As farmers work to reduce the amount of pesticides they use, providing crops with the nutrition they need to function and be resilient is essential.

A crop with a balanced diet, so to speak, will be in a better position to fight disease and deal with stress, such as weather and pest attack. In grass crops, nutritionally balanced plants can also provide important minerals to animals.

These nutrients often come from the soil, but many can become locked up in soil or, depending on soil type, can be deficient in that soil.

Common deficiencies include nutrients such as manganese, magnesium and boron. These are deficiencies that most, tillage farmers especially, will be familiar with. Many farmers are looking beyond these common deficiencies at nutrients such as copper, zinc, selenium, calcium and iron.

Key to correcting a deficiency is identifying the exact nutrients which are deficient and in what amounts. Farmers should aim to correct deficiencies in the plant by correcting the deficiency in the soil in the long term, but in the short term, deficiencies may need to be addressed through foliar applications to plants or through fertiliser applications.

Identifying a deficiency

Once the deficiency is visible in the crop, some damage will already have been done to yield, but there is more often than not still plenty to be gained from applying that nutrient to the growing crop and some deficiencies benefit from attention several times during the season.

In general, early intervention is best. A few weeks ago in the tillage pages, a quick guide to some of the main deficiencies and symptoms were provided. Read the article here.

Some symptoms include pale leaves and brown spotting for manganese deficiency and pale yellow stripes for magnesium deficiency.

Taking a leaf sample will provide early information before symptoms show or provide clarity when you can’t decide on a deficiency or a problem area in a field.

Taking a leaf sample

When taking a leaf sample, the principles of taking a soil sample can be followed. You need a representative sample, so take a number of samples across the field and avoid areas of fertiliser overlaps, areas where farmyard manure may have been tipped or areas right beside tramlines.

Pull the plant and cut the plant at the base using a scissors.

Once a significant sample has been gathered (about 40 plants or so), mix the plants together and take a sub-sample or leave this job to the laboratory.

Keep the sample in a ziplock bag and keep in the refrigerator until it is being sent to the lab.

Samples should be sent to the lab for analysis as soon as possible.

What to test for?

Most laboratories will have a standard list of tests which they carry out and include nutrients such as:

  • Nitrogen.
  • Phosphorus.
  • Potassium.
  • Magnesium.
  • Sulphur.
  • Calcium.
  • Manganese.
  • Copper.
  • Zinc.
  • Sodium.
  • Boron.
  • Iron.
  • Aluminium.
  • The analysis will show nutrient deficiencies and toxicity, as well as an imbalance in nutrients if one is present. Livestock farmers should look for a mineral scan which will include other important nutrients like selenium for example.

    Why take a leaf sample?

  • Identify a nutrient deficiency.
  • Identify nutrients available to the crop.
  • Check if the plant is taking up applied nutrients.
  • Identify nutrient toxicity.
  • Identify a nutrient imbalance.
  • Applying nutrients

    Nutrients can be made available to the plant through seed dressings, granular fertiliser or foliar feeds.

    Nutrients needed in smaller amounts than N, P and K can be included in granular fertiliser. Liquid foliar feeds are a common method of application and are often particularly useful when there is a severe deficiency as some foliar feeds contain just one nutrient.

    Known deficiencies in a particular field, such as manganese, for example, can be tackled with a seed dressing to make sure the plant gets off to a good start. A follow-up foliar feed may also be needed.

    Nutrient mixtures are also available in liquid form where appropriate.

    Salts can provide a mixture of different nutrients and many farmers find them easy to use where deficiencies are mild.

    Unlocking potential from soil

    Comparing soil tests and leaf analysis is important as there may be nutrients in the soil which are locked up and cannot be released for one reason or another.

    The basics should always be looked after first, such as correcting soil pH and N, P and K levels as these will have the biggest influence on yield.

    Increasing biological activity is key to releasing nutrients. Farmyard manure, slurry and other things such as molasses, bacteria and fungi can help to get your soil working and releasing nutrients that are needed by crops.

    Bio-stimulants can also play a role in crop nutrition as they can reduce plant stress and stimulate natural processes in plants to promote nutrient uptake and nutrient use efficiency.

    Consult your adviser

    Always consult your adviser or agronomist to ensure that the nutrients that you are applying are compatible with other products being applied in the spray tank.