After plugging the drainage holes in another batch of terracotta pots I have embedded them in my garden beds. Sealing holes in terracotta is not as easy as it may seem. You need to check to see if they sweat rather than leak. Watching beads of moisture form on the outside of the terracotta for the first time is a thrill.
To then entomb them in situ is like making an offering to the soil.
With over 50 pots in place in my garden -- standard plant pots and terracotta wine coolers -- filling them is now a routine chore. I suspect that if I stiffen the end of the hose by wrapping a rod to it topping up each pot will be easier and I won't have to crouch down so much.
But each time you visit a pot station I get to inspect local ecology.
Instead of using tiles I'm now preferencing heavy white dinner plates I get cheap at Op shops as lids atop the pots. Facing up they sit snuggly on the pot lips and the white stands out in the garden beds. As the plants grow and more mulch is scattered on the beds you need a marker to find the pots when refuelling otherwise they get hidden.The snugger fit offered by the plates makes it harder for crows, passing canines or escaped chooks to displace the lids. If a lid is ajar there is more evaporation, and mosquitoes or cane toads will move in. The white plates also reflect heat and reduce evaporation.
Even though my newer pots are mass produced Italian imports not all pots are equal and the sweat rate varies probably because of the clay mix and idiosyncratic effects of firing times. The rate at which these pots drain is dependent on variables I don't, as yet, understand.
If the soil is already wet they'll drain faster than if it is dry. Where pots have ' settled in' and the local soil and flora have adapted to their presence there is remarkable plant growth compared to non-pot places which are water neglected. But the interaction takes time -- maybe weeks-- to consolidate so it is not like hosing a garden bed. This is a subtle almost passive irrigation process driven by gravity but facilitated by the plants themselves, the amount of soil carbon and biota .
The slow release is ideal for my sandy soils as all other approaches I've used ended soon after I stopped watering as the water would drain away into the aggregate below each bed.
Research done by the University of Pretoria in South Africa confirms how effective these pots are in reducing water usage.
The clay pot used for irrigation is an unglazed indigenous earthen pot which has many micropores in its wall. The microporous wall does not allow water to flow freely from the pot, but guides water seepage from it in the direction where suction develops. When buried neck deep into the ground, filled with water and crops planted adjacent to it, the clay pot effects sub-surface irrigation as water oozes out of it due to the suction force which attracts water molecules to the plant roots. The suction force is created by soil moisture tension and/or plant roots themselves
So with that in mind, watching the beds adapt to my sub surface rig is going to be interesting. The South African research recommends that the pots should always be kept wet "by not allowing water to deplete beyond 50% capacity. This will counteract possible clogging and enhance water flow out of the clay pot".
This means I need to keep checking my water levels. It is still too early to establish a strict routine but I suspect I may need to top up the pots every 3-4 days in order to run the system at primary efficiencies.
Compared to my current watering schedule this is less labour intensive. It also offers a ready feedback on what's happening in the soil. That's something I appreciate as it will focuse my attention more.
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