OSR Establishment – After the heatwave: Part 2
13 Aug 2018
Expanding on the advice from Pete Berry and Clare Tucker in Part 1, here cultivations expert Philip Wright, of Wright Resolutions, shares some more detailed advice on seedbed preparation and moisture levels.
Cultivations by soil type
High shrink/swell clay soils currently cracked deep are well on the way to being self-structured, especially if there are a good number of relatively narrow cracks. These are a sign of better structure than a few, wide cracks with highly compact blocks between.
“Shallow “chip” cultivate the surface and put a few clods into these cracks”
Rather than moving such soils deeply at present, a better option is to very shallow “chip” cultivate the surface and put a few clods into these cracks, where they will help to keep them open in places as the soils wet up and swell. In turn, this then will produce more cracks, and further help the self-structuring. Avoid making too fine a surface though which would be prone to slumping and sealing.
On high sand or silt/sand content soils which are not naturally cracking, these actions are less appropriate. Establishing oilseed rape into such a surface without deep loosening may be an option, if deep loosening would produce large boulders and a very poor surface tilth and seedbed.
Where soils have slumped due to the wet spring, direct drilling of WOSR is not advisable as roots will struggle through these layers. Here, loosening with low surface disturbance to just below the problem depth can be achieved if some rain helps to soften this layer, allowing it to crack rather than be lifted out as large lumps. Sufficient tilth for the seeds can be helped by a leading disc ahead of each loosening leg – a narrow fluted, wavy version could provide more tilth around the seed for efficient germination.
In all cases, where soils have had little or no rain for weeks and are very dry to depth, avoid putting seed into such conditions as this is a very high-risk strategy.
Some rainfall – enough to dampen the surface and germinate the oilseed rape, allows it to grow into dry soil beneath. A subsequent dry period risks germinated seed having no moisture reserves and burning off. Established seed into dry soil below relies on more rain after the crop germinates to keep it alive.
I would suggest not drilling the crop until the dry conditions have passed, as it is then highly likely to burn off if the above situation occurs. A balanced view and risk strategy may be better – drill an amount of the crop that is acceptable to lose if the weather conspires against us.
“Where rain is more plentiful, and the soil becomes moist to a reasonable depth – 15/20cm – then risk is low”
Where rain is more plentiful, and the soil becomes moist to a reasonable depth – 15/20cm – then risk is low and also cultivation is easier, so here, where compacted layers exist, these can be loosened (provided large clods are not lifted and exposed) when drilling in the usual manner.