So it looks like I will have one last summer living where I am, then it will be moving day. This means that the 4x4 foot garden bed I have been making will be used this spring/summer or never. I call it the cucurbit expansion because it is outside the deerfence and was planned to hold cucumber zucchini, maybe squash, as well as some strawberry plants I plan to kick out of my deer-proof prime growing beds this spring.
I have covered the existing landscape gravel with about 1 foot of leaves, a layer of cardboard then another foot of leaves. Mixed in are thin sticks pruned off deciduous stuff around the yard, a meagre smattering of kitchen waste, some seaweed and....roll your eyes two garbage cans full of cedar sawdust. In the spring it will get capped with a layer of garden-store dirt. Whoops! That cedar will be lovely organic matter at least 3 years from now when my family is long gone. :/
The PNW rains are currently soaking everything down well but this summer will most likely be a nasty drought which is why I was trying so hard to pile up organic matter. I have started putting the woodstove ashes on top (we do one burn each evening so it's not tons) and maybe 12L of urine a week. I stirred the pile a bit today and saw that the bark is rotting off the twigs mostly and the cardboard later is melting, but there were patches of dry sawdust still. The leaves under the cardboard were shreddable by hand but looked un-rotted. The dirt and first succession of spring plants will go in at the start of March. Will I have enough nitrogen on there by then or will I have resort to adding store bought fertilizer?
Is there a way to tell if more nitrogen is needed before planting? I'm not going to get a soil test for a 4x4 bed that is going to be used for 1 year.
hau Genevieve, your lasagna bed sounds like it will do well for you. One thing to remember is that most wood ash is basic and will had the pH up into the above 7.0 neutral range, most plants want pH in the 6.8 to 6.5 range (slightly acidic).
There is nothing wrong with cedar sawdust, add some fungi slurry and woo hoo. If you are worried about not enough N being available you have some choices, leave as is and see how it does, add spent coffee grounds (also adds fungi and bacteria along with some great slime molds that are good for soils), or use some ammonia that has been diluted 1:5 (ammonia to water), any one of these will make lots of N available over the year. My personal favorite is spent coffee grounds since they do so many great things for soil.
The easy way to assess N in soil is to put some in a pot and sprout a plant, if there is too much N the shoot will grow tall and fall over from a weak stem, it there isn't enough N the sprout will grow slowly, it is about right the plant will grow normally.
Thanks for the information Redhawk! As soon as the dirt gets mixed in/heaped on I'm going to plant a sacrificial cover crop, so I'll observe how those sprouts do.
I'm not too worried about the pH as all the leaves and whatnot are acidic (I beleive) plus we have 2 more months of rain at the very least - most things wash through faster than normal here.
Do you recommend letting the coffee grounds sit for a bit before application? If I'm slow emptying out the kitchen bin I've noticed the grounds fuzz over in 4 days, but when I get a big bag from the coffee shop I just throw it in (or on) as soon as it gets home. I'm contemplating letting them develop an eco system before releasing them to the garden.