Kelly Morgan
University of Florida (UF) researcher Kelly Morgan discusses a study of how citrus growers are adjusting irrigation water pH levels, and what pH levels seem to work best. The acid level of citrus irrigation water has become an important consideration since HLB was discovered in Florida groves in 2005.
“Jim Graham (a fellow UF researcher) has been conducting a survey of growers, primarily in the Ridge area but also in the Flatwoods, looking at their acidification processes. We all know that bicarbonates have become an issue now with greening (HLB). The … lack of acidity in the water has become a problem for deep wells where (water is) coming from the limestone aquifer. The bicarbonates are very high, and the pH is high, sometimes as high as 8 or 8.5. That pH needs to come down … And he’s been documenting how growers are doing that (lowering pH) on their own.
“We’ve also conducted some research at two different locations, looking at different amounts of acid being injected into the irrigation systems, as well as sulfur applied to the soil, and looking at how that affects the uptake of nutrients. And we found that if you reduce your pH down to the low 6s or high 5 area, which is what we’ve suggested for decades in citrus that the pH should be, you get the optimum uptake. You get more uptake of nutrients, particularly of phosphorus, calcium, zinc and manganese, than you do at pHs lower than 6 or higher than 7. So that’s where we need to be.
“The only caution is that for soils with high copper, there is a possibility of toxic levels of copper if the soil pH is at 6 or lower. We haven’t seen that with greening, but the situation exists that you could have some copper toxicity.”
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