Farming is a way of life and is anything but predictable. That's why your farm must be efficient and resilient enough to grow crops both sustainably and profitably now and in the future.
Spring barley nutrition is no different to any other crop but growth happens a lot quicker so the focus has to be on maintaining its momentum and ensuring nutrients are readily available when needed.
Spring crops need to quickly develop an efficient green canopy and at the same time build an effective root system to support the crop through to maturity and harvest.
All crops need balanced nutrition and if any nutrient is limiting or unavailable to the plant when needed then growth will slow down and there will be a reduction in yield or quality.
Nitrogen is the most important nutrient and drives yield however, nitrogen utilisation determines grain quality, particularly if applied too late. Sulphur works hand in hand with nitrogen to drive growth and allows nitrogen to be used efficiently. Phosphate and potassium are the next most important nutrients, followed by the key micronutrients copper, magnesium, manganese and zinc.
All nutrients have an important role to play in contributing to yield and although individual influences on yield may be small the cumulative effect can be significant.
Research has shown the benefits of a complete nutrition package that supplies all required nutrients, each of which has an important contribution, to aggregate smaller individual yield increases into a significant overall gain.
An efficient green canopy achieves high levels of intercepted radiation as soon as possible and maintains this through to maturity and harvest.
The fundamental agronomic principles behind barley production are to first build an efficient leaf canopy and then keep this photosynthetically active for as long as possible through to harvest. An effective crop nutrition programme is necessary to achieve both of these objectives.
There is a classic linear relationship between light interception and total biomass produced by barley, with biomass production being driven by the amount of light intercepted by the crop. Until GS30 most of the biomass produced goes into leaf formation, but after GS31 more goes into stems until leaf production ceases at GS39 and ear growth accelerates. It is also known that by harvest, approximately 50% of total biomass (harvest index) will be converted to grain yield.
These simple relationships form the basis from which we develop our agronomic principles in growing barley. In order to intercept the radiation, we need to develop a sufficiently large canopy (not too big) of healthy green leaves to capture 90% of the incoming PAR. This canopy must remain green and healthy during the grain-filling period. There are therefore two distinct objectives: canopy construction and canopy duration.
The objective of a spring barley crop nutrition programme is all about maximising early vigorous growth through supplying available nutrients when needed by the plant and then using nutrients to maintain an efficient canopy that lasts right through to harvest. Premature canopy dieback needs to be prevented since this will lead to high grain nitrate-nitrogen / low protein content.
Construct the leaf canopy as soon as possible to intercept more light and drive early growth.
Maintain a green canopy as long as possible to continue intercepting light through to grain fill.
If we take a typical spring barley crop, we recommend a total of 140 - 160 kg N is applied. When fertilising for yield, actual rate should be based on the economic optimum which is calculated based on the nitrogen response data, adjusted to current crop and fertiliser prices. Check out our spring barley N-Response calculator to see how changing the price of fertiliser and crop affect the economic optimum N rate.
It is important to match nitrogen availability with uptake. As can be seen below, there is an overall uptake rate of 0.9 kg N /ha /day but this varies through the season with an initial nitrogen requirement soon after drilling followed by a rapid uptake of nitrogen during stem extension and then a lower requirement through to maturity. This means a good proportion of nitrogen should be applied at drilling with the balance applied by mid tillering.
Having a strategy to split nitrogen, rather than applying all at drilling or shortly afterwards, enables a more targeted and ‘fine tuning’ approach to enable ‘nitrogen supply’ to be synchronous with ‘nitrogen demand’. Split dressings also allow the use of variable rate technology such as Atfarm or Yara N-Sensor, which reduces lodging, evens up protein and increases yield by approx 3%.
Around 30-40% of this nitrogen should be applied at drilling either surface broadcast, incorporated or preferably combine drilled, using an NPKS compound fertiliser such as YaraMIla Actyva S or YaraMila 52S. The balance of nitrogen should then be applied as a second application at GS30-31 using YaraBela Axan.
Often people ask about applying urea, however, this can often be risky. Urea won’t have the same effect as an ammonium nitrate based fertiliser as it takes between 10 days and 6 weeks to hydrolyse and convert into plant-available nitrogen. This is not ideal if we are looking for quick plant uptake to establish the crop as soon as possible.
Trials show there is a linear relationship between applied nitrogen and grain protein. Approximately for every 20 kg N per ha an increase of 0.06% grain N was observed.
If high grain N is required (= high protein) it is important to be fertilising for yield, otherwise sub-optimal applications will be diluted, leading to low protein.
Plants need sufficient levels of sulphur to be able to utilise nitrogen efficiently. Together, nitrogen and sulphur are vital building blocks for protein, so N and S should be applied at the same time.
Sulphur behaves in a very similar way to nitrogen in the soil, readily leaching in the sulphate form just as nitrates do therefore this should dictate that you’d treat it the same as nitrogen. You wouldn’t apply all your nitrogen in one go and expect it to fulfil the crop requirement through the growing period, so why treat sulphur like this? Applying sulphur in one application means that there is a large potential for a lot of it to leach away through the soil profile and is then not available to the crop. The type of sulphur also has an impact upon its leachability; with calcium sulphate leaching significantly less than ASN.
So it makes sense to apply sulphur little and often with each nitrogen application. Yara's sulphur recommendation for wheat is to apply 8-10 kg S per ha during the season at the same time as nitrogen. A YaraMila true compound NPKS fertiliser such as YaraMila Actyva S is a sensible choice for the first application. This should then be followed by a YaraBela NS fertiliser such as YaraBela Axan for subsequent applications through the rest of the season.
'Little and often' applications of sulphur ensure a season-long supply to the crop.
Sulphur is immobile in plants so to reach new growth a continuous supply is needed.
Phosphate is an important nutrient to apply early to spring barley as this is when levels of available P in the soil are at their lowest and cannot supply the crop requirements.
Phosphorus availability within the soil is affected by the pH, soil temperature, aeration and waterlogging. Typically in spring, we have cold soils meaning that P-availability is low. At drilling, soils may only be at 4-5°C whereas phosphate isn’t available from the soil in any kind of useful quantities until it reaches 8°C and above. Consequently, there is a potential period when crops aren’t able to access this key nutrient. The last thing we want to do is hinder crop development at this key growth stage, just as the crop begins to grow, so by adding some fresh available P to the soil it will act as a starter fertiliser until soil-P becomes available.
Phosphorus is the most important nutrient for root development. The rapid development of an effective root system is particularly important for spring barley as this allows quicker development of the crop canopy so the crop can begin building biomass. Equally important is to build an extensive root system that will support the crop through to maturity and prevent premature senescence, particularly relevant on the lighter soils typically used for growing spring barley.
Trial results have consistently shown a response to fresh phosphate, even on soils with reasonable levels of P and K. This shows the benefit of having sources of nutrients that are immediately available to the plant. Yara's recommendation for P and K is typically 75 kg/ha K and 8-10 kg/ha P, assuming target soil indices.
When it comes to micronutrient deficiencies, prevention is always better than a cure and avoids yield losses from unseen 'hidden' deficiencies.
Adequate nutrition including both macro and micronutrients has always been important for autumn-sown crops, not just to ensure successful establishment but to set the ultimate yield potential of the crop, so micronutrients should be an integral part of any crop nutrition programme.
Over the years trials have also taught us the importance of getting these micronutrients on at the key timings before any deficiency starts to appear. A preferable mindset is to think about ensuring sufficiency of supply. This is where the importance of historic farm data comes into its own, enabling proactive decisions to be made. If such data is not available, an alternative proactive approach can be taken by using crop-specific products that have been designed to deliver the key nutrients for crop growth and development.
To keep things simple you can use a crop-specific micronutrient mix for cereals such as YaraVita Mancozin, which contains manganese, copper and zinc This covers the key micronutrients for cereals and therefore is a useful option if you don’t want to do tissue testing. Another option is YaraVita Gramitrel, which also contains manganese, copper and zinc as well a useful source of contains magnesium.
Trials work has consistently shown benefits of additional micronutrients in spring barley.
If you think that you’ll have particular deficiencies then it is a good idea to take some tissue tests however, once you begin to see deficiency symptoms you are already negatively affecting the yield and it is too late, especially in spring crops with such a short application window Tissue testing and grain analysis are best used to look-back and see what micronutrient deficiencies occurred with a view to addressing them in future crops rather than in the current crop.
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