As nutrient application looks set to become increasingly regulated, improving soil health could be key to getting more from land. Hannah Park finds out more about work in recent maize undersowing trials.
The concept of undersowing maize with grass is gaining traction, providing a field cover option post-harvest to avoid bare stubbles over winter.
Improved soil structure, more options for slurry and digestate utilisation, as well as a way to reduce soil erosion and nutrient leaching are among the benefits it can bring, says Agrovista’s technical manager Antony Wade.
Putting the concept under scrutiny, he has been involved in some of Agrovista’s maize undersowing trials which have covered establishment techniques and timings, row spacing and the importance of suitable grass mixtures to achieving the desired outcomes.
He says: “Maize is often seen as a high risk crop as it has the potential to receive high-levels of nutrients coupled with the exposed soil we see for a prolonged period, so the potential for soil run-off is high, especially in heavy rainfall or flooding."
“It is likely that maize cropping will face increasing levels of legislative scrutiny, which could mean farmers in some areas may not be allowed to leave bare stubbles over winter in the not too distant future.
“We are also increasingly moving into territory where nutrient application is becoming increasingly regulated, so getting soil into better health is crucial to making sure more of the necessary nutrients able to be released from the soil.”
Undersown grass in maize can be established in two ways, either once the maize crop is at the four to six leaf stage or into the maize seed bed as a companion crop.
Agrovista has carried out trial work on the latter, as an alternative to the more commonly practised later establishment method.
“Because maize grows quickly once it is in the ground, there is a danger that the opportunity to undersow grass at the correct growth stage can be missed using the later method and is why we are exploring dual sowing as an alternative.
“A service was set up to trial this last season in Cheshire, which sees a specially adapted drill put the grass seed in at the same time as the maize.”
Although the concept still gaining momentum, Mr Wade says the longer term benefits to be gained to soil are insurmountable in the value it can bring to soil health and soil structure.
“The biggest gains to be had are longer term, but initial improvements to the ground will be seen in the general benefits a cover crop brings, in improving rooting and drainage and providing a more fibrous soil for the following crop.
“The whole concept of undersowing does require a bit of a mind-set change, as for years it was about taking grass out of the crop but we live in a changing landscape where there is increasing pressure on improving the soil rather than degrading it.”
Mr Wade explains that selecting the right grass mixtures with the right growth habit and rooting capability is important to provide the optimum soil stabilisation through rooting and biomass cover.
“A mix of species is crucial. For the undersowing option within the standing crop we have found that advance tall fescues will provide deep rooting, and mixed with perennial ryegrass which gives thick ground coverage for maximum soil surface cover.
“Both these species establish well without growing too vigorously within the crop but then grow away really well after the maize is harvested.”
Barry Jones, together with his brother, Pete, and son, Henry, have been undersowing grass into maize for the past three years at Hilley Farm, Pentre, Shropshire.
Run over 324 hectares (800 acres) in total, the farm is currently growing 46ha of maize as a cash crop on the farm’s medium clay-loam soils, alongside combinable crops, a 175-head commercial suckler herd and a poultry rearing unit.
The family plan to double the area down to maize to 65ha (160 acres) this season, as they say the crop does not carry as much risk as growing winter cereals on the farms flood-plain land.
Explaining why the concept works for the farm, Barry says: “Soil is a farm’s most important asset, but it dawned on us that we were guilty of not looking after it as we should be.
“Each year we lose soil as a result of compaction and run-off. Therefore providing cover over winter, it is hoped this will prevent this soil and nutrient loss at the same time improving soil structure – we may not be allowed to leave bare stubbles over winter before long.”
Several in-field trials were set up in conjunction with Agrovista, undersowing maize with a various mixes in a bid to improve soil health.
“Italian ryegrass and tall fescue produced the best cover and root mass in our opinion, which is what we were looking for on our ground and system.
“We now undersow the grass once the maize has reached the four to six leaf stage, sowing at around 10 kilograms per hectare (4kg/acre) using a contractor. As the practice is becoming more common, more are offering this service.”
Barry explains that there is an element of cost and the farm has budgeted £75/ha (£30/acre) this season, which includes the cost of the seed and the establishing it.
“It is difficult to quantify a value into investing in soil health, which is what undersowing does and even if a ban on leaving bare stubbles over winter does not come in, we need to address the problem of losing soil each year – it is the most important ingredient we have.”