In-season nutrition adjustments 'key' to optimising cereal crop performance
During the NUTRI-CHECK NET advice webinar, ADAS crop physiologists Dr Sarah Kendall and Dr Kate Storer explain that checking and adjusting nutrition strategies throughout the season is vital for good crop performance and efficient input use.
Throughout the spring season, growers will be conducting routine visual checks of their crops to identify incoming pest and disease attacks. Dr Sarah Kendall explains that by paying attention to the crop growth stage, ground cover, plant count, shoot number, leaf colour, and rooting, it is also possible to spot early signs of crop nutritional deficiencies and to adjust fertiliser applications appropriately.
“The first phase of nutrient management planning normally happens when buying fertiliser. However, simply sticking to that plan means not taking into account how well crops have established or seasonal factors. That’s why it’s important to refine that initial plan with in-season checks and react as the season progresses.”
Keep an eye out for problem signs
With free online resources available to help identify nutrient deficiency symptoms, Dr Kate Storer recommends that growers familiarise themselves with what to look out for when crop walking and to keep an eye out for potential problem areas.
“It won’t be possible to do in-depth checking in every field and every location. To save time, familiarise yourself with symptoms listed in the AHDB Nutrient management guide (RB209), and then look for areas in the field where something may warrant further investigation. Are you seeing it in just in one field corner, or is it appearing across the whole field, or in multiple fields?”
When to investigate (and when not to)
If a symptom is found, Kate stresses it is equally important to understand whether it’s possible to do anything to fix it before jumping into an in-depth investigation, with products not always effective or efficient in every situation.
“We know that some products may to only improve crop nutrient uptake by less than 10% of the nutrient that they contain. So it’s important to be aware of that and to correct for the efficiency of the nutrient uptake and any adjustments that you make.”
For issues too uncertain or too far gone in the season to resolve, checking during the season, and then following up with grain analysis can allow growers to get ahead of the problem the following season.
“It’s important to note that even if you can’t resolve the issue in season, it doesn’t mean that doing the checks isn’t a valuable thing to do. Grain nutrient analysis will help you identify any patterns and then perhaps next year, you might be able to make some adjustments.”
Adjusting nutrient applications
If there is a nutrient deficiency and it is possible to treat it, the next step would be adjusting the nutrient application and ensuring what is applied addresses the nutrient demand. A simple way to know would be by missing a tramline to leave one area untreated for later comparison.
Kate explained “You don’t want to bias the results so if you’re going to miss a tramline with a particular treatment, make sure you’re not selecting a tramline which may have other issues like waterlogging or a different soil type.”
How to check crop nutrient demand
There are many different methods growers can choose to check their crops’ nutrient demand or status in-season, particularly for mobile nutrients such as nitrogen and sulphur.
Estimating Soil Nitrogen Supply (SNS)
Soil mineral nitrogen can vary widely from field to field which is why it’s important to get an estimate of SNS index to avoid over or underapplication. One method to estimate the SNS index is the field assessment method looking at soil type, previous cropping and winter rainfall. The other approach recommended in RB209 is the measurement method which involves sending samples for testing. Deciding which to use depends on the situation says Kate.
“Anywhere where you might have high or uncertain soil nitrogen supply, possibly due to a wet winter, is where you want to focus your efforts on checking and adjusting your nitrogen requirements based on the measurement method rather than the field assessment method.”
Using NDVI for crop canopy estimations
NDVI is a popular tool for estimating the greenness and size of the crop canopy and could be helpful for identifying problem areas and to indicate how much nitrogen has been taken up by the crop. Kate warns to use with caution as the crop canopy can be impacted by factors other than nutrition.
“Where we’ve used NDVI in ADAS crop trials for monitoring, we’ve noticed it is helpful for identifying treatment differences, but those effects can change over time and our predictions using NVDI alone didn’t necessarily match the yields at harvest.”
Leaf analysis – is it worth it?
Broad spectrum leaf analysis is gaining traction as a ‘snapshot’ tool but lacks significant independent data to fully interpret the results. However, when used as a comparison tool, Kate acknowledges that it does take some of the uncertainty away when making nutrient decisions.
“The jury is still out on whether leaf analysis is worth it, but using it to compare samples from the affected crop and samples from an adjacent, better looking crop – it is potentially a very good tool to figure out what’s going on.”
“The important thing with leaf analysis is to always use the same lab year on year, as results can differ from one lab to the next”.
Beware of Sulphur deficiency
Reductions in emissions from power stations and industry over the past 50 years have led to a significant drop in crop available sulphur. This, compounded by natural sulphate leaching in wet winters, is leading to more frequent sulphur deficiencies. Kate mentioned that the difficulty with sulphur deficiency is that once physical symptoms appear, it is often too late to take corrective action so, if in doubt, growers should submit leaf samples for a malate sulphate test to detect sulphur deficiency in leaf tissue.
“We’ve noticed in our crop trials that sulphur deficiency is becoming more of a problem, particularly in winter wheat. We recently conducted malate sulphur tests at six winter wheat sites – with two leaf samples taken two weeks apart. On plots where results indicated a definite sulphur deficiency, we applied sulphate and the crops responded.”
Measuring nutrition on farm
Andrew Williamson
Andrew Williamson farms 900 acres of wheat, barley, oats, OSR and beans in South Shropshire and has been part of NUTRI-CHECK NET Crop Nutrition Club trials.
“I’m a big believer in the crop telling us what they need. There’s a big variation within the crops, and adjusting in real time, using variable rate nitrogen technology, as you go across the field is invaluable. When it comes to testing it’s easy to measure stuff, but it’s understanding what we do with it and whether it’s representative of the whole field, that’s the challenge.”
“I would like the data to be more mobile and that’s why I like the N tester – you can go out, try in the field and it gives you a snapshot of how things are moving. The other thing we’re looking at is field probes looking soil moisture and temperature which is giving us real time data on the phone. That’s quite valuable I think because it gives us a better idea when putting fertiliser on.”
David Aglen
David Aglen has been managing a mixed farming business in Fife and has also been undertaking trials as part of NUTRI-CHECK NET. Nutrient analysis has been an important feature of how he farms for several years, with the belief that if crops are healthy and nutritionally balanced, they won’t succumb to disease as readily, reducing fungicide requirements.
“There are so many tools out there – I’ve tried soil mineral nitrogen sampling but it’s so variable. I tend to go with my gut this time of year. We’ve got a wonderful spring, you can pick your days to do anything but it’s still early season, the soil’s cooler and there are limiting factors to the plant taking up nutrition, especially up North where things don’t get going until later in April.”
“We’ve used the N tester on some tramlines and it did recommend us to apply more N. We did get a response to that but when it’s pushing you toward 300 kgs, a bit of personal judgement needs to come in there. It certainly seems useful and picked up differences we couldn’t spot by the eye.”
“We used SAP analysis for a while when it was all the rage and sent samples to Holland. The turnaround was good, the results appeared useful but it’s harder to get samples to the continent now. It became very time-consuming and when it takes five to seven days to get results back, crops could have changed. But if we can get live data in field, then we can get the products or something on the next day to help things.”