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Tissue sampling provides complete story on plant health

Corey Catt Published on 14 August 2013

We had an unusual start to the season, but thankfully, the majority of corn and alfalfa is up and growing. From the moment moisture hits the seed’s germ, the plant growth cycle begins.

The life cycle is driven to the ultimate destination – reproduction. The newly germinated, pale, sun-starved plant busts through the soil surface, and the new leaves begin to bathe themselves in heat and light, and the natural life cycle process called photosynthesis begins.

The pale color turns into a rich, vibrant green, the color synonymous with life and health.

I like to compare plants to a self-sustained, growing corporation. Much like a growing business, the plant life cycle involves manufacturing, and most importantly, building an infrastructure to meet the intensive demands of a rapidly growing plant (on a very short deadline).

The plant’s leaves are comparable to a corporation’s factory – if something is visibly wrong in the operation, you know there’s a problem. The color of the foliage is a quick way to alert you of potential plant health issues so you can check further. Healthy foliage is vital, even though it represents a very small portion of the whole plant structure.

A significant part of the plant’s functions are performed underground, hidden from the eye, similar to the office work that takes place within a corporation. The brains of the whole operation, the plant’s CEO, is housed in this underground root system.

The root represents the operations office, home of shipping and receiving, transportation and distribution as well as health and safety. The root is constantly searching for nutrients and water in addition to collecting and distributing them to the rest of the plant.

During emergence, the first major root is like the artery of life that sinks itself deep into the earth and scavenges for nutrients and water. It provides the initial pathway for nutrients. It expands fast – adding root hairs and additional root structure, as well as depth and diameter.

It’s like building an expressway into a major city. The roots work very hard expending valuable energy; the more they have, the more they can scavenge and extract nutrition from the soil. It stands to reason that a plant’s root system, growing in nutrient-rich soil biology, will be much more efficient.

This process inside the plant gives us the ability to test tissue. It provides us with a real-time measurement of the plant’s basic metabolic functioning and a more accurate baseline of the nutrients present.

Just like doctors use blood tests as the first method of identifying problems with humans, we use tissue sampling to, in part, help determine where we are in balancing nutrition. In the past, we relied on decades of general scientific testing and trials to determine key elements important to growth and health.

It was found the basic fundamental nutrition for most plants is N, P, K, S, with various rates applied to corn, soybeans and alfalfa, all based on nutrient removal. Today, our scientific methods and tools have amplified, making it cost-effective to better design a diet that will correlate to current plant needs, rather than a one-size-fits-all approach.

Science has revealed there is a delicate balance of approximately 16 essential elements utilized in some way to meet the maximum yield capacity. At the present time, we haven’t tested our soils for every one of them, meaning we likely haven’t been replacing them either.

The good thing is that most growers who are diligent in soil sampling, grid sampling and plant tissue sampling, have experienced the positive plant health and yield advantages from this precision testing and designer plant diets.

Emerging GPS and computer-based crop management programs have also assisted growers by adding technological tools to help manage all this newly found information and to track the yield and economic benefits.

Tissue sampling – how it’s done
Tissue sampling has become very popular in the last couple of years. It much more accurately represents plant nutrition versus the traditional soil sample. Soil samples are still important; tissue sampling just adds more depth of real-time plant nutrient balance.

Tissue sampling should take place as early in the season as possible to properly detect nutrient deficiencies and make adjustments to reduce yield loss.

To take an accurate test, avoid testing plants showing severe signs of stress from factors not related to nutrients. This includes damage from insects, drought or flooding, temperature, chemicals or machinery. Also be sure to test normal plants in the same stage of growth for better evaluation.

When testing alfalfa plants from beginning stages through the first flower, it’s important to sample from the top six inches of the plant. Because it’s in early growing stage, collect around 35 samples.

When sampling alfalfa closer to or at harvest for comparison, test the whole plant. Collect around 25 of these samples. Additionally, collecting soil samples simultaneously can be helpful when paired with the plant analysis to identify nutrient deficiencies, toxicities and imbalances.

Soil samples should be taken from the same area where plant samples were collected and taken at a 6-inch or 7-inch depth.

Once samples have been collected, remove foreign particles, such as dirt, without washing the plant. Place the samples in a paper bag or large envelope to help prevent them from developing mold during shipment. Soil samples can be put in a waterproof container and should have a correlating label to the field and tissue sample from which it was taken.

Depending on the lab you use, some reports for plant samples will reveal the concentration of N, P, K, Ca, Mg, S, Zn, Mn, B, Cu, Fe, Al and Na within the plant.

Soil samples submitted with the plant sample will be analyzed for pH, organic matter, P and K, as well as special soil test results. Nutrient levels will also be interpreted for soil and plant samples to identify any nutrient issues and potentially offer recommendations. It’s important to note that nutrients can then be soil-, seed- and foliar- applied.

As we continue to unearth cost-effective tests, I’m excited about the yield possibilities. I’m also excited about having the ability to react by applying timely nutrition. I encourage you to try an experiment on your farm.  FG


Corey Catt
Forage Product Manager
Latham Hi-Tech Seeds