Analytical testing

Analytical testing is a useful tool for growers to check the nutrient status of crops, water and/or fertilizer solution.


Irrigation water test
Analytical testing of water is used to detect elemental levels of water and is essential to design a proper fertilizer program. For example, water alkalinity directly impacts the pH of the growing medium. Alkalinity is not pH, but is a measure of the “dissolved limestone content” and has the ability to increase the pH of the growing medium overtime. Potentially acidic fertilizers are used to counteract the effects of water alkalinity. However, when alkalinity level of water is excessive, acid is often injected to neutralize some of the alkalinity and to keep growing medium pH from rising.

Water in almost all cases, does not contain sufficient plant nutrients. Fertilizer adds nutrients that are missing from the water and creates competition for unwanted elements found in the water. Typically calcium, magnesium and sulfate are not provided by most fertilizers and low content in water influences what fertilizers to use. Water often contains waste ions (sodium, chloride and fluoride) that can be problematic for plants if present in high levels. Excess waste ions and high salt levels can accumulate in growing media, therefore growers need to frequently leach crops or use of reverse osmosis to purify irrigation water.

When sampling irrigation water, obtain a sample directly from a tap. The sample bottle should be a new, unused bottle that contains a minimum of 8 ounces. Let the water run for about two minutes before sampling. Fill bottle so there is no airspace and secure cap tightly. Complete the sample label, dry the outside of the bottle and adhere sample label. If you are injecting acid, it is recommended to submit a sample of untreated and acidified treated water. For acidified water, take the sample from the end of the hose after all fertilizer solution has been flushed out.

Fertilizer solution test
This test measures fertilizer element levels applied to the crop and is used to verify fertilizer application rate, EC (electrical conductivity) and pH. This test verifies that your injector is working correctly and/or the fertilizer stock solution is mixed properly. When preparing a sample, use a new 8-ounce plastic bottle and take the sample from the end of the hose at the point of application to the plant. Let the fertilizer solution run for two minutes before sampling to be sure that all plain water has been flushed out of the hose and that the fertilizer solution is at the correct concentration. Fill bottle so there is airspace and secure cap tightly. Complete the sample label, dry the outside of the bottle and adhere sample label.

Growing medium test
Testing of growing medium is important since this gives a snapshot of the pH, soluble salts and individual nutrients retained in the growing medium at the time of sampling. The pH of the growing medium influences the availability of all nutrients. If the pH of the growing medium is outside the ideal range of pH 5.5 to 6.0, an adjustment to the fertility program is needed by the grower to counteract undesired pH movement. This is important for micronutrient availability since they are greatly impacted by pH. Macronutrient availability is less influenced by growing medium pH. A deficiency is easily corrected with fertilizer applications and excessive levels can be leached with plain water.

When you take media samples, begin by selecting plants that are representative of the crop. For a comparative analysis, it is a good idea to submit samples from both affected and normal plants. Limit each medium sample to a crop of the same cultivar, age and growing conditions. Discard the top half-inch of medium from the pot or growing bed, since fertilizer salts collect at medium surface from water evaporation. Remove a core or wedge of medium from eight to 10 plants. The core should run from the top to bottom giving a profile of the root zone. Thoroughly blend the samples and fill plastic bag(s) with 1-1/2 to 2 cups of growing medium. Complete the information on the sample label and attach to each sample bag.

Plant tissue testing
Plant tissue analysis is used to confirm what elements are present in plant tissue and to troubleshoot nutrient deficiencies or toxicities. Tissue testing provides a historical view of what nutrients have been taken up by the plant. When used in conjunction with a growing media analysis, both tests provide two reference points in time for plant nutrition. To diagnose crop problems, provide plant tissue and growing media samples from normal and abnormal plants for comparison.

Remove spray residues and growing medium from the leaves with plain water. Then sample recently matured leaves from the upper portion of several plants. Limit each foliar sample to plants of the same cultivar, age and growing conditions. Submit tissue from both affected and normal plants for comparative analysis. Provide at least one cup (one ounce) of clean dry tissue per sample and pack into the paper bag provided. Complete the information on the sample label and attach to each sample bag.

Lab results
It is best to take samples and ship them early in the week so that samples arrive at the laboratory before the weekend. This will give the lab time to prepare your samples for testing. Be sure to clearly label all samples and include a completed sample submittal form with your samples. Pack samples in a small box or tear resistant envelop. The United States Postal Service Priority Mail is an efficient and cost effective means for shipping samples. It generally takes about three business days for the results to be completed after receipt of samples at the laboratory.

Premier Tech Horticulture offers analytical testing of water, growing medium, plant tissue and fertilizer solution. Premier Tech offers testing from its in-house laboratory and the company also works with several independent laboratories in the U.S. and Canada. Their standard cost for testing is $30.00 per sample, and they periodically offer free tests to customers and to assist growers. With all analytical testing, Premier Tech Horticulture’s Grower Services team is available for interpretation of results and to provide recommendations to assist you with your growing needs. To learn more, visit www.pthorticulture.com