Balance in the high tunnel

(Sponsored) Given the many advantages of high-tunnel vegetable production, it’s easy to overlook the challenges, says Dean Konieczka, consultant agronomist with OMEX® Agrifluids.

Perhaps the most pressing point is maintaining adequate and consistent nutrition to the plants within the greenhouse.

For plants cultivated in this environment, a ‘less-than-soil’ mix is commonplace. Options vary, and everyone professes their own ideal mix, but the usual constituents usually include varying amounts of bark, peat or coconut coir — the latter often in blocks or bags.

Each presents its own set of challenges, but coco-coir has a unique characteristic: it’s inert. While it may look like soil, it may act like soil — but it contains no nutrients. So nutrients need to be supplied — and the pH managed carefully — to ensure it performs as intended in high-tunnel situations.

What’s more, coco-coir has a low, if not non-existent, cation exchange capacity. This presents even more problems in attempting to provide sufficient nutrition to the growing plants: deficiencies easily occur when feeding individual elements. Thus it becomes extremely important to provide a balance of nutrients, both macro and micro. There’s a very strong case for treating coco-coir systems as a hydroponic system.

It’s not always realized, but substrate selection plays an important consideration in high-tunnel fertility management programs. Different substrates — perlite, rockwool, coconut core — have little no cation exchange capacity. And when bark or mulches are used as a component of the substrate, it must be completely composted: otherwise, it will continue to compost within the container, robbing the plant of nitrogen and other nutrients.

So it’s vital that high-tunnel growers start off with a balance base fertility program. Start out right, and you’ll be preserving your yield potential from the get-go.

That said, also a word of warning. Nutrition formulation is complicated at the best of times, yet many growers take it upon themselves to build their own mixes of nutrients — unaware that they may be setting up complex antagonisms within their formulations, or fueling chemical reactions that see those much-needed nutrients tied up, inaccessibly, within insoluble compounds unavailable to plants.

A properly balanced nutrition formulation overcomes all these hurdles. OMEX® USA has developed Balanced 10-10-10, a formulation that’s especially designed for high-tunnel greenhouse production as an equal feed, plus micronutrients.

As a rule, most plants grow best under high frequency fertigation, with low doses of fertilizer. Standard practice is to water and fertilize frequently — aiming to keep the soil substrate moist — then use tissue tests to monitor the results

In adding nutrient solutions, you’re adding both salt and water to your substrate. But evaporation removes the water, leaving the salts behind. Sometimes these levels can rise to a point where they are damaging to the growing plants. To avoid this situation, it is always best to allow some water run-off — allowing removal of some of the salts and preventing an unhealthy concentration to build.

Both tissue testing and the use of a balanced nutrition program will help to reduce the chance of nutrient imbalances in high-tunnel greenhouses. For example, OMEX® Balanced 10-10-10 has been formulated with a set of nutrients that ‘play nicely’ together in solution, unlike other nutritional complexes that are known to leave more salts behind.

For more information about OMEX® Balanced 10-10-10, with its blend of nitrogen, potassium, phosphorus and micronutrients designed specifically for hydroponic or soilless systems, visit www.omexusa.com.

The OMEX® team is always available to answer queries and questions from growers about fruit and vegetable nutrition within the high tunnel.

Learn more at www.OMEXusa.com.

The product names and brands referenced here are registered and trademarks of OMEX® Agrifluids, Inc.

© OMEX® Agrifluids, Inc. 2021.