2. Soil Preparation

Mechanical processing of soil so that it is in the proper physical condition for planting is usually referred to as tilling; adding nutrients and trace elements is called fertilizing. Both processes are important in agricultural operations.

Prior to planting, the soil needs to be prepared, usually by some form of tillage or chemical "burn-down" to kill the weeds in the seedbed that would crowd out the crop or compete with it for water and nutrients. Tillage methods can be divided into three major categories, depending on the amount of crop residue they leave on the surface. Residue slows the flow of runoff that can displace and carry away soil particles.

2.1. Tilling

Tillage is the manipulation of the soil into a desired condition by mechanical means; tools are employed to achieve some desired effect (such as pulverization, cutting, or movement). Soil is tilled to change its structure, to kill weeds, and to manage crop residues. Soil-structure modification is often necessary to facilitate the intake, storage, and transmission of water and to provide a good environment for seeds and roots. Elimination of weeds is important, because they compete for water, nutrients, and light. Crop residues on the surface must be managed in order to provide conditions suitable for seeding and cultivating a crop.

Generally speaking, if the size of the soil aggregates or particles is satisfactory, preparation of the seedbed will consist only of removing weeds and the management of residues. Unfortunately, the practices associated with planting, cultivating, and harvesting usually cause destruction of soil structure. This leaves preparation of the seedbed as the best opportunity to create desirable structure, in which large and stable pores extend from the soil surface to the water table or drains, ensuring rapid infiltration and drainage of excess or free water and promoting aeration of the subsoil. When these large pores are interspersed with small ones, the soil will retain and store moisture also.

Seedbed-preparation procedures depend on soil texture and the desired change in size of aggregates. In soils of coarse texture, tillage will increase aggregate size, provided it is done when only the small pores are just filled with water; tillage at other than this ideal moisture will make for smaller aggregates. By contrast, fine-textured soils form clods; these require breakage into smaller units by weathering or by machines. If too wet or too dry, the power requirements for shattering dry clods or cutting wet ones are prohibitive when using tillage alone. Thus, the farmer usually attempts tillage of such soils only after a slow rain has moistened the clods and made them friable.

Some soils require deepening of the root zone to permit increased rate of water intake and improved storage. Unfavourable aeration in zones of poor drainage also limits root development and inhibits use of water in the subsoil.

The value or efficiency of tillage depends upon character, thoroughness, and timeliness. Both the character and the thoroughness of tillage count for much in vegetable gardening, for in growing crops of high cash value gardeners should be certain that tillage operations should be of the right kind and be fully completed before work is discontinued. Timeliness is of primary importance, for to plow, harrow, cultivate, hoe and weed at just the right time may make the difference between profit and loss. Conditions may be satisfactory for plowing today, while rain tomorrow may fill the soil with too much moisture for the most effectual plowing, and so much rain may fall that plowing, harrowing and planting may be delayed a week or more. Such delays often result in reaching the market too late for the best prices. The failure to cultivate a field at the right time frequently results in the weeds taking possession, a situation causing unnecessary expense in hoeing and hand weeding, and in addition producing later maturing crops and reduced yields. There is a proper time in vegetable gardening for every tillage operation and fortunate is the man who not only knows when to till but who usually does the work when most advantageous.