Arable News

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Direct Action – October 2013

Soil husbandry specialist Steve Townsend turns his attention to the fundamentals of no-till nutrition

Soil husbandry specialist, Steve Townsend of Soil First Farming turns his attention to the fundamentals of no-till nutrition. Re-learning our nutritional ABCsOf all the letters in the nutritional alphabet, one should stand head and shoulders above the crowd in our crop nutrition thinking. No, it’s not N. Or even P, K or S – important, though they are.C for carbon has to be the key. We know it’s the single most crucial component of plant life. But because it doesn’t come in a bag and because we know plants fix it from the atmosphere it’s all too easy to lose sight of it. Especially so in its contribution to the health and efficiency of our crops’ stomach – the soil. And the role it plays in facilitating the availability of another key nutrient we ignore at our peril – H20 – as well as nitrogen and all the essential minerals.Crop performance depends, more than anything else, on getting the right balance of all these nutrients with the primary cell building block that is carbon. This depends on the crop’s ability to absorb them from the soil in the right balance at the right time. Which, in turn, depends, on sufficient biological activity in and around the root zone to make them available as plant growth requires. Which ultimately depends on sufficient soil organic matter or humus – otherwise known as soil carbon.’Carbon first’ thinking is a fundamental part of a modern no-till approach. The ideal carbon to nitrogen ratio in autumn soil for optimum fertility is about 10:1. But crop residues contain very much more carbon than nitrogen. And cultivation is the best way of depleting soil carbon – by promoting oxidation of organic matter to CO2 – as well as nitrogen loss through mineralisation and leaching.So when we force air into the ground through ploughing or deep cultivation we’re actively promoting carbon loss and releasing fertility. We’re also seriously disrupting soil bacterial populations.No-till, on the other hand, preserves soil organic matter and bacterial activity. This is hugely valuable for soil fertility and structure, leading to much more consistent spring and summer nutrient availability from slow-release humus built-up by microbial activity – not to mention valuable overall fertiliser economies and environmental emission reductions.However, the more carbon-rich immediate soil environment no-till creates and the greater microbial activity it allows increases the need for nitrogen to maintain the best possible C:N ratio. That’s why direct drilled winter crops typically profit from a small amount of their nitrogen applied in the autumn. As they may also do with phosphate.It’s all about managing nutrition for both the soil and the crop. The crop needs nutrients which its roots can take-up readily in roughly the right ratios, aided by the soil bacteria they support. At the same time, the soil bacteria need encouraging if we are to maintain an organic store which can maintain the best balanced nutrient supply.Add to this the superior moisture-holding capacity provided by sufficient soil organic matter, and cultivation practice that optimises carbon nutrition also gives crops a huge advantage in buffering both flood and drought. This year, for instance, we’ve seen no-till spring cereals survive the dry July far better than other crops alongside them to deliver noticeably higher yields.By ensuring the best continual nutritional balance for the soil type and farm conditions, some of my no-till clients have also found it perfectly possible to cut 20-30 per cent off their annual crop nitrogen requirement without affecting yield.When we get nitrogen applications balanced with carbon levels and other key nutrients and the soil biology and chemistry working in harmony we find far fewer problems with crop disease too. This is mainly because the nitrogen is being used so efficiently by the crop that there is little, if any, free nutrient available for fungal growth.*Steve Townsend explores other important aspects of nutrition in his next column. He is more than happy to discuss any tillage or soil management issues, interests or concerns with Farmers Guide readers by e-mail on [email protected] or by phone on 01452 862696.


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