Irrigation in the Vegetable Garden
Regular watering and sensible irrigation is essential to the development and healthy growth of any plant. Water is drawn from the root of the plant and transported through its capillary system, transferring valuable nutrients collected from the soil. Eventually it's released through the plant foliage by evaporation and transpiration. This water needs to be replaced in order to sustain steady growth. The moisture content of the soil or compost must be maintained for this to happen, taking into account losses due to surface run-off, drainage and evaporation.
When watering the vegetable garden during warmer spells of weather, it's best to do so early in the morning. In higher midday temperatures the water can evaporate before the plant roots get a chance to fully absorb it. It also gives the leaves time to dry thoroughly - damp leaves can sometimes cause issues with mildew or plant disease. Another factor to take into account is your soil type. Sandy, fast-draining soils will need more frequent irrigation than clay or loamy soils, while clay soils tend to hold on to water and result in more runoff. Loamy soils are probably the best kind to work with when irrigating, hitting just the right balance between water retention and good drainage.
Be aware that overwatering can cause problems with your plants. It affects their ability to process oxygen and carbon dioxide, and can cause root damage and fungal growth. Excess water also encourages slug and snail activity. Water requirements vary between plant species and will change during the different stages of plant development. Gardeners will only know if demands are being met by checking beds regularly. The needs of outdoor plants are dictated by the weather, with water availability being affected by wind, rain and temperature. Plants grown in polytunnels or greenhouses cannot rely on rainfall - therefore a strict regime, adjusted throughout the growing season, needs to be in place to accommodate plant demand and temperature fluctuations. Steady or phased watering is important to prevent irregular growth, impaired fruit development or excess foliage.
A wide range of systems and equipment are available for watering the vegetable garden, from rainwater harvesting to sprinklers and dripper hoses.
Hoses, Connectors and Nozzles. Hoses are vital in transporting water around the garden, from water butts and taps to beds and greenhouses. It is possible to build a complete irrigation network using sections of hose and incorporating timers, manifolds, drippers and soakers.
Sprays and Sprinklers. Lawns and larger beds can be watered by installing sprayers connected through a network of tubing. Spray systems deliver a fine mist whereas sprinklers cover a wider area, with larger droplets which are less prone to evaporation.
Timer Systems. Mechanical or electrical timers can be used to control watering in a vegetable bed. This is ideal for periods when you are away from the garden, but most systems will not take into account ambient temperature and changeable weather conditions.
Soaker Hoses. Polytunnels will require constant watering to maintain the correct environment for vegetable cultivation. Soaker hoses laid upon the surface of the soil and covered with shallow mulch can provide a steady, regulated water flow, compensating for temperature fluctuations. They are made from a continuous porous material and provide a constant delivery, best used in conjunction with a timer or manual intervention to prevent overwatering.
Drippers. Plastic tubing is buried into the soil with small emitters placed near the plant roots for direct, targeted watering. The water is efficiently used with this method, avoiding the risk of flooding and overwatering. The supply can be regulated to water the plants only when necessary. Like soaker hoses, the dripper systems prevent foliage becoming wet - which could lead to mildew and fungal problems.
Wicking and Capillary Watering. Using the natural phenomena of capillary action, wicking systems provide a self-watering supply. Capillary matting allows water to be drawn from a tray as and when the plant requires, avoiding problems with overwatering and water deprivation. Individual wicks can be linked to a hose supply to service each plant’s specific demands. This system works well with container gardens, and with some adaptation it can be incorporated into larger beds.
Rainwater Harvesting. Rainwater is naturally soft, without any of the additives of mains water. It contains soluble nitrates, perfect for feeding growing vegetables and has a balanced pH of 6.5. It is a free resource, without any cost to the environment or your water supplier. Collect it from your roof guttering system using adapter kits, and store in tanks or water butts. Cover any storage container to prevent the build up of algae.
Watering Can. This time honoured method provides the opportunity to engage with your garden at first hand and take advantage of the therapeutic benefits of pottering about. Hand watering is still the best method for feeding and for targeting individual plants that need special attention.
When watering the vegetable garden, always concentrate on the root of the plant: this is where absorption and nutrient uptake happens. Excess water on the plant foliage is unnecessary and will promote disease. Good mulch is crucial in retaining moisture, preventing evaporation and deterring wasteful water run-off. As a bonus, the mulch will eventually break down and improve the soil structure and health as it does so. Examples of good mulches are well-rotted garden manure, homemade compost and grass clippings. Always prevent the soil surface from drying out and developing a crust, which will affect absorption.
There a few rules on when to water - it is generally dependent on weather, soil condition and plant demand. Regular inspections of your garden will give you a better idea of when and how to water. Poke a finger into the bed and if comes out wet your soil is moist enough. Another way of checking is to dig into the soil with a trowel: if the soil is still dry two inches below the surface, it's in need of watering. For more precise and definitive info, you can use a moisture meter, some of which double as pH meters. Plants that are wilting or showing signs of heat stress will need your immediate attention. You should always adjust your timers or watering regime to provide a regular, steady water supply while taking into consideration the prevalent conditions.