Tailoring all nutrient inputs closer to crop uptake can bring better results from today’s high-yielding cereal crops, according to CF Fertiliser. CPM summarises the theory and recent trials work that substantiates it.
By Rob Jones
Cereal production is evolving and optimum fertiliser use isn’t necessarily keeping pace. That’s the message from CF agronomist Alli Grundy in the light of results of recent trials work carried out by the company.
“You only have to look at the advent of new high yield, high potential milling wheat varieties, the recent move towards spring cropping and increasingly strict demands of the market, to realise there’s a change underway,” she says.
Add in updated national fertiliser recommendations (RB209) being launched in May and fluctuating grain prices putting added pressure on input performance and there’s a compelling case to review fertiliser practice on cereal crops.
“Optimum crop production is increasingly about what matters on individual farms and how the system can achieve this while making sure management stays within best practice guidelines,” she continues.
“Whatever the crop you’re growing, the real concern is to make sure fertilisers are used as efficiently as possible so money isn’t wasted and nutrients intended for the crop don’t end up somewhere in the wider environment causing unintended consequences.”
It’s not just about nitrogen
If you’re focusing on optimising nitrogen utilisation, you have to make sure all elements of the nutrition equation are right, Allison Grundy says.
“Phosphate and potash are essential plant nutrients in their own right but they’re also key in maximising recovery of nitrogen from the soil. If you have a soil index of less than 2 for either of these, no matter how much nitrogen you put on, it won’t be used efficiently.
“Potash and phosphate have to be kept in balance to make full utilisation of nitrogen. Low indices of potash reduce N uptake and phosphate is essential in promoting root growth. So without adequate levels, the plant’s efficiency to take up nitrogen is severely limited.”
In recent years, Sulphur has also become one of the main limiting factors with regard to crop yields and quality, she adds.
“Sulphur is vital in protein synthesis and without adequate supplies, specific long-chain protein production is limited reducing productivity and crop quality.
“Environmental concerns regarding industrial emissions and acid rain have led to a tightening of regulations that has seen a dramatic drop in sulphur from the atmosphere – from around 75kg/ha SO3 a few years ago to little more than 8kg/ha SO3 now.”
Soil acidity (pH) also affects nitrogen uptake and unhelpfully interferes with the balance of other nutrients in the soil. Restricting availability of some while encouraging that of others –usually the ones which are less helpful to crop growth, she adds.
Know your soil
Knowing your soil begins with an understanding of its type, structure and pH and almost as important is understanding what it can contribute in terms of nitrogen.
“The latest RB209 offers very valuable recommendations for fertiliser application but by its nature they’re very general. The real lifts in nitrogen utilisation and cost-effectiveness come when we can take a more field-specific approach.
“We’ve pioneered the CF N-Min analysis because we believe it’s the only real way of assessing soil contribution properly. Most tests measure soil mineral nitrogen (SMN) but this only gives a reflection of what has been mineralised in the soil up until the date of sampling.”
N-Min also estimates additional available nitrogen (AAN) – the nitrogen that will be mineralised in the soil between the time of sampling and harvest, she says.
“When measurement of SMN and AAN are combined, this allows the overall soil crop N contribution to be determined with greater accuracy, particularly in those soils with higher organic matter content, having manure inputs or following leafy crops.”
In fact, across eight farm trials where calculated nitrogen need was compared to existing farm practice, not only were better results achieved with the more precise approach, margin improvements of between £75/ha and £150/ha were also recorded.
Know your crop
As well as understanding exactly what the soil can contribute it’s essential to estimate the demand of the crop and this requires an understanding of end market and yield potential, Allison Grundy advises.
“If you have a good starting point from N-Min, then using N-Calc to work out what you’ll need to meet your yield objective is the next step.
“Modern varieties like Skyfall and KWS Trinity have huge yield potential but there’s no point targeting 12t/ha crops if the farm, field or soil structure isn’t really up to delivering this.”
While you don’t want to starve a potentially high yielding crop, if you apply more nitrogen than the crop can realistically utilise, not only will it impact on margins it could also create environmental issues, she points out.
“Last year’s trials with Skyfall in Yorks using SingleTop (27N + 12SO3) showed that the more nitrogen you apply, the more able it is to build yield while keeping proteins relatively stable, so the highest nitrogen rates gave the best margins (see table below.)
Fertiliser response in Skyfall, 2016
“While with Trinity using KayNitro Sulphur (25:0:13 + 7S03) and Nitram (34.5% N), the trials showed the optimum rate for the variety could be 20-30kgN/ha down from those needed for Skyfall.”
Where higher rates were used, these continued to improve protein levels but without always adding to yield, she explains. (see table below.)
Fertiliser response in KWS Trinity, 2016
Hand in hand with nutrition knowledge comes choosing the right fertiliser, argues Allison Grundy, and growers should look beyond price per tonne of inputs.
“It’s about minimising your cost of production rather than simply looking for the least cost option. If you spend 10% more on your fertiliser but get a 20% response in yield then you’re actually reducing your costs per tonne of production.
“What’s more, a better quality of product is less likely to give you problems with uneven distribution, volatilise before the crop has a chance to use it or end up somewhere you don’t want it.”
Defra trials using urea in cereals have shown losses of between 2-43% of the total urea N applied, she adds.
“Economically, this is nitrogen that has been paid for that’ll contribute nothing to plant growth. In fact, the Defra researchers worked out that to maintain crop yields and quality, the optimum N rate using urea would have to be, on average, 20% higher than with ammonium nitrate (such as Nitram).
“On average, winter cereals using urea were shown to have yields 0.3-0.4t/ha less than their counterparts with AN-based fertiliser plans.”
According to ADAS head of crop physiology Pete Berry, research confirms good quality AN has a lot to offer growers over urea.
“Replicated experiments funded by Defra since 2003 have shown that at a rate of 200kgN/ha AN yielded more than urea in 77% of cases and gave a yield advantage of more than 1t/ha in one case. AN also gave a higher grain protein content than urea, illustrating its suitability for milling wheats.”
Professor Roger Sylvester Bradley of ADAS has seen similar limitations with urea use in wheat. “In trials when we’ve applied 30kg/ha of nitrogen as foliar urea late in the life of wheat, we’re probably only getting 6-10kg/ha of nitrogen into the crop. The rest is simply being lost.”
Tailored N brings a higher wheat yield
At Chris Richardson’s Grove Farm at Swaton in Lincs, careful nitrogen management is showing the way to achieving yields approaching 12t/ha at the all-important 13.0% protein.
In CF trials carried out in 2016, using Skyfall, the farm’s standard practice of applying 250kg N/ha delivered a yield 11.19t/ha whilst the N-Min advised application rate of 215kg/ha from DoubleTop and Nitram applications, produced a yield of 11.57 t/ha.
The combined effect of the 16% saving on applied nitrogen – £139.75/ha compared with £162.50/ha – and the additional yield produced add up to an increase in margin of £72.91.
Despite the lower application rate, the N-Min crop produced 13.0% protein, proving to Chris Richardson that the approach delivers cost savings, higher yields and optimum quality.
“All our crops now get 150kg/ha of DoubleTop as a first application so we know we have the right amount of sulphur going on,” he explains.
“This provides 40kg N/ha and, depending on what N-Min is telling us, we’ll then follow this up with two dressings of straight 34.5% AN as Nitram to provide another 90-240kgN/ha for the seed crops.”
While these crops typically receive 200 – 250kgN/ha of additional fertiliser this way, an extra dressing of N is usually applied to the milling crops taking this up to around 300kgN/ha, he says.
“We learned that if we want to get a 10t/ha crop of Skyfall, – 11t/ha if possible – at 13.0% protein, we have to fertilise the crop as if it was a 12t/ha crop.”
On-farm fertiliser trial, 2016