How much water to apply depends on

• the size of the plant - the larger the plant the more it will need.
• the sort of leaf - different types of vegetables require different amounts. Runner beans like a lot of water, sweetcorn & carrots rarely need watering.
• the type of soil - sandy soils need more water than clay
• soil capacity - it is very important to give enough water to bring the soil up to full capacity, but not to overwater & make the soil waterlogged. The little & often approach is bad because the soil at the top will be dampened, but the roots deeper down will be in soil which has a deficit. These roots will die & surface roots will be encouraged which will dry out in the sun & not be able to use the soil nutrients to the full.

Where to water - The leaves form a canopy which usually covers the width of the root ball. It is thus sensible to water an area which is the same size as the leaf canopy. This means that the water is being placed directly over the root area.

Place the water under the canopy, so the leaves are not wet. This will:

•  prevent the wet leaves from being scorched by the sun
•  keep the water out of direct sunlight, and so reduce evaporation.

When to water
Watering in early morning means that the water has time to soak into the soil before the sun gets hot enough to evaporate it.

Watering at night results in the leaves remaining damp.  Damp leaves will be vulnerable to fungal attack, which will weaken the plant.
Application methods. Small droplet size:

• prevents damage to leaves
• avoids washing small seedlings out of the soil
• prevents damage to soil structure

If a heavy stream of water is poured onto clay soils, a pan (thick crust) is produced, which will reduce drainage in the future & stop water getting away. The pan forms cracks in hot weather which exposes & damages the roots.

The droplet size can be varied by attaching a rose to the end of the watering can spout. The rose will have holes of a particular size. The smaller the holes, the smaller the droplet size.