Planning notes for fertilizing the orchard(s)

Pruning trees is a good time to look them over and think through management plans for the coming growing season.

I did not fertilize most of the trees that I pruned last winter. Removing 1/2-to-2/3 of their canopies nearly always causes rampant new growth the following year. Adding fertilizer exacerbates the problem. Lush, rampant growth makes the trees susceptible to fire blight and makes the next year's pruning (which is this year's) more work.

Commercial orchards send leaf-stems (petioles in botany-speak) to laboratories for chemical analysis. They use the results to fine-tune their fertilizer applications, sometimes on a month-by-month basis.

I use more primitive methods because those lab tests are not cheap and I don't need to squeeze out every last 40 pound box of apples to make payroll.

I tweak my fertilizer plan to produce a target amount of shoot growth each growing season. I aim for a minimum of 24" of growth on dominant side-shoots while I am growing the tree to fill its allotted space and 12" of growth after they have fill their "place".

Most of the heavily pruned trees gave me 18" or so of shoot growth and will produce substantially less next year unless I add fertilizer. Those trees are now carrying a lot more vegetative and fruiting buds. More shoots means fewer nutrients per shoot. More fruit means more carbs being pumped into the fruit.

Always be suspicious of round-numbers

One rule-of-thumb for fertilizing apple orchards is to broadcast 100 pounds of Nitrogen-per-acre at the beginning of the growing season. It is hard to think of a number that is "rounder" than 100lb/acre.

One detail that gets glossed over is "Do you also fertilize the grassy aisle-ways?" 

My inclination is to NOT fertilize them. More aggressive grass growth means more competition for moisture and if you cannot irrigate it means fewer pounds of apples. 

The trees in the Upper Orchard are planted 15' between trees in the row and 25' between rows. That is low-density by modern standards but I am not running a modern orchard.

Beneath the trees, the area sprayed with herbicide varies between 6' and 10' in width. If I split the difference (i.e. 8' wide by 15' per tree) and go with the 100lb/acre that means I need to apply about 0.6 pounds of urea per tree. Key point, the fertilizer must be scattered evenly over the 120 square-feet per tree.

The more vigorous trees like the Empire on MM-106 I might use a bit less than a half-pound. 

The less vigorous trees like GoldRush will get the full 0.6 pounds because they are struggling to fill their allotted space. 

Trees that were planted last year will get a half-pound of urea over the a circle with a 10' diameter centered around them and will get extra weed control.

Newly planted trees will get hand-watered with 300PPM Nitrogen water.

Very early May is a good time to broadcast fertilizer in Michigan. In many years we go into a period of low rainfall starting in late-May through most of  June and I want the fertilizer dissolved and carried down to where the roots are BEFORE that happens. 

Weed control

Weeds compete with your trees for nutrients and moisture.

A fertilizer-plan is only half of the game just like the offensive game is only half of the football game. Weed control will be a composite of herbicides (primarily glyphosate but it may include a pre-emergent like Simizine) and mowing. Most grass that is mowed short has much shorter roots than grass that is not mowed. That is why a lawn that is "scalped" is the first lawn on the block to brown-out in the summer.

Orchard floors do not need to be groomed to city-park standards but I do have to stay on top of mowing if I intend to reap the benefits of the fertilizer I apply.