When plants are deprived of water, growth stops and their resistance to pests and food value declines markedly. Conservation of water is a fundamental objective of our gardening practices consistent with their emphasis on a sustainable eco-system.
In the face of the trends of significant below average rainfall and above average temperatures – undoubtedly due to climate change – the established water conservation techniques in organic gardening become crucial. These techniques include:
Rainwater is the best for plants and its free. The dissolved nitrogen, low contamination and low pH make it ideal for all kinds of plants. Even if you are collecting it you may still be reliant on mains water. This water is chlorinated and because of its higher pH it may have an adverse impact on soil microorganisms, but for most organic gardeners this is unavoidable.
The best way to water your plants is by hand using a watering can or a hose with a trigger nozzle. While this takes time, you have control over where and how much water you give each plant and you can have a close look at their condition and any pests at the same time. Check the soil after you have watered to see how deeply the water has penetrated. A handy tip for plants that need regular water, is to sink an empty plant pot or a piece of agricultural drainage pipe down to soil level next to these plants and water into it. This takes water straight down into the soil.
Sprinklers are a very inefficient watering method in vegetable gardens because of the wastage through indiscriminate dispersion and evaporation in hot weather. COGS does not permit the use of sprinklers in its community gardens for this reason.
Overhead spraying of some vegetables actually encourages some diseases; for example, powdery mildew on cucurbits. The fruit of capsicums will often rot on the vine if water from overhead spraying continually lies on the fruit near the stem.
Any watering method needs to deliver water to encourage plants to establish and maintain a healthy root system. Infrequent deep watering is generally much better. Young plants and seedlings may need water every day in warmer weather. However, when plants are watered every day they are discouraged from sending roots wide and deep into the soil and their shallow root development is more prone to stress.
Dripper systems can be very effective for some vegetables plants which have similar needs. Covered by mulch, these drippers are kind to the soil and water loss form evaporation is negligible. These systems need to be able to cope with crop rotation and can be impractical in smaller gardens with a diversity of plants with different needs.