Update on Deep Pool Hydroponics Trial (week 25)

Following a visit last year to look at a lettuce hydroponics system, the  HDC have funded a small project to investigate the possibility of growing flowers (especially stocks) in such a system.  The facility was generously built (at his own expense) by Phil Collison (J A Collison & Son) in a small glasshouse with a concrete floor.

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A number of different “rafts” were made up from dense polystyrene to look at a number of variables including, plugs, blocks and different sized air gaps and holes.   The first planting took place on the 5th of April using column stocks and a few lettuce blocks as a “control” species.

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Initially the stocks in blocks grew away well but the end of April the stocks were very variable and very few plants looked like they would produce marketable stems.  The roots were quite brown and in general they did not look healthy.  By contrast the lettuce grew away very vigorously with a mass of healthy white roots.

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The growth of the lettuce demonstrated that there is nothing fundamentally wrong with the system but obviously it needed modifying to be able to produce stocks.  Further plantings were undertaken using a range of brassica (to see if there is a fundamental problem with brassica growing in water), aster ericoides, lisianthus and statice.   All of these new species grew away vigorously but the stocks continued to struggle even though some of the rafts were modified to increase the air gap.

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But what is very strange is that the odd stem of stocks grew away well despite having brown roots (contrast this with the healthy white lettuce roots in the bottom left hand picture or the aster ericoides in the bottom right picture!).  This tends to indicate that stock production is possible in such a system but modifications are obviously required to reliably produce a crop.  There is general agreement that increasing the oxygen content of the water is the first thing to modify and to this end a dissolved oxygen meter has been purchased and oxygenation equipment is on order.

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We will post another update in a couple of weeks or so.