Saturday, October 3, 2015
Sometimes a small change to a way something is done can lead to a huge change to the system. Sometimes the change is big enough to be called a completely different type of system. Take hydroponics. The core of the system is that the plant roots grow in water, not soil. A nutrient broth is added and monitored to give the plants everything they need but used to get from the soil. Then along comes aquaponics. One thing was changed. Recognizing that fish waste is darn close to the nutrient broth the plants need, the nutrient reservoir was replaced with fish. The small change made for big changes. All of a sudden you are producing fish as well, and the system fixes some of the problems of traditional aquaculture. It adds whole new levels of functionality and complexity. It changes everything.
When I started gardening outdoors in
I knew that water would be a problem. Aquaponics seemed a good solution. You
can set a timer and water 8 times a day (yes, that is actually how often I
water) and whatever water isn’t used by the plants just drains back to the sump
tank and gets used again for the next watering. As an added bonus, tilapia do
very well here, with just a little water cooling needed in the summer and heating
for a few months in the winter. There is just one problem. For those of you who
have read the rest of my blog, I am a soil guy. I love the living system that a
vibrant soil ecology creates. I wasn’t willing to sacrifice that. So I decided
to see if I could do aquaponics with soil instead of growth media. In short,
yes you can. And it changes everything. Phoenix, Arizona
First of all, I need to come up with a name. I have been calling it aquaponics, as the name is handy and was a good fit, at least at first. Any time you have to say “except for…” more than a few times, you are probably best with a new name. This is no easy task. Most of the combinations of eco and hydro and culture and what-not are already taken. Most of the good portmanteaus, like bioneer and permaculture, were already taken as well. So I looked instead at the features the system provides. To me, there are two strengths of this system. The first and foremost is that the removal of the –ponics and its replacement with actual soil allows the soil ecosystem back into the mix. But the addition of circulating water through the system means that you actually have a little mini-ecosystem that you are managing, with all the pieces working together to foster the health of the system as a whole. The second important piece is water conservation. In the heat of an Arizona summer, with the system in full sun all day and temperatures around 115 degrees Fahrenheit (sometimes it feels like Celsius), my system, which is 40 square feet of lush growing area, uses about 20 gallons of water a day. And that includes the water used to cool the system. That’s about as much as an average shower. I am working on finding a name that incorporates those features.
So how different is this system, really, from aquaponics? Imagine a spectrum. It is the spectrum of how natural a gardening method is, or, alternately, how technical it is. On the left side of the spectrum you have a natural garden. You till the garden (or not, no till gardens are great as well), amend with compost, and plant your plants. It closely mimics natural processes and uses living soil to achieve high yields. It is not without difficulties, though. It takes a large amount of back breaking labor in terms of bending over and weeding and is prone to pests and soil borne diseases.
On the other side of the spectrum, you have hydroponics. There is nothing natural about hydroponics. Soil is removed entirely and replaced by a system of pipes and pumps that feed a tightly controlled nutrient solution directly to the plant roots. By eliminating soil borne pathogens and giving the plants exactly the nutrients they need in high quantities, it achieves high yields. It is not without difficulties, though. It takes a huge amount of capital costs both up front and in terms of nutrients. Constant monitoring is required to make sure that the nutrients stay in the right balance for ideal growth and the operator has to have a lot of knowledge and do a lot of chemistry. Plus, the buildup of salts means that the water has to be changed somewhat regularly, negating some of the water usage benefits.
Let’s go back to your organic garden and take one step closer to the center of the spectrum. Next you have a raised bed garden. It eliminates the need for bending over. It also allows you to avoid whatever native soil you are stuck with and either haul in better soil or make it yourself. Weeds are less of a problem because a) you have brand new soil, and b) it is up high, so it is a little harder for weed seeds to blow in. However, there are still problems. Soil borne disease is still an issue, but it just might take a little longer to show up.
Now let’s jump back to the other side of the spectrum and take one step in from hydroponics. There you have aquaponics. Aquaponics replaces the chemical solution with a natural one: living fish. You feed the fish a healthy diet and their waste feeds the plants. The ammonia that the fish excrete turns into nitrate, which is fertilizer for the plants. The system tends to balance itself and requires less maintenance than hydroponics. However, the waste solids from the fish can plug the media and you still have to find a way to make sure the micronutrients are available to the plants without poisoning the fish.
What I have been doing the last two years fills the center space of that spectrum. My garden takes advantages from aquaponics. I have the circulating water, which helps me catch and reuse the water. I have the fish, which helps me load that recirculating water full of nutrients. But I use soil. That allows me to build a web of life and create a living system. I use hugelkultur concepts with wood in the soil. I even grow mushrooms in the soil. The soil helps buffer the water and keep the system balanced. The living soil happily catches all the solid waste from the fish and the worms break it down.
Are there still problems with the system? Sure there are. I still have to add micronutrients, just infrequently. The water usually isn’t clear enough that I can see what my fish are doing. Filtering the soil from the water such that my drains don’t plug has been a problem as well. But overall, the system functions very well with minimal effort on my part.
Oh, and for all of you who asked where I went, I am still here. I have just been a little busy on a voyage of discovery in my own back yard. But don't worry, I am back and I will tell you all about it.