Joe’s Journal: Winter Edition – Bed Prep, part 2
In part 1 of our Bed Prep journey, we discussed preparing beds for seeds and gardens, and getting a hoop house set up to assist with growing.
In part 2, we’ll go over what to plant, how to prepare the soil, and why you need soil nutrients!
In the hoop house, to get an even earlier start on hardy spring greens, I got the straw decomposition going. I am tracking the heat of fermentation in the “substrate” using a compost thermometer. This is virtually “free” bottom heat.
(see the header image for what a compost thermometer looks like!)
To calculate the amount of fertilizer to add, first determine the amount of carbon you’re using. According to the USDA, wheat straw has a carbon to nitrogen ratio of ~80:1. Ideally, soil microbes will convert fresh materials when the ratio of C:N is about 20:1. Therefore, for every four parts of wheat straw, we need to add one part of nitrogen.
The two raised beds in the hoophouse have a total surface area of 36 sq. ft. However, to soak the straw to 12” (1.3 cu. yd. by volume) will require approximately 25 gallons. The basic label rate for ArborPlex is 1.6 fl. oz. (48 mls) /gal. [or, 40.5 fl. oz. (1200 mls) of ArborPlex in 25 gallons]. Giving the straw a good soak ought to jump start the process. I’ll check on how the fermentation (composting) is progressing periodically with the soil thermometer.
Hardy Greens for the Late Winter Hoop House
- Brussels sprouts
Once the straw begins to heat, I’ll spread a one-inch layer of mushroom compost to make a seed bed.
GARDENING TIP: Mixing carrot and radish seed at sowing will help to mark the slower to germinate carrots in the row.
Sow hardy greens out of doors once the soil has warmed to 40F; plant every two-weeks for continued harvest of spring greens.
Woody plants and herbaceous perennials do benefit from soil amendments to correct pH, improve drainage, and water holding capacity. Amending the soil is also an opportunity to feed the soil biome. Proper soil preparation cannot be over emphasized, particularly when including long-lived plants (e.g., asparagus, rhubarb) in the mixed bed.
First some soil basics.
Soil is derived from parent material (i.e., rock). Underlying soil strata is termed an “horizon”. The parent layer is the C horizon. The C horizon is degraded (broken up) into smaller particles; the B horizon. The coarsest particulates are sand and the finest are clay. Intermediate in size is silt. All three often existing in various proportions, or sometimes not at all. Above the B horizon, the soil particles mix with the organic material from above, the O horizon. In undisturbed soils, organic matter (e.g., fallen leaves) accumulate on the surface. The fresh organic matter is broken down by microbes, saprophytes (bacteria, actinomycetes, fungi) and soil micro- and macro-fauna (springtails, earthworms). Roots that anchor plants will extend deep into soils (if need be) in search of water and nutrients. This is particularly true in regions where natural rainfall is sparse. Plants with tap roots venture deep mining the lower horizons for minerals.
The Real “Whoville” Under Your Feet
You know now that the soil occurs in layers, that inorganic layers are the source of plant minerals, and the organic parts are home to the microbiome. This biome needs what we need: air, water and gas exchange. The soil under your feet is alive!
What Roots Need and Why Organic Matter Matters
Plant roots need water, minerals, and gas exchange. Roots absorb water and dissolved solutes (minerals), but they also respire. That is, they need to take in O2 and release CO2 to the environment. A soil that is well aggregated has a structure that holds moisture and minerals, but is open enough (that is, permeable) for internal drainage. The large woody roots anchor the plant and move water and solutes to the rest of the plant. The non-woody, fibrous roots are the site of absorption and where exchange with the soil environment occurs.
Coarse (sandy) soils are well drained; can be droughty, and have a low mineral holding capacity. Dissolved minerals in these soils leach easily. Fine (clay) soils hold on to minerals, but tend to be poorly aerated. They can be overly wet, drain poorly or hard as rock when dry. Intermediate in particle size and characteristics is silt. Of course, your soil is apt to be a mix of varying proportions of the three; some are pure sand, silt or clay.
Organic matter (OM) has a moisture and mineral holding capacity improving sandy soils. In clay soils, it will help to aggregate particles, gluing the fines, in effect opening soils to infiltration and aeration. Organic matter also helps to buffer against pH extremes. It is the secret ingredient and essential element in climate gardening. By its nature, organic matter encourages beneficial soil organisms that support plant health.
Beneficial Soil Organisms
Soils are alive. Or at least, healthy soils are. Healthy soils are home to micro- and macro-organisms. For simplicity, we will discuss the key organisms in the soil. Let’s start with bacteria. Free living bacteria include nitrogen fixers and nitrifying bacteria. The nitrogen fixers take in atmospheric nitrogen (N2) and convert it to nitrite (NO2–) in soils. The nitrifying bacteria convert nitrite to nitrate (NO3–) which plants can absorb and use. Legume roots infected with Rhizobium leguminosarum (a symbiotic bacterium that incites gall formation on the fine roots) fix atmospheric nitrogen. When the plant dies, the fixed nitrogen becomes available to other plants.
Moreover, 90% of the earth dwelling plants are dependent on fungi that infect roots. Beneficial fungi that infect roots are called mycorrhizal. Mycorrhizae (“mycor” meaning fungus, and “rhizae” meaning root) that form an exterior reticulum around the root are termed ectomycorrhizae. Those that invade the root cortex are termed endomycorrhizae. Mycorrhizal fungi grow mycelia into the soil and mine it for both water and minerals. In exchange, the plant provides the fungus with sugars, a mutualistic arrangement, in which both, benefit. Interestingly, mycorrhizal fungi need the same environmental conditions as plant roots – they require aeration, moisture, and gas exchange to thrive.
Earthworms are an example of macro-biota. They improve soils by breaking down organic matter, improving soil aggregation, and create aeration channels through the soil profile.
SIDEBAR NOTE: Feeding the Microbiome versus Fertilizing a Plant
I wrote earlier that amending the soil is an opportunity to feed the soil microbiome. Many of the soil microbes important to plant health and growth are heterotrophs, that is they need to take in carbohydrates (carbon) for energy and nitrogen (nitrate, ammonium) as building blocks for proteins, enzymes, and so forth. Therefore, these can be fed. Plants on the other hand are autotrophs, that is they make their own food by capturing the suns light energy, absorbing carbon dioxide and water to make sugars. You cannot feed a plant. All you can do is fertilize a plant, that is, to provide it with the other 13 essential minerals for growth, which are nitrogen, phosphorous, potassium (N, P, K respectively), sulfur, calcium, magnesium (macro-elements), and iron, manganese, zinc, boron, copper, molybdenum and chorine (micro-elements). Therefore, we can feed the soil, but only fertilize plants.
Next week we’ll get more into soil conditions.
~ Signing off for now, Joe