As Australians face a warming climate, it is increasingly important that we consider water management that works with nature to keep moisture in the land we steward. This is equally necessary for large rural properties, smaller gardens and urban backyards. Rehydrating landscapes involves mimicking natural processes to increase the water-holding capacity of the soil, storing the water under and in the land, not on top of it.
Rehydrating landscapes relies on small and slow solutions, and therefore the benefits start small and build over time. Benefits include reduced erosion and salinity and increased soil health and productivity. But they also increase your property’s resilience to fire, drought and some aspects of flooding; and are a key part of any permaculture disaster risk management plan.
Build Organic Matter
The best and simplest way to rehydrate landscapes is to build organic matter – or humus – in the soil. Lush, healthy soil with a rich structure and diverse soil life enables water to infiltrate deeply into hard, dry or clay soils. It also creates an environment that retains water because of the capacity of humus, the soil’s organic component, to store it. There are a number of ways to build soil humus:
- Adding compost is a simple way to build humus in the soil. As well as adding abundant organic matter to build rich soil, good compost also supplies fertiliser and enriches your soil with microbial life (see below).
- Mulching reduces evaporation and adds organic matter to the soil as it breaks down. Good mulch options include utilising an otherwise waste product like spoilt hay, animal bedding or fallen leaf litter. Sugar cane mulch or pea straw are commercially-produced options.
- ‘Chop and drop’ mulching is where perennial plants and trees are heavily pruned and the clippings added to the soil. Both the clippings as mulch and the root network underground add to the organic matter in the soil.
- Paddock slashing/green manure crop. Slashing paddocks of oxidised or otherwise unused pasture or using a mulching mower returns the organic matter to the surface of the soil. In smaller gardens, another way is to grow a green manure crop and plough it or crimp it to return it to the soil.
Stimulate Soil Life
Stimulating soil life assists greatly in building humus and water-holding capacity. Biodynamic preparations and liquid garden ‘teas’ boost micro fauna and flora and support the work of the soil builders.
- Biodynamic preparations such as BD500 assist in the
- formation of humus and the compost preparations BD502 to 507 help break down the organic matter into plant food. (For an introduction to biodynamic preparations, see Pip issue 11.)
- Liquid teas are easily made at home. Compost tea, chicken-poo brew and weed tea add bacteria, fungi, protozoa and nematodes to the soil, enriching the diversity of soil life.
Making Weed Tea
- Fill a bucket with weeds from the garden (a bucket with a lid can be useful to prevent water from evaporating).
- Cover the weeds with water – make sure weeds are completely submerged.
- Leave for one-to-three months, stirring occasionally.
- It’s ready when the plant matter disintegrates and falls to the bottom as sludge – the nutrients are now all in the water.
- Compost the debris from the weeds.
- The liquid that remains is a nutrient-dense fertilisation tea. Dilute one part tea to 10 parts water, before adding to your garden.
Maintaining ground cover helps retain topsoil and protects against erosion. It improves moisture retention by slowing run-off, enabling water to infiltrate the soil. This builds the soil moisture profile.
- Green manure crops can keep the soil of garden beds covered during rest periods.
- Use perennial pasture to ensure coverage continues
- year-round. Encourage a diverse range of plants, including local endemic species.
- Themeda triandra (kangaroo grass) and Austrodanthonia sp (wallaby grass) are good choices for pasture cover in large paddocks.
Clockwise from above left: Kangaroo grass is a good choice as pasture; Swale at Purple Pear Farm distributing water across the farm; Mulching around plants to protect soil and stop evaporation.
Bare or compacted ground can be bought back to function by using deliberate and thoughtful animal impact. This type of impact breaks up hardpan and baked soils to allow for plant establishment and water infiltration.
- Feeding large livestock, such as sheep or cattle, in an affected area, can create a positive animal impact as the effect of hooves breaking up the land allows for better pasture growth and infiltration of water. This can pose a risk of soil compaction, but can be mitigated by regularly rotating the animals through different enclosures, ensuring they do not stay in the same place for too long. Additionally, undigested hay or food mulches the soil, and manure and urine help boost fertility – all leading to improved humus and water retention.
- A similar effect can be gained in small gardens by using smaller animals, such as chickens or other poultry in ‘chook tractors’, or guinea pigs or rabbits in hutches, that graze your grass and scratch the soil.
- No matter where the water comes from – rainwater, town water, greywater, irrigation from rivers and creeks – the key is to make as much use of it as possible before it leaves the system. When uncontrolled, gravity in a water system can lead to erosion and flooding and the landscape misses out. But when it is stored high in the landscape and released slowly, we ‘make running water walk’, allowing it to permeate the soil. Earth works can be expensive, but properly planned they will repay the investment many times over. A well-positioned dam allows for water storage and flood watering of the soil. A swale is a water harvesting ditch on contour that allows for the passive movement of water through the landscape. It has a soft mound on the downhill side which allows the infiltration of water stored in the swale.
- These design features can be incorporated into a small garden setting by scaling down the design. For example, a dam becomes a pond at the high point of a suburban backyard. Instead of swales, garden beds are placed on contour with mulched paths in between to catch and absorb excess water in the landscape. Water-loving crops such as bananas can be planted at the lowest point in the garden to make use of the water before it leaves the property.
A Case Study: Purple Pear Farm
Purple Pear Farm is a market garden and education centre on 14 acres in temperate New South Wales. The property was previously used for cattle grazing. When acquired by the current owners, the land demonstrated dry, compacted soil with minimal pasture.
We have used the strategies outlined already in this article to help manage soil hydration. The property now supports a community-sponsored agriculture scheme, growing produce for up to 50 households, as well as food forests, a nut orchard, and supporting a small amount of grazing livestock.
When we first moved to the property, we added as much organic matter to the land as possible. The paddocks were initially covered in fireweed, which were slashed and returned to the soil as organic matter.
We initially used a tractor fitted with ripping tines to lightly loosen soil compacted by grazing animals. This was a onceonly activity. In a backyard, a similar affect could be achieved with a garden fork or broad fork. Soil humus is built through the regular addition of biodynamic preparations and organic matter as mulch and, especially, compost. Plant diversity has markedly increased, as has soil humus.
We covered the bare soil in the market garden with a green manure crop then used chickens in chook tractors to turn this in. Afterwards we planted either food plants in the productive seasons or cover crops in the cooler months. We regularly plant green manures or cover crops in the market garden beds, at the expense of food production, to ensure the ongoing fertility of the soil.
After cleaning out two dams at the lower front of the property, the dredged sediment and other organic matter was transported to the top of the slope; over time, rainfall helps create a nutrient flow down the slope. Additional earthworks included building two irrigation ponds and installing a pipe to channel all the water from the market garden and living areas and direct it – with nutrients and pollution – into the soil on the front slope of the property; here it provides water for fodder, shade trees and pasture.
Another dam was constructed in the fire sector and the overflow from this feeds the swale. This water-harvesting ditch, on contour, runs the width of the property, collecting water from the market garden, nut orchard and hard surfaces around the house and shed. This re-use water then irrigates a food forest, and provides slow irrigation across the pasture and into the tree lot on the other side of the swale.
Holistic management helps us make further decisions about how to best hydrate the soil. Rotational grazing ensures livestock do not overgraze pasture. The cover of perennial, mostly native, grasses ensures pasture coverage that assists water infiltration and avoids soil erosion.