Tissue Testing- Staying Ahead of Changing Conditions

By: Reid Abbott, Regional Agronomist

The 2019 crop is thankfully in the rearview mirror. When looking back at last year’s growing
season as a whole, many of the variables growers dealt with were simply out of their control. Poor
or delayed planting conditions, flooded fields, untimely fertilizer and pesticide applications, and
late harvests were just some of the challenges that growers faced. While it is tempting to throw
up your hands and move on to 2020, there are some lessons to be learned to be better prepared
when Mother Nature throws a wrench in our plans. One effective way to stay ahead of changing
conditions throughout a growing season is to enroll in a tissue sampling program.

agroliquid staff member taking a tissue sample

Evaluate a Crop In-Season

While tissue sampling should never replace a sound soil sampling program, routine sampling throughout a growing season can very successfully indicate trends in plant health and nutrient efficiency as a crop is dealing with its environment.

Nutrient deficiencies can dramatically limit a grower’s yield potential in many cases. But “hidden hunger” (a term we use for nutrient deficiencies that show little to no outward symptoms) can be yield limiting as well. Tissue sampling can catch those deficiencies early in a plant’s life cycle while there is still time to take corrective action. Even though tissue testing generally looks strictly at nutrient levels, when paired with proper field scouting and an understanding of nutrient relationships, a grower can radically improve their ability to recognize all kinds of variables that are limiting their crop. Growers, in general, do not intentionally under-fertilize their crops. So, in many cases, deficiencies in one or more nutrients on a tissue test can be indicative of a larger problem. Using 2019 as an example, you could bet there were many tissue tests that came back low in nitrogen when adequate nitrogen was applied to start the season. In many areas, farmers were scrambling to figure out how to rescue-apply nitrogen to crops that had endured heavy leaching. But, what about other leachable nutrients like boron, sulfur, and in some cases potassium. To the untrained eye, some of these deficiencies could have even been mistaken for nitrogen deficiency or maybe they did not drop below the threshold of hidden hunger. A tissue test can provide that answer and allow a grower to better stay ahead of those needs amid challenging environmental hurdles. Compaction, drought, disease, insect and weed pressure, to name a few, can all contribute heavily to a crop’s efficient (or inefficient) use of applied nutrients. Tissue testing can be another tool in your toolbox to successfully navigate all of the trials your crop must undergo to reach physiological maturity.

The Proper Steps

For all of the benefits tissue sampling can bring to an operation, careful planning and execution must be taken to be able to rely on the results. Unfortunately, despite popular theory, there is more to tissue sampling than throwing some leaves in a bag and waiting for 3-5 days for the results. One of the most common mistakes is taking the wrong plant part for the designated growth stage or misreporting the crop’s growth stage altogether to the lab. Labs report nutrient levels by what is sufficient for that crop at a particular point in that plant’s growth cycle. For example, you can imagine the sufficiency range for many nutrients in vegetative growth stages differs from that of reproductive growth stages. Reporting the proper growth stage and collecting the correct plant part for that respective growth stage is imperative to getting accurate results. Of course, as with any sample work, collecting a representative sample of a given area is many times overlooked or lackadaisically done. Questionable or unexplainable results are often the result of statistical outliers that played too big of a role in the average. In addition, care should be exercised when
considering the condition of the samples received at the lab. A few basic hints:
• Use paper bags to hold the plant tissue instead of sealed plastic to avoid mildew
• Avoid keeping samples on the dashboard of a pickup or even in the toolbox where they risk drying out
• Do not take samples too soon after a foliar application has occurred to avoid skewing the results. Instead give the plant time to absorb and metabolize the supplied nutrients before measuring the effect they had on the tissue levels.

A Part of the Plan

After a proper soil test and solid fertility recommendation, tissue testing is the next step a grower can take to improve nutrient management and efficiency on their operation. While tissue samples only represent a single point in time during a growing season, when taken at multiple intervals, trends can be recorded and multiple angles of crop health diagnostics can be investigated. When planning your nutrient management strategy for 2020’s cropping season, investigate the possibility of deploying tissue testing on your operation with your local retailer or crop advisor.