Grower’s responses to erosion in Maize
The River Lugg Catchment is currently failing its water quality targets due to sediment and phosphorus arising from soil erosion, mainly under Maize cropping. Two Cranfield PhD projects are looking at different components of the erosion issue. Project 1 considers how to prevent erosion in-field, while Project 2 considers how to prevent unavoidable erosion from creating off-site impacts.
Maize production continues to raise concerns in the press, not least with respect to its links with soil erosion. However, as a consequence, ways of reducing the impact of maize production on the wider environment has and continues to be investigated. The bad press from the Soil Association has reiterated the importance in promoting good practice after Maize harvest, and this has led to a growing body of advice targeted at maize growers.
In 2014, 183,000 ha of maize was grown in England alone, equating to 3% of its arable area. Approximately 17% of this was for Anaerobic Digestion (AD) biogas production, with the remaining 83% cultivated as a forage and grain crop. Due to the high potential for maize as a biogas crop, DEFRA and the NFU are expecting the area of Maize production in the UK to continue to increase.
In the UK conventional maize cultivation, even on gentle slopes, can produce serious erosion issues due to:
- Drip-tip lines from the Maize leaves resulting is concentrated flow paths;
- Post-harvest over wintered maize stubble, leaving bare soil and;
- Late harvest in often wet soil conditions, increasing compaction and runoff risk.
- <80% surface cover even at maturity
A recent survey of members of the Maize Growers Association (MGA), by Cranfield University, has highlighted that 55% of the survey respondents had, at some point, noticed soil erosion occurring on their maize fields. Of these respondents, 95% had implemented some form of soil erosion mitigation measure, and the remaining 5% were actively looking at different options. This survey also highlighted the positive contribution that targeted advice seems to be having. In Catchment Sensitive Farming (CSF) areas, 100% of the respondents had implemented some form of soil erosion mitigation measure.
The survey also revealed that maize growers often implement a combined approach to manage soil erosion. The most popular combinations included cover cropping (Project 1) with changes to the ploughing regime and use of end-of-pipe solutions, such as buffer strips. Cover crop preference was influenced by local climate, with farmers preferring to sow cover crops post maize harvest instead of undersowing them post-emergence. Survey results indicate that ryegrass was the preferred cover crop overall, followed by forage rye, vetch and clover. The least preferred cover crops were linseed, millet, oats and barley, which were considered either to compete with the
maize, were not appropriate for the local conditions or were not seen to have any advantages over the use of a grass.
Post maize harvest, ryegrass and forage rye were favoured due to their value as forage crops, with the additional benefit of soil erosion protection through dissipating the energy associated with raindrops, and disruption of surface runoff. The longer term benefits of these cover crops, such as increasing soil organic matter, improving soil structure and adding nitrogen, were also valued. Clearly maize growers are implementing both short-term fixes to soil erosion and longer term solutions to soil quality.
Survey respondents, who did not implement end-of-pipe soil erosion control options instead of or in addition to agronomic solutions, did not do so due to concerns about the costs of the sediment control technology. However, they were found to be the most concerned about the off-site impacts of soil erosion, and therefore these respondents are those most likely to implement end-of-pipe solutions, such as filter socks (PhD project 2) as part of their soil erosion management. The preferred fill media for using filter socks as an end-of-pipe solution were jointly woodchip, and compost with nutrient sorbing bacteria, whilst compost with a seedbank, and silica sand were the joint second preferred fill media. The majority of these respondents were based in the south west where soil erosion risk and associated off-site impacts are high.
The effectiveness at reducing soil erosion of the soil management solutions suggested above and new emerging techniques remains untested. To address this there are ongoing investigations, including the 2 projects from Cranfield University (co-funded by Douglas Bomford Trust, The Wye and Usk Foundation, and the EA), looking at soil erosion control techniques in the Lugg Catchment, Herefordshire.
According to the Cranfield survey, Maize growers recognise soil erosion is an issue, which the majority of respondents were dealing with. However over the 2013/14 winter, 375 million litres of runoff were generated per 10 ha2 of Maize production, impacting on the rivers water quality. This highlights that the issues surrounding soil erosion are still prevalent and more effort needs to be put into making Maize production more sustainable. CSF areas have had the most targeted erosion management training, however to continue to reduce soil erosion from Maize across the UK, these messages also need to be rigorously tested as well as targeted over a wider area.
Authors: Alexandra Cooke and Agnese Mancini
A longer version of this article, with details into the 2 PhD projects was published in the September 2015 issue of MGA times by the Maize Growers Association.