I always think it is just so cool to watch a compost bin in action. When we first built this bin it was full to overflowing with popcorn stalks and weeds. I watered it almost daily to lend an assist to the decomposition process, and in the past couple weeks nature has also helped out. Regardless of the water, though, the height of the bin has dropped considerably. I shouldn't be surprised. After all, this is what is meant to happen; however, it still amazes me each time. (An old high school friend recently remarked on what an exciting life I lead, and I think I'm just giving him more evidence of that with this post!)Even as I write this, the level has dropped again. After harvesting the squash and tossing in the vine remains, the top was taller than the cement wall behind. Yesterday when I dropped off our latest bucket of coffee grounds, nashi bits, eggshells, and salad skeletons it was lower still. (The aforementioned popcorn stalks are visible at the bottom of the bin in the photo above.) I can just imagine all the little nematodes, microbes, and other critters fattening up and pooping out the stuff my garden so ardently desires. It makes me pathetically happy.
The same holds true for the lasagna bed, too. The bed seems to be coalescing now into an organic mass, and the thick layer of newspaper below seems to be doing its job of holding down the weeds. I do want to bring in a couple more bags of composted manure to top it off some, and help hold the grass in place as winter approaches. I don't want to lose any of those precious greens bits, although I do worry a bit about too much nitrogen. My aphid experiences this summer make me a bit more cautious than before. Then the decision about what to plant comes - another favorite!
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Soluble nitrogen is almost anything you add which contains nitrogen, except compost. All fresh manures, fertilizers, etc contain soluble nitrogen.
Fixed nitrogen on the other hand is what gets put into the ground by nitrogen fixing plants and what the compost pile produces. There is also nitrogen in the air, and what the compost pile does is convert between the three forms until what remains is all mostly fixed.
What's also important to understand is composting is not a very efficient way of getting fixed nitrogen into the garden, and nitrogen fixing plants are more efficient. For example, if you compost manure and you don't have enough carbon for the nitrogen to bind with, the soluble nitrogen will mostly either wash away or be released into the air.
The important difference between fixed and soluble nitrogen, is soluble nitrogen is immediately available to the plants. This means if it's in the ground, the plants will absorb it right away, causing the plants to grow quickly and get very green and lush. Soluble nitrogen is usually stressful to plants, and can cause the problems you describe with the aphids. Soluble nitrogen can also wash away or be released into the air, meaning it needs to be reapplied or it will become depleted.
Fixed nitrogen on the other hand can remain in the ground for some time, and tends to be released as the plants need it. This kind of nitrogen is mostly unavailable.
If you are having problems with your plants getting too much nitrogen, it's probably because your manure isn't fully rotted. Especially chicken manure is very high in soluble nitrogen.
Manure normally takes about 2 years to fully rot, or if it's composted only about 1 year, but then it needs a lot of carbon to bind to. So much carbon that it's often not practical for a home gardener. By weight, manure needs about a 1:10 ratio with a high carbon material like straw, in order to properly compost.
I feel I'm entering a stage in my growing career - food growing, that is - where I need a better understanding of these things. I don't like just randomly adding stuff and hoping for the best.
I've been day-dreaming about what I think might be scarlet runner beans. A logical choice for eating and building up the soil?
I'm sorry, in that last comment I had some cut and paste problems and a number of typos. If you have any questions, please send me an email, and I'll clarify it. My email address is in the contact page of my blog.
Most people don't need to do anything special to their garden in order to build up the soil. If you don't know of any specific problems, this is probably also true with you too. A good way to find out if you have problems is with a soil test, but if this isn't available an equally good way is with 'indicator weeds'. Of course you can also just look for obvious problems; flooded or swampy ground, brick hard clay, etc.
I haven't written anything comprehensive on my blog about indicator weeds, but there's lots to be found with Google. The idea is you identify the most common weeds in your garden and research the soil conditions they grow best in. This will most likely describe your garden. By changing your soil according to what you find, you will have fewer problems with these weeds in the long run and your soil will be healthier.
For example, if you find you have weeds that like acid soil, adding lime will help the situation. If you have weeds that thrive in poor or sandy soils, adding compost is what's needed.
The most common soil problems are solved with nitrogen fixing plants and compost. These are also a good idea for everyone to have in their garden anyway. If you grow annual plants, you should rotate them every year together with some nitrogen fixing plants, and if you grow perennials, you should make sure you maintain a good mix in order to maintain soil fertility.
If you discover you have a very severe problem with your soil, and it happens, then often the solution is to build a raised bed on top of it. Preferably filled with homemade compost, but if this isn't available, then something purchased.
This is about it.
Blogger is complaining this comment is too long, so I'll make a second one.
I made some posts about how I make my garden beds each year:
http://www.patnsteph.net/weblog/2010/05/mulching-sheet-mulching-lasagna-gardening-and-raised-beds/
http://www.patnsteph.net/weblog/2010/05/beds-ground-cloth-and-water-butts/
Runner beans sound like a great way to fix nitrogen.
One of the things I discovered in my garden is I have a pretty chronic shortage of nitrogen. I've been experimenting with nitrogen fixing trees, and it's been working pretty well for me so far. They do take a year or two to become established.
http://www.patnsteph.net/weblog/2010/08/black-alder-and-companion-planting/
In Fukuoka's book, One Straw Revolution, he mentions acacia trees work well in Japan. By the way, if you would like a copy of this book, let me know and I'll email it to you.
The land isn't mine, so I work mostly with annuals. And as it's in Tokyo, I don't know how long it will remain a farm. Some big changes are afoot even now, and I am not entirely sure what they are. We continue to grow as before, but something is definitely happening.
Back to the soil...I think I'll give the runner beans a go this next year. I'm tracking what I plant where and when so I can rotate, and I like the idea of giving a bed some time off, too. I'm not sure if my train of thought is accurate on this count, but by planting one bed fully in garlic I think I'm giving it a bit of a rest. I'm planning to fill it good doses of compost, etc., and then let the garlic have its way. Logical?
I've also heard about indicator weeds before. Years ago a friend studying both geology and botany made a similar suggestion, and it makes lots of sense. It will also be good to properly identify the weeds, too.
I can't thank you enough, Patrick! Great information to mull over and ideas for a post or two. Thanks a million!