The Agricultural Journal of the Cape of Good Hope, Volume 17: 134-136 (1863)

Drainage.

As showing the importance of drainage to market gardeners and fruit-growers, the appended article is reproduced from the Fruit-grower:—

"No soil can produce useful crops when it is permanently saturated with water. Such soil may grow reeds and rushes, but not useful crops. The best condition of soil for successful plant growth is found when the particles of soil are moist, but when there is no standing water between these particles. Whatever means will bring about this condition will accomplish all the results stated as being accomplished by underdrainage. In wet seasons, if no adequate means are provided for removing the excess of moisture that falls upon the soil, it will be continually saturated and the crops will be drowned out. Underdrainage, by furnishing means for the escape of the surplus water, prevents this. It needs no argument to prove that underdrainage enables the ground to be worked earlier in the spring and sooner after rains, but horticulturists should consider the advantage connected with this. The success or failure of a crop may often be determined by the time when the ground for it can be prepared. Water standing in the soil causes the vegetable matter to undergo acetic fermentation, thus rendering the soil sour and unfit for cultivation; of course underdrainage removes this evil by removing the cause. If the soil is full of water, that which falls upon it in rain must flow off over the surface, carrying with it much of the best and finest of the soil, and often doing much damage. Underdrainage leaves the pores of the soil empty, so that the water falling upon it sinks directly in, to be ultimately carried off by the drains. As an illustration of this may be noted that even steep hillsides, where the soil is gravel, which forms a natural underdrainage, do not wash at all, while comparatively level fields resting on tough clay or hard pan are continually being gullied out by surface water.

All these points are clear, but we now come to a claim that at first seems paradoxical: How can draining land keep it moist and the crops growing in a dry season? By enabling the grower to thoroughly pulverise the soil, which fits the soil for drawing up moisture from below by preventing the soil from becoming baked and cloddy. When a soil is saturated with water, and becomes dry simply by evaporation, it hardens and bakes so that it is incapable of receiving moisture either from the air above or the earth below. By causing the plants to send their roots deeper into the soil. When a plant begins to grow in the spring in an undrained soil, the roots will not penetrate into the cold lower soil, filled with stagnant water, but run along through the few inches of drier surface. When the dry weather comes the sun completely dries this out, and the plant, having no other source of supply, perishes. On land that has been underdrained, in the condition described as most favourable for plant growth, moist, but with no standing water between the particles, the plant sends its roots far and deep. When the summer sun dries the ground the plant has communication with the cool, moist soil far below. Last year demonstrated the truth of this claim. The best crops were grown on the well-drained fields.

Underdrainage makes the ground warmer by admitting the warm air into the soil. As fast as the water is drained off from below the warm air follows, penetrating and warming the soil—a dry soil can be warmed more readily than a wet one because evaporation is avoided. Everybody knows that if a jug of water is wrapped up in a wet flannel, the water in the jug will not get warm as long as the flannel is kept soaked with water. Just so with the soil. It will not get warm as long as the surface is full of water. Experiment has demonstrated the truth of the theory in this matter. One experimenter made a number of tests in two adjoining fields, one drained, the other undrained. The average temperature of the soil in the field that had been drained was 6 1/2 deg. higher than in the other. Further experiments have fully confirmed this. And this adds another to the reasons why drainage enables the earlier cultivation of a field and lengthens the seasons—the ground becomes warmer so much earlier in the spring and remains warm later in the autumn. Drainage increases the fertility of the soil in exactly the same way as pulverising does, by enabling the soil to absorb fertility from the atmosphere. Drainage marks the line between unprofitable and profitable horticulture, and is an absolute necessity in present day market gardening."