Project 002-072 Self-Watering Garden Beds
Project Name: Self-Watering Garden Beds
Project Details
Reference Sponsoring Entity Commenced Status Budget
22-23 23-24 24-25 25-26
002-072 KIRRAag (Ka) 08-09-2023 In-Progress $ - $ 968 $6,200 Unallocated
Project Overview
With water scarcity, a different, more controlled manner of growing our own food is required. With the small number of gardens and limited crops currently in production, a water use in excess of 100 litres per day was not sustainable. So, we purchased a number of small self-contained raised garden beds.
Each garden bed is 1200 (L) X 900 (W) X 300 (H) mm and made of sheet tin. 17 were purchased at $24.00 each.
Although not a new concept, we wanted to make our vegetable gardens a little more tolerant of the harsh conditions that are experienced in our environment. We knew from past experience that we didn't have sufficient water to simply continue to water and watch the water evaporate, then reapply.
We decided that wicking beds or self-watering beds were a much better alternative, as they gave us the ability to fill the bottom of each bed with water, which would only be consumed by the plants and not be subject to the normal evaporation, experienced during our gardens last season.
Wicking beds are able to wick water to about 300 mm above the water level. The selected raised garden beds are exactly 300 mm so this will be easily achieved and sustained.
Aim
Improved food production and more controlled water use for cropping operations in a soil/compost based growing medium. We are seeking a sustainable outcome for cropping in arid environments that uses water responsibly and conserves it where at all possible.
It will be important to measure and capture data which demonstrates relationships between factors, so that clear patterns can be established. This will allow the formation and establishment of patterns and practices in this area.
Method
Establish a environment for our self-watering bed experiments.
After assembling each of the metal raised garden beds the following was done to each raised bed.
STEP 1: At about 1/2 way up the height of the raised garden bed, drill a hole to allow excess water to escape and prevent the garden from flooding.
STEP 2: Line each assembled raised garden bed with black plastic or some other water proof membrane.
STEP 3: Add blue metal gravel or sandstone rocks to the bottom of each raised bed. A height of about 110 - 130 mm was achieved. This bought the level of the gravel up to the hole drilled in the side of the garden bed.
STEP 4: Add a 300mm (12") length of 25mm (1") poly pipe in one corner of the raised garden bed. This allows you to add water to the bed without having to water it from above. This reduced mildew and rot, and conserves water.
STEP 5: Add a layer of geotext fabric over the gravel in the bottom to separate the gravel from the growing media, mulch, compost or soil etc.
STEP 6: Add a reasonable but thin layer of mulch or material that will easily compost and continue to feed the plants.
STEP 7: Top up the raised beds with quality soil, potting mix or whatever you are going to use to grow your plants in. We used potting mix from last years planting, with some compost, rooster booster organic fertilizer and a small amount of sand to lighten the mix up.
IMPORTANT: While the plants are getting established and finding the reservoir of water at the bottom of the raised bed, the plants need to be watered from the top. This should take about 2 - 3 weeks.
BED #1
LEFT: On the 6th of October 2023, the seedling starts were transplanted to the self-water raised garden beds.
RIGHT:Photo taken on the 15th of October 2023. Mulch had been added to further reduce evaporation and some rooster booster added to the top of the bed. Additional space was used to plant some beetroot.
Still watering from the top.
This bed was made using blue metal.
LEFT: Photo taken on 10th of November 2023.
We have already started to harvest zucchini and beans from this raised bed.
Watering via the pipe only now.
35 DAYS from seedlings to crops.
BED #2
LEFT: On the 6th of October 2023, the seedling starts were transplanted to the self-water raised garden beds.
RIGHT:Photo taken on the 15th of October 2023. Mulch had been added to further reduce evaporation and some rooster booster added to the top of the bed.
Additional space in front of the lettuce was used to plant spring onions.
Still watering from the top.
This bed was made using crushed sandstone from the pond excavation.
LEFT: Photo taken on the 10th of November 2023.
Watering via the Pipe only now.
35 DAYS from seedlings to crops.
Conclusion
The project seems to be very productive as a whole. The initial planting has yielded some exceptionally quick growing leafy vegetables like lettuce. As the project continues planting will include some more demanding crops such as pumpkin, melon, cucumbers and tomatoes. As it is now late spring, the planting of the next crops like chilli and capsicum with tomatoes will continue.
Water Use
In the height of Summer, the current water use for each of the raised beds is around 60 litres per week. This makes a total consumption of around 240 litres per calendar month. If this is considered against the soil garden requirements of around 105 litres per day (3,255 litres per calendar month) the water saving is around 92.66%.
Amendments
The amendments to the beds have included some additional rooster booster and mulched aged horse poo.
Cost-Benefit Analysis
The raised garden beds that we purchased were $24 each. Today they are $28.00 each. Each bed uses about 1/10 th a m3 of blue metal, a m2 of geotext which costs around $31 per raised bed. Other imports included potting mix, and fertilizer added about $12 per bed. The raised beds are a once-off capital expense, which should last many years, while they could also be made from tree logs, bricks and other materials which would significantly reduce the cost. It is also noted that many of the soil garden inputs are required annually, and are therefore ongoing.
Changing the potting mix for home made compost would also significantly reduce the cost.
This project should be up-scaled to 100 raised beds (as defined by the increased budget for 24-25. 100 X $56.94 + pipe, timer and water storage), with an automatic watering system and return piping to capture the overflow water, which is then returned to be re-applied in the next watering cycle. The return water pipe could also replace the need for the vertical watering pipe. Like the hydroponic garden system, this should also be controlled with a timer, that measures soil moisture, and supplied with water on an automated as-needed basis.
In this array of 5 self-watering garden beds, the first 2 were completed nearly 3 months ahead of the last 3 beds. The last 3 beds were completed on the 26/11/2023 (Images below)
