St Maarten, like many other small islands, relies on desalinated water. This is not only expensive, but requires extensive use of energy (and fossil fuels) to produce. We should reuse as much water as possible, and DIY gray water irrigation is a fantastic and easy way to establish new fruit trees.
What is Gray Water?
Gray water is household waste water that is not contaminated with human waste (black water, or sewage). Toilets (and the kitchen sink) should be connected directly to a septic system. If you are cloth diapering, the washing machine should also be treated as black water.
Showers, hand basins, and other water sources can and should be used for irrigation.
Gray Water Safety
Gray water can be used for fruit trees, ornamental plants, and vegetables which are cooked before consuming. The water should be dripped (preferably under mulch), not sprayed, around the natural drip line of the tree.
Gray water should not be used on lettuces or herbs, and should not be poured over the foliage of any plants.
Ideally, gray water should not be stored longer than 24 hrs, or else the bacteria multiplies rapidly causing a stinky black water mess that belongs in the septic.
Gray water should not be used anywhere where it may run into potable water sources, ponds, or the sea. It needs to be held in the soil where the roots and soil bacteria can clean it and use it.
DIY Gray Water Irrigation
Is your house not connected to a gray water system? The easiest way to conserve your water is to shower standing over a bucket. A flexible durable tub is great, because it can double up as a child’s bath or a laundry basket. The average shower uses about 15 gallons, so plan accordingly.
After your shower, simply connect a pump to a garden hose out the bathroom window. If your new fruit trees are lower than your shower, use a siphon. If they are higher, spend a little extra and get a marine grade manual bilge pump.
What about soap?
If you have a septic system, you should already be using biodegradable free and clear soaps. Not only are they better for the environment, but they are also widely considered better for us. Most plants can handle gray water, although some may need a good flushing with potable or rain water occasionally.
How much water does your new tree need?
This depends on the type of tree, the size, and how well established it is. For example, a newly planted coconut palm could require between 15 and 30 gallons per week, while an avocado might require 60 gallons per week in its first two years. It is often considered best practice to water deeply a few times a week, rather than in small increments continuously.
Once established, many native trees thrive in the seasonal rain/drought fluctuations as these encourage flowering and fruiting. However, even established trees may need a deep watering during extended drought.
Water as a Resource
Water, as a valuable resource, should be used sparingly. However, gardening is important for food security, wildlife, and surrounding ourselves with beauty. The best landscapes are ones which are suited to the micro-climate they are growing in, but anyone who has tried to establish a mango or avocado tree knows that the first two years are crucial to develop strong deep roots and a healthy tree.
Resources: In St Maarten we get around 1,000 mm of rain annually. Bilge pumps and siphon pumps can be bought at ship chandlers like Budget Marine.
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