Dairy Farming Sustainability – the answer is in the soil

David Atherton of Thomson & Joseph

Challenges

Sustainable dairy farming is all about producing milk in a way that does not damage the environment—but more than that, brings positive benefits to health all the way up the food chain from soils to human consumers.

Human life is dependent on soils, which supply 95% of our food.  But soils are under pressure like never before, from erosion, compaction and poor soil health, which affects fertility and ultimately crop yields and nutritional quality.

Soil health, which is an indication of soil life, is essential for the proper functioning of soil including:

• Nutrient release from soil reserves
• Improving water quality
• Providing a habitat for biodiversity
• Sequestering carbon
• Creating a stable soil structure
• Supporting high yields of quality grass

For the past 60 years we largely ignored soil health and adopted a “route one” approach to supplying crop nutrients directly from slurry and bagged fertiliser.  This has been an extremely successful model, particularly for growing more grass.  But it has come at a price to the environment.  Water quality has deteriorated, and Greenhouse Gas Emissions from livestock production continue to be a significant contributor to UK emissions.  With a focus on moving towards carbon neutral farming, which is at the heart of the NFU’s “Achieving Net Zero – Farming’s 2040 Goal” strategy, there has been a renewed interest in   restoring soil health, primarily for 2 reasons.  Firstly, soils have a tremendous capacity for sequestering carbon. Soils contain 3x more carbon than all the vegetation on the planet, including trees and 2x more than is in the atmosphere. But increasing carbon “lock up” in soils is dependent on a living, healthy soil.  Secondly, a biologically active “open” soil has the ability to store and filter water, thereby reducing surface run-off and associated pollution.

Soil compaction

Soil compaction is the single most significant threat to soil health and growing more grass and can reduce yields by up to 40% in severe cases.  Even moderate compaction can reduce grass growth rates by around 25%.

Some of the causes of compaction are well known, such as Cattle Poaching and Heavy Machinery.  Less well known is the effect of Heavy Rainfall (short, sharp showers), Slurry and Soil Mineral Imbalances.

Effects

The main effect of compaction is reduced grass growth, but there are many other consequences, including:

• 2.5 X more Nitrogen fertiliser to grow grass
• Shorter growing season
• Grass feeding quality is lower, due to reduced nutrient uptake
• Less soil life due to reduced oxygen levels
• Poor rooting
• Increased weed burden

There are also adverse environmental consequences including:

• Increased risk of nutrient run-off into water courses
• Flooding due to restricted drainage
• 30% higher Nitrous Oxide emissions (Greenhouse Gas x300 more potent than Carbon Dioxide)

But the single most important effect of compaction is to kill off soil life, including earthworms.

Three inputs are essential for soil life:  air, food and water.

Food and water are rarely limiting, it is COMPACTION squeezing AIR from the soil and suffocating soil life, that is the greatest threat.

The only way to check the depth and extent of compaction is to dig a hole!

Soil Health Improvement Plan (SHIP)

Soil has three distinctive fractions: physical, chemical, biological

all of which play a role in compaction.  The soil health improvement plan has been developed to tackle each of these fractions.

Physical (Soil) – AERATION/PAN BUSTING on a regular basis (spring and autumn) to disrupt surface compaction (top 6”), improve surface drainage, encourage rooting and allow AIR penetration in support of soil life.

Chemical (Nutrients) – SOIL TEST for lime and available Phosphorus and Potassium, but also measuring Organic Matter and Calcium and Magnesium balance.

Biological (Life) – AEROBICALLY DIGEST SLURRY with microbial inoculants such as BioAg’s DIGEST-IT, to improve  fertiliser nutrient status, reduce Ammonia and switch the microbial balance away from Anaerobic (putrid and smelly) to Aerobic, with good AIR breathing bacteria.

Action

Taking action to reduce compaction by improving all three soil fractions (Physical, Chemical, Biological) creates the conditions for soil life to flourish and for health to be restored, to the benefit of:

• Higher Grass DM yields and nutritive quality
• Lower Chemical fertiliser applications, as nutrient utilisation from soil and slurry is improved
• Better environmental outcomes with a reduced risk of surface run-off and water pollution, and Nitrous Oxide emissions.

Soil Health Improvement Plan (SHIP), a step in the right direction to bring life back into soils in support of sustainable and profitable dairy farming.