Under-sowing maize with a forage or green manure crop to reduce soil erosion and nutrient loss post-harvest may become mandatory. Simon Wragg reports.
Commercial trials are already demonstrating some of the opportunities and pitfalls maize growers face. John Ball, of seed supplier Agrovista, has been working with Reaseheath College, Cheshire, through 2016 looking at the practical implications of under-sowing maize. Both drilling technique and companion crops have been under scrutiny.
At an open day at the college’s maize trial site, he told growers: “Lessons have already been learned.”
Drilling maize with a companion grass or a leguminous crop is possible in a single pass. This has been achieved using a high spec Pottinger Aerosem drill this year, but it immediately presents growers with a challenge over herbicide use particularly where residual grass-weed burdens are high.
Mr Ball said: “Emerging maize suffers from competition from weeds so herbicide use is common. Obviously, we do not want to kill off a companion crop which makes choice of spray critical. We have also looked at drilling companions a month after the maize to give it a head start.”
The Reaseheath crop of Pioneer 7326, which will be fed to the 230-cow dairy herd, was drilled in early May using 75cm (29.5in) spaced rows with a 15cm (6in) gap to the companion crop to reduce risk of crop competition and ‘yield drag’. That had proved largely successful, said Mr Ball.
This year’s companion crops included creeping red fescue, tall fescue, perennial rye-grass and different varieties of hybrid rye-grasses – some with clover and vetch seed included in a mix.
Tall Fescue survived the best of the companion crops.
Mr Ball said: “We saw good establishment almost across the board. However, by early August canopy shading from the developing maize crop had a big impact on many species. Of all the companion crops tall fescue was head and shoulders above the rest in its survivability.”
A review of trial plots post-harvest – with this year’s maize crop achieving a yield of 49t/hectare (20t/acre) freshweight – demonstrated other ‘surviving’ companion crops had limitations. Shallow rooted creeping red fescue had been churned up by field traffic despite this year’s harvest being relatively dry.
For growers looking to establish a grazing ley within maize, other factors needed consideration, he said. Tall fescue, while robust and winter hardy, had a low digestibility factor for livestock. Several grass mixes were simply shaded out by the maize canopy to near total loss.
There were also the cost implications. Companion seed costs varied from £29/ha (£12/acre) for creeping red fescue to £98(£40/acre) for black oats drilled post-harvest. Further work will be carried out to establish how any outlay is returned to the grower whether through improved nutrient retention and/or follow-on opportunity to graze livestock.
Despite this approach, Nicola Hall, farm environment services adviser at Reaseheath, said growers had to see under-sowing as a means first and foremost of staying ahead of tighter controls imposed by legislators and environmentalists concerned at the crop’s impact on the environment.
She said: “As an approach to mitigating risk it has to sell itself on its agronomic value rather than an opportunity to establish a follow-on grazing crop. In the next two or three years we can expect to see much innovation as the NFU expects the maize crop area to increase substantially by 2020.”
For those growing maize for the biomass sector, the development of companion crops would allow an opportunity for nutrient capture where digestate or other manures were applied post-harvest, said Mr Ball.
This year’s maize crop will be analysed in the next few weeks along with a review of post-harvest drilled cover crops which include black oats to determine best advice for growers.
Mr Ball said: “I would hope in the next year we can do more work on herbicide chemistry and look at establishment techniques.”