Nitrogen(N) Phosphorus(P) Potassium(K) shoots - fruits - roots
noble.org/news/publications Back to Basics: The Roles of N, P, K and Their Sources By Jeff Ball Posted Jan. 3, 2007
leereich.com/2014/05/ To Fertilize or Not To Fertilize, That is the Question By Lee A. Reich | Published: May 30, 2014
- cottonseed meal
- soybean meal
- alfalfa meal
- cottonseed meal 7-3-2
- Soybean meal provides mostly nitrogen and potassium 7-2-1
- alfalfa meal mostly nitrogen and phosphorus
For a quicker effect or where compost is not available, a concentrated organic fertilizer, such as soybean meal, might be in order. You might have guessed that soybean meal is high in nitrogen — 7 percent — since soybean seeds contain 40 percent protein and proteins are about 16 percent nitrogen.
More recently, I’ve also been using alfalfa meal as a source of concentrated, organic nitrogen for plants or beds that need it. Being a legume, alfalfa is also high in nitrogen, but the meal is made by grinding up leaves and stems rather than seeds, so it is less concentrated in nitrogen (2 percent) than soybean meal. Alfalfa is a deep-rooted perennial whose roots forage far and wide for nutrients to possibly offer a bigger smorgasbord to plants than does soybean meal. Alfalfa meal also contains triacontanol, a natural compound that stimulates plant growth (not that I’m necessarily looking for any artificial stimulation fro my plants, whether from sources natural or otherwise).
Both soybean meal and alfalfa meal are mostly used as animal feeds; as such, they are readily available at feed stores.