Pulverizing and Consolidating Implements

PULVERIZING AND CONSOLIDATING IMPLEMENTS After land has been ploughed it must be broken down into very fine particles and consolidated in order to form a seed-bed. The chief pulverizing implements are cultivators, harrows and rollers. Cultivators and harrows work practically on the same principle and use either tines or teeth, which are drawn through the soil, or disks which cut into the surface; but the cultivator works to a greater depth than the harrow. Except in the case of seed har rows, rigid tines are generally inclined forward to penetrate the soil. Spring tines, which depend upon C or S springs or coiled springs, are curved forwards and so attain the same end : they are less liable to breakage than rigid tines and are as a rule more effective in pulverizing the soil. Tines may be provided with de tachable and replaceable points varying in shape, according to the purpose in view, from chisel points to broad duck-foot shares, the latter being intended less for pulverizing the soil than for under cutting weeds. Disks are particularly useful on hard ground or when turf has been ploughed in.

Cultivators.

In Great Britain these implements are chiefly used to break down the furrows and bring up perennial weeds, harrows being employed subsequently to pulverize the soil still further and to comb out the weeds that remain. In America culti vators are widely used for of ter-cultivation and have been modi fied accordingly. The main features of a cultivator are two large travelling wheels with a small swivel wheel in front and a triangu lar frame to which sub-frames carrying the tines are attached, as well as the driver's seat and the mechanism for raising and lower ing the tines : these are set in echelon six or more inches apart and vary in number according to the width of the implement and the nature of the work. In tractor cultivators curved tines are at tached to straight stems which are specially strengthened to with stand the strain involved : the stems may be flexibly mounted to reduce breakages. Cultivators for use with cable sets are made with rigid frames and rigid adjustable tines. When so used the cultivator is employed in particular for breaking up fallow and stubble for autumn sowing.

Harrows.

In addition to completing the work of the culti vator, these implements serve to cover seed and fertilizers, to aerate the soil, to encourage tillering or root and stem develop ment, to break crusts and form a soil mulch, and to uproot weeds. The heaviest harrows, often called drags, have long curved teeth of varying shapes and sizes. Some drags are mounted on wheels with lever adjustments while others have handles for clear ing weeds. They are made in sections which consist of zig-zag beams connected by straight cross-members, the teeth being fixed at the intersections. These implements are hitched at two points to ensure each tooth cutting a separate track. Seed or smoothing harrows may have wood or iron frames and straight or curved teeth, either fixed or adjustable. Iron-framed harrows are con structed on the zig-zag principle but wooden-framed harrows are rectangular, the teeth being inserted at different points along the cross members. These harrows are used to refine the soil before drilling, to comb out weeds, to cover the seed after sowing, and to aerate and mulch land bearing growing crops. Lever harrows have straight teeth fixed to cross-members in such a way that by the movement of a lever the teeth may be inclined either forwards or backwards or set vertically. Spring-tooth harrows are widely used in America to perform the same functions as drags in Great Britain. They are really light cultivators with a variable depth of work, the depth and pitch of the curved tines being adjustable to suit different soil conditions. The tines can be easily raised to clear weeds. In America, these harrows usually have a riding at tachment, the wheels being utilized for adjusting the depth of work and for transport purposes.

Disk harrows have saucer-shaped disks from i 2 to coin. in diameter which may be set at varying angles to the direction of travel. The disks pulverize and loosen the soil by their eccentric motion, producing much the same effect as a disk plough but giving a finer tilth. They are particularly useful for preparing a seed-bed when turf has been ploughed in, and are also used in America be fore ploughing hard, dry ground, to facilitate subsequent opera tions. They will also aid in working out annual weeds, but if used upon land infested with twitch or couch grass will tend to spread the weed. The disks may be either full-bladed or cut-away. The former are used for general purposes and the latter for deeper and coarser cultivation particularly on stony land. Disk harrows for tractor haulage have transport wheels and lever adjustments which usually work on the self-lift principle. A common practice is to use two disk harrows tandem fashion with tractors, the front disks throwing the soil upwards and the others inwards.

Rotary Tillers.

The modern rotary tiller consists essentially of a series of tines made to revolve round an axle. An internal combustion engine supplies the motive power. Various attach ments may be added. The object is to pulverize the soil and to produce a seed-bed at one operation, in this way replacing the implements already described.

Excellent work has been performed by these machines and for garden and orchard cultivation and for some forms of tropical agriculture their usefulness appears to be established. It is yet open to question whether in temperate regions rotary tillage can satisfactorily replace the action of the weather in breaking down furrows set up in autumn ploughing.

Rollers.—These implements are used to consolidate the soil, to crush clods and to smooth the surface. The consolidation of the seed-bed affects the aeration and moisture content of the soil and the proper use of the roller is of great importance. The fiat, smooth or land roller which may be of steel, wrought iron, wood or even stone, is constructed in two or three sections to facilitate turning. A common width for a roller is seven feet, with a diam eter from 18 to 20 inches. The weight may vary between 7 and i 2 cwt., Cambridge or ridge rollers consist of a number of rings two to three inches wide which taper to a point and are used for crush ing clods as well as consolidating the land. Size for size they are slightly heavier than the flat roller and have a slightly heavier draught. Since the ribbed surface which they leave is less liable to coalesce after heavy rain than a flat surface, they are very useful on heavy land. In America it is a common practice to use two sets of rollers so hitched that the front ridges are cut by the sec ond set. For clod crushing on heavy land bar or tubular rollers may be used and also crosskill rollers which have serrated rings. Land pressers or subsurface packers, consisting of a number of heavy wheels about three feet. in diameter, are used in dry dis tricts to consolidate the soil at the bottom of the furrow.