I'm trying to cook up my own fertilizer recipe but struggling a bit with units; volume vs weight. I've long used Steve Solomon's recipe:
8 parts seed meal for N
1 part bone meal for P,
1 part kelp for K (plus lime.)
Now I want to increase the P&K ingredients. (I don't have access to a testing lab but my greens generally look very healthy while roots & fruits tend to be too leafy or stunted: poor producers.) 2 things are tending to confuse me about NPK values:
1. I've always assumed Solomon's 8:1:1 was intended as proportions by volume (I still think so) but maybe not. If by weight then my by-volume mix could be understandably out of whack. And it's quite difficult to convert to NPK by-volume numbers
2. It would be a PITA to convert the NPK proportions-by-weight into volume proportions, which is how I would rather do the mixing. Also it complicates the task of assigning numbers to tweaked recipes, especially if I substitute kelp with wood ash which weighs almost nothing. It would take a big weight of ash to get much potassium.
Has anyone wrestled with this and found or invented a simple solution? (My attempt to explain my confusion may itself be confusing .)
"People understand me so poorly that they don't even understand my complaint about them not understanding me." - Soren Kierkegaard
Couldn't find specific weights for fertilizer ingredients so I did my own measuring. Here's what I've come up with: Don't be fooled by the 3-place decimals. The computer produced them but they're calculated from rough-&ready assumptions: 1.5L is the size of the jug on my scales
Pending adjustments, amendments, corrections. Comments welcome; assumptions, arithmetic, mix proportions - how much to apply per 100 sq. ft ... etc, etc ??
Sorry for the poor formatting - couldn't find a way to make things line up properly.
I just happen to be reading Steve Solomon's book, Gardening When It Counts, right now. He gives some recipes for fertilizer and specifically says mix this by volume, not by weight....
The Steve Solomon book I have is 'Growing Vegetables West of the Cascades' 2nd edition. I originally had the first edition and there are quite a few changes, including the fertilizer recipe. I've come to take some of his advice with a pinch of salt but he's an interesting writer about gardening. What do you think of 'Gardening Where it Counts?' I haven't read it.
Maybe this question should be in the books section of the forum.
applestar wrote:I’ve been following this thread with interest — but math is not my thing as most old-timers here know by now
applestar; when I was 15 this would have been easy as falling off a log. Nowadays ... well I won't say how long it took, or how many backtracks & corrections. It isn't even math, really - just plain old arithmetic!
I tried a second, simpler mix; equal parts Alfalfa, Bone, Ash & Kelp. The ratios came out not much different but I prefer the first one. It uses less bone & kelp which are the most costly ingredients. My wood ash comes from the stove .
I figure on using about 20-25 cups per 100 square feet. That should be 0.1-0.2 lb nitrogen per 100 square feet, which I read somewhere is about right although it sounds awful small? Online recommended amounts are all over the map; this is at the low end of the 'spectrum.'
Actually, I'm finding the book somewhat irritating. He has a sort of arrogant tone, like everyone else is wrong and I am right and here is how to do it the right way. He is very anti raised beds-- I do all my veggie gardening in raised beds. He has one stereotype of what it means to garden in raised beds "closely spaced, deeply and doubly dug raised beds, with vegetables painstakingly transplanted in precise hexagonal interplanted patterns."
I do raised beds, closely planted, but no little digging and no double digging, and no precise hexagonal patterns. I do plant in rows, but several different kinds of things in one bed, some mixed rows and a lot of just popping things in (hmm, where should I put this basil plant, oh here's a spot). He insists that raised beds require a lot more water ("massive irrigation") and a lot more fertilizer. I keep my raised beds well mulched and use very little added water, once they have passed the seedling stage. I use no fertilizer, only compost, mulch, and compost tea.
rainbowgardener wrote:Actually, I'm finding the book somewhat irritating. He has a sort of arrogant tone, like everyone else is wrong and I am right and here is how to do it the right way.
Hah, that's interesting RBG (your take on Steve Solomon's garden book.) I think those are the things that I liked about his writing when I first started growing veggies - he was so authoritative, seemed to really know what he was talking about and was letting me in on it. I'm a lot more skeptical now about gardening advice in general. Maybe especially if it's being used to sell books & other merchandise. Enough said about that, maybe . I'm open to most ideas. They may work for others and that's always interesting but if they don't work for me I don't persist with them.
This is an interesting topic. I never really thought about mixing my own fertilizer. Except for hydroponics which is a closed system and it is necessary to provide specific nutrients for each type of plant, I never think about it.
I have learned to always add organic matter everytime I replant. I till in the healthy crop remnants, and add about 3-4 inches of compost. I have looked up my local compost analysis. It is very alkaline, so I have to sulfur the garden plots that are already alkaline. My acidic plot can use some buffering. I test my soil every three years or so, and I only need to have nitrogen, so I only add sulfate of ammonia in one or two side dressings.
In my pots. I add osmocote to my potting mix. For heavy feeders like tomatoes, squash, and cucumbers, I add 1/2 cup of 6-4-6 or 9-12-12 fertilizers with slow N. at the beginning and side dress with a tablespoon monthly. Most of my other pots are not fertilized regularly, they are lucky to get repotted before they break the pot.
I know I do need to add more potassium. The extension agent said, that if my root crops only produce tops it may need more potassium, even if the soil tested fine, the other elements are so high, that potassium uptake is being restricted. I have tried to avoid adding more phosphorus for the last 8 years and I still don't need any more for several years more.
If you are doing strictly organic, you will need to supplement more and replace what is taken out of the system. Organics usually have low percentages of nutrients but higher amounts of carbon which is good for supporting the soil community. Minimal tilling also preserves the soil ecology better. Organics by their nature will have variable percentages of nutrients depending on the feed stock. Some things like wood ashes, chicken manure, and some types of leaves, can change the pH as well. It does take up to 2 years for all of the nutrients to become available and soil organisms are less active when the soil is cold. Since different plants take up nutrients at different rates, and since nitrogen is the hardest element to get organically, nitrogen sources would have to be supplemented.
I still prefer to at least get a baseline soil test to see what is needed and customizing the mix to what your garden needs. I find soil tests don't change much except for pH. Compost does buffer pH to make the soil behave more neutrally despite its' pH. However, there is no way I can grow gardenias in any of my alkaline plots, as the pH there was 7.8 at the last check.
I tend to grow similar things throughout the year, and I have access to only certain kinds of feedstock and compost. I don't make my own compost. I don't have the space for a large pile and vermicast and bag composting does not make enough. I do some trench composting when I have enough to make it worthwhile. As a result, I pretty much know my soil recommendations won't change that much for at least 3 years and mostly all I have to do then is adjust pH. Liming the acidic plot or adding chicken manure along with the compost. Chicken manure has the same effect as liming and will raise my pH a half a point in 6 months. For the alkaline plots, sulfur works temporarily. Peat moss, gets quicker results and holds the pH longer. Ultimately, the the plots I have always want to revert to their baseline. All I can do is grow the kinds of plants that is best suited for each environment.
Before I did soil testing, I just added the same amounts of all purpose fertilizer with high phosphorus (our soils are high in aluminum, so phosphorus is bound), and I limed every two years. I also used miracle grow every two weeks on the entire yard. It got to the point where okra would not grow at all, only cabbages did well in the garden. I had a lot of lush growth and the orchids were huge and they bloomed well (or so I thought).
I had added so much lime every two years and the phosphorus was so high that it adversely affected the plants. After 42 days and nights of rain, and I could not give the plants any more miracle grow, (I lost a lot of plants to the rain), the orchids bloomed even better the next year. Although, they suffered more the year after that because they needed to have some fertilizer.
I got the soil tested. Actually, if what works for you, is working there really is no absolute reason to test your soil. It can save you some money and troubles later on by not adding what you don't need. I had been adding some compost, but apparently I needed to add more. So, instead of one inch of compost, I added 3-4 inches instead. I stopped using chicken manure on the alkaline plots. I still occasionally use steer manure. After getting the soil test, I found the phosphorus to be off the scale, and high in everything else. PH was fine in my home plot pH 6.6. The other plots had a lot of compost that was alkaline and chicken manure added over the years and their ph was 7.4 - 7.8. Those plots are good for growing root crops but not so good for tomatoes. My home plot is good for growing leaves and tomatoes but not for root crops ( I get a lot of tops instead).
I have saved a lot of money since I no longer miracle grow everything all the time, although, I will use it during the orchid growing season, since it is easier for me to fertilize them that way. I don't buy high number fertilizers for the potted plants and I have a 20 lb bag of sulfate of ammonia that I have had for about 4 years now and only used about a quarter of it. I don't need to add a lot of nitrogen either. I only give what was recommended by the soil test. The soil test only recommended adding more compost and small amounts of nitrogen. The soil test actually recommended urea for the acidic plot but it is only available in 50 lb bags.
I felt sorry for my grass again this year and fed it. It is nice and green now. I am already regretting having to mow more. The last time I felt sorry for the grass was two years ago. It may be another two years before I feel sorry for it again.
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