When it comes to watering, there are no standard rules. It is a understanding that depends on the type of plant, the soil, the weather, the time of year and many other variables. Fortunately, there are some averages we can use to start to figure out what to do.
- First, we need to add compost or manures to our soils. This will not only add biology and nutrient but will also increase its water holding capacity. For every 1% carbon, we can improve in our soils, we increase its water-holding position by 16.8 litres per square metre.
- We need 100% ground cover 100% of the time. This can be a living ground cover or straw/sugar cane mulch. This will allow our soils to hold onto the moisture and suppress potential weed growth.
- Understand the water requirements of our plants. While there can be a variance in the amount of water need due to types of soils and plant types, there are some averages we can work with. For a kitchen garden, you need approx. 5L per square metre per day in peak heat periods. Less in colder periods, but in permaculture, we are designing for extremes.
- I had my mini market garden, it was 150sqr metres so at 5L per square metres per day over the 150 sq. Metres it was using 750 Litres per day in summer, on average. Much less in colder seasons.
- Water only when needed. Make sure to watch the weather, and reduce watering frequency when rainfall or heavy dew is abundant. Too much moisture is just as damaging to plants as can too little, and it will leach nutrients out of your soil. Remember 1mm of rain equal 1 litre per square metre and that a dew event is the equivalent of 1mm.
For trees is is approx 5L per tree per day, at the drip line, in the heat of summer
- Focus watering in the root zone.It is the roots that need access to water, not the leaves. Wetting the foliage can be a waste of water and can promote the spread of disease.
- Water deeply and thoroughly. For seasonal vegetables concentrate their roots in the top 18 to 20 cm (6″ to 8″) of soil; for perennials, shrubs and trees, it’s the top 25cm (12″). Always use the finger test to see how moist the earth is.
- Water in the morning. This gives the leaves time to dry out, if you do get moisture on the leaves
- Use the right tool for the right job. Efficient watering at the root zone we can use a drip irrigation system instead of a sprinkler, though there can be much satisfaction in watering by hand with the right hose nozzle or watering can
Ultimately going through the above, lead me to choose to use drip irrigation. The one I use has the drips already inbuilt, which made it cost-effective and gave precise delivery.
It has also allowed me to work out how long I need to water my garden to the most significant advantage with little waste.
While I no longer grow vegetables in a market garden style, the lessons learned have translated across to my Permaculture Potager. Knowing that I need roughly 5L per square metre per day, in peak summer and that there is a dripper every 30cms, having 3 rows means 9 double holes. Each hole releases 2L per hour, so that is 36L of water per hour per metre. Some simple maths at this point shows me that to achieve 5L per sqr metre I only need to run the irrigation for 9 minutes per day in the heat of summer to give the garden what it needs to thrive.
Simple, efficient and shows the power of design.
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