Soil analysis is normally carried out within a three to five-year cycle on tillage farms throughout the UK and Ireland.
However, the additional benefits that can be accrued when the information generated by grain analysis is included within a crop planning process are significant.
Crop physiologist at the UK-based consultancy ADAS, Dr. Sarah Kendall, explained: “Soil testing delivers valuable information where pH, potash, phosphate, and magnesium levels are concerned.
“We can add to this information dataset with leaf analysis.
“This is an approach that allows farmers to make in-season crop nutritional checks, linked to any specific deficiencies that may have been highlighted.
“Crop post mortems are new. However, we at ADAS believe they provide better monitoring to improve crop nutrition.
It’s a perspective totally endorsed by fellow ADAS crop physiologist, Dr. Tamara Fitters, who said: “Reviewing is very much about making a check list.
“It’s a process that includes looking at what is happening mid-season as well the results derived from the harvest.
“This approach allows us to review the whole growing season, instead of just taking a snapshot of it.
According to the ADAS crop physiologist, as the harvest has commenced, it is “very important” to check results.
“For example, this year no one was expecting it to be this dry. This factor alone can make a big difference to what was expected relative to what is actually happening.
“The next challenge is to work out why a difference may have arisen in the first place.
“Then it’s a case of working out how this can be mitigated against into the future. In the case of the weather, this is not possible.
“But there might be other reasons why final crop performance levels were lower than might have been previously expected,” Dr Fitters added.
Crop nutrient management plan
Soil assessments are the key starting point when it comes to developing a crop nutrient management plan.
Dr. Fitters said: “Soil Index values can be used to determine a crop nutrient plans for the coming season. Other factors to be added in at this stage include the availability of organic materials and chemical fertiliser options.
“We want to know the sort of yield we normally get. This gives a good ideas as to what a certain filed is capable of.
“Past harvest results are important in this regard. We also look at weather patterns. It’s impossible to determine the exact nature of weather patterns at the beginning of a season.
“However, there are general weather patterns that we can avail of it and, at least, try to take this into account.”
In-season crop analysis requires the taking of leaf samples. Subsequent laboratory analysis delivers a full nutriment breakdown of the tissue.
“This will give us an idea of how much the plants have already taken up from the soli stores,” Dr. Fitters said.
“It will also give us an idea if the crop is on track. We know which stage of growth the tissue samples were taken. And this means we should have an idea of what the nutrient values should be.
“If these are not adequate, then we can adjust upwards, thereby boosting plant growth rates accordingly.”
Subsequent grain analysis can take place at the end of the growing season. This gives a definitive perspective on what has happened, from planting through to final harvest.
According to Dr Fitters, this process quantifies the amount of nutrients actually taken up by the growing crop.
“We know what we put in and we know what was in the soil prior to planting,” she said.
Evidence-based approach
“Grain analysis constitutes an evidence-based approach, so the information obtained is of tremendous significance in terms of decision making for the next season,” Dr. Fitters said.
But other factors also come into play.
“We don’t know how much nutrient is lost in the water or to the air,” stressed the ADAS crop physiologist.
“So, going forward, in terms of finding out what’s happening in our fields, we want to focus on those bits that we can work out.
“Losses to the air and water will be very hard to determine. Special measuring equipment would be required to get those numbers.
“But what we can measure are the outputs. And it would be very valuable to do this on a regular basis.”
Fertiliser uptakes
Significantly, grain nutrient values can vary quite a lot. Analysis has shown that when measured across a number of fields, grain nitrogen, phosphorous, and potash levels will follow a form of normal distribution curve.
However, actual in-field values for these nutrients may well vary from what are regarded as UK standard estimations.
Dr. Fitters points out that current, assumed UK values for grain nitrogen are pretty much spot on, where nitrogen is concerned.. However, they may well over estimate the phosphorous and potash content of grains.
She added: “We can’t always rely on standard numbers. Each farm will be different: each field will be different. So it’s important for farmers to identify exactly what is going on within their own crops.
“However, we can use average numbers to provide a form of benchmark.”
Significantly, actual grain nutrient values can allow for the calculation of fertiliser response values.
Nitrogen is particularly important in this regard and, according to the ADAS representative, performs quite neatly to this form of analysis.
“We can effectively work out the optimal response rate by using this approach,” she said.
“This is an economic optimal value.
“If insufficient nitrogen is applied, there will be quite a high yield penalty. Adding nitrogen fertiliser above the optimal value can quickly lead to significant economic losses being incurred.
Dr. Fitters pointed out that similar response curves have been generated with regard to nitrogen applications on wheat and barley crops.
However, she said where oats are concerned, the drop-off in relative response rate to nitrogen is “much more significant beyond the optimal input level”.
“It’s important to realise that we can accurately quantify this loss in come from non-optimal nitrogen usage,” she said.
“The end objective is to get both a good crop yield and optimal grain nitrogen content.
“The data that is generated for particular fields and specific crop varieties can then be checked against standard figures.
“If there are major differences, then it’s a case of working out how these came about.”
Within a feed wheat scenario, ADAS figures show that grain protein values that are 1.5% below optimal values can result in losses of up to £50/ha.
And all of this comes down to securing optimal nitrogen fertiliser application rates in the first place.
Crop offtakes
Three factors now come into play – crop offtake, crop capture, and crop application.
“It should also be possible to calculate a crop residue, which can be used for the next season,” the ADAS crop physiologist commented.
“Another thing we can do with grain analysis is diagnose nutrient deficiencies and excesses.”
Dr Fitters said this process starts with the development of a full inventory of all fertiliser sources used, including organic manures.
“It’s then a case of calculating the nutrient harvest from each field. This is the yield multiplied by the percentage of each nutrient.” she explained.
“So to do this we need our grain analysis results.
“We can then do a field nutrient count. The difference between the soil and grain analysis will tell us if the crop left significant nutrient analysis for the benefit of the next crop or there is a requirement to build up soil nutrient stores again.”
