While it may not be a ‘silver bullet’, integrating cover crops as part of a conservation agriculture system is proving successful for one Yorkshire farmer. Abby Kellett reports.
While it is tempting to think of cover crops as a quick fix for many soil related issues, Yorkshire farmer Guy Leonard is well aware that a whole farm approach is key to getting the most from a cover crop-based system.
So when he started his journey with cover crops in 2012, Mr Leonard, who farms 445 hectares at West Hill Farm near Hull, committed himself to a conservation agriculture-type system – replacing his cultivating equipment with a Cross Slot drill and altering his rotation to include more spring crops.
In doing so, he believes he has helped ‘future-proof’ his arable operation. He says: “Looking to the future I think nearly everyone will have to move to a no disturbance farming system in order to make production costs competitive in the world market.
“Previously we were doing a mixture of min-till and ploughing depending on what was coming up in the rotation – I grew vining peas for Birdseye which required me to plough the land and so in switching I have missed out on growing some fairly lucrative crops, but I am fully committed to our new system.”
Cover crops are now grown ahead of most spring crops and during summer when land would otherwise be bare for long periods. During the six years Mr Leonard has been experimenting with cover crops, he has seen his soil organic matter levels rise from about 2.5-3.5%.
Wheat yields on the farm currently average between 10.5-11 tonnes/ha, but Mr Leonard is still striving for even higher yields.
“One of the reasons I moved away from a traditional farming system was because we have been achieving the same yield for 25 years. I want to be able to grow 12t/ha wheat crops, which is what we should be doing on these silty clay soils and I think our new system should allow us to do that.”
But while there is a lot to be gained from ensuring there is a growing root in the ground whenever possible, Mr Leonard says it can be a management challenge. To get the most from the practice, he suggests treating cover crops as you would a cash crop.
“Putting a cover crop in the ground can be a big investment so you have to treat it as a proper crop and that means getting in the ground early – one growing day in August is equal to two growing days in September, so early sowing is key to good crop growth.
“I also apply ferric phosphate to all my cover crops because slugs can be a big problem in a no-till system.”
He currently grows two early maturing wheat varieties, Graham and Siskin, to ensure he can get early entry for his following cover crop. While both varieties possess good septoria disease ratings, he believes healthy soil can also alleviate disease pressure.
To gain good seed to soil contact from his more expensive cover crop mixes, Mr Leonard direct drills most cover crop seed at the required depth straight into the stubble. However, some summer-sown cover crops are spread onto the soil surface using a slug pelleter on the tractor’s front linkage and scratched in using tines.
“The more expensive mixes which contain larger seeds tend to get drilled because it is really important to get the depth right, but some of the cheaper summer-sown mixes with smaller seeds, such as the mustard-phacelia mix, which I establish after wheat and before barley, get broadcast.
“The crop generally grows well providing we get enough moisture,” he adds.
Both Mr Leonard and his Kings cover crop adviser, Clive Wood believe there is a balance between having too few and too many species within a cover crop mix.
Mr Wood says: “Very rarely do we achieve the result we are after with just one or two species – we generally get the best outcome when we use four or five. When you get about 10 species in a mix you often find plants end up competing with each other too much.
“In a summer-sown cover crop, a larger number of species seem to work but in autumn, we seem to do better with fewer.”
In an attempt to get a better understanding of cost versus return, Mr Wood and Mr Leonard calculated the cost of the plants established per sq.m as opposed to the cost of seeds sown per sq.m.
Mr Leonard says: “Cost has to be at the top of the agenda at all times. We know if we put too much vetch in the mix, the cost would go up so we have blends that are in the £20-£50/ha range which we can choose from.
“The blend we pick depends on if we are wanting to put a lot back into the soil, in which case we may be willing to spend £50, but if we are sowing a catch crop that may only be in the ground for eight weeks, we may only want to spend £20/ha.
“You have to use species which are value for money. Sometimes I will let volunteers from the previous crop grow, whether that be oilseed rape, beans or oats, because to me that is an additional species that I don’t have to pay for.”
Both Mr Leonard and Mr Wood believe improving the health of the soil is likely to help manage black-grass.
Mr Wood says: “I certainly think there is an interaction between poor quality soil and black-grass populations – by cultivating the soil we are creating a more suitable environment for the weed to grow.
“There is a lot we need to learn about how cover crops can help us in controlling black-grass – whether that’s through allelopathy, shading out, encouraging germination – but we have to be careful that by curing one problem we are not creating another.”
Currently black-grass populations on the farm are manageable. Mr Wood says: “I have got levels of black-grass which I can control, whereas some people in the area can’t seem to control it because they are not adjusting their systems enough – it has to be a whole farm approach.”
Since black-grass thrives in wet soils, he says it is important to maintain drainage systems.
“It is no good thinking cover crops are going to allow you to drain water away – they will allow it to get down to the drains, but you still need a fully functioning drainage system to get rid of the water.”
Mr Leonard is confident that by moving to a low disturbance system featuring cover crops and a greater proportion of spring cropping he is both creating a more sustainable farming system and also improving the environment. However, to enable these types of systems to continue with background populations of black-grass, he says glyphosate is integral.
“If the glyphosate ban had happened, it would have absolutely crucified the people who are trying to do the most sustainable farming system. If you don’t have black-grass, you could probably get away with using crimper rollers to destroy the cover crop, but if you have got black-grass you are never going to crimper roller a black-grass plant and we couldn’t have carried on with the system.”