Knowledge is growing about how to select suitable cover crop species for different farm circumstances, including grazing, as growers attending a recent demonstration day heard.
Using sheep to graze cover crops is increasing in popularity, however, selecting suitable species for grazing and using appropriate methods are important in making this a success.
Speaking at a cover crops demonstration day held by Farmacy in Lincolnshire, company agronomist Rebecca Creasey said the main benefits of grazing sheep on cover crops were improved nutrient availability for following crops, residue management and better soil structure.
Miss Creasey said: “It is important to mob graze 5-6 hectares with 400-500 ewes for 3-7 days.
“Mob grazing allows for uniform residue destruction which leads to an even distribution of readily available nutrition and reduces compaction over the field, preventing animal tracks and poaching, which can cause significant yield loss in the following crop.”
In terms of species selection, Miss Creasey said legumes were good for nitrogen fixing, supplying protein for livestock and had good root anchorage. “Cereals provide good cover over the area and hold the soil together, as well as being nutritious for livestock. Buckwheat is poisonous to sheep so do not include this and phacelia can be unpalatable. Forage rape is good – it is fast growing and produces a large amount of biomass, however, be careful of its inclusion where OSR is already in the rotation. Get the crop drilled as soon as possible so there is enough feed value for grazing.
“There is a financial benefit in that cover crop land provides feed value for livestock and therefore chargeable grazing land. This can often cover the cost of the cover crop seed. If grazed correctly, one less cultivation pass is required as there is less biomass to manage.”
Seeking to improve soil health and reduce black-grass, Ed Pritchard, who farms with his father, Andrew at Redhouse Farm, Waddingworth, Woodhall Spa, where the cover crop demonstration day took place, has been working with Farmacy agronomist Alice Cannon.
Mr Pritchard said: “During the last few years, we have been changing how we do things from rotational ploughing one in three or five years and growing two wheats and a rape.
“Black-grass is a factor – because we are on predominantly heavy land we like to drill winter wheat no later than mid-late October; hence we have increased the spring crop acreage.
“Now we just grow first wheats; we are still growing OSR and also introduced cover crops three years ago, primarily to keep the land we are spring drilling in good order to enable us to successfully establish a spring crop.”
Mr Pritchard grows a mixture of white mustard, which he says dies off naturally, plus crimson clover and phacelia, which is sprayed off with glyphosate two weeks before drilling. Spring crops are direct drilled into the cover crop residue.
This year, he is growing 80ha of spring oats, with 56ha being grown on contract for GFP Agriculture for seed. “We have tried spring barley, spring linseed and spring beans – we are quite new to it and in the process of finding one we get on well with – I have heard good reports about spring oats.”
Cultivation on the farm has been reduced ‘drastically’ says Mr Pritchard. “We are trying to keep to 2-3 passes before drilling winter cereals. This year we used a Simba X-press, followed by a Tillso ultralite subsoiler running at 8in deep. For winter oilseed rape we drilled it into stubble using a Tillso ultralite leg.
“Going forward, we are looking to become more of a direct drilling operation but will carry on putting steel through the land until it is in good order. I hope the soil structure and texture will improve then we will think about direct drilling. I think cover crops are essential to improve soil condition.”
Using sludge as well as cover crops is helping to boost organic matter levels, says Miss Cannon. “There have been remarkable improvements in just 18 months. You can put a spade in easier; previously there were tight areas which impeded crop growth. Visually, there has been a massive increase in worm numbers and a greater variety in worm species, including deeper burrowing worms.”
120ha winter wheat
100ha winter oilseed rape
80ha spring oats
Spring barley has a short growing season and maximising its opportunities early is important to get the most from the crop, said Farmacy agronomist Alice Cannon.
Allowing sufficient time from desiccation of cover crops before drilling spring barley is important, with some mixtures, particularly those containing at least 60 per cent of cereal, needing up to six weeks, she said. “Spring barley yield is set very early in the season with tillering stopping at GS30. Yield is directly driven by grains produced per unit area.
“Earlier drilling will increase tillering potential, which increases yield potential and also positively impacts black-grass control.
“Barley has limited time to compensate for reduced plant populations in adverse conditions. Always drill by seeds/sq.m not weight. Aim for 450-500 seeds/sq.m. Spring barley produces fewer leaves than winter and 19-24 grains/ear – fewer than winter barley - so more ears/sq.m are needed.”
Seedbed quality makes a big difference to spring barley establishment, said Miss Cannon. “Establishment can drop to 55 per cent in poor seedbeds, which have compaction or N lock-up problems if previous cereal cover crop mixtures have not been desiccated in enough time.”
In terms of crop nutrition, nitrogen can initially be locked up, following a cover crop, with brassicas and cereals the worst offenders, says Miss Cannon. “Front load N or increase nutritional inputs. However, be mindful where growing malting barley with overall N applications.”
In soils transitioning from deep cultivation systems to min till or direct drilling, care must be taken to ensure drills are adjusted to take account of differing soil conditions, explained Dick Neale, technical manager at Hutchinsons.
“In year one, soils are not aggregated if they have been in deep till for ages with no cover crop and heavy weather over winter washing out the surface. You end up with a slot through [when drilling] and soil comes apart in blocks which you have to close again. Slot closure is important and in year one closure of the slot may need to be set aggressively.”
In year two of a soil improvement programme, cover crops may have been used and roots will have led to some soil aggregation with residues sitting on the surface, allowing water to percolate through, says Mr Neale. “When you go through with the drill, the soil opens and closes more easily and when the slot is closed it stays closed. You can go more gently with the drill in that soil.”
From year three onwards, roots in the soil are playing more of a role in binding it together and letting it aggregate, explains Mr Neale. “With sands, direct drilling will work, but with clay loam it will not work well. Plain press wheels do not work well as soil is like a spring mattress – the soil needs stitching back together – they need to be serrated, not smooth.”
Mr Neale says: “You need to adjust drills year on year. Soil changes year on year so what you need to do to it changes year on year.”