Making the Most of Your Soil’s Biological Potential

The underlying principle in “soil health” is that soil is a living, dynamic and ever-so-subtly changing whole environment,not just an inert, lifeless growing medium, which modern farming tends to represent. Is it then surprising that soils highly fertile from the point of view of crop productivity are also lively from a biological point of view?

For the author, this quote alludes to the degradation of soil health and the tragedy that most farmers do not fully appreciate the ability of nature to cycle nutrients. They are missing out on the benefits to their agricultural systems that flow from simply growing plants and animals which support soil biodiversity and natural cycling by returning nutrients and organic matter to the soil.

Biodiversity is essential for the survival of all species, including humans. It is the source of our foods, medicines and industrial raw materials. Our economic prosperity is dependent on it, from agriculture to tourism. Farmers have a key role in maintaining and enhancing the biodiversity on their land, while doing their best to manage pests, diseases and weeds in a sustainable way.

Regenerative agriculture (RA) is an approach to managing agro-ecosystems for improved and sustained productivity, while preserving and enhancing the resource base and the environment. Four linked principles of regenerative agriculture which recurreare:

1. Implement a continuous regime of minimum mechanical soil disturbance.

2. Maintain permanent organic soil cover.

3. Maintain a living root in the soil.

4. Plant diverse crop species in sequences and/or associations.

No Doubt
There is now no doubt that soil biology is as crucial to maintaining healthy soil function as soil chemical and physical elements. While science is proving to be both the solution and the barrier to acceptance of this basic fact as it struggles to maintain pace with discoveries in the biological world, this is changing with increasing global support. For example, in 2011, the FAO launched the Global Soil Partnership (GSP) to support sustainable management of soil resources for food security and climate change mitigation. The UN declared 2015 the International Year of Soil, a campaign to raise awareness, support policies, and promote investment toward soil security as well as enhance soil collection and monitoring. And on 4th December 2015, on the occasion of the 12th annual World Soil Day, the GSP released its first report on the state of the world’s soils.

There is need to bring together all willing contributors in the public and private sectors (national governments, local and regional government, companies, trade organisations, NGOs, research facilities, and others) under the framework. The aim is to demonstrate that agriculture, and agricultural soils in particular, can play a crucial role where food security and climate change are concerned.

The questions the industry needs answered are:

1. Why is carbon so important for biological function and can we build soil carbon levels given our cropping system and tropical climate?

2. The role of soil biology in the nutrient cycle: can we influence this through management?

3. Harvesting sunlight: how can our industry make better use of what we have in abundance?

4. How can we emulate nature in our current cropping system through increasing plant diversity?

So What?
There is need to assist all farmers, wherever they are and whatever they farm, to improve soil health, profitability and environmental outcomes. Any action taken should be relevant to all sectors of agriculture that rely on soil for the nutrition of their commodity. It is up to the farmer to decide and verify the best possible course of action, weighing the risks and benefits for him or herself. The most important point is that the following principles need to be applied as a system to gain the greatest potential benefit.

1 Minimise mechanical soil disturbance
There have been limited attempts to reduce tillage in the planting phase and no-till planting is still widely regarded as impossible.

2 Maintain organic soil cover
While green trash blanketing is common practice these days, the impacts of tillage or spray out of the previous crop in the fallow phase could be greatly reduced by immediate cover crop planting. Careful selection of a cover crop species mix will take into consideration the season and objectives of the cover crop.

3 Maintain living roots in the soil
Although some crops are perennial crop and maintain a living root in the soil for the duration of the crop cycle, planting a cover crop such as legumes immediately the fallow phase has started is good.

4 Greater plant diversity is better
Most crops in a healthy soil develop strong root system with huge potential to build soil carbon levels. While multi-species fallow management once every five to six years offer potential for soil improvement. It is important to introduce plant diversity into the crop.

5 Test and evaluate soil and plant health
Comprehensive soil sampling highlights several underlying nutrient issues that need to be addressed to enable biological function and enhanced production: There is much more than the nutrient management standard that can be done as various forms of soil and crop testing become more cost effective and accurate. The onus is on the grower to fully inform themselves of the nutrient requirements for their crop and to consider that Six Easy Steps is merely the starting point for a nutrient management plan and not the end point.

6 Alleviate compaction
With the challenges of an industry reliant on large, heavy equipment expected to work in wet conditions to maintain the industry’s only real attempt to address compaction to date is to move to controlled traffic farming with row and wheel spacing’s matched to spraying and harvesting equipment.

Building soil organic carbon can go some way towards not only increasing water holding capacity and nutrient cycling, but also helping the soil recover after a compaction event.

7 Reduce synthetic inputs
There are several ways that growers can replace synthetic inputs with products that will either do less harm to soil biology or perhaps even assist soil biology to proliferate. For instance, replacing superphosphate with soft rock phosphate and muriate of potash with sulphate of potash, both of which are “kinder” to the soil. Regular rotation crops can reduce the amount of applied nitrogen by as much as 80% of the Six Easy Step recommendations.

In addition to the recommendations above, two further options:

Biological amendments and stimulants.
In spite of the vast array of these products available these products are very unlikely to work in isolation without first applying all of the above recommendations. Buyers need to inform themselves about each product and why it is needed.

Integrating livestock into the rotation.
This provides the opportunity for a pasture fallow, the best way to build soil carbon, but is also likely to be the most difficult scenario for change due to the need for basic infrastructure such as fencing and water facilities. For the gurus of regenerative agriculture, livestock are widely thought of as the missing link in many modern cropping enterprises.