Vegetables require a regular supply of nutrients. Most garden soils are low in nitrogen, phosphorus and potassium. However, the exact quantities required vary among crops and with time of year.
The demand for certain nutrients is greatest when plants are getting established and when they flower and fruit. These are the times to sidedress a vegetable crop with additional fertilizer.
Soil Test
Soil testing provides a wealth of information about your soil. It can reveal nutrient deficiencies, pH imbalances and excess soluble salts. It can also help you determine the best timing of your fertilizer applications. Although it is possible to get the information you need through a variety of DIY tests, it is best to get a lab to conduct a standard test. It will provide a more complete picture of your garden’s nutrient status and allow you to target specific problems rather than treating the entire garden.
The process is fairly simple, but requires you to work carefully in order to obtain a representative sample of your soil. The soil-testing lab should provide a set of instructions, either with the sample kit or by request. The instructions will explain how to collect a sample, which usually consists of randomly selecting 5 to 10 spots in the area to be tested. For vegetable gardens, flower beds and shrub borders, separate samples should be taken for each type of plant.
Once the soil-testing lab receives your soil, they will dry it and test it for the levels of various elements. They will then prepare a report, which contains a summary of the results and recommendations on how to improve the soil. A standard soil-test report typically includes information on the amount of nitrogen (N), phosphorous (P) and potassium (K) in the top 7 inches of the soil, as well as the pH, humus content, cation exchange capacity and percent base saturation.
Before you begin making changes to your soil, it is important to read the entire report to ensure that you understand all of the information contained within. The first section of the report will indicate the information that you entered on your field and soil sample forms. Make sure that the name and address you enter are clearly visible and use a permanent marker or a sharp No. 2 pencil. For the field code, it is helpful to make up a five-digit code that is easy to remember, such as “lawns” or “veggie.” You can also write this on the box.
Fertilizer Rate
Before you apply fertilizer to your vegetable garden, make sure that the amount and rate is appropriate for your vegetables. Over-fertilizing can lead to nutrient imbalances and damage your crops. Follow the application recommendations on the fertilizer package or those recommended by UF/IFAS. Also, keep in mind that some plants require additional nutrients than others, such as calcium (Ca) for leafy greens and phosphorous (P) for flowering and fruiting vegetables.
Choose an organic or synthetic fertilizer based on your soil test results and the specific nutrient requirements of your vegetable crops. Organic fertilizers are derived from natural sources and slowly release their nutrients, improving soil structure and fertility over time. Synthetic fertilizers, on the other hand, provide a more immediate source of nutrients and can be tailored to your crops’ specific needs.
Work the fertilizer into the soil before planting, or lightly sprinkle it over the surface of the soil as a top dressing. Avoid letting the fertilizer come into direct contact with plant stems or foliage, as this can cause foliar burn and stunt growth. After applying the fertilizer, water thoroughly to ensure that the nutrients are dissolved and distributed evenly throughout the soil.
During the winter, when your vegetable garden is dormant, it’s important to provide the vegetables with an even supply of nutrients to help them prepare for the upcoming season. During this time, you can use a fertilizer high in phosphorous and potassium to promote root development.
For the rest of the growing season, the vegetable crops’ nutrient requirements will vary depending on when they are ready for harvest. For example, cabbage, cauliflower, and kale plants need more nitrogen after transplanting, while beans, peas, squash, cucumbers, and muskmelons benefit from a side-dressing of nitrogen after blossoming begins. A nitrogen side-dressing can be applied as a granular fertilizer worked into the upper 3 to 5 inches of the soil, or as liquid fertilizer sprayed on the leaves and flowers of the vegetables. However, the application of a nitrogen side-dressing is usually avoided for broccoli, tomatoes, and peppers, as they are sensitive to excess nitrogen that can delay or inhibit fruit production.
Time of Application
When applied at the right time, fertilizer can provide all the essential nutrients needed by your vegetable plants to thrive and produce a bountiful harvest. Taking the time to perform soil tests, carefully choose a fertilizer with the proper nutrient ratios and release rates, and follow the recommended application rate will ensure that your vegetables are getting all they need to grow.
Mid to Late Growth Stage
During the middle and late stages of growth, your vegetable crops have increased nutrient demands. At this time, you may want to apply a fertilizer with a higher nitrogen content to encourage leaf growth and a higher phosphorus content to support flowering and fruit set. You should also consider a slow-release fertilizer to help ensure continuous availability of nutrients.
Pre-Bloom and Fruit Set
Providing adequate nutrients at this time is crucial for successful pollination and fruit set. Vegetables such as peppers, eggplants and tomatoes will benefit from a fertilizer high in phosphorus, which supports fruit formation and development. A slow-release fertilizer may be best at this time, as it will help to avoid excess nutrient buildup in the soil.
End of the Season
As the growing season comes to a close, your vegetable plants will have additional nutrient demands as they prepare for dormancy. A slow-release fertilizer can be helpful at this time, as it will help to promote strong root systems for healthy winter vegetable growth.
One of the most common mistakes that vegetable gardeners make is over-fertilizing. Over-fertilizing can result in stunted growth and reduced yields, so it is important to follow the recommended application rates and nutrient recommendations. It is also important to avoid applying fertilizers when it is hot or dry, as this can cause plant burn. If you are unsure how much fertilizer to apply, it is a good idea to consult with a gardening expert or local agricultural extension office. They can provide you with detailed information on your specific soil type and the nutrient requirements of your vegetable crop. You can also find many helpful resources online. These websites often feature calculators that will determine the amount of fertilizer needed for your specific garden site.
Equipment
When applying fertilizer to vegetable garden, it’s important to use the proper equipment. Using the right tool for the job makes the task much easier and saves you time in the garden. Choosing the right spreader also helps you get the most out of your fertilizer investment.
There are many different types of spreaders available, ranging from large, walk-behind units to handheld devices. When using one, be sure to read the manufacturer’s instructions carefully and calibrate it properly. This step will help ensure that you get an even spread across the entire vegetable garden area. During the application process, be sure to keep the fertilizer away from hard surfaces and any other plant parts to prevent it from burning or leaching into the soil. Also, be sure not to apply fertilizer when rain is in the forecast. Rain will wash the fertilizer off hard surfaces and into storm drains, where it can then leach into bodies of water or groundwater, contributing to pollution.
Vegetable plants have varying nutrient demands throughout the growing season, and it’s crucial that you time fertilizer applications to these needs. Overfertilizing vegetables can lead to lush, green plants that produce few fruits or leaves, while underfertilizing may result in stunted growth. It’s important to follow the recommended rates and application times for each crop when fertilizing a vegetable garden.
Fertilizer is the material that provides the energy for plant growth, and it’s made of the elements nitrogen (N), phosphorus (P) and potassium (K). Most chemical fertilizers contain all three nutrients in a balanced combination.
Organic fertilizers, such as cottonseed meal or kelp, are also good sources of natural nutrients. For a quick boost of nitrogen, side dress the vegetable garden with 1/2 cup ammonium sulfate (21-0-0-24) per 10 feet of row, and then water it in. This is especially helpful for leafy greens and peas. If you notice a yellowing or pale color, this is a sign that the plant is lacking nitrogen. If this is the case, try side dressing again in a few weeks. For a larger harvest, fertilize the vegetable garden in early spring for lettuce and leafy greens and midsummer for corn, squash and tomatoes.