The importance of water

Press, 29 January 1982, Page 11

The importance of water

GARDENING

by

M. Lusty

Most of the vegetation growing in our gardens relies on water to thrive. A lack of moisture can often cause problems of various sorts. Recent research in commercial orchards for instance has shown that under dry conditions irrigation has a more significant effect on the yield than fertiliser. And while there is an awareness that it is necessary to feed plants to get good or better results the importance of watering, particularly on a regular and proper basis, is frequently not fully appreciated.

There are some critical or important stages for watering. It- is most important to water seedlings to get them established quickly without setback. Vegetable plants such as lettuce, cabbage and beet al! require unchecked growth. If they get dry and suffer they often run prematurely to seed; other side effects are also possible. The leaves of a plant are normally exposed to the air and they will lose moisture by evaporation (unless the air is saturated with water vapour). The sun’s heat vapourises the water inside the leaf and the vapour passes out through pores, called sto-

mata, and escapes. This loss of water, called transpiration, may occur in all parts of the plant exposed to the air, but most of its occurs in the leaves. The more foliage the plant has the more water it loses through transpiration. In sunlight an average plant will transpire about 50ml. of water per square metre of leaf surface per hour. An average corn plant uses more than 225 litres in the course of a growing season and a medium-sized tree will transpire that much in a single day. Many factors govern this natural loss of water by plants, quite apart from therf size. Tomatoes in particular may need watering daily or even twice daily when they are irito their full cropping stage. When grown in a glasshouse they could require water three or four times a day.

Wind greatly increases the loss of water from plants, and often during windy, showery weather, moisture may actually be lost from the soil and plants need watering. ' Most vegetables and fruit require extra water to achieve their potential. Unchecked, steady growth provides not only greater quantity but also has a verysignificant bearing on the quality of the end product. The most critical period in fruit growing occurs from fruit-set when insufficient moisture will cause fruit to be undersized, dry and lacking in taste. Water can be. applied in various ways and it can also be conserved with certain treatments to reduce' the

watering required. Conservation methods are especially essential where water is in short supply. One ’ of the most inept methods of watering is to go round the garden with a hand-held hose or garden sprinkler, a method which must be regarded as little more than a token gesture, useful only for damping down, or “washing off the dust.”

Hand directed watering

can actually wash seeds out of the soil and disturb the ground if it is not carefully handled. Apart from this, it is impossible to adequately gauge the amount applied, and is usually insufficient as well as inefficient. There is now available a very wide range of watering devices for just about every situation. The most common are the various types of fixed head sprinklers, closely followed by those which rotate. Suitable units are available to cover everything from very small plots to large areas from a single position. Permanent installations, such as pop-up sprinklers in the lawn, enable whole areas to be watered from one point. Soak hoses enable long and narrow strips of ground to be

watered in a quiet and efficient manner.

A number oN trickle or drip irrigation systems are now being offered and once installed little more than periodic checks to see that they are functioning properly is necessary to keep them operative — and even this aspect can be fully automated. As with the installation of permanent sprinklers, some paper work is required to work out effective utilisation and position of the system.

Conservation of moisture can be achieved by means of mulching. In this respect polythene, straw, bark chip, sawdust and compost provide some of the most popular ways of covering the ground to conserve moisture and suppress weeds.