By: Scott Eckert, County Extension Agent, Horticulture
Plants require 17 essential nutrients for growth with the nutrients most frequently lacking for growth being nitrogen, phosphorus, and potassium. Why is each one important?
N (Nitrogen) – This nutrient element provides dark green color in plants. It promotes rapid vegetative growth. Plants deficient in nitrogen have erect stems, pale or yellow foliage showing first on older leaves, and smaller-than-normal leaves. Overuse of nitrogen can lead to lots of foliage and poor fruit set.
P (Phosphorus) – This nutrient promotes early root formation, gives plants a rapid, vigorous start and hastens blooming and maturity. Plants deficient in this element have shortened stems and the leaves often develop a purplish color. Soil in Harvey County often already has an excess of this nutrient. Add only according to soil test recommendations.
K (Potassium) – Potassium or potash hastens ripening of fruit. Plant disease resistance as well as general plant health depends on this element. It is important, also, in developing plump, full seeds. Plants deficient in this element have graying or browning on the outer edges of the older leaves. Soil in Harvey County often already has an excess of this nutrient. Add only according to soil test recommendations.
The content of N, P and K is specified on bags of chemical fertilizers. The analysis or grade refers to the percent of nitrogen, phosphate and potash (in that order) the bag contains. Thus a 10-10-10 fertilizer contains 10 percent nitrogen (N), 10 percent phosphate (P2O5) and 10 percent potash (K20).
To calculate the amount of fertilizer needed for an area, consider the recommendation for the particular nutrient needed and the fertilizer analysis. If you need to add 1 pound of N per 1,000 square feet, and you have a 10-10-10 fertilizer (which contains 10 percent N) you will have to add 10 pounds of this material per 1,000 square feet to achieve the needed amount of N.
The Ratio
Sometimes the term, ratio, is used when referring to fertilizer analysis. The ratio is the relationship of the contents of N, P and K to each other. For example, a 1- 1-1 ratio means there are equal proportions of N, P2O5 and K2O such as 10-10- 10 analysis. However, a
2-1-1 ratio means there is twice as much N as P2O5 and K2O such as is true for 10-5-5. The ratio does not indicate the content of the elements but only their relationship to each other.
Other Nutrients – In addition to N, P and K there are 14 other elements that plants require, 11 of which come from the soil. It is not usually necessary to add these elements since they are often present in sufficient quantities in Kansas soils. However, on occasion it may be necessary to add one or more of these secondary and micronutrients. One of the most common of these micronutrient elements found lacking is iron in high pH soils commonly found in western Kansas.
The symptom of iron deficiency is a pale yellow color that develops in the new growth of the plants. This can be corrected by a foliar application of iron or by reducing the soil pH. There also may be need for sulfur or zinc on very sandy soils or garden areas with topsoil recently removed.
