Latest News - April 06
24.04.06 - MAKE MOST OF ORGANIC MATTER
Improving the soil’s organic matter levels is the key to good soil management, as it both helps its structure and improves its fertility, cultivations specialist Steve Townsend told a Simba/Southern Harvesters seminar at Petersfield, West Sussex.
But farmers need to take care when incorporating stubble and chopped straw, and ensure they do not bury it too deep, or they risk causing problems that may damage soil structure and inhibit crop performance.
Organic matter – typically 5% of the total soil composition – has a huge impact on fertility and the soil’s ability to maintain structure, he says. Achieving good levels could also be financially beneficial:
“Several of my clients report that their fertiliser bills have dropped by 20% because they have incorporated chopped straw and stubble and built soil fertility and that is now helping feed the crop.
“Residues need to be incorporated in the top few inches of soil – where the bacterial activity is greatest – so they are broken down efficiently. If you bring up last year’s stubble when cultivating this autumn then you have buried it too deep.
“Burying residues too deep risks causing anaerobic conditions in the root-zone. In addition the anaerobic bacteria will extract air from the soil and cause it to “go tight”. As a result the crops do not benefit from the release of nutrients and may struggle to develop effective root systems”.
Increasing worm numbers was also important, he added, as they helped incorporate and process crop residues, while also aerating the soil, with the holes created by deep-burrowing species also assisting drainage
Similarly the holes left by plant roots helped improve structure. For this reason he advocates using cover crops whenever the land is not being used to grow cash crops:
“Select the cover crop best suited to your soil types. Their leaves prevent rainfall landing on bare soil and causing capping or erosion, while their roots both stabilise the soil and continue the aeration process.
In financial terms, the cost of establishing and incorporating them normally offsets the contribution they make to soil restructuring and nutrient recycling”.
CREATING a seedbed in as few passes as possible should be any arable farmer’s key target, Steve Cook, agronomist with Hampshire Arable Systems suggested at a joint Simba/Oakes Brothers seminar near Kingsclere, Hampshire:
“You need cultivators that can work on ploughing, in reduced tillage systems or – in the case of drills – to establish the crop direct.
“Farmers have a tendency to do too much work. Many of the chalk-based soils in Southern England are self-structuring, so there is no need to work deep. If you only have a few inches of topsoil then work with that. Going any deeper risks bringing stones up into the seed-bed”.
The benefits of minimising cultivations are apparent in both dry and wet years, he says. In dry years you minimise the risk of moisture loss, while in wet years lighter workloads would improve timeliness and help them get drilled up and so avoid having to complete fieldwork late in the autumn or in unsuitable conditions.
