Those of you who read chapter three of The Holistic Orchard with me this week will probably feel like you were drinking from a fire hose.  The section took me days to digest and I suspect I'll be trying out Phillips' techniques for the next several years.  Feel free to comment about other parts of the chapter (of which there were many), but I want to focus my post on soil health this week.

It's very handy to read this chapter with soil test results in hand.  I didn't actually test my orchard soil last winter, but I have test results from the back garden, which started with the same type of soil, even if it has been treated slightly differently over the years.  Here are the relevant portions of the test results:

Phillips follows an Albrecht-like ratio approach to soil health, focusing on the relative (rather than absolute) amounts of nutrients.  When I got my results back for the garden, all of the cations were listed as "very high", so I figured I was fine.  But Phillips notes that if there's too much magnesium (Mg) in relation to the calcium (Ca) in the soil (for example), plants will accidentally take up magnesium while looking for calcium and may end up deficient in the latter.  In addition, he points out that calcium tends to spread soil apart, which can be handy for drainage and aeration in clay soil, while magnesium pulls soil particles together (useful in sand, but not elsewhere).

The optimal Ca:Mg ratio (compared using the percent of base saturation figures, not the absolute ppm figures) is 5:1 for sandy soil and 7:1 for clay.  As you can see, my ratio is 4.5:1, meaning that some of my drainage issues might be improved by boosting calcium.  However, since my pH is already too high, I don't want to just add lime, so I'll need to look into gypsum, which increases calcium content in soil without sweetening the ground.

Similarly, you want to consider the ratio of phosphorus (P) to potassium (K).  Phillips recommends P:K values of 2:1 to produce the most nutrient-dense fruits, although 1:1 is okay in young orchards.  My P:K value of 0.9:1 is typical and signifies a need to boost phosphorus levels without increasing the soil's supply of poassium.  I'm going to have to do some research into phosphate amendments to see which ones won't raise our pH, but Phillips lists black rock phosphate, colloidal phosphate, Tennessee brown phosphate, bonemeal, and bone char as possibilities.

If your head's awhirl with numbers, here are some non-numeric soil factors to consider.  As I've mentioned previously, the goal in orchard soils is to boost fungi at the expense of bacteria, which Phillips explains results in more nitrogen being available in the form of ammonia.  Bacterially-dominated soils tend to have nitrogen in the form of nitrates, which results in happy-looking trees and big fruits, but low nutrient density and flavor, along with more susceptability to disease.  Phillips recommends keeping your soil fungally-dominated by making special compost for the orchard out of deciduous wood chips slow-composted with animal manures.

When should you apply that compost?  I've always thought that early spring was the best time, but Phillips gets more scientific.  He explains that the white feeder roots that suck up nutrients are even more ephemeral than leaves --- they generally only live 14 to 60 days before dying back.  Trees produce multiple flushes of feeder roots throughout the year, generally during periods when growth on top of the tree has slowed, and if you time your compost applications to match root growth periods, you'll get more nutrients to the tree.  Trees focus on blooms in early spring, roots in mid spring, leaves in early summer, and roots in late summer and fall.  Cutting herbaceous plants under the tree canopy (like grass or comfrey) during peak root growth can help feed your tree at just the right time, and so can spreading compost in autumn when half of the leaves have fallen.  Meanwhile, a heavy mulch in the fall can keep the roots growing later into the winter, and can also muffle spring warmth so trees bloom up to ten days later and miss fruit-killing freezes.

If you can handle another eye-opening chapter, we'll read chapter 4 "Orchard dynamics" for next Wednesday.  Those new to the club might want to check out previous chapters on beginning a holistic orchard and techniques for designing a holistic orchard.  And, as always, I'm looking forward to hearing your thoughts on this fascinating subject.