Arable News

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Early management pays with biogas maize

Dominic Kilburn investigates how to set the crop up for good establishment this spring

With an increasing number of arable growers securing contracts to supply operators of anaerobic digestion (AD) plants with maize, Dominic Kilburn investigates how to set the crop up for good establishment this spring; including tips on seedbed preparation, herbicide programmes and what to watch out for in variety choice. With the majority of maize grown for biogas AD plants on lighter soils, structural problems coming out of this winter, and ahead of planting this spring, could be minimal despite the very wet weather experienced by many growers across the country. However, where crops are planned for slightly heavier land, growers must be very careful to ensure seedbed conditions are suitable if they are to get the very best from their crops, warns an independent adviser.
According to maize specialist Simon Draper (left), as much as 55-60 per cent of the yield from maize is derived from the soil structure beneath it and crops planted into a poor seedbed, with compaction, will suffer. “If we then get a cold and wet summer like last year, then maize will really struggle,” he says.
“On the heavier land this spring it’s going to be asking an awful lot of growers to get the condition of the field right before planting maize, but, on the lighter land, even where there’s a mess following roots, there should still be the opportunity to get it right,” he comments.
Simon explains that it’s critical that growers remove any compaction from the top few inches of the seedbed. “Maize is a very weak plant during the establishment phase and any compaction such as a plough pan or blockages beneath a plant will prevent roots accessing sufficient moisture or nutrients, causing a detrimental effect on yield.
“About 10 per cent compaction in the topsoil equates to a 10 per cent loss of yield,” he stresses.
Simon says that growers preparing land for maize grown for biogas should think along similar lines to a sugar beet seedbed. “It has to be as good as that,” he points out. “For those that don’t have sugar beet; it means that land should be ploughed and then knocked down to the extent that is should be possible to push a spade down into the soil profile with one hand. Avoid using a power harrow – they can compact soil at a three to four inch depth, upsetting the growth of the plant.
“Maize must be able to get its roots down fast so that if a drought does occur it has roots down into the subsoil channels where it can chase after water,” he adds.
For any land currently waterlogged, and where maize is planned for the spring, according to Simon it’s important that an attempt is made as soon as possible to clear the surface water before anaerobic conditions occur – potentially killing the roots of maize plants. “Growers should go through it with a shallow mole at 10-12 inches deep, these can then be subsoiled or ploughed out later to ensure they do not become a permanent feature,” he suggests.
“With the wet weather that we’ve had, it’s often the case that a plough pan will have formed beneath the cultivating depth, and when things are drier in the spring it’s best to break open any compaction that might have been caused using a subsoiler, provided the land at subsoil depth is dry enough to allow it to fracture.  For land that has yet to be ploughed, growers should try and get it done in early March and give it time to dry out.”
He believes that nutrition will play an important part in the early development of the crop this season particularly if soil conditions are not ideal. Maize requires about 150kg N/ha, 80kg P/ha and 250kg K/ha in a season, and growers with access to manures will be able to supply much of that requirement from them, claims Simon.
“Half the nitrogen, and all the K should be mixed into the topsoil pre-drilling, giving the crop an immediate and much-needed boost during establishment, while all the P should be applied at drilling and the remainder of the nitrogen at the cotyledon 2-leaf stage of the crop.”
Prior to drilling, soil temperatures should have reached 8C consistently for a week, he points out, but the earlier the drilling date the longer the seed takes to germinate, remaining at the mercy of any further cold and wet weather. “A rougher seedbed will aid drainage early in the season while a finer seedbed suits later plantings,” adds Simon.  Accuracy at planting
Aiming for 110,000-120,000 plants per hectare established, Simon explains that row spacing for maize being grown for biogas should be at 15-20 inch widths, giving the plants the maximum opportunity to tiller and deliver potential yield. “For supplying AD plants we want maximum overall height and bulk of crop and therefore closer rows are better.
“Seed depth needs to be consistently at two inches and the maize drill needs to be travelling very slowly to achieve this – something that needs to be monitored if the drilling is contracted out,” he says.
“If seeds are placed too deep or too shallow, then you will lose yield,” adds Simon.
He reminds growers that the earlier the crop is planted in the season then the earlier the harvest date, but this comes at a compromise to yield. “An arable farmer would be tempted to choose a variety that promises all out yield, but it could also mean a harvest date of October, or even November.
“Certainly later maturing varieties on offer point to bigger yields but if most growers are thinking about getting a wheat crop in the ground in September, they will need to choose a variety that is relatively early to mature and which could mean a 10-15 per cent yield differential compared with a later maturing type,” he explains.
“Ask the question; when is the crop likely to be harvested?” says Simon. “Farmers have to realise that they can’t have it all ways. Experienced maize growers will be drilling in April for a mid-September harvest but if the plan is to drill in May then they’ll be looking at a late September/ October harvest.
“Every AD plant has a different requirement in terms of its feedstock and people, at this stage, are not really sure of the best type of variety required, but for an arable farmer growing maize for biogas, my advice would be to produce as big a heap of crop as possible, with the priority being to get it out of the field in time ready for the next crop to go in. As long as the crop is dry enough at 27-28 per cent dry matter, then that should suffice.”  Herbicide options
BASF product manager, Jonathan Ball points out that the company is focusing more of its attention on maize being grown for biogas, particularly as an increasing number of arable farmers secure longer-term contracts supplying anaerobic digestion plants.
He says that yield is the key driver when growing maize for AD plants, compared with forage maize where quality is a key ingredient in terms of feed, and it’s vital that competition from weeds is minimised at an early stage. Trials have shown that controlling weeds while maize emerges and through until at least the 2-leaf stage of the crop is important for maintaining the yield potential and so the best approach is for reliable pre-emergence weed control, he explains.
“This allows the best establishment of maize in a weed-free environment, keeping weeds at bay until the crop becomes competitive,” he adds.
Launched in 2011, and having its first full season on farm last year, BASF’s new pre-emergence herbicide Wing-P (dimethenamid-p + pendimethalin) is claimed to have broad spectrum grass and broad-leaved weed control with increased activity on key weeds such as annual meadow grass, as well as reliability in dry conditions.
“The reliability of pre-emergence herbicides is sometimes questioned, especially if applied to dry soils or prolonged dry weather persists after application,” comments Jonathan, “there is, however, good evidence that pre-emergence herbicides can be just as effective as post-emergence applications even in dry conditions,” he says.
“A pre-em application will give maize grown for biogas the best basis for maximising yield and delaying applications until post-emergence of the crop can limit yield potential.
“Wing-P provides two complimentary active ingredients boosting the range of weeds controlled and also the activity on key weeds compared to straight pendimethalin products, without compromising residual activity.”
Jonathan adds that Wing-P applied at 3.2 litres/ha is an effective use rate but if growers are facing high weed pressure then 4 litres/ha is advisable. An additional benefit for growers is that Wing-P (when applied pre-emergence of the crop) can be applied in mix with liquid fertilisers, helping to ease the workload while it also has a recommendation for an early post-emergence application (from leaf 1-4) adding in extra flexibility if required. Opportunity to hit black-grass
Maize offers an excellent opportunity for the removal of problem weeds such as black-grass, says Syngenta portfolio manager Gary Jobling (left).
He warns, however, that despite maize reaching a height of 6 feet and more, the crop is notorious for its ‘shyness’ in its early life and a simple approach to weed control, including a pre- and post-emergence spray is often required.
According to Gary, the moment weeds appear, maize detects them from changes in light quality and it adopts a ‘shade avoidance’ strategy and starts growing away from the weeds; causing smaller roots and elongated shoots. At this point the plant is now programmed for sub-optimum growing conditions and, potentially, yield loss can become irreversible. “Based on numerous trials the latest stage of weed removal without yield damage should be no later than the 4-leaf stage of the maize crop,” he suggests. “The benefit of a field free of weeds from the start is that it allows maximum light quality and maximum yield,” he adds. Gary says that moist soils are ideal for pre-em applications, while many growers will already be familiar with the ‘forwards/ backwards’ benefit of the Defy nozzle for both pre- and post-em applications offering good coverage of soil and early established grass weeds. “Avoid dry, cracked and cloddy seed beds for pre-em sprays, and large clods will mean poor coverage by the spray. In addition, as the clods breaks down, weed seeds harboured inside will not be controlled as they won’t have received the pre-em herbicide.” For annual grasses and annual broad-leaved weeds, Gary points out that Syngenta’s herbicide Dual Gold (S-metolachlor) can be applied at pre-em (only), and at 1.4 litres/ha, followed up by a post-em option of Calaris (mesotrione + terbuthylazine) at 1.0-1.5 litres/ha; offering good persistence and knock-down control of annual broad-leaved weeds and also annual meadow-grass.
“For true grass weed control growers can combine ALS inhibitor Samson Extra (nicosulfuron) with Calaris, or with our other post-em herbicide Callisto (mesotrione). Like other ALS products, tackling small black-grass plants in the spring with Samson Extra will result in better control of weeds and, combined with either of the other two products, is really a ‘belt and braces’ approach.
“It’s another option in the constant battle to keep on top of black-grass,” he stresses.
While following crop restrictions for maize herbicides are not such an important consideration for growers in more western areas where rotations include predominantly forage maize and grass, Gary reminds arable farmers that they need to be aware of any following restrictions for the more diverse range of crops grown in their rotations. “The bulk of herbicides used on maize are based around post-em applications and while products are safe in most crops that follow on such as cereals, oilseed rape and ryegrass, there are specific restrictions that growers should be aware of for mesotrione-based products; specifically that peas, beans and sugar beet cannot be drilled for 18 months after the last application.”
Growers should seek advice from an agronomist or adviser for more detailed information, he adds.  Growing for yield
Biogas growers are being warned not to make the mistake of thinking that a biogas digester is simply a concrete cow. According to KWS UK maize manager, John Burgess, university research confirms that the key to high methane yields is dry matter.
“The work confirms that starch content – a key parameter important for maize grown for cattle – has no effect on methane yield per acre. 
“Subsequently our advice is to grow for DM yield selecting a range of varieties that will suit your region, soils and harvest window,” he says. The study at the University of Hohenheim, which analysed the gas output from 10,800 maize lines confirmed a direct correlation between DM yield and methane output.
“This is why in Germany, almost all of the 800,000ha of maize being grown for anaerobic digestion plants is down to dedicated biogas types and the same holds true here.”Specialist varieties should form the bulk of the biogas mix, says KWS UK maize manager, John Burgess.
While the UK is playing catch-up, John Burgess says that the energy maize hybrids have proven capable of providing some very high DM yields with maturities to suit our conditions.
“Fabregas has set the pace, with some consistent yields from an earliness that suits all maize growing regions. Trials last year suggest that newcomer Barros could be just as successful.
However, in regions that can cope, such as the south east and eastern counties, there is scope to grow later, higher yielding types such as Ronaldinio and Francisco.
“It is important though that growers select a mix of varieties with a range of maturity dates to enable them to manage the large area needed,” he says.
In most regions this will be a maize with an FAO number of 190-220.  It will also pay to select a variety with good vigour and proven standing ability, notes John.
“However with 50 per cent of the running costs of a biogas plant in the feedstock, the key remains selection of a variety with a high DM to optimise cost per tonne,” he says.  What the AD plant requires
Specialist seed merchant David Bright of Salisbury-based Bright Seeds, says that when it comes to variety choice for arable farmers looking to grow maize for biogas, they must first consider what the AD plant operator really wants to be supplied with.
“We’re seeing demand for maize increase across the country as AD plants continue to be built and, with quite a wide selection of varieties available, it’s important for growers to ask the fundamental question as to the type of maize that is required,” comments David.
“Some operators have been running AD plants for four or five years and they know what they want from maize to make up the ration, but there’s a number of criteria they will be looking for in terms of content,” he explains.
“Some just want bulk, some will want high levels of energy, and some want digestible fibre – it’s a real mix,” he adds.
Other factors affecting variety choice include soil type, geographical location and even height above sea level, points out David, who, above everything, stresses the need for maize to be grown on compaction-free soil to allow roots to penetrate downwards for good establishment.
“Finally, growers have to weigh up their agronomic priorities and any potential restrictions that may affect other crops in the rotation; such as when they are able to get on the land in the spring for planting and when the crop will be harvested.
“All these factors will have a bearing on variety choice,” he says.
Highlighting a selection of varieties offered by the business, David points out that a good all-rounder that fits most situations would be NK Falkone, from Syngenta, which, although it was bred as a grain and forage maize, has a nice balance between yield, fibre and energy.
Normally planted at the end of April or in early May, Falkone has medium maturity, early vigour and produces a big plant. “This one suits growers who are new to the crop,” he suggests.
If out and out yield is a priority, David believes that French variety Mas 18T is a good option with a yield of over 20t/acre, some 5t/acre above average yields for maize.
Later maturing, the variety is low in energy and starch, but higher in fibre, and should be grown on lighter, sandy soils that can be harvested in late October.
Another variety for a late harvest is Happi – a very tall variety at 9-10 feet needing a ‘warm’ site for good growth. According to David, Happi is very high in fibre and high yielding.
For an earlier harvesting type, he suggests Beacon; which has good starch levels and early vigour. Although lower yielding, the variety is higher in starch and energy.
“Arable farmers are good at growing these types of varieties, and they understand the importance of variety choice when making decisions about all their cropping, and with maize in the rotation they are getting a very good break crop.” Later maturing varieties on offer for biogas production point to bigger yields but if most growers are thinking about getting a wheat crop in the ground in September, they will need to choose a variety that is relatively early to mature.  Cut slurry and digestate losses
Maize growers planning pre-drilling applications of slurry and AD plant digestate may benefit from protecting against nitrogen volatilisation and nitrate leaching by adding a nitrogen stabiliser to the material they are spreading, suggests Rob Buck of Gleadell Agriculture.Contractor Oliver Arnold’s team last season used Piadin with AD plant digestate on trial areas of crops grown on contract to Future Biogas.
Oliver Knowland of Future Biogas says that, despite a difficult season in which application was delayed, results from trials with Piadin-treated digestate suggested the product went some way to preventing leaching and volatilisation losses, although weather delays to application caused issues with maturity and harvest date.
“This year we hope to be able to use it with earlier digestate applications, in February and March, and will be adding 1,800 litres to sufficient digestate to cover 300-400ha of the 1,000ha we are growing for two plants, at a digestate application rate of 30-35cu m/ha.”
In trials under comparable north German conditions, biogas maize varieties planted into soils where Piadin-treated slurry had been applied showed an average yield increase of up to 11 per cent. Gleadell is now working with biogas specialist Future Biogas to show the effect Piadin, from German firm SKW Piesteritz, has in practice under UK conditions. “Piadin will be used on 10 per cent of all energy maize crops this coming year, with Defra and energy maize seed breeders carrying out in-depth trials into its environmental effects and yield benefits,” adds Rob Buck.

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