Fertilizers are designed to supplement the nutrients already present in your soil. Too much fertilizer can damage roots, and the excess can reach your local stream, leading to water pollution problems.
Timing of Fertilizer Application:
Some crops require more of some nutrients than others. Root crops require less nitrogen fertilization than leafy crops. Corn is a heavy feeder and may require nitrogen fertilization every four weeks. A general rule of thumb is that nitrogen is for leafy top growth; phosphorus is for root and fruit production; and potassium is for cold hardiness, disease resistance, and general durability.
Proper use of nutrients can control rate and character of plant growth. Nitrogen is the most critical nutrient in this regard. If tomatoes are fertilized heavily with a nitrogen fertilizer into the summer, the plants may be all vine and no fruit. This is also the case with potatoes, which will show excess vining and poor tuber formation. If slow-release fertilizers or heavy amounts of manure are used on crops that form fruit or vegetables, the plant will keep producing leaf or vine growth, and fruit or vegetable development will occur very late in the season.
Remember that a nitrogen application will have its greatest effect for three to four weeks after application. If tomatoes are fertilized heavily on June 1, there may be no flower production until July 1, which will delay fruit ripening in late August. For this reason, it is important to plant crops with similar fertilizer needs close together to avoid improper rates of application.
- Broadcasting. A recommended rate of fertilizer is spread over the growing area and left to filter into the soil, or incorporated into the soil with a tiller or spade.
- Banding. Narrow bands of fertilizer are applied in furrows 2 to 3 inches from the garden seeds, and 1 to 2 inches deeper than the seeds or plants that are to be planted. If the fertilizer band is placed too close to the seeds, it will burn the roots of the seedlings. For plants widely spaced, such as tomatoes, fertilizers can be placed in bands 6 inches long for each plant, or in a circle around the plant. Place the bands 4 inches from the plant base. Banding is one way to satisfy the needs of many plants (especially tomatoes) for phosphorus as the first roots develop. When fertilizers are broadcast and worked into the soil, much of the phosphorus is locked up by the soil and is not immediately available to the plant. By concentrating the phosphorus in the band, the plant is given what it needs, even though much of the phosphorus stays locked up.
- Foliar Feeding. Nutrients applied to foliage are absorbed and used by the plant quite rapidly. Absorption begins within minutes after application, and with most nutrients, it is completed within 1 to 2 days. Foliar feeding is best when your soil is too cold for the plants to extract the dry fertilizer. Foliar nutrition can be a supplement at a critical time for the plant, but cannot replace soil fertilization.
- Side Dressing. Dry fertilizer is applied as a side dressing after plants are up and growing. Scatter fertilizer on both sides of the row, 6 to 8 inches from the plants. Rake it into the soil and water thoroughly.