Running a greenhouse is a demanding business, and it is easy to overlook the need to proactively monitor your resources.
But doing so is the best way of ensuring that the health of your plants is not impacted by nutritional imbalances.
With fertilizer prices rising dramatically, laboratory testing is a worthwhile investment to ensure adequate crop nutrition, and to make sure you can identify and address problems before they become too severe. For example, testing can confirm that a visual diagnosis of pale leaf margins is caused by a potassium deficiency, or that yellowing leaves are caused by chloride toxicity.
Equally, positive test results can confirm good crop management and deliver peace of mind.
What tests should you be carrying out?
The routine sampling of raw water, nutrient solutions and recirculated solutions for laboratory testing is far more accurate and reliable than simple handheld pH and electrical conductivity (EC) meter tests. And with crops’ needs changing as they grow, a weekly testing program is the safest course of action.
You should consider regular laboratory analysis for the following:
No matter the source of your water – whether municipal or untreated from a well or pond – significant mineral concentration variations can occur, especially across seasons. Seasonal water testing reveals changes in pH, EC, bicarbonate concentration and nutrient levels, allowing you to make appropriate balancing adjustments to your tank mix.
At the very least, you should consider carrying out sample testing prior to each new crop or growing season. Samples are also easy to collect – simply run the water for a few minutes, and then collect your sample in a laboratory-supplied plastic bottle.
Confirming the nutrient concentrations, pH and EC of your solution with a laboratory test ensures the tank mix has been prepared accurately. It can also diagnose any potential mechanical problems, such as when an injector is clogged. And by matching this analysis of the nutrient solution to the nutritional demands of your crop, you can support a smooth growth and maturation process.
Most laboratories will provide a “standardized analysis” alongside your test results to make it easier to compare results from the same source over time.
Testing fertilizer to confirm the guaranteed analysis of N-P2O5-K20 and other essential nutrients helps to ensure the correct amount of each nutrient is being added to the feedwater. As more non-traditional fertilizers enter the marketplace, it may also be wise to check that heavy metals are within acceptable levels.
When recirculated solutions are used, it is important to test for detrimental components such as chloride and sodium that can accumulate over time. While excessive sodium levels can interfere with nutrient uptake, chloride can accumulate in leaf tissue and cause stunting, chlorosis and, eventually, necrosis.
A media test should be performed before planting your crops, as some products may require leaching to lower any high-level components. Testing by saturated paste will measure background nutrient levels, pH and EC.
It is common to need to leach salts out of fresh growing media, and the pH level should also be adjusted before planting as it will influence nutrient availability and the efficiency of nutrient solutions.
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, it is possible to detect hidden hunger deficiencies that may be identified and rectified before visual symptoms appear – such as interveinal chlorosis or overall paleness.
Keep in mind that 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 testing.
Food safety programs typically require growers to test regularly for microbiological elements such as E.coli and Total Coliforms in the feedwater, washwater and equipment that handles produce.
The submission of symptomatic tissue – and any notes on the development of symptoms – helps a plant pathologist to best determine which test is required to confirm or diagnose a suspected infection. The most common issues to diagnose are root rots caused by Pythium, Fusarium or Phytophthora, or stem rots caused by Sclerotina or Rhizoctonia.
Reliable, Regular Testing Is the Way Forward
Clearly, carrying out regular and reliable testing can help you identify potential issues in your greenhouse crops before they can become very serious. And by accurately adjusting the nutritional balance and chemical composition of your nutrient solutions, water and fertilizers, you can ensure that you are optimizing the efficiency of your plant growth and maximizing your output.
As global specialists in testing and certification, SGS can help you make a difference with reliable, accurate, and high quality laboratory testing.
For further information, contact:
Branch Manager and Agronomist
SGS Canada Inc.
t: +1 519 837 1600