CHAPTER XVIII

THE AFTER-CULTIVATION OF CROPS

The term “after-cultivation” is here used in referring to those tillage operations which are performed after the crop is planted.  Synonymous terms are “cultivation,” “inter-tillage,” “working the crop.”

After-cultivation influences the texture, ventilation, heat, plant food and moisture factors of fertility, but most particularly the moisture factor.

Under ordinary circumstances the greatest benefit derived from after-cultivation when properly performed is the saving of soil water for the use of the crop.

LOSS OF WATER BY EVAPORATION

Soil water is seldom at rest unless the soil be frozen solid.  When rain falls on a fertile soil there is a downward movement of water.  When the rain ceases, water begins to evaporate from the surface of the soil.  Its place is taken by water brought from below by capillarity.  This is in turn evaporated and replaced by more from below.  This process continues with greater or less rapidity according to the dryness of the air and the compactness of the soil.

LOSS OF WATER THROUGH WEEDS

We learned in a former chapter that during their growth farm plants require an amount of water equal to from 300 to 500 times their dry weight.  Weeds require just as much water and some of them probably more than the cultivated plants.  This water is largely absorbed by the roots and sent up to the leaves where it is transpired into the air and is lost from the soil, and therefore is unavailable to the growing crop until it again falls onto the soil.

In some parts of the country, particularly the semi-arid West, the rainfall is not sufficient to supply the soil with enough water to grow such crops as it could otherwise produce.  In the moister regions the rainfall is not evenly distributed throughout the growing season, and there are longer or shorter intervals between rains when the loss of water through evaporation and weeds is apt to be greater than the rainfall.  For these reasons it is best to check these losses and save the water in the soil for the use of the crops.

SAVING THE WATER

This can be done by: 

Preventing the growth of weeds and by checking losses by evaporation with a soil mulch.

TIME TO CULTIVATE

A seedling plant is easiest killed just as it has started into growth.  The best time to kill a plant starting from an underground stem or a root is just as soon as it appears above the surface in active growth.

The best time to cultivate, then, to kill weeds is as soon as the weeds appear.  At this time large numbers can be killed with the least of effort.  Do not let them get to be a week or two old before getting after them.