Organic oilseed rape is the most profitable crop on Bent Jensen’s Danish farm, as it fetches three times the prices of rapeseed treated with sprays and fertiliser, while his yields are virtually identical.
His highest yields have touched 5.5t/ha – with his only input being seed and an organic-allowable sulphur/calcium fertiliser – and he looks to garden compost and pig slurry to feed his crop.
In his organic system, heavily dependent on grass and clover seed crops, his long-term average oilseed rape yield is 3.5t/ha, which compares favourably with those using agrochemicals and bagged fertiliser.
He oversaw the switch to organic farming some 19 years ago, devising a rotation with a wide range of arable crops. He says that they have seen only a very small dip in oilseed rape yields.
“It’s more fun being organic and more accepted by the general public,” Mr Jensen tells Farmers Weekly from the estate he manages on the island of Zealand just south of Copenhagen.
The oil from the 40ha of organic rapeseed he grows is used by make spreadable butter, while his rapemeal finds a ready home with organic livestock producers in the region. He is one of up to 100 organic growers on the island of Zealand.
The biggest problems Mr Jensen has seen with switching over to farming oilseed rape organically are weed control and fertiliser, but mechanical weeding and plenty of pig slurry have help smooth the changeover.
A long rotation growing oilseed rape only one in every six years and planting vining peas ahead of the rapeseed are key to his success in limiting disease and giving a good fertile soil for the oilseed rape to thrive.
“We started in organic farming because we can earn more money from year one,” he adds.
He manages the 1,250ha Standegaar estate with only 300ha in arable cropping. The rest of the land on a peninsular into the Baltic Sea is largely in grassland and forest, with a campsite for 1,900 tents.
Mr Jensen’s vining peas are harvested in late June, and the land is immediately disced and then ploughed to give control of grass weeds – especially annual meadow grass – and also to loosen up his light sandy silty soils.
The land is disced again and rolled and the oilseed rape drilled usually about the middle of August. Last summer’s crop went into the ground on 18 August.
The preceding vining pea crop has 100t/ha of garden compost applied and this, along with the residual fertility from the peas, is calculated to give 60kg/ha of nitrogen in the seed-bed to give the crop a good start to life.
Even though his soils are light sandy silts, he is very close to the sea, so moisture in the autumn and farming on a northern latitude similar to North Yorkshire is not often a problem.
He grows hybrid varieties as he says they establish quickly and give faster growth, bigger leaves and better pod shatter resistance than conventionals varieties. His main variety is Exclaim, with some Exlibris and Exception – all sown in 25cm-width rows with a 8m-wide drill.
The seed rate is aimed to give 40 seeds/sq m to give about 30-35 plants/sq m in the spring, with the aim of not creating too thick a crop.
With no bagged nitrogen being able to be used on the organic crop, it is essential that the early-harvested peas fix their own nitrogen and so leave good residual fertility, Mr Jensen says.
“It is essential to have a good entry crop in front of oilseed rape – like peas – to plough every year on the farm and have a long rotation,” he adds.
The added compost also makes the soil easier to work, giving it a better structure with more earthworms, while he also incorporates all the his straw.
Mr Jensen is using a GPS satellite-guided mechanical hoe, which uses Garford technology – once in the autumn and again in the spring – but often the crop grows very quickly and away from the weeds.
Weed control, he admits, can be tricky, so is he is looking at more robotics in the future in the form of unmanned hoeing tractors, but thinks the technology is about two years away from him being ready to invest.
Spring nitrogen comes in the form of pig slurry from a neighbouring farm, and it takes four days to cover his 40ha of oilseed rape in the spring. The application via a dribble bar is calculated to give the crop 100kg/ha of nitrogen – giving a total for the crop in the season of 160kg/ha.
He sees few insect pests in his low-nitrogen crops as aphids and cabbage stem flea beetles tend not to like the coastal location of the farm.
Harvesting, as is common across Denmark, is conducted without a desiccant and he waits for the crop to mature naturally towards a harvest – which is usually between 1 and 10 August – is where pod shatter resistance is key for the crop.
Oil contents are high, at about 48-51%, which is common in the organic system where yields can be a bit lower than in other farming systems.
With the crop earning nearly £1,000/t and with few variable inputs, it competes with white clover for seed as the most profitable crop on the estate.
And for the future, Mr Jensen is eyeing organic sugar beet, which once again will give him three times the price of other sugar beet and be a further crop for his long rotation.
This 1,250 ha estate is on the island of Zealand some 40 miles south of Copenhagen. The 300ha of arable cropping close to the Baltic Sea coast includes winter wheat, grass seed and clover seed, oilseed rape, spring barley and spring oats, vining peas and spring beans.
Essentials for oilseed rape in an organic system
- Long rotation – oilseed rape is grown one in six years
- Good entry crop for oilseed rape – a vining pea crop is used
- Ploughing every year to give good weed control
The estate gets special permission to use untreated hybrid varieties in the system, as no hybrid seed is grown organically.