The second article in our 2015 series takes an in-depth look at the potential benefits of growing maize under plastic, revisits advice on drilling depth and looks at the maize market.
It is widely accepted, on average, maize under plastic – also known as film – can cost £296/hectare (£120/acre) more than conventional production methods and it is estimated an additional 7.4-12t/ha (3-5t/acre) of fresh weight material is required, in order to recoup the investment.
However ProCam’s Mike Corp, an enthusiastic supporter of maize under plastic, describes it as a ‘no brainer’ for livestock producers. He stresses the system need not be confined to marginal areas, as it can be cost-effective in virtually any situation, even in a good year like 2014.
“It is easy to become preoccupied by the additional cost of growing maize under film,” says Mr Corp. “However, the real test of performance is the delivery of megajoules of energy produced per acre of land planted.
“Farm-scale trials have shown in a bad growing year, maize under film can be worth £2,000/acre more than maize grown conventionally, when both are compared in relation to the megajoules of energy each crop produces.
“In a good year like last year, this figure will fall to about £300- £450/acre, but it is still a significant increase and most would consider that amount of additional feed value worth aiming for.”
The main reason why film can boost crop feed values lies in its ability to maximise cob production, he explains. “The later-maturing varieties grown under film will normally produce a better quality cob, but to achieve this they will need a relatively long grain fill period between cob set and harvest.
Film can facilitate a 90-day grain fill period; nearly double that of a typical 50-day period for maize in the open.
“A maize plant will keep growing upwards until it reaches the stage where it is ready to set a cob. At that point, the plant will focus its energy into producing that cob.
“Conventionally-grown crops will often reach greater heights than maize under film. This can be deceptive because, in reality, the crop grown in the open has deposited most of its energy into stover production, rather than grain.”
Crops grown under plastic can be chosen for very high forage yields, high quality or early harvest. Early harvesting is particularly important on farms where rotations require an early entry in the autumn, he says.
Even when earlier varieties are selected, they will usually produce higher dry matter yields, by permitting the sowing of varieties which are two to three maturity groups later in the same situation.
Film systems optimise growing conditions for the plants, which thrive in an ambient temperature of 20degC, says Mr Corp. They can increase accumulated heat units by an extra 300 units and In association with Varietal selection should be based on whether the grower is aiming for a significant yield increase or to bring forward harvest date MIKE CORP “ will also act as an insurance policy, in a challenging year.
For those who have always used conventional methods, it is a good idea to seek expert advice before making the switch, he advises.
“Like all growing techniques, growing maize requires attention to detail throughout the process to maximise the crop’s potential. Varietal selection should be based on whether the grower is aiming for a significant yield increase or to bring forward harvest date. In some cases both results will be achievable, although there are varieties which have been deemed unsuitable for certain systems.”
Specialist drills will need to be employed to lay the plastic; these are either four-row or sixrow machines. This will add cost compared with conventional sowing, but the drills can simultaneously deliver a preemergence herbicide and lay the plastic in one pass.
“Basically we are just warming the soil, which, in turn, creates moisture so residual herbicides can work and soil biology starts to work faster. This, in turn, creates an almost perfect environment for the young maize plant to reach its full potential.”
Recommendations for drilling depth have changed in the wake of the genetic advancement of varieties, with many experts pointing to greater flexibility in decision- making.
In the past, growers who require an early harvest have tended to drill their crops at the relatively shallow depth of about 3.8cm (1.5in), which can bring emergence forward by as much as a week.
However, many of today’s more vigorous varieties can be sown at depths of up to 6-7cm (2.5-3in), without incurring maturity time penalties. This deeper drilling in turn creates a deeper rooting zone. It can give plants a significant advantage, especially if lack of moisture becomes an issue during the summer months.
The technology used to make film for maize growing is advancing rapidly and the latest products are starch-based, says Mr Corp. They are designed to be strong enough to create a protective layer, while also allowing the plant to break through the material.
Some films incorporate pinholes, in order to release trapped air and keep the material in close contact with the soil after sowing. These holes also help to prevent excess heat build-up later on in the season. Many films are degradable, with up to 90 per cent of the film breaking down in the first season and 100 per cent degradability within two years.
Growing maize under film using a system such as SAMCO, which was developed in Ireland to suit maize grown in cooler climates, gives UK growers the opportunity to sow high performance varieties which are currently used in warmer European countries which might be viewed as to late maturing in this country, he adds. Some of these varieties are particularly suitable for producing a high quality livestock feed.
“It is interesting to note in France, where the climate is warmer, the area down to maize under film is three times higher, compared with the UK market. French growers recognise good grain quality is the most important factor.
“I used to recommend the SAMCO system on fields where maize was difficult to grow, but techniques and materials have moved on in recent years,” says Mr Corp. “Now I usually suggest it is used right across the farm. This will include the most productive fields, which are capable of producing the ‘rocket fuel’ maize under film is renowned for.”
The numbers of acres devoted to maize for biogas continues to increase, with estimates plantings are up by 5-10 per cent, compared with last year, says John Burgess of KWS.
In some regions, growers are taking the risk of sowing crops destined for anaerobic digestion plants which have yet to be built. There are even reports of maize land being allocated for proposed plants which have yet to receive planning permission, he says.
The reduction in cereal prices is having an effect on the market.“Diminishing returns for cereals have freed up land for maize silage, but these low prices have also resulted in a decline in the area of maize grown for grain,” says Mr Burgess. “Meanwhile, about 75 per cent of our seed sales are for varieties intended as forage; this figure has changed little over the past few years.
“The three crop rule does not seem to have made much impact of the maize market to date, but 2013 was not a bad year and 2014 was exceptional. On some farms, clamps are only just being opened,” says Mr Burgess.