Investigate Garden Nutrient Disorders LSU AgCenter Horticulturist Advises

Thomas J. Koske  |  5/27/2005 1:43:57 AM

News You Can Use For June 2005

The vegetable garden is a busy place. Plants grow, most develop flowers and then bear fruit. Proper nutrition is essential, says LSU AgCenter horticulturist Dr. Tom Koske.

The soil’s mineral nutrients help create the power and building blocks for growth and development. Six major soil nutrients and at least six significant minor soil nutrients direct your plant’s growth. Macronutrients include nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S). The micronutrients are iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo) and chlorine (Cl).

A soil test gives values for K, P, K, Ca and Mg, plus any lime requirements.

"With the recommended use of commercial fertilizers and lime, you usually have a proper balance and availability of major and minor nutrients," Koske says.

The horticulturist notes that when things are not sufficient or not in balance, growth and development suffer. Yields and produce quality go down. Disease incidence also may rise with poor nutrition.

Obvious deficiency symptoms often appear on the foliage. N, P, K and Mg move to the plant top, and deficiency symptoms appear first on lower, mature leaves. Low N shows a thin, pale plant, and low P shows a thin, purple-green plant. Low K has leaf edge chlorosis, and low Mg shows up as yellowing between the veins of lower, mature leaves.

The ability of an element to move from one plant part to another is called mobility. Some plant elements have poor plant mobility, and deficiencies show first on the young, upper, expanding leaves. Calcium and boron problems first appear in the terminal bud or as flowering head failure. Low Mn, Fe, S or Cu show a chlorosis of younger leaves.

Other factors can affect foliage color even though soil nutrient levels may be adequate. Soggy soils, soil pH extremes and salty soils all can affect nutrient availability and cause foliar discolorations. Herbicide drift also may distort foliage colors and mimic nutrient deficiency.

"Before jumping to any conclusions, evaluate the site and recent history," Koske cautions. Was anything sprayed nearby? Is the garden suffering from cold "wet feet"?

High salts usually stunt plants and crisp up lower leaf edges. The sun can scald, newly transplanted plants if they are still tender.

"A proper evaluation usually requires a soil test and site history review," the horticulturists says, advising, "Keep good notes and be observant."

For related topics, look for Gardening and Get It Growing links at the LSU AgCenter Web site, Additional yard and garden topics are available from an extension agent in your parish LSU AgCenter office.


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