Extension Educator, Horticulture
Take two pounds of poultry manure and call me in the morning. Plants can't exactly tell us what's wrong when they look sick. They can, however, give us hints when they have nutrient deficiencies.
Plants need at least 16 different nutrients. Carbon, hydrogen, and oxygen are needed in large quantities, but plants usually get these in sufficient amounts from air and water. Plants also need nitrogen, phosphorus and potassium in relatively large quantities. Nitrogen promotes leaf and stem growth. Phosphorus is involved in flowering, fruiting, root development, and seed germination. Potassium promotes disease resistance, winter hardiness, and root development.
The micronutrients of sulfur, magnesium, calcium, iron, copper, manganese, boron, zinc, molybdenum, and chlorine are just as important but are needed in smaller quantities. Plants require differing amounts of all the nutrients. The amount of plant available nutrients can depend on soil pH (acid or alkaline).
Symptoms of common nutrient deficiencies:
Unfortunately it's not as simple as a quick diagnosis of symptoms then immediately conclude it's a nutrient deficiency. Environmental problems, diseases, and pests can cause similar symptoms. Just think of how many different things give us headaches – bad food, bad manners, bad hair days. A soil test may help to determine deficiencies. Rule out environmental conditions such as too much water or too little water before assuming a nutrient deficiency.
Fertilizers (often incorrectly called plant food) can correct nutrient deficiencies. Plants make their own food through photosynthesis. Fertilizers contain plant nutrients. All fertilizers have a guaranteed analysis such as 10-20-10 listed as three numbers on the label. The analysis on the fertilizer container shows the percentage of each nutrient by weight or ppm.
The first number is nitrogen. Second number is phosphorous (phosphoric acid). Third number is potassium (potash). Amount varies according to fertilizer purpose.
Fertilizers are inorganic or organic. Inorganic fertilizers do not contain carbon. Some are naturally occurring minerals such as muriate of potash, rock phosphate, etc. and some may be synthesized by people such as ammonium nitrate (33-0-0) or ammonium sulfate (21-0-0). Some inorganic fertilizers may also have herbicides in them such as "Preen and Green" and "Weed-n-Feed".
Organic fertilizers are derived from living organisms. This would include items such as dried blood meal, cottonseed meal, Zoo-Doo, fish emulsion, manures or seaweed extracts.
Inorganic and organic have advantages and disadvantages.
Not everything needs to be fertilized. To prevent nutrient deficiencies and encourage good plant health concentrate on feeding the soil with compost or other organic matter rather then feeding the plants. Plants need a balance meal too.
Sat, March 17, 9am-4pm and Sun, March 18, 1pm-3pm. Rare Himalayan Blue Poppies at the University of Illinois Plant Biology Greenhouses at 1201 South Dorner Drive in Urbana. www.life.uiuc.edu/plantbio/greenhouse