If you have ever taken a soil sample, and if not-why not, the information you get back from the University indicates the proportion of potassium, and phosphorus in the soil, how acid or alkaline it is and what percentage of humus your soil contains.
There is no mention of nitrogen in the report. There is a good reason for that. The availability of nitrogen depends on many factors including the temperature and moisture of the air, the soil composition and condition and the activity of soil organisms. As these conditions can change so rapidly, labs can’t test for it. Since nitrogen is critical for plant growth, there is always a suggestion from the lab as to how much should be added to your soil.
Signs of nitrogen deficiency are usually easy for even the most inexperienced gardener to see, yellowing of older leaves and slow growth even in the best growing conditions.
Heavy users of nitrogen are corn, lettuce, squash and roses. Vine crops love it but attempt to cover the garden with vines and forget to set fruit. Since nitrogen is necessary, and usually lacking in heavy enough percentages to encourage the best growth, the gardener must replace it each year.
There are many amendments that do just that. Organic materials, particularly those that contain proteins are grains, seeds, legumes and animal by-products. Composted manure can be purchased in bags like potting soil, or you can gather your own raw manure. Do compost manures at least six months to kill weed seeds and reduce the amount of ammonia in the manure.
Too much ammonia can “burn” your plants. You can apply the fresh stuff to your garden in the fall, after harvest and till it in a month before planting in the spring. This is an iffy project here as the soil could be too wet then. Till over wet soil and you have a problem all summer.
Another option is blood meal. It, too, can burn seedlings so mix it with water and add to your irrigation system or water well after applying.
Fish emulsion is really stinky and needs to be re applied monthly. It can be used as a foliar spray.
Feather meal, dried pelleted feathers, doesn’t break down readily so it is an excellent long-term source of nitrogen. Alfalfa meal not only adds nitrogen but micro-nutrients to the soil. Soybean meal is another fairly slow release source.
Of course, you can always buy a bag of chemical nitrogen and send organic gardeners into the vapors. Do add some nitrogen for your best ever garden.