AHDB-funded research is aiming to help growers maximise the benefits of cover crops. Andrew Blake reports.
Autumn weather can dramatically affect the establishment and value of cover crops, AHDB-funded research has revealed.
Seasonal differences were all too obvious during the three-year research project*, says project leader Anne Bhogal, of ADAS.
The project started in August 2016 and aims to maximise such crops’ economic, agronomic and ecological benefits.
Dr Bhogal says: “In autumn 2016 we did not manage to get our cover crop trials in until mid-September and then it stayed very dry.
“This season we got them sown in mid-August and then it rained soon afterwards. So instead of only about 1t/ha of dry matter in the cover we have had up to 3t/ha dry matter. However, we have also had quite a good cover of volunteers.”
Cover crops have great potential to boost sustainable crop production through several mechanisms, explains Dr Bhogal.
“These include improving soil structure and quality; greater soil nutrient and water retention; reducing the risk of soil erosion, surface run-off and diffuse pollution; and by managing weeds or soil-borne pests.
“Cover crops can also count towards Common Agricultural Policy greening requirements.
“However, their potential benefits are not always realised on farms because of lack of evidence about which species are best, how to manage the crop in different situations, limited knowledge of the options; and, in many cases, reliable cultivation technologies do not exist.”
The project has four clear aims:
“We hope to provide practical science-based information for cover crop selection and management, as well as new knowledge on how such crops can be used to enable deeper, more extensive crop rooting,” says Dr Bhogal.
The project has three components, she explains.
In the first, three large-plot experiments have been established (one in autumn 2016 and two in autumn 2017) where seven cover crop species sown as ‘straights’ and three mixes of those species are being evaluated and compared to an uncovered control (see box).
Dr Bhogal says: “We are looking at cover crop establishment, biomass and rooting down to 60cm, and the impact this has on the establishment, rooting and yield of the following spring barley crop.
“We are also evaluating the potential effects of the different cover crops through to the following winter crop, as benefits are not often realised until later in the rotation.
“As well as assessing crop rooting and yield, we are also looking at key soil physical properties to understand the potential effects of the different root systems on soil structure after the cover crops have been destroyed and in the winter crop.”
Straights (individual species):
The second package involves taking some of the treatments from the large plots and evaluating them in a series of tramline trials on three AHDB Monitor farms and Hutchinsons’ demonstration farm.
The first set of tramline trials is examining the effect of two of the cover crop mixes and an uncovered control on the performance of the following spring and winter crops – and including a more limited set of soil and crop assessments.
The second set of trials is exploring three establishment techniques, namely strip tillage, direct drilling and the use of a cultivator drill.
Four of each tramline trials have been established – two in autumn 2016 and two last year.
The third package is undertaking a full cost/benefit analysis at each of the trial sites.
“We are about half-way through this project,” says Dr Bhogal, who lists some preliminary messages:
“It is a long-term investment which needs to be evaluated across the whole rotation. By continuing measurements into the following winter crop we hope to evaluate this further,” says Dr Bhogal.