A good friend reached out for some advice to get her garden beds ready. She had a disappointing year last year and was looking supercharge her soil by rototilling in some clover cover crop and adding manure.
As I wrote out a reply to her, I thought that my cyber-universe friends might also appreciate some of this information. This weekend is PERFECT for this kind of work.
First question to ask…
Did your plants look yellow last year? Or were they just not very productive?
Nitrogen is the biggest of the big three NPK. In our local Willamette Valley soils, and soils with lots of organic matter, there is plenty (to the point of too much) phosphorus (P), and adequate potassium (K).
To get a good look, a lab soil test is awesome. I use A & L Labs. There are many other nutrients, macro and micro, that could be causing problems, and a lab test is the only way to know which is the bottleneck and how best to amend for them. For example, a boron deficiency can inhibit plant growth, but the amount needed to correct it can be really tiny and have negative consequences for over application.
What You Can Do Today
Unless your soil seems pretty compacted, I’d skip the rototilling. If it is, go for it, then let’s talk about putting gardens to bed in the fall. Rototilling inverts the soil structure and disrupts the microbiology of the soil. All the dead microbes release a flush of nitrogen that was locked up in their bodies that plays out quickly then leaves your soils more depleted.
Instead, I knock down the weeds or cover crops using a scuffle hoe or by cutting them down at the soil line. As the root systems rot out they become pore spaces in the soil for new roots or microbes, water, etc. (Some do have to be pulled, like grasses and tap rooted weeds that will re-grow.) I use a digging fork to gently aerate the soil (no turning, just insert and lift a little) this keeps the microbe communities and soil structure, like the macro and micro pores, intact and oxygenates the soil. Then most of my amendments are topped dressed and maybe lightly worked into the top inch.
Nutrients
Nitrogen is the biggest player and many garden veggies are heavy feeders. For that I use a product called Feather Meal which has lots of nitrogen (N) but no P or K. It is an organic source which means it takes a while—a few weeks or so depending on soil health and temperature—for the microbe community to process it to make it bioavailable to plants. So you can apply that now and work into the top 1/2-1″ soil layer. Nitrogen is a mobile nutrient so water will move it down the soil profile to the rhizosphere.
Transplanting
Because the nitrogen takes a while to become available, when I transplant into the bed, I use a liquid nitrogen fertilizer (I like Fox Farm products) so the nitrogen is right there to help the plant establish.
Manure
If it is well rotted, you can rototill it in as you were planning, or top dress as you would a compost addition. I avoid using manure anywhere there are acid loving plants, manure tends to be salty and raises the soil pH. Also the source is important; some manures can contain herbicide residues that pass through the animal. https://smallfarms.oregonstate.edu/smallfarms/herbicide-carryover-hay-manure-compost-and-grass-clippings. If you have a good source of “clean” manure, top dressing your beds and layering between leaf blankets in the fall can be incredibly beneficial to your soil. Especially if you sprinkle some winter cover crop in the top layer.
Happy gardening, my friends!
Second Breakfast Gardens 