Recalling early challenges with recirculation

September 26, 2017
Written by Gary Jones
October 2017 – Preparation for painting my home office/study recently required a serious clearing out, and I undertook a somewhat enforced go-through of my filing cabinet. You know the feeling. (If you don’t, do it sometime, it’s pretty liberating. But be warned, it will take you much longer than you think!) Three drawers packed tight with technical crop information from the late ’80s onwards. (Now you see why it was liberating.)


Photocopies of articles, confidential Ministry technical releases, faxes (Google it if you’re too young to know), even microfiches (ask your grandfather). Of all of these, hand-written notes brought memories back of grower visits, meetings and conversations as if they were just yesterday. (For any students reading, it’s been shown that typing notes into a laptop fails to generate the same level of long-term memory. Just sayin’, like.) I even came across a copy of Volume 14, Numbers 7 & 8 (July-August 1991) of Alberta Technical Notes, edited by a certain Dr. Mirza Mohyuddin. (Mirza’s gift when visiting me in Sussex, U.K. at that time!)

In the “For Sale” section at the back, apart from two greenhouse businesses for sale, Joe Doef was selling a 1977 Dodge postal van, “heated with roll-up door.” No price mentioned.


RECIRCULATING NUTRIENT SOLUTION

Given the theme of this month’s Greenhouse Canada, one particular article caught my eye. In his 1990 piece entitled “Testing the case for recirculating nutrients”1, Stuart Lambie, then a technical advisor for Grodan, discussed the potential challenges of the (then) new concept of re-circulating the nutrient solution in rockwool growing systems.

He mentioned the probable savings in feed and water costs, but also pointed out “there is little practical knowledge of how to deal with crop nutrition, cope with the build-up of sodium, chloride and sulphate levels and clean recirculated water – or of which systems actually work.”

He posed two major questions that “still need to be answered” (“How should the feed program be modified?” and “How should the return feed be cleaned of bugs and diseases?”) and described 12 possible configurations for channel systems.

Lambie closed with, “At present there is no clear view as to which [disinfection] system will succeed. Much more research is needed before any major investment is carried out on the nursery (greenhouse).”

MAINTAINING HEALTHY ROOTS

Stuart also pointed out that “maintaining healthy roots is key to success.” Some concepts are just timeless, but we often forget that oxygen is an essential plant nutrient just like the solid and liquid ones we put in the feed tanks, and we’d do well not to forget that. Plants with roots that are stressed due to oxygen depletion are more susceptible to root diseases than are healthy roots. I’m sure Dr. Mohyuddin (yes, the same one from 1991 Alberta Tech Notes!) has even discussed this in recent issues of this magazine!

What of this rather reflective trip down the memory lanes of horticulture?

Well, we’ve come a long way in the intervening 27 years and gone a very long way to answering Stuart’s questions. For example we have gutter systems that are now pretty much industry standards. We have ion-specific electrodes and nutrient management systems that can adjust return feed solutions to intended recipe targets. And we have multiple options for effective disinfection of dirty return solution. Answers have come through government-funded research, supplier innovations to meet market-place needs and the hard work and curiosity of growers. Progress in our industry is always a team effort.

But as well as the timeless concepts (such as healthy roots!), we realize that we’ve never quite “got there” – there is always something new to discover, a better way of doing things, new ideas to move forward. I wonder what we’ll look back on in another 27 years as new ideas that will then be common place.

One question remains however. Did Joe Doef ever sell his ’77 Dodge postal van? Joe?

1 Lambie, Stuart, “Testing the case for recirculating nutrients,” Grower magazine, August 1990.


Gary Jones is co-chair of Horticulture at Kwantlen Polytechnic University, Langley, BC. He serves on several industry committees and welcomes comments at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .



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