Soil health at the core of suckler beef group's recommendations

That was from the report from a farmer-led group discussing how a modern suckler-based beef industry could play a major role in farming's efforts to become a net zero business, with a focus on carbon sequestration and reduction in greenhouse gases.

Within the report, soil health was seen to be a key area of focus – and it will also be a likely focus area also for the imminent arable, sheep and dairy sector reports being put to government.

Recognising the urgency of the situation, Scotland has responded with ambitious targets, aiming to reduce its greenhouse gas emissions by 75% by 2030 and become a net-zero nation by 2045.

In order to ensure that these targets can be met, every sector including the farming industry will be required to implement effective and high impact measures to drive down total greenhouse gas emissions and protect already existing carbon stores within our environment.

A recent study showed that the Scottish suckler beef sector had the potential to cut greenhouse gas emissions by 24% to 39% and that the adoption of 10 different on-farm measures could lower greenhouse gas emissions per unit of output by almost 38%. Soil health was just one of those, but was inter-related to other focus areas, such as grassland improvement and the use of legumes.

Summary of soil health focus in the Scottish Suckler Beef Climate change group report:

This aims to encourage participating businesses to take steps to protect and maintain existing soil carbon stores on their farmland, increase soil carbon sequestration where this is possible and reduce greenhouse gas emissions from their production systems, or as a result of soil carbon losses through poor farmland management by:

* Improving the health of the soil through better management of soil acidity, soil organic matter and carbon levels, and by preserving or restoring good soil structure and enhancing microbial activity;

* Better targeting field management to enhance input utilisation and reduce fuel use.

The management options proposed form soil health will also benefit the wider biodiversity by enhancing suitable habitats for a wide range of animals and soil micro-organisms, all of which rely on and contribute towards the healthiness of soils, said the report.

It added: "It is relevant because soil is one of the most important resources available to any farming business, relying on a combination of different and complex physical, chemical and biological factors and processes, all of which are crucially important to preserve good soil functioning.

"If managed properly, healthy soils not only provide a suitable medium to facilitate good grass and crop growth as well as a habitat to a wide variety of animals and micro-organisms, but they provide an effective solution for storing carbon long-term and can help to reduce the impact of flooding or drought thanks to a greater water infiltration and retention capacity.

"Their ability to draw carbon into the ground means that carbon losses can be minimised during the event of wildfires, where vast quantities of above-ground carbon stored in vegetation can be released.

"With climate change causing increasingly more frequent extreme weather and weather-related events including wildfires, it is therefore crucial to maximise below-ground carbon storage.

"A good soil structure with suitable aggregation, ie sufficient porous space, is important to not only facilitate movement of water and air into and through the soil, but it enables for nutrients and minerals to travel freely to where they are required, and for plants to grow extensive root systems that can access additional reserves of water, air and nutrients.

"Organic matter and the carbon contained within help to stabilise such a soil structure and provide a habitat for important soil life, micro-organisms and fungi to thrive and make nutrients and minerals available to plants in return for sugars which are released as root exudates into the soil by actively growing plants capturing carbon from the atmosphere via photosynthesis.

"A healthier soil enables greater soil microbial and animal activity which helps to improve the condition of the soil as a growing medium and to make more nutrients and minerals available to plants. The plants experience improved performance as a result which increases their growth and with it the level of photosynthesis being carried out.

"This leads to greater quantities of carbon being captured from the atmosphere and drawn into the plant and soil to provide important sugar food sources, which in turn maximises the flow of carbon from the atmosphere into the soil, thereby boosting soil carbon sequestration.

"It is, therefore, absolutely crucial that farmers take steps to preserve the soil health of their farmlands. This will help protect and maintain current soil carbon stores and encourage additional carbon capture from the atmosphere for long-term soil sequestration where possible.

"Good soil health will also promote better plant performance, enhance input utilisation efficiencies, and support local biodiversity and soil life.

Correcting soil acidity

Relevance: The acidity or alkalinity of soil greatly depends on the base rock material that the soil is made up of. Calcareous parent material typically leads to very alkaline soils with a higher pH whereas peaty base material causes the soil to be acidic and have a lower pH.

Rainfall is naturally acidic and can cause further acidification of soils, particularly in areas with high annual precipitation. Sandy soils are more likely to experience a faster rate of acidification than heavier clay-based soils, and a drop in pH can be further accelerated through the application of synthetic nitrogen fertiliser.

If soils are too acidic, they limit the growth, development and productivity of plants due to a reduced nutrient and mineral availability as a result of restricted soil microbial activity. This affects overall sward performance both in terms of feed quality and total output, and can cause poorer input utilisation efficiency, thereby increasing the emissions intensity of sward production along with the carbon footprint of the cattle enterprise.

Ultimately, this may result in the need to purchase additional feed off-farm to make up the shortfall in home-grown feed production which further impacts on the emissions intensity of the farming enterprise and reduces overall cattle profitability.

Soil acidity can cause additional nutrient problems within systems seeking to supply N from within the sward via legumes because a low pH can either prohibit or severely restrict the proper development and functioning of the rhizobia bacteria responsible for forming the root nodules required for fixing N.

Acidic soils are also believed to be the main source of agriculture-related nitrous oxide (N2O) emissions and recent research has identified the correcting of the soil pH to be a crucial factor to reducing emissions of this potent greenhouse gas.

With regards to the potential for soil carbon sequestration, restricted soil microbial activity as a result of a lower soil pH not only limits sward performance, but reduces soil carbon sequestration.

Aim: Within the proposals, this management option aims to encourage participants to establish baseline information about the current pH level of their farmland soils where this is currently unknown, and to correct soil acidity issues on any fields receiving inputs where this is required.

This will contribute towards overall soil and microbial health to help enhance and increase soil carbon sequestration, and ensure that the plants are able to efficiently and effectively utilise any nutrients and minerals available within the soil or being added onto the farmland in order to reduce the emissions intensity of the cattle enterprise, along with any associated input wastage.

Assessment option: Participating businesses should identify the current soil pH of their improved farmland areas and correct soil acidity issues on any fields receiving inputs in line with recent soil analysis results and lime application recommendations.

Increasing soil organic matter

Relevance: The loss of soil organic matter is believed to be one of the major factors causing the increase in anthropogenic carbon dioxide emissions over the last 50 years.

It has been recognised by a range of organisations, including the Scottish Government, as a key issue requiring attention due to its ability to not only enhance food and biomass production, but also because soil organic matter is a crucial factor in facilitating soil carbon storage and sequestration, contributes towards important habitats for local biodiversity, reduces soil erosion, maintains good soil structure, and helps to regulate water flow and quality.

Soil organic matter (SOM) is important for storing significant quantities of carbon as it is the main medium for soil carbon storage. It typically contains a large proportion of carbon which can make up as much as 58% of the total mass of soil organic matter.

The majority of organic matter is usually present within the soil in a stable form that allows for potential long-term carbon storage depending on the field management. As such, the levels of SOM and soil organic carbon (SOC) are closely correlated and provide a good indicator for overall soil health and the contribution of different soils to mitigating the effects of global warming.

Aim: If implemented this management option aims to encourage participants to identify current soil organic matter levels of their farmland through soil analysis and focus on field management that can increase the proportion of organic matter within their soils.

This will contribute towards maximising long-term soil carbon storage and potentially further sequestration, and help to preserve or reinstate good soil structure for optimum water, nutrient and air holding capacity along with a greater water infiltration rate.

A greater nutrient retention and availability will furthermore improve overall soil health and boost plant growth and development, thereby ultimately helping to reduce the emissions intensity of the cattle production system by allowing plants to better utilise nutrients and reducing input levels and/or wastage.

Assessment option: Participating businesses should identify the current soil organic matter content of their improved farmland areas and take steps to maintain existing stores and, where possible, increase their soil organic matter levels.

Applicability: This management option is applicable to suckler herds and finishing units.

Minimising soil disturbance

Relevance: The extent to which soils can capture carbon for long-term storage greatly depends on the tillage system that is adopted on the farm and the resulting level of soil disturbance that is impacting on the soil structure and health.

Research has found that conventional tillage could lead to the loss of 80% of the carbon that may be accumulated within the soil over a period of one year, whilst reduced and minimum tillage appeared to result in much lower losses of 12% and 2%, respectively.

Another study identified conventional tillage as having a net warming potential of 26% to 31% higher than zero tillage, and concluded that zero tillage systems may play an important role in reducing greenhouse gas emissions due to enabling increased soil carbon sequestration and leading to reduced emissions associated with fossil fuel use.

This is supported by evidence from a study that found soil carbon levels to be twice as high in the top 5cm of soils where no tillage was applied compared to a conventional tillage system, whilst soil carbon levels at a depth of between 5cm and 15cm appeared to be 10% higher for no-till than for conventional tillage.

When compared to zero tillage systems, conventional tillage has furthermore been found to negatively affect the activity and structure of soil microbial communities, thereby compromising the health of soil life and reducing the levels of soil carbon and nitrogen.

Mechanical soil disturbance as a result of field tillage also negatively impacts on the structural integrity of the soil which can greatly affect the air, nutrient and water holding capacity, and lead to a poorer water infiltration rate, which in turn can make soils less resilient to drought or flooding issues.

Switching to a reduced tillage system can improve the ability of the soil to infiltrate and retain water, thereby enabling it to better cope with periods of lacking or excessive rainfall.

In order to maximise soil carbon sequestration and minimise greenhouse gas emissions associated with field cultivation, it is therefore crucial to review tillage systems currently being adopted on suckler beef farms, and to encourage the move from conventional to reduced/minimum and ultimately no-tillage strategies.

Aim: This management option, if adopted, would encourage participants to adjust soil tillage systems by reducing reliance on heavy-tillage implements, and reduce mechanical soil disturbance where possible in order to optimise soil carbon sequestration for long-term storage.

It can also preserve or reinstate good soil structure for optimum water and air holding capacity along with a greater water infiltration rate. This will contribute towards overall soil and soil microbial health and the reduction in net greenhouse gas emissions from the cattle production system.

Reduced tillage will furthermore reduce fuel and machinery use which leads to a reduction in the emissions intensity associated with field management whilst lowering the cost of production to the business.

The scheme would recognise that many farming businesses across Scotland apply a field management system that includes ploughing as part of a multi-annual crop rotation or reseeding programme instead of carrying out annual ploughing.

This delivers distinct benefits compared to annual ploughing in terms of greenhouse gas emissions. Based on a 2013 study, a business switching from annual ploughing to ploughing every five years as part of a five-year crop rotation and/or reseeding programme, could potentially reduce the proportionate losses of the annually captured and stored carbon from 80% to 16% per year.

Although this still exceeds the measured losses from reduced tillage (12%) and zero-tillage (2%) systems, it results in significant carbon sequestration benefits by potentially quadrupling the quantity of carbon left in the soil when compared to annual ploughing.

Assessment option: Participating businesses would review the tillage system that is applied on their improved farmland on an annual basis, and take steps to reduce tillage where possible.

For the purpose of this management option, the following definitions would apply:

* Conventional tillage: The inversion of soil, possibly along with a previous crop or crop residue, involving soil disturbance to a depth greater than 10cm; typical implements include ploughs and disc or power harrows amongst others.

* Reduced/min-till: the manipulation of all or parts of the topsoil layer, possibly along with a previous crop or crop residue, involving soil disturbance to a depth of no more than 10cm; typical implements include cultivators and rotavators along with harrows operating to an adjustable working depth amongst others.

* Zero tillage: no inversion of the topsoil or any previous crop (residue); soil disturbance limited to topsoil slotting and scratching, or subsoil drainage and/or compaction management; eligible field management includes direct-drilling, tine-harrowing and aerating, as well as sward-lifting/sub-soiling/mole-ploughing with subsequent rolling to close over gaps caused by subsoil cultivation.

Applicability: A management option for both suckler herds and finishing units.