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severe drought

Posted by Michael Phillips 
severe drought
August 10, 2012 07:59AM
Much of the country is experiencing high heat coupled with no rain. We’re not too bad here in northern New Hampshire though it’s nudging towards the dry side. This is to generate discussion about the physiology of trees and sufficient water, along with the sorts of ecosystem connections that help our orchards better deal with extreme drought stress.

It’s considerable work to haul water to individual trees. I consider that a must for first-year trees and then tend to be less consistent about making sure that two and three year-old trees get that proverbial one inch per week. That's the equivalent of 5 to 10 gallons per young tree once a week in the three foot "donut zone" around each trunk. It's critical to get moisture down deep than do more frequent shallow watering. Any dwarf planting is going to need irrigation for the long haul regardless. Choosing larger rootstocks provides that much greater root reach. Mycorrhizae fungal hyphae deliver water to roots as well. Any sort of mulch will help conserve soil moisture.

Yet when things turn this dry even a heavier clay isn’t going to provide a buffer. Annual shoot elongation and flower buds for next season depend on water as much as healthy green leaves. Continuing to deliver deep nutrition and competitive colonization has value in the summer months for young trees. Spraying every 14 days or so will help insure that aphids, leaf hoppers, Japanese beetles, and leafroller moths will be less inclined to attack your trees. Two caveats: Hold back on spraying with neem oil in the mix until it's cooled down in the evening (no higher than 70F) so as to avoid the sorts of phytotoxic damage caused by any oil in high heat. And do take liquid fish out of the mix by the end of July so as not to interfere with the hardening off process with that supplemental nitrogen. Holistic sprays are good nutritional support whatever curveballs the weather offers up in a particular growing season.

All trees will decline gradually under drought stress, in my experience. Much like we observe in corn fields. The real challenge this year is what can be done for mature trees already bearing fruit? Growers of yore would shallow cultivate about this time to knock down understory competition. A diverse cover going to seed is not unlike mulch, however, in that those "other plants" are shutting down as well. Permaculture folk are big on keyline plowing in preparing ground to better distribute water flow throughout the farm. Deep pockets of woodsy organic matter designed into the planting are a biological means of holding ground water in reserve.

Lost Nation Orchard
Zone 4b in New Hampshire

Edited 1 time(s). Last edit at 08/10/2012 02:16PM by Michael Phillips.
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