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Gardening: Once your garden’s set, be sure to use the right fertilizer

Thu., May 29, 2014

Now that we are past Memorial Day, the gardening season has begun in earnest. Once all the vegetable seeds and transplants are set in the garden, it’s time to think about when and how to fertilize them so you get good production.

Vegetables are generally broken into three nutrient requirement categories. Heavy feeders like corn, tomatoes, squash, cucumbers and eggplant need a lot more nutrients than light feeders like carrots, potatoes, onions, garlic and peppers. Crops like beans and peas and cover crops like field peas are in the legume family and fix nitrogen in the soil by the action of bacteria in their roots. This nitrogen is then available to the light and heavy feeders through crop rotation.

To start a good fertilization program, build up the organic matter content of your soil by applying well-aged compost and manure. Organic matter helps retain moisture and provides a home for soil bacteria and microbes that help break down nutrients into forms that plants can use.

Apply 3 to 4 inches of compost to beds in the fall and work it in. Use a good crop rotation system that moves your crops around the garden each year. If a heavy nitrogen user like corn is planted in a bed one year, then a nitrogen fixer like peas or beans should be planted in the space the next year to rebuild nitrogen levels. Crop rotation also helps break up insect and pathogen cycles, which will reduce bug and disease issues.

There are many types of fertilizers available that can provide the nutrients your plants will need. In general, you want to use a balanced fertilizer, which means that numbers on the bag that represent the nitrogen, phosphorus and potassium content should be equal; as an example 5-5-5 or 10-10-10.

Too much nitrogen creates a lot of leaf growth at the expense of fruit development. Most conventional fertilizers release their nutrients quickly into the soil, providing the plants with a quick blast of food that they quickly use up. On the other hand, most organic fertilizers release their nutrients much more slowly, allowing the plants a more consistent supply of nutrients. A consistent supply of nutrients means the plants can maintain steady growth.

Keep in mind that most organic fertilizers are much lower in nitrogen than conventional fertilizers. Don’t rely on compost and manure as your only source of nutrients. They usually contain less than 2 percent nitrogen and are best used as a source of organic matter.

Heavy feeders will need to be fertilized once a month with your choice of fertilizers with a special application made as the plant blooms or in the case of corn, when the plant begins tasselling. Low nitrogen users will need an application as they begin growth in the spring and then again in about a month. Garlic and onions need only a spring application.

Apply the fertilizer according to the directions on the bag and work it into the top inch of soil and water well.

Pat Munts has gardened in Spokane Valley for more than 35 years. She can be reached at pat@inlandnw

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