07 May 2010

Watering Vegetables Plants & Seedlings

You may have noticed how everything really took off a couple of weeks ago after a few days of rain. Most vegetables benefit from a good soaking of the soil as water is taken up by the roots and then evaporated through the leaves. However, too much water can result in nutrients being washed out of their reach and encourages shallow, surface rooting. Waterlogging (see picture) can result in plants dying as their oxygen source will be cut off. Generally, however, more water is lost through evaporation than through bad drainage.

As a guide water thoroughly and gently. Don’t be tempted to put the hose on full blast on each plant for a few seconds or you risk damaging seedlings and young plants. You’ll also notice if you check the soil (stick your finger in it) that the surface area might be wet but the area you’re trying to reach (where the roots are) is still dry. So aim to keep the top 20cm of soil moist (not sodden).

Soaking the soil with about 10 – 15 ltrs per sq metre per week will really benefit brassica crops in a drought. Water directly to the base of the plant – an upturned cut off plastic drinks bottle propped in the soil next to an established plant (especially squashes and tomatoes) is great for sending water directly where it’s needed.

Watering in the evening is also the prefered method, as the plants will absorb the water rather than losing it to evaporation. In the morning the soil will be soft making for easier weeding. Make sure that the leaves are dry before nightfall however.

A few guidelines are:

  • Germinating seeds need water so always sow into moist soil or compost.

  • One of the biggest killers of seedlings is watering incorrectly. They prefer to be watered from the base so stand them in trays and water the trays if possible. Alternatively use a watering can with a very fine ‘rose’ to prevent swamping the compost or try using a mister. Once compost has dried out it’s very difficult to wet it through again.

  • Fruit and flowering plants such as tomatoes, beans and cucumbers need water to encourage their fruits to swell so heavy watering at this stage will increase yields.

  • Root crops need a steady supply of water – too much will result in more foliage rather than big roots so only water if the soil starts to dry out, increasing the frequency as the roots start to swell.

  • Crops that are grown for their leaves – spinach, lettuce, cabbages, etc need more water than root crops.

  • Plants are more prone to fungal diseases if their leaves are watered rather than their roots.

  • Dig in as much bulky organic matter (compost or well-rotted manure) to increase the water-holding capacity of the soil.

  • Mulch the soil surface after watering to prevent evaporation (use straw, compost or leaf mould).

  • Avoid cultivating soil in dry weather, as it will bring moisture to the surface, which can then evaporate.

  • Keep the soil as weed free as possible as the weeds will compete with the plants for water.

  • Put up wind breaks. Wind dries the soil quickly, again increasing the rate of evaporation.


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