Managing excess moisture in the vegetable garden will be on the minds of most vegetable gardeners today as the impacts of Cyclone Debbie are revealed along most of the eastern seaboard of Australia. In Brisbane we’ve had about 300mm in 24 hours.
Food gardeners in Australia are more often presented with the challenge of keeping their organic gardens moist than managing excess moisture. I recall some years ago chatting with my son who was doing his biodynamic farming training in North Yorkshire in the UK, a very wet and cold place. The pastures had lots of drainage to take water away and peaked garden beds designed to shed water. A different world to my experience in Australia.
In managing excess moisture in the vegetable garden, the two major aspects are: water flow and water-logging.
Excess water flow can cause:
- Increased soil erosion – Your garden beds will erode away and may be completely wiped out if its a big flow.
- Loss of top soil and fertility – The thin layer of top soil you have worked on to improve can be washed away overnight with a big flow of water.
- Loss of plants – Seeds and seedlings are very sensitive to any weather extreme. Water flow will wash seeds and cover seedlings with soil.
Water-logging can cause:
- Lowered soil fertility – Too much water reduces oxygen levels in the soil. The oxygen level has a big impact on root growth and the life force of the soil and plants.
- Lowered nutrients – Nutrients are lost from the soil. Nitrogen loss can be high. Beneficial microbial populations are affected, making it harder for plants to take up essential nutrients from the soil.
- More plant disease – As plants weaken from their roots being in too much water and experiencing lack of oxygen, fungal diseases often increase.
- Lowered seed germination – Too much water will kill seeds. They are very sensitive to the right balance of moisture and heat.
A loam or sandy loam with a reasonable mixture of sand, clay and organic matter is ideal for growing food and this type of soil holds moisture and nutrients very effectively. It also drains well and does not get so effected by water-logging. A soil that is heavy in clay will get very sticky when wet and suffers with too much water. A soil that is quite sandy and sits on a clay base will become quite gluey.
Both water flow and water-logging make it more difficult to work in the garden. Fungal growths that increase with high moisture levels are carried around your garden on your shoes. Where any weight is placed on the soil, compaction is much higher when its wet and compaction impedes root growth.
What can you do to reduce excess moisture impact?
- Observation – Observe the patch for your garden in a big dump of rain before you build it and see what happens with waterflow, ponding of water and water-logging.
- Garden position – Make sure your garden gets enough sun. Don’t position it in a major water flow path unless you plan to divert the water. If the patch is often boggy, it will need drainage to consistently remove the water.
- Garden design – Your garden orientation should be across a slope on contour, otherwise flowing water will quickly erode your garden beds. Combine this with slightly raised beds and you will find they hold moisture when its drier and also drain very effectively when its wet. If you choose to use beds in raised structures such as corrugated iron, then make sure these have many drainage holes.
- Soil quality – Having consistent practices to build soil quality is the tonic for most things in food gardening and it also helps with drainage. Make sure you know your soil type to begin with as this helps in determining how to improve the soil. of you have used consistent organic practices supported by biodynamic methods, you will see a healthy build up of humus which hold moisture when its drier and drains well when its very wet.
- Compaction – Don’t walk on very wet garden beds as this will increase compaction.
- Containers – Make sure they can drain well from their bottoms and move them into the sun if they are sodden.
- Change the water flow – Put up barriers or dig drains that alter the water flow away from the garden beds and consider appropriately design swales to manage water flow.
- Planting – Hold off on planting when a big wet is coming or has just hit.
- Weeding – Its often wetter around full moon time and this is when reproductive forces are at their highest on earth. If you choose to pull weeds when its very wet, you will increase the potential for additional weed growth even though they will be easy to pull out.
- Plant and soil tonics – As the soil looses nutrients, life force and fertility in excess water situations, you will need to support your plants, especially if they are young. There are a number of very helpful organic and biodynamic gardening practices to reduce the impact of high moisture and fungal growth. If you are growing curcubits, beware, they can succumb to mould very quickly. I use equisetum tea and BD horn silica as one remedy for managing excess moisture in the vegetable garden.
An effective food garden design that enables good drainage and considers overland and overhead water flow, supported by appropriate organic garden management practices, will deal with most of your problems before you have to take remedial action after a major rain event. However, in extreme situations unexpected flooding will force you to take action, nature can be unpredictable.
Our mentoring and food garden design and build services are aimed at preparing your garden to thrive, being pro-active in growing rather than mostly re-active in cleaning up problems. You still need to hone your observation, the garden will not run on autopilot!
I see managing excess moisture in the vegetable garden as a good problem, imagine if you lived in a desert.
Authored by Peter Kearney – www.myfoodgarden.com.au