Crop Rotation Considerations & Planning for a Better Season
After an awful 2020 growing season, it is time to consider cropping for next year (we hope it will be much kinder than the last!). Unfortunately, many growers were caught out last season with the wet autumn, which meant minimal winter cropping and many Oil seed rape crops did not even make it that far. This forced farmers to grow anything they could and has caused rotation headaches further down the line.
Managing Grassweeds in Your Rotation
Whilst it has generally been a good year for blackgrass control this is generally because a large percentage of cropping has been in spring and shows the benefit of cultural control to the rotation. Sadly, whilst everyone will be keen to forget the miserable conditions and drill crops early this autumn, Blackgrass does not forget and could catch growers out looking to drill early. For those growers now on top of Blackgrass or at least have some ‘cleaner’ fields there could be an argument to start drilling a little earlier. For some still battling Blackgrass, spring cropping such as Barley, Oats and Maize are all good choices for cleaning up high populations over several years. Brome is something else to consider, whilst much of the control is similar to Blackgrass for Sterile/Great brome, it is worth remembering Broadway Star herbicide is still effective in Winter Wheat which is not permitted in Barley or Oats. Meadow/Soft/Rye Bromes are becoming more problematic and must not be incorporated straight away after harvest.
Addressing Take-all Disease Through Rotation
Take-all can be a devasting disease which will affect yield particularly at the end of the season, once all the growing cost has already been incurred. Many growers will be considering Winter Wheat after a spring wheat or barley after last autumn and should consider the take all risk, particularly on lighter soils. The pathogen thrives on oxidising manganese, once oxidised the manganese is no longer in plant available form and causes a deficiency, which should be a management consideration. Biological seed drenches are a good way of fighting off the disease naturally than using an expensive chemical seed dressing. AF Bioplus T contains several species of bacteria and fungi which is selected for the suppression of growth of pathogens and produce growth promoting compounds in and around the root zone. Oats are a good way to suppress take-all whilst avoiding unreliable ‘true’ break crops, the release of ‘Avenacins’ actively suppresses this disease giving the opportunity to grow a Wheat crop. The issue of course is the low value of oats on the grain market which means other crops have been more favourable until more recently. It is also not advised to grow Oat crops if wild oats are a big problem on farm.
Considering OSR and Other Break Crops
Unfortunately, many growers are now looking for alternatives to growing Oilseed Rape as it has proven too risky to grow now from CSFB pressure. Although, some are persevering in low cost / low risk ways of growing it such as early drilled home saved seed and delaying herbicides until the latest possible time. Early drilling requires pre thinking about the preceding crop such as winter barley or whole-crops taken in June/July, growers should be careful not to drill too early opening the door to other pests such as cabbage root fly and more CSFB larvae later on. Dropping OSR could be a blessing in disguise, as brassicas lack Arbuscular Mycorrhizal Fungi (AMF) association, greatly increases slug pressure and requires high input and management. This makes it a poor crop of choice for sustainability and soil health particularly in close rotations. Oats as previously mentioned offer a low input option and will build AMF as well as reduce slug pressure, they are also aggressive rooters and suit strip or no-tillage systems. Alternative true break crops include, Beans/Peas, Linseed, Maize, SBeet, Quinoa, Borage, Soya, Canary seed, Mid-tier options as well as grass leys. Most growers are now allocating some (if not all) of the OSR acreage to pulses and or oats, the rest is dependent on local opportunities and soil types. There are numerous niche crops, hopefully in future Hemp will be a viable commercial option for growers which offers a low input spring break, more processing and government backing is required for this to happen. Grass leys and grazing is becoming more popular, perfect for improving soil structure, organic carbon, biological activity and also pest/weed problems.
Benefits of Extending Crop Rotations
Extending rotations wider, growing Wheats, Barleys, Oats, Pulses with cover crops and incorporating grass leys means pest and disease problems are reduced and over time soil health and sustainability will improve.
Integrating Cover Crops into Rotations
The benefit of cover cropping is completely dependent on the success of establishment and time in the ground. The bigger the cover crop and more time it is actively growing the more biology is being stimulated, bigger roots and more nutrient uptake taken place. If an expensive mix of species is grown but only reaches 10cm from the surface the benefit is only small especially if it has only been in the ground 4-5wks. Planning the rotation around establishing cover crops is now more of a consideration similar to OSR especially in northern parts of the country. Sowing a cover crop before a spring crop the following year allows longer for the cover to be in the soil. Equally growing crops which come off early provide opportunities to grow bigger covers which will provide larger benefits to the soil and rotation. With dropping OSR from the rotation it is also possible to start using brassicas in cover crops, particularly mustard which is very quick to establish. It is important to consider speed of development with sowing date of the cover, later sowings requiring quicker establishing species. Drilling ‘on the green’ into living covers should only be advised once the soil biology has been improved and stimulated over several years in order to have the capacity to decompose and digest the organic material and avoid starving the crop being established. A way to negate the possible effects on the following crop establishment from a large amount of green material could be to use a low rate of starter fertiliser and biological seed drench to aid establishment.
