Is there a ‘middle way’ for conventional livestock farmers looking to adopt a more sustainable approach to soil management? Chloe Palmer finds out how biological farming might have some of the answers.
Finding sustainability solutions to increase the productive efficiency of farming systems is the focus for a group of Nuffield Scholars who believe the answers lie in soil.
Wil Armitage is a dairy farmer from Leicestershire and one of the group of Nuffield scholars which organised a conference in Market Harborough to explore the themes around healthy soil.
More than a hundred conventional and organic farmers and industry advisers attended the two-day event where they shared practical experiences of innovative soil management techniques.
Opening the conference, Mr Armitage described the biology of the soil as the ‘renewables nobody is talking about’, arguing ‘plant diversity and soil microbiology will take agriculture to the next level’.
Mr Armitage cited his goal of achieving ‘high feed integrity’ and he believed this would result from the way he managed his soil.
“Our aim should be to use plant diversity and mobilise the nutrients in soil. In today’s agricultural systems we are not making use of natural synergies and interactions and so we have lost many of the efficiencies provided by soil.”
His views are shared by Kevin Ashford, regional soil agronomist for Sustainable Soil Management. Mr Ashford points to the type of problem farmers needed to address.
“If a soil cannot hold the weight of a tractor or a hoof, there is a problem and it will restrict what can be done on those fields. We need to recognise the symptoms when soil biology is not functioning.”
Mr Ashford describes the role of the ‘four big soil cations’ – sodium, calcium, magnesium and potassium – which define many of soil’s characteristics.
“Calcium attracts more air whereas magnesium tends to bring in more water. It is possible to take advantage of these traits, for example by applying gypsum to clay soils as it will improve aeration.”
Using pH to guide lime applications on grassland can be misleading, says Mr Ashford.
“Active pH is only a measure of acidity, it does not tell us how much lime to apply as it does not take soil’s buffering ability into account.
“For example, limestone soils have a high buffering pH but may have a low active pH. They only require a little lime to restore them to optimum levels."
RB209 and the traditional soil analysis which it relies on also has limitations according to Mr Ashford.
“Do not be satisfied with a soil test which only measures phosphate, potash and magnesium. What is more useful is the total exchangeable capacity (TEC) which is a key measure of the soil’s ability to hold and exchange soil nutrients.
“The TEC can demonstrate you have a soil with the required nutrients but they are not available to the plant, so you need to mend the system.”
Mending the system was the theme of a three-hour presentation from biological dairy farmer Gary Zimmer, the founder of MidWest Bio-Ag. Mr Zimmer now employs consultants across the United States delivering advice to farmers on the principles of biological farming.
“I am not an advocate for organic farming but I promote best practices. Not all land can be farmed organically but there is a need for a balanced relationship with the soil which will produce a viable living for the producer.”
Mr Zimmer describes the crops grown across his own farm, Otter Creek, in Wisconsin.
“We are looking to create maximum diversity in our swards because this is good for cows and soils. We no longer graze the grass short as it does not help to fix soils. We must allow the plant to return organic matter to the system.
“If I can double my root system, I can cut my fertiliser and water bills in half,” he says.
In the UK, crops of lucerne are typically established and then cut for silage repeatedly before they are ploughed out four or five years later and re-seeded. In contrast, Mr Zimmer advocates leaving lucerne in the ground for just two years.
He said: “We use tight rotations which include legume swards and cover crops and we do not allow anything to get old on our farm. Our seed costs are just $50 per hectare (£33.50/ha) and we graze rather than plough in our cover crops.”
Mr Zimmer recommended ‘minimum disturbance’ to soils. He said: “We never work bare ground. As long as the tools are not hitting the soil, it is not a problem.”
Mr Zimmer said he looks to maximise water infiltration, plant diversity, nutrient cycling and the living root system when managing soils, defining soil health as ‘the capacity to function without intervention’.
He says soil health is not simply about what grows on the surface of the soil and he emphasises soils will not work without minerals.
“If the minerals are in the right balance, everything else will fall into place. The correct ratios between key elements are influential in relation to plant growth.
“Use sulphur to make the magnesium available to the plant. High calcium is the trucker of all minerals and it will cause the levels of all the other minerals to increase.
“Boron is the steering wheel and it is not possible to achieve the right levels of calcium without it. Always apply calcium with boron to avoid the risk of boron toxicity.”
Accurately assessing the levels of available minerals was not possible purely from a soil test, he said.
“You must test soil and plant tissue as these will tell a different story. A soil test will not tell you what the soil will produce, it only tells you what it contains. Soils giving a perfect soil test rarely grow perfect crops.”
Mr Zimmer highlighted the importance of sulphur to healthy forage crops, pointing out plants cannot make complete proteins without it.
He maintained insects were more likely to attack plans containing incomplete proteins.
“If I could take one chemical out of conventional farming, it would be ammonium sulphate,” he said, reiterating Mr Ashford’s recommendation to use gypsum as an alternative source of sulphur as it has the benefit of adding more calcium to the soil.
Mr Zimmer says his principles and approach are equally applicable to organic and conventional systems but the aim must be to minimise the use of chemicals.
“Build your soil and the biology will come. Every time you use an input think about what you will do differently to avoid using it next time.”
The availability of nutrients and minerals in the soil to plants is influenced strongly by pH. The graph (above) shows how the main nutrients and minerals required for healthy plant growth are most available at neutral pH ranges (6.5-7.5). Nitrogen is available across a broad spectrum of pH values whereas phosphorous is only readily available to the plant at pHs above 6.5. Elements which can be damaging to plants at high concentrations, such as iron, are more available at lower pH levels.