Spring nutrition needs to maintain crop momentum
Once winter cereals begin spring regrowth then that momentum needs to be maintained by making sure all the required nutrients are available when the crop needs them.
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.
Some nutrients are more important than others. Nitrogen is the most important nutrient at this timing, however, sulphur works hand in hand with nitrogen to drive growth. Phosphate and potassium are the next most important nutrients, followed by the key micronutrients copper, magnesium, manganese and zinc.
How does nitrogen affect tillering?
When conducting the first nitrogen applications a few things need to be considered: the crop’s current density, is the crop actively growing, what nutrients are required and application rates.
When determining the crop’s current growth we need to think ahead. The target number of shoots to aim for is 1000/m2 in April. In order to reach that we need about 250-260 plants/m2. The early nitrogen timing is when we can manipulate the number of tillers which is, of course, the key to getting to that desired target number. Trial data shows that higher, early rates of nitrogen can increase the number of tillers by 20%, therefore we can manipulate the more backwards crops into producing more tillers to reach our target numbers.
Before applying anything we need to ensure that the crop is actively growing. If we apply when the crop is still dormant then we run the risk of nutrients leaching; which could potentially then cause environmental issues in watercourses. To check for growth we need to get out in the field with a spade. By digging up some plants we can look at the root tips. If they are a nice, fresh, white colour it shows that the crop is actively growing and looking for resources. Therefore we can apply the first fertiliser application as we know that the crop is able to take up the nutrients.
What rate of nitrogen should I apply?
If we take a typical wheat crop, we recommend 50-60kg N of an NPKS product such as YaraMila Actyva S at the first application in mid-end of February (so long as conditions are conducive). This gives the crop the best chance of building the foundation of biomass before the cut-off date in mid-March.
If we are looking at a late drilled or backwards wheat crop then we recommend 70-80kg nitrogen. This will help struggling crops to tiller more increasing all-important biomass. Because this nitrogen needs to be immediately available to the crop the preferred source is nitrate-based rather than urea. In the case of very late-drilled crops, you should consider splitting the first application into two applications of 30-40kgN/ha, with the first being applied as soon as possible and the second a week or so later at mid-end of February.
Often people ask about applying urea at this time, however, this can often be risky. Urea won’t have the same effect as AN as it takes between 10 days and 6 weeks to hydrolyse and convert into plant-available ammonium and nitrate. Therefore, if your crops are looking ‘sick’ then opt for immediately available ammonium nitrate.
Forward crops should be treated the same as a typical wheat crop. There is often a temptation to delay early applications but such an approach risks slowing down the crops' all-important momentum. However, it is important to ensure these crops have a robust growth regulator programme.
Planning your first N-applications
Why is sulphur timing so important?
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
'Little and often' applications of sulphur ensure a season-long supply to the crop.
Minimise leaching
Avoid applying sulphur 'all at once' to reduce the risk of losses by leaching.
- Plants need a regular supply of sulphur throughout the growing season, so a 'little and often' approach to sulphur management is essential.
- Sulphur can be readily leached through the soil, just the same as nitrogen, so shouldn't be applied 'all at once'.
- Sulphur is immobile in the plant so cannot be moved from old to new leaves when it is needed, this means fresh sulphur is still needed later in the season.
- Nitrogen deficiency is easily confused with sulphur deficiency so if you think you are seeing nitrogen deficiency on younger leaves it is probably caused by a lack of sulphur.
Why is phosphate availability low in spring?
Phosphate availability within the soil is affected by the pH, soil temperature, aeration and waterlogging. Typically in spring, we have cold, wet soils meaning that P-availability is low. Crops will start to grow 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 start to grow but aren’t able to access this key nutrient.
The last thing we want to do is stop the momentum at this key growth stage, just as the crop begins to grow, so by adding some fresh available P to the soil it will bridge the gap between the kick-off of growth and soil-P becoming available.
The phosphate source is particularly important and needs to be one that is NOT immediately ‘locked up’ (TSP, MAP, DAP based fertilisers), and gives season long, continuous supply.
Another reason for spring P is that that is when the crop demand is highest! 70% of P is taken up in a 4-8 week period March to May. P is liable to be precipitated out or adsorbed to other ions within the soil so applications carried out in the autumn won’t be available to the crop when the peak demand is there.
Foliar phosphate gives the crop an ‘energy boost’
An application of foliar phosphate will get crops off to a good start since foliar P is taken up into the crop a lot more efficiently than solid forms especially when soils are cold.
What are Yara's recommendations for spring phosphate?
The combination of a YaraVita foliar phosphate product along with an application of YaraMila soil-applied phosphate will energise the crop for early, rapid spring growth and development to recover and build biomass for an improved grain harvest. Indeed, recent Yara trials have shown wheat yield increases from 0.23 – 0.6 t/ha. These trials have also shown that a rate of 10-20 kg P is required in the spring, independent of soil indices.
An application of foliar phosphate such as YaraVita Magphos K at 5 l/ha during tillering, ideally GS 25-29, will give a much needed 'energy boost' to get crops moving again. This should coincide with the application of a YaraMila true compound NPKS fertiliser such so that the crop doesn’t run out of momentum.
Micronutrient deficiencies should be prevented
When it comes to micronutrient deficiencies, prevention is always better than a cure and avoids yield losses from unseen 'hidden' deficiencies.
What should I do about micronutrients?
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.
Prevention is always better than a cure
Crop specific mixtures avoid uncertainty
How do I decide which micronutrients are needed?
To keep things simple you can use the crop-specific micronutrient mix for cereals, YaraVita Gramitrel, which contains magnesium, 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.
Trial work has shown that on average over the past 6 seasons there has been a 0.30t/ha yield increase from an application of Gramitrel in the autumn and the spring.
If you think that you’ll have particular deficiencies then it is a good idea to take some tissue tests a couple of weeks prior to your application so that you can order the specific micronutrients. However, once you begin to see deficiency symptoms you are already negatively affecting the yield, so try to catch them before they are visible.
The only way to prevent 'hidden' deficiencies is through routine tissue testing and/or applying crop-specific mixtures like Gramitrel.
The recommended rate of YaraVita Gramitrel in spring is 2-3 l/ha at GS 30-32 which will typically coincide with T1 fungicide applications.
Key actions
- Decide on the appropriate nitrogen rate for the first application based on crop vigour:
Forward crops - 50-60kg N per ha (remember robust growth regulator programme will be needed)
Typical crops - 50-60kg N per ha
Backward crops - 70-80kg N per ha (consider splitting if crop is very backward) - Apply an NPKS fertiliser to supply the above nitrogen rates AND also in the region of 8-10 kg S and 10-20kg P. Often an ideal choice will be YaraMIla Actyva S depending on the 'best-fit' with these rates.
- Apply foliar phosphate as YaraVita Magphos K at 5 l/ha during tillering, ideally GS 25-29 (T0)
- Apply further nitrogen applications using YaraBela Axan at second and subsequent application timings.
- Apply a crop-specific mixture of micronutrients as YaraVita Gramitrel, at 2-3 l/ha at GS 30-32 (T1)
Recommended fertilisers
Where can I buy Yara fertilisers in Ireland?
Yara supply our branded fertilisers and crop nutrition products to the Irish market through a network of local merchants and co-ops Use our interactive map to locate your nearest suppliers.
Related agronomy advice articles
Improve your farm's nitrogen fertiliser efficiency
Improving nitrogen fertiliser efficiency is one way your farm can become more productive, profitable and sustainable. Try our quiz to find out how you can improve your farm's nitrogen fertiliser efficiency.
Read more about improving nutrient efficiency
Future-proof your farm
Find out how your farm can become more productive, profitable and sustainable by future proofing your resources, your profit and our planet.
Have you heard our latest podcast ?
Grow the future podcasts will keep you up with all the latest crop nutrition information, advice and much more.
