Multi-species planting and pasture cropping can provide a number of benefits to the soil, including improved soil structure, weed control, increased organic matter, and improved nutrient cycling.
The use of multi-species planting for pasture cropping can be particularly beneficial for improving soil fertility, to a greater extent than single-species cover, and it should be noted that pasture cropping goes hand-in-hand with pasture management and holistic grazing practices.
Pasture cropping is a combination of cropping and grazing for the benefit of both enterprises and benefits the farmer economically and the environment.
Colin Seis, founder of pasture cropping refers to it as perennial cover cropping or “zero till sowing of annual crops into living perennial pasture”.
The system follows no till sowing a crop into the window of dormancy of a pasture.
- The crop could be a cereal, a broadleaf or a mix species planting.
- Sowing winter grain crops into summer pastures.
- Sowing summer grain crops into winter pastures.
- Sowing forage crops in either of the above climates.
Why is Plant Diversity Beneficial?
Plant Root Variation
Plant diversity creates a variation of roots, for example, some plants have deep tap roots, and some shallow. Plant roots form underground cooperatives. Rather than being competitive, all the plant roots work together to help support the biomass in soil structure.
Constant Ground Cover
With a diversity of plants it also means the ground is always covered, offering soil moisture and temperature moderation. Having pasture cropping diversity means there are always plant roots in the ground helping to form soil structure, which leads to more stable beneficial microbe communities and plants that are more resilient.
Improved Soil Health & Fertility
One of the main benefits of multi-species pasture cropping is that they can dramatically improve soil fertility. This is because different plant species have different root systems and produce a variety of different exudates. As a result, a wider diversity of microorganisms develop in the soil that take up different nutrients and make them available to crops.
Improved Soil Stucture & Water Infiltration
In addition, the different plant species in your pasture cropping can have complementary effects on soil fertility. For example, one plant species may improve soil aeration while another improves water infiltration.
A Diversity of Plants Means a Diversity of Microbes
A seed or plant’s microbiome is the collection of all the microbes that live on and inside the seed or plant. These microbes include bacteria, fungi, viruses, and protozoa.
The plant’s microbiome is shaped by the plant’s environment, including the soil, air, water, and other plants. The microbiome also changes as the plant grows and develops.
A healthy microbiome is important for the plant’s growth, development, and resistance to disease.
Studies have shown that trees that were being ‘attacked’ by bugs, and were not producing fruit, started producing once the ground was covered in a diversity of cover-crops. The trees were still carrying the same bacterial load, and were being inhabited by the same bugs, but they were no longer being affected.
A Healthy Soil Plant Cycle
Plants capture light energy and convert it into glucose (sugars).
Plant sugars (exudates) come out of the roots to feed the microbes that are around them.
Microbes produce the enzymes (inside plant root aggregates) that make the minerals available to the plants.
Why Beneficial Microbes Need Plant Root Aggregates
Water stable aggregates and rhizosheaths are important for carbon capture and plant nutrient acquisition because they provide a specialised micro-aerobic fixation site for microorganisms to break, eg. nitrogen bonds, and turn them into plant available forms. This is the only place where natural nitrogen fixation can occur.
When we use N fertiliser the formation of rhizosheaths and water-stable aggregates get inhibited, and the ‘signaling’ system becomes disrupted. As a result, plants have difficulty growing under stress, and they cannot cope with pests or diseases, because they lack the soil biology that communicates to each other using Quorum Sensing.
What is Quorum Sensing?
‘Quorum’ is the minimum number of ‘members’ that have to be present in order for a decision to be made, or a task to be accomplished. In the soil, Quorum Sensing (QS) refers to a density dependent behaviour of microbes for example, when a minimum density of microbes reaches a required threshold, they can switch genes on and off.
Every Microorganism Species has its own Unique Signal
When the signals reach a critical level, they regulate gene expression in the microbial population and or in the plant or animal host.
Mycorrhiza support a wide diversity of plants. The plant diversity ensures that there will always be some plants, at any given time, sending energy down to exchange nutrients, and water. This support provides a steady stability for soil biology to perform their various functions, and results in healthy plants with direct access to exactly the right nutrients when needed.
For more information about Quorum Sensing see Dr Christine Jones Video ‘Quorum Sensing in the Soil Microbiome’
Studies have shown soil health and fertility improves best when growing a variety of plants selected from different plant families. Plant examples may be grasses, legumes, clovers, wild flowers, tall herbs and short herbs.
To give your plants and soil biology a boost, consider using Biological Fertiliser made from fish or seaweed with your seed germination. Seaweed has natural growth hormones and can greatly assist seed germination and early growth. Read Article ‘Maximise Seed Germination with Biological Fertiliser’.