Silvopasture & Agroforestry
Silvopastures are one of the different types of agroforestry systems, with agroforestry being defined as a land use management system in which trees and/or shrubs are grown around or among agricultural land (usually crops or pastures).
Coming from silva, which means forest in Latin, silvopastures integrate fodder trees and other types of woody plants together with the grazing of domesticated animals in a mutually beneficial way.
Beside silvopastures, other agroforestry systems include:
- Forest farming, where high-value crops are grown under the protection of a managed tree canopy,
- Alley cropping, a form of forest farming where crops are grown in between rows of productive and support trees,
- Syntropic farming, as a tropical and sub-tropical form of alley cropping based on the intensive management of successional ecology and forest stratas (niches in time and space),
- Food forests, which are permaculture-designed woodlands grown with a wide variety of perennial food plants, (we could hence say that alley cropping systems are food forests organised in a row pattern),
- Timber production (managed in a regenerative way, as opposed to conventional logging),
- Shelter belts, such as fire shelter belts and windbreaks,
- Riparian forest buffers (often as a form of erosion control, ecosystem protection and wildlife habitat),
- Wildlife corridors (areas of reforestation and revegetation connecting native habitats for wildlife).
Our project is for a small-scale hobby farm that has goats for milk and meat production, among other permaculture systems under development, and the owners contacted me to help them setup a regenerative system for their goats as their paddocks were very run down due to overgrazing with horses by previous owners.
As per the permaculture design process, the first step was an onsite visit of the property and paddocks to determine the owners’ vision and goals as well as the ecological influences of the climate and landscape and of course any opportunities and limitations of the grazing system itself.
The initial diagnosis was chronically understocked and overgrazed pastures, with very few paddocks containing browsing material that would normally be the main staple of the goats’ diet, heavy clay-based soil, rock hard dry during summer and wet and boggy in winter.
We decided to proceed in stages and limit the scope of work to 4 paddocks initially (stage 1 in green below). This allows us to trial and error the system and phase expenses before expanding to larger areas.
For clarity for the reader, this blog article will focus on the bigger paddock (northeast of the stage 1 areas).
Baseline & Visual Soil Assessment
The VSA was based on in-field soil tests that were sampled at the end of February 2022 and highlighted the following results:
- Ground cover: predominantly weeds tolerant of compacted and waterlogged conditions with varying fertility levels depending on the areas (dock, plantain, capeweed, sweet vernal grass, yorkshire fog grass, buttercup, thistle, kikuyu grass…). No sign of legumes or other more palatable species
- Some bare areas
- Structure: Very compacted. Neither O (organic matter) nor A (top soil) horizon.
- Texture: Dispersive and hydrophobic silty clay. Fine silt particles, no agglomeration and no plasticity as found in clay. Clay layer remains cloudy for 12+ hours in jar filled with water.
- Colour: Very light in colour, severe lack of organic matter.
- pH: 5 – 5.5
- Root penetration: shallow root layer (approx. 5 cm)
- Soil biology: No visible sign of earthworms or other life form apart from one larva,
- Observations: Soil is very dry in summer and wet and boggy in winter. There is a suspected in-ground water stream running through the west side of the farm equipment area, then shed and then duck paddock that keeps the cover green in summer but also induces some plants and fruit trees to drown in winter.
- Infiltration test: It took 11 min to absorb 1 inch of water
- Geology: Siltstone
Design Objective, Elements & Strategies
The objective of the design is to improve or restore the 4 ecological processes:
- Solar / photosynthesis cycle through increased plant mass and broad-leaf plants
- Water cycle through improved infiltration, retention and drainage, and reduced evaporation
- Biological & mineral cycle through improved soil structure and biology
- Diversity & resilience through polycultures, shelter-belts and niches
The elements and strategies of this design include:
- Water Systems: Greywater treatment system (upslope), swales and spillways, design on contour, and in-ground water management
- Soil Conditioning: Decompaction / aeration, soil amendments, improved structure, increased diversity, biology and fertility above and below ground
- Silvopasture: Regenerative agriculture principles and practices, diverse perennial ground cover including green manures, legumes, grasses and forbs, and nitrogen-fixing and fodder trees and shrubs
- Grazing Management: Permanent plus mobile electrical fencing, watering systems, rotational grazing plan
Each element and strategy and their expected benefits together with the technical specifications are then described in greater detail in the consultancy report.
Part of those specifications include for instance the planting plan for the silvopasture rows, starting with species selection based on attributes (fodder, nitrogen-fixing, wildlife attracting, etc.), ability to withstand chop-and-drop or pollarding, tolerance to drought and waterlogging, and then positioning of each individual relatively to each other according to size, deciduous or evergreen character, again tolerance to pruning to allow space for canopy growth in turns, etc.
In the first year we prioritised conditioning the soil to create more welcoming conditions and increase the chance of survival of subsequent plantings.
We first dug the swale on contour at the top of the paddock, that now collects greywater from a reed bed and the overflow from a rain tank upslope. The spillway of the swale will later be connected to the first tree row below and wave all the way down the paddock through each bed.
The pasture work entailed some shallow decompaction work on contour with a chisel plough, which gently raised and aerated the soil either side of the implement without turning it over. The immediate result was a greener cover alongside each furrow.
We then applied gypsum to floculate the clay particles and increase water absorption, as well as lime and dolomite (containing calcium and magnesium) to correct the pH acidity. With the first rains of the autumn break, we then broadcasted a multi-species seed blend over the existing cover and made a pass with chain harrows to increase seed-to-soil contact. The seed mix contained vigorous annual and perennial species that would be able to compete with the existing weeds. It included brassicas, biological tillers, legumes, forbs, mineral accumulators, cereals and grasses.
In spring time, we planted the first trees from cuttings taken on parent trees on the farm (as a way to reduce costs) and protected them with tree guards. The rows were made on contour 3m apart from each other in order to allow the passage of the farm machinery. We also divided the paddock in smaller grazing cells with temporary fencing and brought the goats in to graze the areas that grew well while allowing the poorer areas to keep resting, then quickly moved the animals to the next cell, tested the pH again, re-applied lime and overseeded with a spring and summer seed mix.
After the initial grazing, we continued the rotational cycle. The 4 initial paddocks in scope were divided into a total of 12 grazing cells, although 3 of them were kept ungrazed because they didn’t regenerate as fast as the others and didn’t offer as much feed. Used in combination with the other pastures (that will be part of the project’s stage 2 and stage 3 work), we were able to rest the pastures until the mix grew back. We then brought back the animals in the first cell 7 weeks after the first grazing.
We also made the second pass with the chisel plough, this time a bit deeper than the first pass.
By the end of February 2023, after 2 months without rain, the plants started to dry and go to seed while still showing dense and green growth at the base. We decided not to bring the animals again in order to keep the ground cover healthy and protect the soil from the heat and minimise surface evaporation.
We repeated the soil tests just 1 year after the initial testing (25.Feb.2022 vs 27.Feb.2023) and with similar summer conditions both years. The results were very encouraging:
- Ground cover: much denser and greener than 2022, more grass and palatable species, very few bare areas
- pH test: Up to 6 from 5 – 5.5 initially
- Infiltration test: 6 min to absorb 1 inch of water, i.e. nearly twice as fast as 2022
- Penetration test: 11cm; in line with root depth at approx. 10cm, i.e. twice as deep as 2022
- Biology: 3 earthworms counted over 10 samples (not much moisture on the soil surface in the summer months)
The swale that is now constantly fed water from the reed bed (as greywater treatment) stays full and started rehydrating the pasture downslope. As the soil is heavy clay-based, it takes time for the water to travel through but we can definitely notice the progress of the water overtime as the cover becomes greener a bit further at every visit.
In March, we then started pollarding the existing poplar trees and gave them to the goats as supplementary feed to bridge the feed gap until the next autumn break.
We also started formalising the silvopasture rows by forming the beds that will welcome more trees, shrubs and herbaceous plants over the coming weeks and then winter.
We tilled the contour rows with a rotary hoe, weeded, applied a mix of goat manure, chicken manure and spent hay (sourced on site) that we mixed into the soil, formed the beds, shaped a swale on the upslope side as well as the centre of the beds into a concave shape, and last added some wood bark mulch sourced on site from fallen gum trees.
We are now busy adding more trees and soon will follow the other sub-canopy layers. Trees are planted 3m apart from each other, then shrubs are added 1-2m apart in between trees, and forbs and herbaceous plants will fill the space in between. The reason why trees are planted closer than the width of their future canopy at maturity is because we selected trees that tolerate fairly frequent hard pruning and pollarding, either for chop-and-drop of nitrogen-fixers and biomass, or for fodder. A few examples include alders, hazels, mulberries, poplars and wattles. Some other trees such as birches, chestnuts and oaks can be pruned on a slower cycle.
Some trees will come bare-rooted and hence will only go in the ground mid-winter. Meanwhile, we started planting the potted trees as well as some shrubs including tagasaste, wormwood, and salt and berry bushes, while the herbaceous layer will include fodder and medicinal species like arrowroot, comfrey, jerusalem artichokes, pepino, chamomile, chicory, parsley, peppermint and lemon balm.
We also recently overseeded a pasture mix again to further boost the regeneration of the ground cover and are seeing excellent germination. Last, some of last year’s sown species including clover, peas and radish seem to have self-seeded after we left the pasture ungrazed towards the end of summer and have had a head start with the first seasonal rains. Once the tree rows are fully planted and before bringing the goats back again, we will pull an electric tape along both sides of the beds to discourage them from trying and browsing the system too early or damage the paper guards and wire cages. As soon as the trees will reach above browsing height, we will adjust the fencing according to the animals’ behaviour.
It will be very exciting to see the silvopasture once all plantings are in the ground, and to continue monitoring the soil health and increasing the diversity and quality of fodder for the goats. As it usually takes 2 to 5 years to regenerate a degraded pasture (depending on the soil condition that we start with), we will also have to be patient and let Nature do her work.