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How and why to tissue test your plants

Many farmers believe that the health and productivity of their soil is one of the largest influences on their farm’s productivity and profitability. Successful farmers know that while many of the properties that make up our soil are static and change very slowly over time (if at all), nutrient availability is one of the largest single contributors to a good crop. Fertility management has become much more intensive and heavily scrutinized as we look to improve our productivity and management whether by using higher fertilizer application rates, or zoning into multiple applications per field.

Fertilizer and crop nutrition decisions are an important part of the variable input decision making on most farms. The majority of us make these decisions based on soil tests and develop fertilizer recommendations on this information. Recently, farmers have also started to show more interest in tissue testing during the growing season.

Tissue testing was once considered mainly for more more valuable crops such as greenhouse or horticultural crops. But as technology and genetic advancements have become more readily available, many grain and oilseed farmers are showing a definite appetite to improve their production per acre. Tissue testing for in-crop additive nutrition may have a fit for some farms in Western Canada.

We are all familiar with soil tests, but I would guess very few farms (including my own) have had tissue tests completed. Both soil and tissue tests are designed to work together and can provide information towards the same end result — an adequate, balanced crop nutrition plan. However the information derived from each test is very different. Soil tests identify the soil’s nutrient reserve and supply rate to the crop; tissue tests measure the actual nutrient uptake of the crop.

3 Reasons to Tissue Test

1. Confirm visual nutrient deficiency symptoms: It can be very hard to determine if a plant is experiencing nutrient deficiencies by just observing it in the field. Many individual nutrient symptoms look alike, and it can be hard to pinpoint exactly if a nutrient is deficient or other stress symptoms are present. A tissue test can confirm if a crop is suspected of being deficient of a specific nutrient.

2. Monitor and adjust your crop fertility plan: Tissue testing can provide information to confirm if your fertility plan is working and help you evaluate new fertilizer placement or timing techniques. Tissue testing can also provide guidelines to farmers that are looking at applying a base level of nutrients with seeding and then topping up nutrient requirements in a foliar treatment.

3. Detect “hidden hunger”: Crops can experience minor nutrient deficiencies without showing any visual symptoms. A tissue test can point towards these minor nutrient needs that would otherwise go undetected. An application to address a small need can contribute to obtaining the crop’s top end yield potential.

Proper Sampling Techniques

Similar to soil tests, tissue test results are only as good as the sampling done to complete them. Samples must be collected and handled correctly to ensure that the sample that arrives at the lab can be analysed to provide the most accurate reflection of the status of the plant. Improper sampling and handling can place doubt in the validity of the sample results. It is important to decide which lab you are using for the analysis, and find out their preferred protocol prior to taking the samples.

There are different recommendations as to what portions of the plant to collect, as well as the crop stage to collect at. This is dependent on what crop you are sampling as well as what analysis is needed. For example, if you are concerned about treatment of a three- to four-leaf cereal plant you must cut off the plant above the soil surface and submit the entire plant. If you are concerned about a cereal crop during early heading, only the flag leaf should be submitted.

Getting the best samples

Sample good and bad areas of the field: If you are trying to determine if a nutrient deficiency is occurring, it is good to have a comparative sample from both an affected and non-affected area to compare. Often a corresponding soil sample from the same area can provide additional helpful information in determining the cause of concern.

Submit useful plant samples: Do not submit a sample of a plant that has been showing suspected nutrient deficiency for a week or more. A longer term deficiency can cause misleading results; if the plant is unhealthy, the tissue test may not pinpoint the original deficiency. For example if a plant is deficient in nitrogen for long enough, the deficiency can affect the overall plant health enough that it can not access sulphur, causing it to also be deficient in sulphur. The tissue test will not be able to pinpoint the original deficiency problem, which you would want to treat.

Submit healthy plant samples: Do not submit a sample of a plant that has been infected by disease. Both root and leaf diseases can make the plant unhealthy which can affect nutrient uptake, making the test results inaccurate.

Submit representative plant samples: Don’t submit plant samples that have experienced other stresses such as wet soils, herbicide drift, or mechanical damage.

These plants are not representative of the problem you’re hoping to solve, and may result in inaccurate results.

Proper sample handling

Proper care of your samples will ensure that the results are accurate. Once again, each lab has its own protocol and material requirements so it is important to contact the lab prior to collecting the sample. General guidelines are:

  •  Remove excess dirt and dust from the plants.
  •  Use a ventilated sample envelope.
  •  Keep samples refrigerated.

The information coming back from a tissue test can vary depending on the crop submitted as well as the lab used for the analysis. Samples are analyzed for nutrient concentration, to determine if that level is deficient, adequate, or excessive (depending on the crop stage). Labs often use these nutrient levels, as well as ratios among nutrients, to determine deficiency levels of each nutrient. Taking the results of all of these tests together, the lab report will tell you what each nutrient level is: deficient, low, sufficient, high, or very high.

The difficult part is taking that information and acting on it. One benefit of using this type of analysis is that you will get the raw information about your nutrients, and will then be able to look at all treatment options and products available to your crop. You will need to determine which nutrient is of concern, whether you can apply just that nutrient to correct this, or if you are looking at one of the many formulated products in the market, as well as what treatment rate you will need to apply to rectify the deficiency.

Nutritionals by UAP

One other method of tissue testing available to farmers is Nutritionals by UAP. Tyler Kessler, sales agrologist at Weyburn Inland Terminal has been taking plant samples and making recommendations with this program for the last couple of years. He has completed plant samples on canola, durum, and lentils with a main focus on whether or not micro-nutrient deficiencies are occurring.

The Nutritionals by UAP program provides an easily interpreted results sheet showing bar charts of averages and suspected deficiencies. The results are followed up with a recommendation of a particular UAP product to address the deficiency. Kessler says the results are available very quickly, “within days,” and that some of their producers did apply boron to their canola as a result of the tests. While he says it was hard to determine the effect the boron had on the canola, they are interested in the UAP program and plan on continuing to offer it to their producers again.

While the results given through the Nutritionals by UAP program are tied exclusively to the products they sell, Kessler definitely likes the usability of this program and the clarity of the resulting recommendations.

There are different reasons to look at tissue tests. Whether it be to determine a deficiency or as part of a regular top dress fertilizer application, being able to correctly sample the field and handle the sample is important. Being able to interpret the results and act on them quickly (often within days) is paramount in treating the nutrient requirement and protecting your crop yield. †

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