Blog by Alli Grundy of NRM on Grain Analysis - 2 August 2022.

View original LinkedIn blog here

Along with longer days and hot summer breezes comes harvest time for thousands of farmers across the UK. Whilst they will be very busy at this time of year revving up their combine harvesters, they also need to be consulting with agronomists and advisors to determine how this year’s harvested crops can help us understand the needs of their future crops.

We are being encouraged more than ever before to measure all aspects of the crop production process, from the soil to inputs and plant tissue to grain. All this data helps to guide decision making and indicates the impact of previous decisions taken.

Read on to find out more on why it’s important to analyse grain after harvest, how insightful data can affect decision making, and how NRM’s handy GrainCheck calculator and analysis services can help.

The importance of grain analysis

Analysis in season describes the here and now. Accurate, reliable results give you the power to act to remedy issues or take the advantage of the theory of marginal gains to support or eke out more yield potential.

Grain analysis is all about gauging how well the crop did in the previous season and where might you have made different decisions. Could changes in certain practices have led to better quality, higher yields, or reduced risk to the environment?

Whilst it’s too late to affect the crop that has just been harvested, grain analysis is a valuable tool in helping us understand the impact of the season. It also encourages us to think how a different agronomic approach to the next crop could help improve production or mitigate against future cropping challenges.

Analysis data also functions as evidence. Grain analysis helps us justify our nutrient decision making, supporting inputs and checking the availability of nutrients from organic sources and the soil. The reliance on inorganic fertilisers over the past 50 years has induced a fear of change because of the revolutionary impact they had on crop yields and quality. Even though current economics are driving businesses to review the cost of production, changing a system to one perceived as unknown or unfamiliar adds another variable to manage.

The agricultural industry is changing, meaning that analysis is more important than ever before. Knowing what to measure and why you are measuring it is important to reassure farmers and advisors of the benefits of changing farm practices. Ultimately, grain analysis is a good benchmark of how well the season has performed and if changes made the year before resulted in the anticipated impact(s).

How can grain analysis data help?

Knowing how well a crop has recovered nutrients at a specific yield is important for replacing the soil supply of nutrients. This helps to support the future needs of the next crop and maintain the soil index.

Whilst guidance exists within RB209 on the removal rates of major nutrients such as phosphate and potash, this advice is based on typical values contained per tonne of fresh crop material. Even though this approach is accurate on average, knowing exactly what the crop has removed at the seasons end is valuable because it enables a site-specific approach to the management of soil indices. For example, higher yields overall will remove more phosphate and potash, but specific analysis of grain from your farm provides a barometer of how well the soil:plant system is functioning. Knowing the concentration of nutrients within the grain is also important because they could vary from what standard guidance suggests.

The chart below shows the distribution of phosphorus (P) and potassium (K) concentrations measured in more than 1,200 wheat grain samples harvested in 2021. As you can see, the median value for P is slightly lower at 0.303% than RB209’s advised figure of 0.32%. Grain nutrient content that is reported repeatedly below 0.32% for P, for example, indicates that yield has been affected by reduced uptake by the plant.

The median value for K was 0.45%, but the range was between 0.33 and 0.75%. The critical grain value for K (as defined by ADAS) is 0.38%, but this level has a degree of uncertainty attached and should be applied cautiously.

Using NRM’s analysis data described in the chart above, the phosphate and potash offtake removed by the grain can be calculated.

If you look at the table below, it is interesting to observe the differences between the NRM analysis data and typical kg/t values. The calculated values in the table, which are based on measured median sample values, are very similar but suggest a slightly reduced offtake of potash and a slight increase in phosphate.

Comparison between analysis and guide figure: 8.0t/ha yield 15% moisture, grain only

Based on NRM wheat grain analysis 2021 (1,200 samples). P median value 0.303%. K median value 0.45%. Grain yield at 15% moisture content. RB209 kg/t fresh values adjusted to yield at 85% DM for comparison.

To calculate the crop offtakes based on laboratory analysis and the actual crop yield, the following formula can be applied:

Nutrient removal = fresh yield * P/K % content * conversion factor

The conversion factor accounts for adjusting the fresh yield t/ha to 15% moisture, from % nutrient in grain to kg/t and between the nutrient element and its oxide.

Conversion factor = (85/100 * 10) * 2.291 [P205] or 1.205 [K2O]

You don’t have to calculate this all yourself. Use NRM’s handy GrainCheck calculator instead.

GrainCheck Calculator: Start Grain Check – NRM

NRM has developed an easy-to-use nutrient offtake calculator alongside its GrainCheck service. All you have to do is enter the yield, grain moisture at harvest, and the analytical result. The output is the calculated phosphate and potash offtake (kg/ha) removed by the grain only. The amount of phosphate and potash contained in the straw isn’t calculated but should be estimated if you are baling and removing from the field.

Guide figures where both grain and straw are removed from the field are available in RB209.  The straw yield is assumed to be 50% of the grain, but if this is known, standard offtake figures can be applied, and offtake values calculated.

It is also worth noting that potash concentrations in straw can significantly reduce between maturity and when the crop is harvested. As such, it is a good idea to determine the nutrient content by taking a representative sample and sending it to a laboratory for analysis.

Comparing your results to the typical average gives you a good indication on how well you are managing nutrients. It prompts you to make further investigations if grain concentrations and offtake levels were smaller or larger than you expected. No analysis result should be taken in isolation of other measurements, and quite often it leads to a more thorough look at soil supplies, the balance of nutrients from the soil, inputs, and how they are utilised.

ADAS, through its Yield Enhancement Network (YEN), has highlighted the importance of grain analysis and how that data can be used to improve crop nutrition decisions and optimise productivity. This includes helping farmers benchmark and compare against data across the country. To be part of the YEN programme, follow this link: Join the YEN Community | The Yield Enhancement Network (adas.co.uk).

With harvest in full swing, now is the time to plan the collection of grain samples. For more information or to arrange analysis, speak with your agronomist or contact NRM directly.