Answer: There are several ways to increase the nutrients in the soil. One is to use a commercial fertilizer. Every fertilizer is labeled with three numbers, such as 5-10-5 ie N-P-K. The first number represents the nitrogen content, the second represents the phosphorus content, and the third represents the potassium content. There are formulations for both immediate and longer term release, and formulations with different proportions of the three. Select an appropriate one and apply it according to the label instructions.
Another method is to use products such as blood meal or manure which are high in nitrogen, and rock phosphate which is high in phosphorus. These tend to release their nutrients slowly over time so they are more evenly available to the plants through the growing season, but in some cases the nutrient content will be approximate rather than exactly measured as it is in synthetic fertilizer.
Many gardeners use a combination of fertilizer and other materials, particularly including compost since it supplies many micronutrients as well as improves the soil structure by adding organic matter. If you test your soil regularly you will be able to judge how much of what to add each year, and should see improvements over time if you are careful to add organic matter on a regular basis. You will also want to monitor the pH since most plants prefer a soil that is close to neutral and this helps them be able to use the nutrients that are present in the soil.
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