USING TISSUE MONITORING TO ENSURE CROPS ACCESS ADEQUATE NUTRIENTS

March 2, 2021



Although crop nutrition planning should always start with soil analysis to identify the available nutrients in the soil in each field, checking nutrient uptake during the season is the key to optimising nutrient use efficiency, yields and margins. Understanding the nutrient content of your crops means you can take remedial action before the crop starts showing deficiency symptoms and can cover everything from nitrogen to micronutrients.

Tissue analysis is popular with agronomists and growers because it identifies nutrient concentration as well as crop nutrient content. We also recommend biomass monitoring, which is straight forward to do: simply take a number of single square metre plots, cut and weighed, and ask for dry matter content on the laboratory booking form.

The AHDB crop growth guides give benchmarks for dry matter and nitrogen accumulation through the season. There are target uptake tables for micronutrients as well as the macronutrients nitrogen, phosphate and potash. It’s important to note that all crops require large quantities of potash, as without it they will be more susceptible to drought. Regular tissue testing means you can monitor your crops and take action if nutrient uptake is falling behind target. This is as important for micronutrients as it is for NPK.

The uptake of most nutrients will be restricted by acid soil, where nutrient availability is compromised at a pH below 6.0, and by compacted soil where root growth is restricted. For manganese, puffy spring seedbeds can lead to poor uptake. In all these situations, soil analysis coupled with tissue monitoring provides the best chance for improving nutrient use efficiency and yields.

All crops need adequate nitrogen and magnesium, a central component of the chlorophyll molecule, to support photosynthesis. With oilseed rape, it is particularly critical to ensure that the upper leaves, whilst small, can photosynthesise effectively to contribute to yield. For winter sown crops we recommend tissue testing in April, to pick up any deficiencies and cross check the results of in-field nitrogen testing. With spring sown crops, the window for monitoring is narrower. These crops have a very short nutrient uptake period of only seven to eight weeks, so there is insufficient time to modify nutrition plans once deficiency symptoms show. Taking samples around growth stage 31 will identify shortfalls, particularly in micronutrients, enabling you to correct them immediately.

Further monitoring later in the season will give an understanding of the quantities of nutrient taken up, which is valuable for longer term nutrition planning. For growers of milling wheat, there are specialist products available for boosting nitrogen to achieve the protein specifications required by millers, but to consistently achieve 13% protein grain, accurate analysis through laboratory testing is the most effective way to identify those crops which need the additional late nitrogen.

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To make sure you have the necessary sample kits available when you need them, contact your agronomist now to order some supplies. We are happy to send out kits in advance and have committed to a 24 hour turnaround of samples so you can act on the results the next day.