Investing in Lab Analysis
It Can Either Nip Problems in the Bud or Give Peace of Mind
July 13, 2015 By Jack Legg
August 2015 — Submitting samples for analysis can often be overlooked with the usual day-to-day demands of a greenhouse operation. However, proactive monitoring of greenhouse resources is a far smaller sacrifice than could be required if plant health declines and diagnostic testing is needed to determine the nutritional imbalance, not to mention the loss of a crop.
It is a small price to pay to ensure that nutrition does not cause less-than-optimum plant growth. If problems are detected and corrected before impacting the crop, the value is evident. And if everything goes well and the test is simply confirming sound management, it offers peace of mind.
As well, different crops have different demands for nutrients, which can be balanced based on analytical results.
Routine sampling of raw water, nutrient solutions and re-circulated solutions is important. Handheld meters can give a quick glimpse of water pH and EC, but may not be as accurate as laboratory testing. Other nutritional constituents are routinely analyzed in the lab, but are not measured by meters.
Raw water: No matter the source, whether municipal, or untreated from a well or pond, it is possible to have variability in mineral concentrations, especially with seasonal influences.
Water pH, EC, bicarbonates and nutrients can fluctuate and can be accounted for by adding the appropriate ingredient(s) in the tank mix to balance.
Seasonal water testing is suggested, but at the very least a sample should be collected and analyzed before each growing season or crop. When collecting samples, let the water run for a few minutes before taking the sample, and package it in a plastic bottle supplied by the laboratory.
Nutrient solutions: Confirming the nutrient concentrations, pH and EC in a solution with a laboratory test ensures the tank mix is prepared accurately. It can also diagnose any potential mechanical problems, such as a clogged injector.
Matching the analysis of the nutrient solution to the nutritional demands of the crop will keep the maturation of the crop running smoothly.
Many laboratories present test results alongside a “standardized analysis,” which converts the tests to an expected value if EC were at a set level, which eases comparison of results over time.
Re-circ water – When re-circulating solutions are used, it is important to have it tested so that detrimental components are not excessive.
Chloride and sodium are examples that can accumulate over time and need to be monitored.
Media: A media test should be performed before planting, as some products may require leaching to lower any high level components. Testing by saturated paste will measure background nutrient levels, pH and EC. As well, the pH will influence nutrient availability, or the efficiency of nutrient solutions, and should be adjusted before planting.
Plant tissue: Testing tissue for nutrient levels is often a valuable diagnostic tool when crops appear symptomatic or less robust than expected. However, when used as a monitoring tool, deficiencies may be identified and rectified before symptoms appear. It is important to submit a large enough sample, so that it is representative of the whole crop and provides sufficient material to perform the tests.
Disease diagnostics: The submission of symptomatic tissue, and any notes on development of the symptoms, allow for the plant pathologist to best determine which test to confirm or diagnose a suspected infection.
Jack Legg is the branch manager of SGS Agri-Food Laboratories in Guelph, and also serves as the staff agronomist.www.agtest.com.
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