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  1. In the last few years it has become increasingly apparent that the concept of placing the autumn N and P fertiliser alongside the seed is being widely adopted and generally accepted as best practice for the establishment of winter oilseed rape.

    However, is placing fertiliser in this scenario based on agronomically sound judgement and what are the other options available, asks Tim Kerr, Hutchinsons fertiliser manager.

    “Phosphate is considered a very important nutrient for crop establishment; phosphate helps to fuel all the major processes in the plant that require energy. In the first 60 days from emergence oilseed rape will require around 15% of its total P requirement. The amount may not sound so significant; however the mechanics of P uptake are why we lend so much importance to P as a starter fertiliser,” he says.

    Mr Kerr points out that phosphate is an immobile nutrient in the soil. “The plant relies on extracting that 15% of P requirement from a small fraction of the total soil.  During the first 60 days the roots will only reach around 5% of the topsoil, and P absorption relies on direct root contact with the soil for it to be taken up by the plant.”

    Tim Kerr

    “Therefore enriching the soil in the immediate rooting zone with water soluble phosphate or plant available P will help to maintain critical P levels in the aforementioned rooting zone over this period.”

    The benefits from placing nitrogen close to the seed may appear less obvious, yet still there are advantages to the system, he adds.

    “Most starter fertilisers that contain nitrogen and phosphate are based on ammonium phosphate. However, there is a proven synergistic effect on plant uptake of phosphate where nitrogen is present in the ammonium form. This may be partly down to a localised decrease in pH where NH3 and P are applied together.

    “This effect is most pronounced in soils with a high pH - increased P absorption when it is applied in conjunction with nitrogen fertiliser, will be partly due to an enhanced physiological capacity of roots to absorb P, brought about by greater root development in the soil with a concentrated area of nutrients from an NP starter fertiliser.”

    Mr Kerr says that better root establishment will improve a plant’s ability to forage for nutrients and water by giving it access to a greater proportion of the soil – and in turn this will ensure yield potential is maintained from the outset.

    Conversely, he points out that in a phosphate shortfall scenario, the yield potential of the crop will be reduced irreparably. “Remembering that phosphate is effectively immobile in the soil and recognising the dual benefits of placing N and P together – there is a compelling case to opt for one of the starter fertiliser options available to growers.”

    Primary_P_OSR

    “DAP (18-46-0) is probably the most commonly used product for this purpose. This is an ammonium phosphate and therefore will offer the benefits discussed earlier, however the ratio is only really appropriate for soils at index 1 or below.”

    At index 2 or above, Mr Kerr suggests alternatives that will supply less P without compromising on the amount of N applied. “If it is not possible to place the fertiliser, then incorporation into the seedbed will be the next best approach.”

    “Micro granular fertilisers are an option based on ammonium phosphate, but it is worth checking that you are getting what you want or need.”

    The main advantage of micro-granular products is the increased availability of nutrients through a much greater surface area, he adds. “Applying the same weight of a conventional granular fertiliser provides up to 400% less surface area of fertiliser. Consequently microgranular products can buffer the soil’s capacity to supply P much quicker than a standard 2-4mm sized granular fertiliser.“

    He observes that five years ago it was not that easy to find seed drills with an option to apply fertiliser along with the seed. “However today the opposite is true – and the choice of application equipment is both wide and relatively low-cost.”

    “When it comes to additional application equipment, the investment required to place liquid fertilisers can be the most significant. However, this is not always the case – and those used to handling liquid fertilisers may already have some of the necessary components.”

    “Liquid fertiliser in solution is by definition 100% soluble and therefore rapidly available. Phosphate is again normally supplied in the ammonium phosphate form, offering the combined benefits already mentioned.”  

    “Solutions are also available in different ratios, offering the flexibility to apply appropriate quantities of P along with the N.  Liquid fertiliser is normally applied in bands – delivering concentrated doses of N and P in and around the rooting zone.”

    Whilst this is by no means an exhaustive list, he points out that the benefits of fertiliser application techniques based on a sound, science based understanding of nutrient availability are sufficiently well understood for the farming industry to invest in and adopt.

  2. The fight against black-grass continues unabated with astonishing levels of infection across much of the country. Experts recommend that the key to reducing these massive black-grass populations for next year is to drastically reduce the number of seeds that are returned to the soil.  

    Incorporating cultural control is critical within the success of any of these approaches to reduce the pressure on herbicides, and one agronomist has decided to take this approach further and is trialling an innovative method of control – weed wiping.

    Mark Spicer, managing director of Norman and Spicer Agriculture, based in Daventry and part of the Hutchinsons Group, has been trialling a range of experimental approaches for  a number of years looking for alternative methods  for tackling increasingly difficult to control weeds mainly black-grass numbers, but also rye-grass and wild oats.

    “We have reached crisis point in controlling black-grass; chemical solutions are under increasing pressure from resistance and any cultural method of control that can reduce black-grass numbers and thereby the pressure on herbicides has to be a positive, and warrants further investigation.”

    “We know that if we have 100 blackgrass plants/m² that equates to a seed return of approx. 1.5t/ha, so any reduction in this seed return has to be of benefit – particularly one that does not require a substantial financial outlay.

    Mr Spicer started looking at the prospect of weed wiping a few years ago, after researching the concept on the internet. “I knew that American farmers were practising weed wiping which is exactly what the name implies, wiping weeds with herbicide from a boom on the back of a sprayer.  

    “So I spent some time looking at how this would work here on some of the more difficult to control weeds, black-grass, oats and rye-grass and this has led to a collaboration with Boston Crop Sprayers. (BCS)”

    “A weed wiper is a kit basically attached to the back of the boom which is made up of a row of sponges that are gravity fed with the herbicide. The kit is currently manufactured by an American company, Schnuker, and is not yet available in the UK, but as the only agency in England, we are hoping that the first unit will be arriving very soon which will allow us to experiment with it fully,” says David Hildred, managing director of BCS.
     
    Weed wiper

    “We were interested in the concept, not just from a cereals weed control concept, but we think it would be interesting to try weed wiping in a range of crops such as brassicas and sugar beet.”

     “A farmer in Bedfordshire had a weep wiper retrofitted to his conventional sprayer to apply glyphosate at a concentrated rate to destroy wild oat and black grass seeds ahead of the next crop, and there is no doubt that we have been able to kill off a large amount of the black-grass and prevent a huge seed bank being returned to the soil. We need to do some further work to quantify this, but the reduction is significant enough to warrant spending more time on the concept,” says Mr Spicer.”

    “What we have found is that timing and speed of application of the glyphosate to the weed  is critical; the black-grass has to be in flower and not yet filled, and the weed really needs to be wetted so a higher speed works better. “

    There are crop factors to take into account, he adds. “There needs to be a gap between the weed and the crop - to ensure that the herbicide is not wiping the crop at the same time as the weed, so a good PGR programme should be used when considering weed wiping.

    “This is only the second year of trialling the approach, so no doubt we still have much to learn about optimising the efficacy and also defining what levels of control we are able to get, but work that we have planned over the next year with the co-operation of the technical team at Hutchinsons should put us in a better position to have a clearer picture.”

    Ruth Stanley, campaign manager with BASF, is interested in the weed–wiping concept having seen the resulting black-grass control it offers. “Black-grass control is so important to get right as populations are increasing across the UK, so anything that offers a glimmer of hope is exciting. It’s great to hear about different innovations that are being tried. “

    Weed wiping

    “At BASF we are interested in any proven innovations and consider alternative cultural solutions that will potentially reduce pressure on chemicals, allowing them to work better.”

    To see how the weed wiper works go to the Norman and Spicer facebook page on ttps://www.facebook.com/normanandspiceragriculture/?pnref=story

  3. After the cold and wet spring of 2016 many are struggling to see a benefit in the use of cover crops. Are they a valid addition to arable rotations, or just an enigma?

    “Results in the field are a far cry from the promise of transformed soil structures, biological enhancements and significant improvements in weed control that were promoted so strongly,” says Dick Neale, Hutchinsons technical manager.

    “For many, the result has in fact been wet, cold, slug infested seedbeds that refused to dry. “The high cost with little apparent return will cause many growers to question the value of using cover crops this coming season.”

    “However, it’s so important to understand why you are growing a cover crop be that as a green manure, for weed suppression, as forage or for generally improving soil structure and organic matter.”

    None of these are mutually exclusive - a cover crop grown to improve soil structure will also store nutrition, stabilise the soil surface, most likely suppress weed growth and increase soil organic matter,” he says.

    He points out that it’s important to remember that a cover crop is the same as any other crop in the soil - it is just being grown in a different context. The multiple benefits of cover cropping are cumulative over years and one year’s beneficial or negative impacts should not be overstated on the one hand, or condemned on the other.
    “Most cover crops will be grown on soils destined for spring cropping. For lighter soils without black grass, this means they can be sown as soon as the ground becomes available in the autumn.“

    “The primary objective on light soils will be increasing organic matter, soil stabilisation and fertility building. Control of difficult weeds like annual nettle will also be a consideration.

    “Seed beds are easy to achieve in light soils, so growing plenty of biomass is not a problem and generally should be a priority on these soils.”

    However when it comes to heavier soils the issues are very different; clay soils are wetter soils, and moisture management is critical says Mr Neale.

    “On heavy soil growers should take the view that they are growing a ‘conditioning’ crop not a cover; we do not want to actually fully cover the ground. Instead sun and wind should reach the soil surface through early March, so the soft friable surface will break down during the drilling process and allow good seed coverage and good seed-to-soil contact.”

    “The cover crop will extract moisture over winter and the lower soil horizons will always be drier than uncovered clay. The issue is that, if the soil surface is in shade from a dense cover canopy, the 50mm zone you want to drill into will remain wet. It is soft, so a drill disc or tine will easily penetrate, but the drill will fail to close the seeding slot and it dries open and the crop fails.

    Cover crop worm structure

    “Heavy soils almost inevitably have black-grass these days, and spring cropping is beginning to feature primarily as a control tool for this weed. Cover crops in this situation have to combine with the overall black grass control strategy, so there is no point in trying to establish a cover until the late September/early October flush has been sprayed out.”

    Sowing in October means the cover must be of robust, late establishing crops like peas, beans and oats. Although brown mustard, phacelia and spring linseed are surprisingly robust as part of a mix at this time, the use of the exotic species should be questioned.

    Late sowing is only important where you have grass weeds to manage out, but in heavier soils the more robust plants do better than small seeded types. Linseed, phacelia and white mustard seem to be the small seed exceptions to this rule.

    Nuffield scholar, Russell McKenzie, who has a keen interest in cover cropping, has been working closely with Hutchinsons at the Brampton site looking specifically at the effects of the cover crop on soil structure and conditioning, as well as nutrient capture.

    “When deciding on what to grow, it’s really important to look at the mix of crops and choose those that are not going to impede nitrogen availability in order to avoid any pitfalls in terms of speed of crop establishment and crop vigour,” he says.

    “Look to use a variety with a penetrating tap root which will have a good effect through the soil structure, also think to include a fibrous rooting species to open up the surface structure and friability in the surface layers.  For example, the mix that I have used at my home farm contained phacelia, linseed, buckwheat, sunflowers, maple peas and fodder radish,whilst that used at Brampton consisted of oats, peas and beans,” he says.

    Cover Crop -fodder radish

    Mr McKenzie explains that to allow the natural recycling of nutrients, the cover crops were grazed off with sheep in November reducing potential nitrogen lock-up, whilst allowing sun and wind to dry the surface which is critical on clay soils in the spring.”

     “We have learnt from our work in tillage systems for black grass and general weed control, that roots draw moisture toward them.  Water is drawn toward the root by capillary action via micro pores in the soil resulting in the wettest zone being immediately around the root ball, so in clay soils the cover crop species and seed rates chosen should allow for good soil surface drying in the early spring.”

    “Covers which are too thick should be killed off pre-Christmas on clay based soils. Once sprayed off, the root ball moisture dissipates back through the soil, while sun and wind dries the surface.”   

    Neil Watson, southern regional technical manager for Hutchinsons adds that the high number of slugs seen in 2015/2016 should not be attributed to cover crops. “The mild winter has seen little mortality in the slug population and fresh food and retained moisture in the base of covers has supported slug survival. However, it is the lack of overwinter kill and the wet spring that are the primary drivers of slug survival - the cover is not the deciding factor here.”

    Oats, cereal rye and black grass produce allelopathy that negatively impacts on following cereal crops is known, but has been largely ignored. “Apart from slower growth, the symptoms of negative allelopathy in spring barley and wheat are very similar to residual herbicide damage - this issue is easily avoided by planning species choice pre cereals, the level of seed inclusion, date of sowing and date of destruction prior to sowing of the spring cereal. The cold soils in spring 2016 will also have slowed the degradation of the allelopathic exudates,” he says.

    Neil Watson
    Monitoring soil condition, Neil Watson, Hutchinsons

    The use of a soil augur allows you firstly to look at soil texture, by examining soil cores from down through the soils profile.

    This may help to identify any issues such as a slow draining permeable subsoil overlying a more permeable top soil which is causing the ponding for which there is little you can do. However, if it is a structural issue caused by compactions it will also be evident.

    With the augur it’s possible to see how deeply  the roots are penetrating the soils profile, and look to see if there are any obvious structural impediments and at what depth.
    A second tool used to look at soil structure is a soil penetrometer, says Mr Watson.

    A soil penetrometer aims to mimic the root development as it moves through the soil profile, by measuring the resistance encountered as it is pushed to depth. The actual amount of resistance encountered and at what depth it occurs is a useful indicator of potential compaction issues.

    An infiltrometer measures how easily water is able to move through the soil profile; this effect can  be mimicked  by using small sections of  drain pipe filled with water pushed into the soil, then measuring how long it takes for water to move through the soil.

    The important point about all three pieces of kit is that they allow you to examine your soils critically and quantifiably in a manner that would not otherwise be outwardly visible.  Doing this before putting a crop in the ground is a less expensive option than waiting for crop yield to reflect any costly structural issues.