Grain analysis and post-harvest reviews can play a pivotal role in refining nutrient strategies for future seasons, urge experts.

While many farmers are diligent about planning their crop nutrition at the beginning of the season, according to ADAS, few revisit and adjust those plans as the season progresses. Fewer still conduct a thorough review.

For those looking to know how well their crop nutrition plan performed ahead of next year’s, taking the time to review nutrient uptake success at harvest is key, says Dr Sarah Kendall.

“Most farms will determine the success of their nutrient management plans by yield alone, irrespective of the fact that non-nutritional factors will also play a role in yield. Grain analysis highlights if the nutrients available to the crop were actually sufficient, deficient, or excessive – without this crop ‘post-mortem’, you could be missing vital data for improving crop performance and streamlining your nutrition plan next year,” she explains.

A true picture

Dr Tamara Fitters, crop physiologist at ADAS, adds that grain analysis can help to uncover the true picture of nutrient uptake. “Farmers are required to assess their soils every 3-5 years so in most cases, we can estimate how much nutrition is in the soil, and we know what inputs we’ve applied.

“However, it’s really hard to determine how many nutrients are lost to the water or air. By assessing grain at harvest, we can identify what nutrients, if any, the crop was missing for optimal growth.”

Very often, growers will look to industry guidelines to create a crop nutrition plan, but Tamara warns that making assumptions about the nutritional requirements of a particular field in this way could prove to be a mistake.

“Through our grain analysis and benchmarking service YEN Nutrition, we analysed the nutrient content of 1700 crops from 2017 to 2021, and compared these with standard nutrient figures recommended in RB209. The analysis showed that depending on the field, nutrient recommendations in RB209 can sometimes overestimate nutrition needs  – particularly with phosphorus and potassium.

“In reality, there’s no average field so there is scope to improve. Benchmarking against the industry standard is good, but it’s important to measure your own fields to see what’s really going on as opposed to simply relying on standard numbers.”


Economic optimum

Without conducting a nutrition review, Tamara believes farmers could also unknowingly miss their ‘economic optimum’ – the point at which fertiliser efficiency and yield are maximised. “Underapplying nutrients could lead to yield loss; overfertilising is an unnecessary cost that will eat into profits and risks environmental pollution. We all want to get nutrition right, but that’s almost an impossible task without understanding what the crop captured or calculating offtakes with grain analysis.” 

Once harvest is complete, she recommends farmers complete a field nutrient account – listing the soil analysis results, total nutrients applied, results from leaf analysis (if completed), and grain analysis results. Viewing all of these nutrient measurements in one place with the final yield should allow growers to determine what nutrients are left in the soil, and provide a starting point for drafting the following season’s nutrition plan.

“While having all the data in place might look daunting, a field nutrient account will help greatly with making adjustments. Taking for example phosphate, the recommendations may say we should apply it, but we know from our field nutrient account that offtakes were less than RB209 predicts, so application rates for the following crop could be reduced.”

Diagnostics

According to Tamara, the other benefit of grain analysis is diagnosing nutrient deficiencies. She says of the 1700 crops analysed with ADAS’ YEN Nutrition grain analysis service, the vast majority – more than 85% –  were found to have at least one nutrient deficiency; most had more than one.

“The problem is, by the time you do see a deficiency in the crop, it’s already too late to do anything about it. Remembering grain analysis at harvest will help you to take the right remedial action next year.”

Michael Brewis runs a 430ha mixed farm with his father near Kelso in the Scottish Borders. With the support of his agronomist Jackie Cotton, he’s been carrying out in-season N testing, soil sampling, leaf analysis, and end-of-season grain analysis for the past few years in response to rising fertiliser prices.

“You can’t take one year of data and treat it as gospel. Quite often there are factors affecting yield outside of your control, so when you want to make changes to your nutrition, you have to be aware of that,” he stresses. “Build data over time and don’t have a knee-jerk reaction based on one bad result.”

Agronomic advice

Michael adds that for him, his agronomist Jackie has been the driving force, using the N tester every week from GS 30 on the farm. Looking back over previous years, Jackie notes that while Michael’s team have been proactive, there’s still some fine-tuning to do.

“Grain analysis results don’t always come back as you expect. We do seem to have cracked nutrition with the oilseed rape crops, getting green results back all the time. But with the cereals – winter wheat, winter barley, spring barley – we’re having more difficulty. Sometimes the leaf analysis comes back fine but later the grain analysis is identifying deficiencies.

“We go to the same places in the field every year for sampling to try and get consistent measurements. Using the same lab for testing helps with making accurate year-on-year comparisons as well,” she concludes.