of plants; hence, it is necessary that the farmer should aid the soil by applying the 

 elements needed in the form of manure of some kind, and also in hastening these chemical 

 changes by tillage, both of which are essential to the highest success in most soils, thus adding 

 to the materials suited to plant-food, and also putting in an available form those elements 

 already contained within it. Both are essential aids, and the best results in agriculture are 

 only reached when they are combined. Prof. Johnson explains some of the reasons for tillage 

 as follows : 



&quot; In soils which have long lain undisturbed by the plow, and carry an inferior growth of 

 vegetation, grass or weeds which have become bound out, in farmers language chemical 

 influences doubtless have oftentimes set in with the effect of gradually filling up the pores, 

 and solidly cementing together the particles of earth by the very processes which, operating 

 through long periods of time, have converted into actual rocks what once were soils, either 

 gravels, sands, or clays. The red rock, so abundant in the central parts of Connecticut, at 

 New Haven is plainly seen to be a petrified gravel; at the Portland quarries it is a consolidated 

 sand. The writing and roofing slates we are all familiar with are petrified clays, while the 

 limestones, so abundant in New York and further west, were once the dust and mud of shores 

 and sea-bottoms, full of shells and lime. Geologists assure us that there is evidence to show 

 conclusively that all the rocks of New England, even her granites, were once sediments and 

 soils. In exclusion of air and of surface-water oft replenished with air, soils petrify or turn 

 to rocks, while in free contact with air, and water charged with air, rocks decay or disinte 

 grate, and crumble into soil. Hard-pan, in many or most cases, is clay or clayey gravel 

 cemented in this manner, and many soils, even sands and loose-textured gravels originally, 

 have been made comparatively impervious by some cementing material. That which acts as 

 cement is sometimes carbonate of lime, or carbonate of iron dissolved in water, and deposited 

 by the evaporation of the solvent. In other cases it is humate of iron, the same as bog iron 

 ore, the same also essentially as the moor- bed pan, which often forms a thin but impervious 

 bottom to peat beds and muck swamps, even when situated on coarse gravelly sands. In 

 other cases silica and various silicates are the petrifying agents, as in the geysers of Iceland 

 and the Yellowstone. They form in the soil itself by the chemical interaction of the 

 substances there. 



A full, consideration of all the facts makes it quite evident that in most soils there are 

 tendencies constantly exerted with more or less vigor, towards mechanical compacting not 

 only, but towards chemical induration or petrifaction, and one of the important offices 

 of tillage is to counteract these tendencies. Tillage accomplishes this office, not by crushing 

 of solid grains, and not to any great extent by any direct mechanical reduction of lumps of 

 coherent particles, but rather by lifting up masses of soil, turning them and letting them fall 

 so that the close contact produced by rest and moving water is broken, and the grains of 

 sand and the minute aggregations of loam are brought into new positions with regard to each 

 other, and to greater distances from each other. The soil ought to be moist when plowed. 

 Moist sands may be thrown up to a ridgey surface, and the mass be full of considerable 

 cavities, whereas dry sand, if plowed, falls into nearly its original level and compactness. A 

 mass of clay soil in a certain stage of moisture is broken by the plow into a multitude of 

 small lumps, which if let dry a little more will yield to the impact of the harrow teeth and 

 fall to smaller lumps, and in part to powder. The subsequent drying of the earth thrown up 

 by a plow has much to do with its loosening. Some heavy clays of the plastic kind require 

 their spring tillage to be done, as it were, &quot; on the wing.&quot; If a trifle too wet, the plow makes 

 paste of them where its pressure is felt, and the upturned soil falls to putty-like clods, which 

 harden on drying, so that the field after plowing ?? as unfit for a seed-bed as before it was 

 touched. If let stand too long before plowing, such clays bake at the surface to a crust that 

 turns up cloddy, and is difficult to reduce. 



