Club members visited a strawberry farm using a hydroponic method. The strawberries are grown in black plastic bags filled with potting mix, on a raised wooden frame. Hydroponic mixture is dripped into the bags.
Stephen We started to grow strawberries in the ground a number of years ago but once I saw an article on growing them hydroponically, it seemed like a time efficient system for our busy lifestyle. With this system you can pick all day long and at the end of the day, you might be sick of picking but you’re not tired so for me the fact that you don’t have to bend over apart from anything else far outweighs growing them in the ground. The system we’ve got here doesn’t suit Joy. We also grew Sugarbaby and Karbarla but some people find Sugarbaby a bit watery. We pick 3 times a week. I would consider growing Karbarla next year because you can grow these at the start of the year when the prices are high. We had a bit of a nutrient deficiency at the start of the year and going by a Consultant’s advice, I gave them a foliar fertiliser and got spray burn over most of the crop.
Sheryl Where did you get your technology from?
Stephen I got it from Ralph King and Brian Biddle from Petersen St. Morayfield. I think Ralph was the originator of the idea.
Sheryl Did you have to buy this technology?
Stephen No, I went to see him and asked him all about it and he tried to put me off.
Sheryl If they’re getting the same amount of water and nutrients, why the varying sizes of fruit?
Stephen Each plant may be at a slightly different stage of growth depending on how good it was as a runner and how strong it is individually as a plant and other varying conditions – perhaps it’s been attacked by something. When we buy the plant off the grower the strawberry will start off with one crown and each time you get new growth you get another crown then another so for each crown you get another hand of strawberries. The first strawberry off is the biggest, then they go down in size with each new strawberry. Two weeks ago we started off with big fruit, we’re now down to large fruit and it will proceed down to small as the plant goes through each stage of growth so when we finish in November, we’ll finish with a lot of very small strawberries. At the end of the season, we’ll pull them all out and replant with new runners at the start of the following season. Another farmer grows zucchinis in his bags.
Tino What’s the yield like compared with an in-ground situation?
Stephen It should be the same but I haven’t achieved the yields that in-ground farmers have achieved and that is something I am working on but as this is only a hobby and I’m away working, I don’t get to manage it as I should.
Irrigation
When the water goes from the dam through the filter from the tank to the injectors, A & B mix through an automatic injector valve, through a timer and out to the farm. I don’t have to check on it all that much. A is calcium-nitrate and iron and B is potassium nitrate and sulphur and I get this mix through Grow Force. I’ve found they seem to have fertilisers that work better for the hydroponic system. The water goes through 3 sand filters that I made myself – they’re not used by a lot of people. The farmer up at Morayfield chlorinates his dam water but I hated the idea of using chlorine. The water goes through very slowly – slower than gravity – living in the sand are micro-organisms that eat the pathogens in the water. By the time this water gets through these 3 filters and goes into the tank, it’s clean – I haven’t had any death from disease. At this time of the year I water them 7 times a day for six minutes and at the end of the year it will be up to 12 times a day for 12 minute intervals. I haven’t had a problem with salts but the way I work out whether I need to irrigate more is I collect the water from underneath the bags. We get an electro-conductivity meter that measures the amount of salts in the water – the salts are the fertiliser. When the water leaves the shed it is 1.3 on the scale. When the water in the containers goes up to 1.7 or 1.8 I increase the water because what that means is that the plant is using more water than nutrient. You don’t use a lot of water using this system.
Sheryl In the home situation we wouldn’t be able to use this system.
Stephen Just use tap water. The chaps at Morayfield use town water but I have a far more complicated system.
Sheryl Do you use any foliar fertilisers at all?
Stephen In the last month I’ve started to use Seaweed spray and it apparently helps to keep fungus diseases at bay.
Sheryl Have you done any control tests to check this?
Stephen No, I try and only use 1 or 2 experiments each year so I don’t get mixed up with how many things I’m doing. I run a trickle tape through the bags and the nutrient I use I mix up myself – it’s suppose to be the same chemical composition as what’s in the plant. The plant will draw out of the water ie if the plant is using more nitrogen or potassium etc. it will absorb that nutrient out of the water; it won’t become toxic but it’s enough for the plant to respond to.
Member At regular intervals?
Stephen All during the day but I might do one irrigation at midnight in a month’s time. They use a lot of water during windy weather.
Sheryl How many litres an hour/day do these sand filters handle?
Stephen 100 litres per hour per filter. I use 4500 litres per day at the absolute peak of the season. Sheryl Any reason for the 3 filters? ie why not 2 or 4?
Stephen I’ll be adding another filter shortly when I put in more strawberries.
Sheryl You also have overhead sprinklers – are these to control frost?
Stephen No, we generally don’t get frost. They’re to start the strawberries off at the beginning of the season. When you buy them bare-rooted in a box of a thousand, we trim them up and put them in the wetted potting mix in the bags and the overhead irrigation just cools the area down. The black plastic is really hot when it’s 35º so it just works as a mister.
Sheryl How do you control the sweetness in your strawberries?
Stephen The sweetness is genetics. I use Camarosa plus the fact that the plants get everything they want under ideal conditions so they’re not stressed. I experiment quite a bit – some things work and others don’t. There’s another variety called Chandler that’s supposed to be good but I’ve heard that they’re soft and don’t travel well. Next year we’re thinking of growing an early variety called Cabala. It’s an interesting hobby for me. There’s not a lot of money in strawberries so you have to get your system right. The DPI are interested in this system and we’re trialling some of their varieties.
Potting Mix and Bags
I use Native Mix from Envirogreen at Stapleton and we bag them ourselves. At the start of the year we have to wet up the bags. We use black UV resistant plastic bags from Dabron at Seventeen Mile Rocks. I’ve experimented quite a bit – we use 6 plants per bag and it doesn’t seem to matter how squashed in they are, they’re still getting all the nutrient they want. If you have them spread out, there’s less chance of disease. What I’ve found is that we get just as many fruit off the strawberries further apart as what we do when they’re jammed up. We’ve had these bags now for 3 years. I haven’t had to change the potting mix – all we do at the end of the year is spray a herbicide onto the strawberries and kill them off which we do around November so for the rest of the year we don’t have to do anything. When we killed them off halfway through November last year, there was another flush coming on and it was tempting to keep going but with the heat coming on I thought enough is enough! In-ground farmers, as soon as the strawberries have finished, have to start preparing for the following year and they have a lot of work to do in the off season whereas I don’t have any work really until I have to plant out again in April. Generally I just knock the bush out of the way or pull it out and replant.
Bruce We could do this in the home garden then plant something underneath
Sheryl Why don’t you use your own runners?
Stephen They’re protected under PBR. We can cut them off and let them go again but I haven’t heard of too many guys who’ve had much success with this.
Sheryl The theory being that if you keep strawberries in the same patch year in year out, then you will get disease?
Stephen I don’t know why I don’t. I’ve asked this question of other farmers who are using this method. In-ground farmers have to fumigate their soil with methyl bromide but it’s being phased out by 2005 I believe. I’ve never found nematodes in my potting mix but this year I found the white curl grub (Longicon?). The DPI spray with Dichlorophos which is like a termite killer at the start of the year then turn the soil over.
Tino We use a couple of sprays of Captan for mould – there’s only a one day withholding period.
Stephen Strawberries usually suffer from black spot or grey mould.
Trays
Putting the trickle irrigation through the bags is a really messy job so I experimented with plastic trays and put the trickle irrigation over the trays but when we get rain the water sits on top of the plastic and the strawberries lay in it. I just use top hat section that you use on a steel frame shed and just lay the bags on top.
Pests
To keep the caterpillars at bay I put in a BugEater – it’s a UV light which has an airstream that pushes the moths into a tray of water below and I add in a bit of detergent to the water. In September we had a massive increase in moths, and I noticed that we also had a huge build-up of fruit flies at the same so instead of emptying the tray after at the end of each week, I’m having to do it nightly. I also use Dipel on a weekly basis which is a biological spray to counteract the caterpillars which when they eat the leaves, it gets into their gut and kills them off, and I’ve found it to be really effective.
Tino Do you use predators? They’re excellent for 2 spotted mites. I use a fellow named Jones up at Caloundra but the mites have to be on the plant in order to use the bugs.
Stephen No, but I might try them in the future.
Fruit Fly Camerosa don’t have the same problem with Spotted Mite but some other varieties do.
Possums
When I put a gnome out for 3 or 4 days, the possum wouldn’t go onto the plants but now he says it’s only a gnome so I now have to look for something else! We have a bit of a problem but he only eats from this first row along to about 3 m. So I’m thinking of putting in an electric fence and keeping the dogs inside the enclosure at night. We have Golden Retrievers and West Highland Terriers. The Retrievers wouldn’t be any good because they’d just jump up and eat the strawberries too!
Sheryl Just put up a long metal sleeve on your posts so they can’t get their claws into it – just like the electricity poles. If you fence and put the dogs in, they’ll bark all night at the possums trying to get in and nobody will get any sleep!
Article compiled by Sheryl Backhouse