Ok so I was in Rona today and was going to buy Bone Meal and food for my other plants and then I thought, hey, instead of buying all different boxes, can I buy NItrogen, Potash, and Phosphate and make my own mixtures? For example, if it's 5-10-5 fertilizer, can I use 5 scoops of Nitrogen, 10 of Phosphate and 5 of Potash? Is it that simple? I'm betting it's not. Help please. Erica
Not quite that simple. Fertilizers are mixed by weight not volume. The sources are not pure N, K or P, so you have to determine what percentage of the element in the compound (Ammonia NH[sub]3[/sub] has three Hydrogen atoms to one Nitrogen, N has an atomic wt. of about 14, H has an atomic wt. just over one, so ammonia has around 82% N [14 of 17].
Sounds like you need a degree in chemisty. Try Art Knapp fertilizers I have found them excellent If you are into chemical Gardening. I have gone off that now. Ray (Islander)
I think that if you can still find them, there is a product line from Sudbury fertilizers, individual elements of N-P-K (0-0-44, 0-44-0 and 44-0-0) you would be able to mix these as a ratio by volume and be pretty close I would imagine.
Sample your soil and have it analyzed before fertilizing. You may find that you only need to supplement one or two nutrients, if that many, and not very heavily. Do not pour on quantities of unneeded nutrients. Unutilized fertilizer components contaminate water sources and may produce a toxicity in the soil that actually interferes with plant growth, rather than promotes it.
Here is a link the a fairly standard homemade plant food. I dont attest to its worth. http://www.butlerwebs.com/garden/default.htm The elements contained in fertilizer can be assembled from pretty standard ingredients. Ammonia (nitrogen) Bone meal (phosphorus & micronutrients) Potash (potassium) So, to answer your question, YES. You can by the plant food elements separately and mix them at home. No, you cannot by them in pure for due to the fact that nitrogen is a gas that cant be absorbed by plant and phosphorus is a metal that explodes on contact with air.... you get the idea. :)
You can buy a soil test kit from a gardening store. You can buy kits to measure nutrient contents as well as pH. I would highly recommend doing both. Nutrients, of course, are important for your plants, but so is pH because it affects the availability of nutrients to plants.
From Rodales' Chemical-Free Yard & Garden (1991), a Mix and Match table: "If you want to mix your own general-purpose organic fertilizer, try combining individual amendments in the amounts shown here. Just pick one ingredient from each column. Because these amendments may vary in the amount of the nutrients they contain, this method won't give you a mixture with a precise NPK ratio. The ratio will be between 4-5-4 and 5-8-5. However, it will give a balance supply of nutrients that will be steadily available to plants and will also encourage soil microorganism to thrive." Nitrogen (N) Phosphorus (P) Potassium (K) 2 parts blood meal 3 parts bonemeal 1 part kelp meal 3 parts fish meal 6 parts rock phosphate 6 parts greensand Because most of my plant are in pots, where one cannot use formulations for the garden containing inorganic fertilzers, for years I have been using a variation on this, mostly 1 cup fish meal and sometimes 1 cup blood meal, 1 cup bone meal, and about one-half cup kelp meal.
All soil nutrient supplementation must at least be based on a soil test or there is really no basis for knowing if the kinds and amounts of nutrients being supplied are appropriate. Soils vary in their nutrient makeup even on the same site. Application of unneeded nutrients is at best wasteful, at worst polluting--even toxic.
Okay, so one would get soil samples from the various areas on a site depending on plant communities? Say Madrona/Doug fir/salal/evergreen huckleberry versus Doug fir/cedar/mahonia versus Doug fir/willow/dogwood/evergreen huckleberry? Are the university extensions the least expensive most reliable sources for the tests? Afterwards, one would still fertilize the plants themselves, which I thought is what the discussion was about rather than amending the soil for planting. Yearly soil samples are not suggested, are they?
Actually, if you wanted to stay on top of it you would sample rather frequently. Soil nutrient conditions change both seasonally and over periods of years. Soil sampling is not perfect, but it's better than fertilizing blindly. Just the problem of overapplied phosphorus--most sites here probably don't need to have any added at all, let alone the high amounts some products contain--producing a toxicity that is not easily remedied is reason enough to be careful. I rarely fertilize so am not up on best way to get soil testing done in this area.
