To fully evaluate precision farming strategies, precise data capture is needed.
According to Bayer, this is a significant asset of its Climate FieldView digital platform, which one group of farmers is using to trial variable rate nutrition in oilseed rape on their farms.
The aim is to achieve better crop evenness, with a green area index (GAI) target at flowering of 3.5.
All have set aside a field to test a variable rate approach against a typical farm standard flat rate.
The 3.5 GAI target is the optimum for light inception into the canopy but it can be tricky to achieve given many growers up seed rates with crops often under attack from cabbage stem flea beetle soon after emergence.
ADAS crop physiology manager Dr Peter Berry says big canopies might look the business but do not always deliver.
This is because their thick flower layer reflects light, restricting photosynthesis and seed set.
“A GAI of 3.5 is ideal because light penetrates through to the lower canopy,” he says.
To achieve each unit of GAI OSR crops need to take up 50kg N per hectare and getting that right can be tricky too.
Hence the interest in improving OSR nutrition strategies.
For Simon Gent, of Waterloo Farm, Stockbridge, Hampshire, WOSR is still the break crop to top all others.
He has tried most alternative options, including niche crops such as millet and poppies, but all have failed to beat OSR for its yield potential and cleaning properties.
Last season’s spring drought kept yields well below the 3.5 tonnes per hectare farm average, but Mr Gent continues to seek improvements and with variable soil and topography he wants to even out performance across the field.
He is already applying variable rate N using precision farming provider Soyl’s biomass imaging but he feels FieldView refines this further.
“It’s the precision with FieldView that I like.
Other platforms have similar mapping and vegetative imaging properties but FieldView has the ability to let me design and manage my own trials in a truly professional fashion.
“Plot boundaries are logged in the platform so there is no need for unsightly canes.
It also makes accurate data interpretation easy.
I can overlay real-time yield data from the combine accurately across soil zones and variable rate applications.” He is using satellite imagery to vary rates by +20% on his trial crop’s thinner areas to -40% on the thickest, compared to the control of 220kg total N/ha.
“We have a lot of undulating terrain here and our better soil gets washed down to lower levels, with the higher ground being more a mixture of chalk, flint and stone.
If I can improve crop evenness across the highly variable fields, I’m likely to see an overall gain in yield,” he says.
The first N dressings were applied in late-February, with the control plot receiving 60kg N/ha.
But uptake depends on numerous factors, soil condition being one of them, which could impair uptake of the 175kg N/ ha to achieve the 3.5 GAI target.
Normally the remainder would be applied in a single application, but this season Mr Gent is also assessing the value of increasing the number of dressings.
“The data coming back from the Yield Enhancement Network [YEN] is showing the benefit of spreading fertiliser applications.
This suggests that feeding the seed is as important as feeding plant tissue.
I will be saving about 40% of the total dose to as late as possible,” he says.
Dr Berry agrees with this approach.
He considers ‘little and often’ to be more effective when it comes to nitrogen splits.
“This approach reduces the time N sits in the ground and the risk of immobilisation.
That can lead to reduced plant take up and ultimately inefficient use of valuable fertiliser.
In OSR YEN trials between 2017 and 2019, we found an association between the number of splits and increased yield.
This averaged out at an extra 0.24t/ha per application.
Small, but enough to justify increased passes.” Mr Gent also wants to use the trial to minimise any lodging risk arising as a result of a miscalculation on N rates.
“A lodged crop is always going to incur a yield penalty.
If I don’t achieve the 3.5 GAI flowering target I’d prefer crops to be a little thin.
“In the past we’ve seen thin crops perform much better than they look through light getting down into the lower canopy,” he says.
A particular concern this season is trace element shortages.
Tissue testing has revealed insufficient boron, copper and molybdenum in the crop.
“We are often short of boron but perhaps the weather has washed nutrients away,” adds Mr Gent.
At Rookley Farm, Hampshire, Tom Monk’s trial is aiming for increased yield.
He grows oilseed rape for seed but also welcomes its break crop properties.
He aims for a farm average yield of around 4.5t/ha, and yields are generally healthy but farm success is based on continual improvement.
Until recently, N has been applied at a flat rate.
Last season this was a total of 255kg N/ha over five splits through September to April.
But Mr Monk wants to refine his nutrition strategies to match the variability in his soils and target inputs more accurately – ultimately pulling up yields in poorer parts of the field.
And there is no better place to do that than on your own farm, he says.
“Of course, you can get some useful insights from demos and research.
But there is no place better than the farm to test products or techniques.” Two 32-metre tramlines running through the middle of the field will get a flat rate application of 250kg total N/ha, with variances of +/-20% for the rest of the field based on satellite images obtained via FieldView’s field health tools.
Mr Monk also prefers the ‘little and often’ approach to keep the crop fed, so some of the variation in rates will be as small as 10kg N/ha on each application.
“The benefit with FieldView is recording all prescriptive, biomass and yield data precisely across the areas concerned, so there will be no ambiguity about the results,” he says.
As well as the N trial he has tested two different drilling strategies to combat cabbage stem flea beetle.
Having acquired a Weaving direct drill, he is comparing drilling directly into wheat stubbles with his current more conventional approach.
“We can’t go down the companion cropping route with seed crops and chemical control isn’t particularly effective.
“Research has suggested beetles are attracted to bare earth, so stubble is a potential deterrent.
If we can trick the beetles and conserve some moisture, hopefully better developed crops system.
The aim is to cause some disturbance but not as much as a conventional drill set-up.
Mr Monk also expects to continue with the N trial as he sees one season’s worth of data as useful, but not complete.
“Every season is different and last year we applied a little boost of N in January to give crops a hand.
But it hasn’t been needed this season with better conditions.
But I want to build several seasons of data so this knowledge can be used to meet the specific situation faced,” he adds.