The Final Word

Hydroponic leek

Leeks growing hydroponically.

Dr Mike Nichols looks at how huge savings in water and fertiliser might be achieved by growing hydroponically in New Zealand. 

“Water, water, every where,
Nor any drop to drink.”

Ode to the Ancient Mariner by Samuel Coleridge Taylor

There is little doubt that Bruce Wills comments in April’s NZ Grower are very pertinent for the future of horticulture in New Zealand. We do have plenty of fresh water in New Zealand, but we use it in a very inefficient, profligate and sloppy manner. The changes in the agriculture on the Canterbury Plains is a good example of what should not be, while the waste water disposal by many of our larger cities is certainly more Third World than First World. The rivers (and the oceans) were never meant to be sewers.

There is little point in a blame game between the dairy industry and the cities, as both are major polluters of our rivers and lakes, but is required to establish a suitable mechanism to reduce this problem. Horticulture is also not lily-white in this respect, and it is only the fact that the horticultural areas are so small, relative to agriculture that it has not been targeted. Certainly from a point source aspect horticulture would be a major offender, due to the very large rates of fertiliser that is applied in order to produce acceptable yields (compared to agriculture).

The work of Plant & Food Research New Zealand with its crop nutrient management studies is a move in the right direction, but in the final analysis there will be a need for much more major rethink on how we produce crops, which require high levels of fertiliser to obtain good yields without raising the nitrogen and phosphate levels in our rivers.

The Dutch are already thinking seriously about this, and have started research programs with vegetables to reduce the quantities of fertiliser being leached from the soil. They are looking to producing field vegetables using hydroponics. Using a recirculating hydroponic system the nutrients are all retained within the system, and a far higher proportion of the fertiliser is taken up by the crop, because there is no leaching/run off, volatilisation or fixing of the fertiliser by the soil.

Hydroponic leek

Growing leeks hydroponically results in a cleaner product and much heavier yields.

Greenhouse crops are more and more being grown hydroponically, and good control systems already exist to monitor and adjust pH and conductivity, and it is only a question of when not if we have suitable systems available to reliably control the levels of the major nutrients (N/P/K) using single ion electrodes. There are a large number of vegetable crops, which can be grown successfully hydroponically (excluding tomatoes, sweet peppers, cucumbers and leafy greens), that could and should be grown hydroponically if we are serious in the need to keep our river systems clean. Leeks are an excellent example, as has already been demonstrated by Erik van Os in The Netherlands, but why not cabbages, cauliflower and broccoli, etc. We have grown leeks in Palmerston North hydroponically, and it certainly has major merits—cleaner product, and much heavier yields.
(see NZ Grower, 66(6), 52-53).

More and more berryfruit is being grown hydroponically under protected covers, but few use a recirculating system; not only a big waste of expensive fertiliser (and water), but also a potential polluter of the ecosystem. Inevitably, this technology will shift into other fruit crops.

I am not sure that I can see extensive horticultural field crops being grown hydroponically, but there again, why not? Think of the huge savings in water and fertiliser, which might be achieved by growing export squash hydroponically. Who knows what the future holds, except that change is inevitable with our diminishing resources.

Mike Nichols

Dr Mike Nichols

About the author
Dr Mike Nichols is a retired lecturer from Massey University and a regular contributor to Practical Hydroponics & Greenhouses magazine. He has travelled around the world consulting on horticulture and is one of only 25 honorary members of the International Society for Horticultural Science (ISHS). Email:  Ω

PH&G July 2017 / Issue 181