Soil Test

Soil Test

• A random sampling of a specific area of soil

Why Test Soils?

• To determine the amount of a nutrient to be added

• Determine pH• Primary nutrients are the main

nutrients tested

Micronutrients?

• Tissue tests• micronutrient deficiencies• Results vary within the growing

season

Soil Test Results

• Farmers, greenhouses, and homeowners evaluate the test results and decide whether or not fertilizer should be applied.

Soil pH

• Measure of the acidity or the alkalinity of a soil

What makes a soil acidic?

• High concentrations of cations in the soil

• Cation - positive ion such as H+

What makes a soil basic?

• High concentration of anions in the soil

• Anion - negative ions such as OH-

Causes for Acidity in Soil

• Acid rainfall• Harvested crops• Most fertilizers• Erosion removes Ca and Mg• Nitrification

Why do we care?

• Soil pH determines the availability of certain essential elements

• Different plants have different pH requirements

Acidic soils

• Plant signals that a soil is too acidic:– Firing– Stunted growth– Slow

germination

Basic Soils

• Plant signals that a soil is too basic– Stunted growth– Slow germination

(Your soil will tell you when something is wrong but you need to get it tested to be sure exactly what)

Relates to soil nutrition

• pH below 5.8, P will react with Fe to form insoluble iron compound

• At a high pH, P reacts with Ca and is unavailable

• The amount of N, P, K available to plants depends on soil pH

The pH Scale• Runs from 0-14• 0 is extremely acidic• 7 is neutral• 14 extremely basic

Requirements for plants

• Alfalfa 6.3-6.5• Corn 5.5-7.0• Potato 5.0-5.7• Soybeans 5.5-7.0• Azaleas 5.0-5.5

• Generally, plants grow best between 5.5 - 8.0

How can we change pH?

• Adding sulfur or gypsum to lower pH

• Adding limestone to increase pH