There are quite a few benefits that plants receive with a good dose of rain, that they don’t get from water supplied via a tap.
Firstly, as rain drops fall, they absorb nitrates from the sky. Nitrates are the most bioavailable form of nitrogen and are essential for plant growth. Most of this nitrogen dissipates from water when stored for an extended period of time. Rain delivers nitrates directly to the plants and they can use them immediately to grow.
Secondly, rain falls evenly across the garden, to create a uniform soil moisture profile. An irrigation system creates areas of high soil moisture, but some areas of the garden remain bone dry. Plants like consistency, and rainfall is the best at delivering this across a garden.
Thirdly, rainfall has an acidic to neutral pH. Mains water is often alkaline. Most plants prefer the pH range of rainwater over mains water.
Finally, mains water usually contains chlorine and other salts. These minerals can accumulate in soils irrigated with tap water. Chlorine and other minerals can be toxic to some plants in high doses. Rainfall can help to flush a lot of these accumulated minerals deep into the soil and away from plant roots.
To say we need rain is an understatement!
Reference Leaf, Root & Fruit Gardening Services ( leafrootfruit.com.au )
