ROLLING
The objects of rolling are:
To compress the surface soil so that the harrow will do its work more efficiently, also to break clods or lumps that may have resisted the action of the harrow.
To smooth the surface of the soil for an even distribution of small seeds, and to firm the soil around such seeds after they are planted so that they will keep moist and sprout readily.
To give compactness to soils that are light and loose and thus enable them to hold moisture and plant food better.
To press into the ground the roots of plants partly dislodged by the frost.
To remove the conditions favorable to the development of many kinds of insects.
To sink surface stones so that they will not interfere with harvesting the crop.
Light porous soils may be rolled at any time, but clay soils can be rolled to advantage only when they are stiff and cloddy.
Spring-sown grain is often rolled as soon as sown. This is all right in ordinary spring weather, but if showers are frequent and the soil is quite moist the rolling should be omitted till after the grain is up. The same practice will apply to autumn-sown grain also. If the soil is dry the rolling helps it to pump water up to the seeds. But if it is moist and showers are frequent the combined action of the roller and the rain is to make so thick a crust that many of the seeds will not be able to force their way through it or will be smothered by poor ventilation. After the grain is up the rolling may be done to advantage, as it then makes a firm soil about the roots of the plants, a condition of benefit to grain crops.