Growing most types of vegetables requires building a level of soil fertility that is much higher than required by field crops like cereals, soybeans, cotton and sunflowers. Field crops can be acceptably productive on ordinary soils without fertilization. However, because we have managed our farm soils as depreciating industrial assets rather than as relatively immortal living bodies, their ability to deliver plant nutrients has declined and the average farmer usually must add additional nutrients in the form of concentrated, rapidly-releasing fertilizers if they are going to grow a profitable crop.
Vegetables are much more demanding than field crops. They have long been adapted to growing on potent composts or strong manures like fresh horse manure or chicken manure. Planted and nourished like wheat, most would refuse to grow or if they did survive in a wheat field, vegetables would not produce the succulent, tender parts we consider valuable.
Building higher than normal levels of plant nutrients can be done with large additions of potent compost and manure. In semi-arid parts of the country where vegetation holds a beneficial ratio of calcium to potassium food grown that way will be quite nutritious. In areas of heavier rainfall, increasing soil fertility to vegetable levels is accomplished better with fertilizers. The data in the previous section gives strong reasons for many gardeners to limit the addition of organic matter in soil to a level that maintains a healthy soil ecology and acceptable tilth. Instead of supplementing compost with low quality chemical fertilizers, I recommend making and using a complete organic fertilizer mix to increase mineral fertility.
Making and Using Complete Organic Fertilizer
The basic ingredients used for making balanced organic fertilizers can vary and what you decide on will largely depend on where you live. Seed meal usually forms the body of the blend. Seed meals are high in nitrogen and moderately rich in phosphorus because plants concentrate most of the phosphorus they collect during their entire growth cycle into their seeds to serve to give the next generation a strong start. Seed meals contain low but more than adequate amounts of potassium.
The first mineral to be removed by leaching is calcium. Adding lime can make all the difference in wet soils. Dolomite lime also adds magnesium and is the preferable form of lime to use in a fertilizer blend on most soils. Gypsum could be substituted for lime in arid areas where the soils are naturally alkaline but still may benefit from additional calcium. Kelp meal contains valuable trace minerals. If I were short of money, first I'd eliminate the kelp meal, then the phosphate source.
All ingredients going into this formula are measured by volume and the measurements can be very rough: by sack, by scoop, or by coffee can. You can keep the ingredients separated and mix fertilizer by the bucketful as needed or you can dump the contents of half a dozen assorted sacks out on a concrete sidewalk or driveway and blend them with a shovel and then store the mixture in garbage cans or even in the original sacks the ingredients came in.
This is my formula.
4 parts by volume: Any seed meal such as cottonseed meal, soybean meal, sunflower meal, canola meal, linseed meal, safflower, peanut meal or coconut meal. Gardeners with deep pocketbooks and insensitive noses can also fish meal. Gardeners without vegetarian scruples may use meat meal, tankage, leather dust, feather meal or other slaughterhouse waste.
