Soil husbandry specialist Steve Townsend examines how best to balance the extra soil carbon in no-till nutrition
Soil husbandry specialist, Steve Townsend of Soil First Farming examines how best to balance the extra soil carbon in no-till nutrition.A better balancing actAlright, as we saw last month, carbon-building has to be firmly at the forefront of our modern no-till thinking. And we know this means feeding the soil bacteria as much as the crop. That way we make the very most of below-ground biological activity and the precious organic matter around which it revolves. This, in turn, builds fertility and resilience, allowing nitrogen applications to be cut by a good 20 per cent or more after a few years while reducing agronomic risk by at least as much.But, like all the best things in life, this doesn’t happen overnight or without effort. Specifically, it needs care, commitment and, above all, an understanding that no-till nutrition is quite different from fertilisation under any regime involving more than very minimal cultivation.The more biologically-active soil we’re creating in building a more carbon-rich growing environment increases the need for autumn nitrogen and phosphorus, in particular – mainly because to fix carbon you need one unit of N for every 10 units of C, and one unit of P for every 60. So the more C you have, the more N and P you need to maintain the most productive carbon ratios.As a direct consequence, I find it’s typically best to transfer 20-40kg N/ha from the spring fertiliser programme to the seedbed for a second cereal and around 10kg N/ha for wheat after oilseed rape. This is especially important where land is being brought into no-till or straw is chopped and left on the surface.In exactly the same way, soils with a good phosphate index may well need extra autumn phosphate – best applied at the three-leaf stage when crop demand is at its highest, rather than to the stubble or in the spring – where crops are established under a no-till regime.Otherwise, it’s all too easy for the greater biological activity we’ve stimulated to hoover-up all the immediately available autumn N and P, leaving insufficient for the developing crop. The net result is slow emergence and poor early root development with series knock-on effects on both the crop’s ability to shrug-off slug attack, and develop and support productive tillers into the spring.At the same time, of course, sufficient attention to autumn manganese and zinc supplies – needed for the most efficient P utilisation – is also crucial in the early days of no-till adoption.We mustn’t neglect calcium, either. Without tillage, it tends to sink through the soil profile. Until we’ve built up our earthworm population to effectively bring it back to the surface and maintain the most efficient pH in the root zone that is. Just the job here, I’ve found, are some of the new pelleted limes on the market these days.Equally, if we struggle to maintain the same quality in milling wheat and malting barley since adopting no-till it’s usually an indication that some extra sulphur will be valuable with the spring N.Additional foliar micronutrients – particularly phosphite-based – can be a valuable way of achieving the best no-till yields and crop quality in many cases too. At least, until the benefits of organic matter-building through altogether better and more sustainable soil management are increasingly realised.
Not injecting large amounts of air into our soils every autumn has important nutritional implications – both immediately and over the long term. As does leaving trash on the surface, maintaining appropriate rotations, effective cover cropping and all the other modern no-till essentials. We need to understand these as fully as we can if we are to get the most from the regime. Costs come under Steve Townsend’s spotlight 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 email on [email protected]or by phone on 01452 862696.