Garden timing, fertilizer

Much of the gardening cadence, at least early in the season, is set by soil temperature and the expectation of rain.

For instance; I use synthetic fertilizer, specifically urea.

Urea is a "salt" of an acid and a "base". In this case the "acid" is a carbonate ion (or carbon dioxide) and the base is an ammonia ion. The nitrogen is contained in the ammonia ion BUT plants cannot use nitrogen in the ammonia molecule. They want nitrate.

Soil temperatures at 2" and 4" from April 1, 2022 until May 15, 2022. Eaton County. It was counter-intuitive that the 4" soil was warmer than the 2" soil even as the air temperatures were warming up day-to-day.

Soil microbes can convert ammonia to nitrate as an energy source which is a happy, happy thing. BUT, those microbes are very slow at converting it when the soil temperatures are below 50F.

If I spread the urea too soon, rains will dissolve and percolate the urea deeply into the soil where it remains cooler, longer. If I spread it too soon, and there is lots of rain then it might leach out of the root zone completely.

So the smart money waits until the upper skin of soil is passing the 50F mark before broadcasting urea. He might also choose to spread it immediately before a significant rainfall since urea can be toxic to worms at high concentrations and a serious rain will dilute it to safe(r) levels. The temperature window happens around May 1 +/- two weeks around here.

Fertilizing late in the season

Fertilizing with nitrogen late in the season can be a problem because trees are likely to put on a burst of growth that will deplete their carbohydrate reserves. Those reserves are what makes the fruit sweet. Those reserves are also critical for cold-hardiness in the trees. A tree entering winter with lots of "soft", new growth is likely to suffer injury, maybe even death.

Similar issues can happen with root crops. Instead of packing away carbs into potatoes, turnips and such, they throw out an abundance of leaves.

One of the trials-and-tribulations of organic gardeners is that organic sources of nitrogen tend to release their nitrogen more slowly. It can be trickier to get enough growth every season without getting too much growth later in the season.

The work-around is to choose fruit tree varieties with a stronger internal-clock and are inherently more winter-hardy. A conventional orchard might get away with growing Gala and Yellow Delicious in a marginal area by judicious timing of nitrogen applications while the organic orchardist might lose significant numbers of trees.

Fertilizing super-late in the season

There was interest (at one time) in fertilizing so late in the season that the trees would not put on a flush of growth. The thinking was that some apple varieties were not very fruitful because of a shortage of nitrogen at bloom-time (May 10) and fertilizing October 1(ish) seemed to address that issue at the expense of potentially having much of your nitrogen leach out of the root zone.

Maybe I am crazy, but there are so many very productive apple, pear and peach varieties that I have no incentive to grow "fussy" ones.