 |
|
|
|
| |
The Garden Plot for July 25, 2008
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: "Nutrient Deficiency"
When plants don’t get enough fertilizer, they begin to show hunger signs. Gardeners can tell which nutrients plants are hungry for based on their symptoms. Nitrogen deficiency is exhibited by a general yellowing of older leaves first and decreased vegetative growth. Older leaves eventually turn brown and dry. Sometimes, excessive nitrogen is also a problem. Plants take up nitrogen preferentially and can easily get too much. Too much nitrogen results in decreased hardiness, late maturity, decreased disease and insect resistance, and poor,(or sometimes absent, bloom. Trees and shrubs should not be given much nitrogen after the 4th of July to avoid diminishing their winter hardiness.
Phosphorus deficiency can mean slow plant growth and late harvests. Phosphorus promotes early maturity, fruit quality, and root development. If phosphorus is deficient in plants, overall growth is stunted, while fruit and flowers may be delayed. A general symptom of deficiency in some garden plants is the purpling of leaf undersides.
In most cases, phosphorus levels in soil are sufficient. The problem is that phosphorus is usually fixed, or bound, in the soil. In alkaline (high pH) soils, calcium-phosphate complexes hold phosphorus. Even humus holds phosphorus. Fortunately, there are ways to ensure the release of phosphorus from bondage. Keep the soil pH at around 6.5 to 7.0, and add organic residues. Not only is phosphorus available directly from residues, but organic matter addition helps to release fixed phosphorus by stimulating microbes who release bound phosphorus.
Potassium deficiency is rare in western Montana. When fruit trees, shrubs, and bushes are deficient in potassium, they are more susceptible to injury by drought, frost, and salts in the soil. Soil microbes need potassium, but at much lower levels than do plants. In fact, when organic residues are decomposed, potassium is released immediately (while microbes hold tightly onto nitrogen and phosphorus). When released into soil, potassium becomes trapped onto clay and humus particles - much like very fine dust winds up in the crevices of ornate furniture.
Calcium deficiency is indicated by tip burn of young leaves, growing point death, blossom or bud drop, weakened stems, and discolored areas on fruit (such as tomato blossom end rot). Plants use calcium in their cell membranes and in the growing points of roots and shoots. Calcium also helps mitigate the effects of toxic materials on plants. Some evidence points to calcium as being a disease preventative. Manures and many cover crops add calcium to the soil.
Micro-nutrients are termed ‘micro’ because they are needed in very small amounts by plants and soil microbes. Iron, and boron are the most critical. Iron is important in the process of nitrogen fixation. Iron deficiency is indicated by interveinal yellowing of young leaves. Boron enhances growth at the growing points of shoots and contributes to the quality of several crops including brassicas, apple, pear, and grape. The pH level affects micro-nutrient availability. Iron is often unavailable at high pH. In high pH western Montana soils, iron deficiency is often seen in ornamental and garden plants.
For more information on nutrient deficiencies and how to correct them, contact your local county extension agent.
Helen Atthowe's new short program of gardening tips
|
|
|
