Agriportal

• Your request for information on aquaponics was forwarded to me by John Riggs. I have experience working with aquaponics, having done this work in the Virgin Islands during the mid to late 1980s. I'm attaching a fact sheet from Jim Rakocy, my colleague and aquaponics project leader. Jim is the world's top expert on the subject. I would give more weight to his fact sheet than to the other document I attach here.  Based on my experience with aquaponics and the four months I spent in Iraq last summer as part of Team Borlaug, I can tell you that I think aquaponics has a place in Iraqi agriculture but I do not think now is the time.  The main reason for my saying this is the unreliability of the electricity supply. A continuous supply is necessary to circulate water and to provide aeration for the fish.  Aquaponics is best done as a clearwater (as opposed to greenwater) system. As such, algae do not do any work for the system (providing oxygen, removing wastes). Thus, moving water around is essential.  I do think that carp is a suitable species for aquaponics in Iraq. I also agree that aquaponics would mainly be a winter-time activity, consistent with most other greenhouse operations in Iraq. It's important to point out that these integrated systems tend to be primarily a plant production system, with fish production a secondary and minor crop.  In attempting to balance nutrient production through the fish with nutrient uptake by plants, a very large plant growing area is required.  If you decide to pursue your idea further, I would be happy to provide you with additional information, or refer you to Dr. Rakocy directly.

• I don't think that I am quite ready to give up on the idea. First I have some more questions that I need answered. I will try to explain things clearly. Would it be possible to utilize one of the ponds currently used by farmers to raise carp commercially and place a greenhouse next to it and set up a aquaponics system? I recognize that electricity is an issue, but my thought is that with the larger area they won't need it 24/7 except when they exchange water between the sytems or is it a constant process? If it could be done twice or once a day perhaps a generator would work. Another question that arose is in a pond situation was due to the larger size would there be enough nutrients in the water for the plants from the fish? I also wondered if the solids removal tank could be removed. I recognize if this system was possible something would have to be inserted in the pond to avoid removal of the sediment from the pond and the difference in elevation of the pond and greenhouse would have to be planned for. I would also be thinking of a hoop type greenhouse with open ends and a shade cloth to prolong the growing season.  Those are my thoughts. Hopefully they are pretty clear. It may not still be feasible, but I still wanted to examine some alternative solutions to the issue.

• I admire your persistance. I'll answer your questions as best I can.

1) On using pond water for aquaponics. There are two reasons why this won't work well. First, as I mentioned in my last email, pond water tends to be "greenwater." What this means is that most of the nutrients in the pond are tied up in algal biomass, not dissolved in water. From the standpoint of hydroponic plant production, these nutrients are thus unavailable to hydroponic crops. Furthermore, and related to the point about greenwater, dissolved nutrient concentrations in most aquaculture ponds, even those with very high feeding rates, are very low, often two or three orders of magnitude lower than concentrations typically used in commercial hydroponics. While such integration has an intuitive appeal, beneath the surface there are many technical constraints.

2) On intermittent water flow. I suppose this would be possible but I think the frequency would have to be greater than twice per day. Ideally you would want continuous flow to avoid water stress, especially when photosynthetic rates are high.

3) On removal of solids capture tank. In truly integrated aquaponics systems, removing solids is very important. Leaving solids in results in bad fouling of roots, thereby inhibiting plant uptake. Even with a solids capture tank, roots often become fouled by fine solids, but this can be restricted to the intial plant growing zone if the fine solids concentration is not too high.

Let me know if you have other questions.

• I think that really clears up the issue in my mind as to whether or not it would be workable. I will discuss it with the DG of Agriculture this coming week and unless he tells me otherwise, I am only going to focus on traditional greenhouse technology. Its unfortunate, since the people are so eager for new technology and sometimes there are constraints that limit what can be offered. I just will move forward and be content that what I am giving them is still a huge step forward.