I'm currently pumping from a river. I'm considering an inline uv filter, but haven't pulled the trigger yet. I'm concerned about contamination with my overhead, but from what i've heard, drip is generally considered safe, so long as the source water passes periodic tests. I'm off grid on leased land so I'm fairly limited in my options. The much larger farm just upstream from me irrigates via drip from the same river, and I assume they have to be FSMA compliant based on their size.
I flood my furrows with pond water. It never touches the crop at or above ground level. The main thing with using pond water is to not allow it to touch the leaf or fruit of a crop. There are some other rules about solarization and overhead watering as long as you wait long enough between irrigating and harvesting it's considered acceptable. I don't know off the top of my head what the time frame is. If you're drip irrigating you're golden.
I am also planning to irrigate from a nearby pond in this coming year. Our well is only 8 gallons per minute and makes irrigating a constant movement of turning valves on and off in order to not irrigate too much at a time. What I was wondering from you all is that the pond I plan to irrigate from grows a lot of duckweed (water lentils) in the summer months. I guess this is a sign of high nutrients in the water. The pond is solely fed from the same field that the market garden is in. That same field is also certified organic by a family member who farms the rest of the field we do not use for Organic Valley. So my question is, should I be worried about the water even if it contains high nutrient levels? None of the nutrients would come from chemical runoff but rather probably just manure runoff when it rains heavily 10 minutes after they coat the field.
Asa, I think irrigating with that pond water could be done however you should think of that as a tea that you're spreading, Thus, using it with drip (filter it first of course) should be okay but DO NOT use that water for overhead. All sorts of risks if it is coming in contact with the end product. Hope that helps.
If the end product is being washed in a packaging area with clean well water then does it matter if there are possible contaminants in the irrigation water? Or would an aerator in the pond be enough to keep oxygen moving in the water, preventing the possible growth of harmful organisms?
The main thing you have to concern yourself with is the presence of pathogens that are a threat to human health. Here's a good link from Cornell University. Careful washing after harvest doesn't absolve you from the need to be diligent about irrigating with surface water. https://gaps.cornell.edu/educational-materials/decision-trees/agricultural-water-production/
P.S. Have that surface water tested, otherwise you're guessing. I test the shallow well I use to wash my product yearly.
dcfarm, Thanks for the link. At first I was thinking to stick with drip irrigation and irrigate from the pond but am thinking that going with overhead wobblers would save me a lot of time in moving drip lines around and for germinating carrots better. I too test the well that I currently irrigate off of yearly (as i need to in order to be able to sell eggs to stores) but did not cross my mind about testing the pond. I will go ahead and do that before doing anything.....maybe I will have to stick with drip if that is the only way I can safely irrigate from the pond. I was hoping to not have to mess with a sand filter..........