In some localities, farmers have modified the moldboard plow into an implement used for subsurface tillage. The moldboards are removed, and the shares are used without moldboards. Straps of steel about 3 inches wide and the full length of the shares may be bolted above them. These raise the soil more and make the implement more effective for killing weeds and volunteer grain. The modified moldboard plow is most often used for the first cultivation of stubble land. It breaks the soil into large clods and at the same time keeps most of the residue on the surface.

The one-way disk, while not a subsurface tillage implement, fits in with a system of subsurface tillage if used with discretion. It is most useful where the residue is very heavy or where there is volunteer grain to be killed. It can operate through heavy residue without clogging. It breaks down the stubble and cuts it up enough so that later use of other implements is made easier. If it is operated at the proper angle and speed, much of the residue is left on the surface. If later operations are performed with sweeps and rod weeders, enough surface residue for erosion control can be maintained from a normal combine stubble. In heavy stubble, more than one cultivation with a one-way may be desirable. The one-way is the most effective implement available for quickly and completely destroying a crop of weeds, and can be used on land too dry and hard for other implements to penetrate readily. However, it pulverizes the surface soil, and in the absence of crop residues its use may lead to serious wind erosion.

Among other tools that might be mentioned is one type of mulcher that rakes combine straw or other loose residue from the side of a strip of land that is being plowed, packed, and seeded in one operation, and spreads the straw behind the seeder. This new implement is being tried on certain soils in parts of the spring-grain area where seeding must be done at the earliest possible time. Under such conditions there is no opportunity to kill a crop of weeds in advance of seeding, and turning under the weed seed on the surface is desirable for weed control. The soils on which it is being tried are principally those that are likely to blow after spring plowing.

Another development, often confused with subsurface tillage and widely discussed in recent years, is keeping the soil organic matter in the surface layer by repeated cultivations with a disk. Disking, because it is a cheaper operation than plowing, was tried out under dry-land conditions many years ago but has lost favor. Where the period of land preparation before seeding is a long one, the disk has all the disadvantages, and not all the advantages, of a one-way. The soil where considerable organic matter is disked in is somewhat more resistant to water erosion than soil where residue is plowed under. Disking residue into the soil, however, does not control erosion so effectively as leaving it on the surface.

The final goal regarding the type of seedbed and the amount of residue desired at planting time must be kept in mind throughout the time of preparing the land. If the residue is so heavy that more than is wanted might remain on the surface at planting time, some of it should be disposed of. Usually that can be done by tillage well in advance of seeding that mixes some of the residue with the surface soil. Except during very dry periods, residues that are in contact with the soil or mixed into the surface decay more rapidly than those on the surface. In other cases it may be necessary to remove some residue from the field. If the residue is scanty, care should be taken to see that it is not unduly destroyed by the tillage operations, and thus expose the land to erosion.

When the soil under a residue mulch that has been pulverized with a subtiller is too loose and open for a good seedbed, supplementary working is necessary. The implements used for preparing a seedbed on plowed land are not satisfactory, as a disk may bury too much of the residue and a harrow may drag it into bunches that interfere with planting or with later cultivation. In the winter wheat area, a shallow rodweeding as the last tillage operation before seeding generally leaves a weed-free seedbed where the wheat may be planted in firm soil. The rod weeder does not destroy the surface cover. To prepare a satisfactory seedbed under a stubble mulch, another implement has been devised that packs and pulverizes the soil in a single operation. It is called a treader and has been used with considerable success. It consists of a certain type of rotary hoe on which the pronged wheels have been reversed. The reversed prongs have more packing and less cultivating effect than when run in the normal position.

The treader can be run over heavy residue without clogging, and it does not bury the residue. It breaks clods and increases the pulverization of the furrow slice. It also acts as a packer in that the prongs go down into the soil and fill open spaces and firm the soil. Some of the residue is pressed into the soil and anchored so that it cannot be blown away. The treader leaves the surface of subtilled soil in good condition for drilling.

Small grains and grasses or legumes require a firm seedbed, and the treader leaves the soil thoroughly tilled but firm. Where an especially firm seedbed is required, a second time over with the treader is helpful. The need for a second operation arises when stands of grasses or legumes like clover or alfalfa are being established on sloping land. For those crops it is important that the soil be very firm but protected by a residue cover while the crop is being started. The cover may prevent the formation of small rills or gullies while the crop plants are making enough growth to protect the soil. If such erosion gets a start in alfalfa fields, it is difficult to control. Residue on the surface at seeding time may be all that is needed to protect the soil through that critical period.

Row crops require less firmness in the seedbed than small grains or grasses, and use of the treader to pack the soil is not always needed. It is often used behind a subtiller, however, when the soil tends to break up cloddy or slabby, in order to kill weeds.