Factors which affect soil structure

1. Factors which affect soil structure Organic Matter Content Soil Organisms Soil Colloids Tillage Freezing and Thawing Water Movement

2. Organic Matter Content May be increased by Adding manure Growing cover crops May be decreased by Tillage Hot, Humid environment It is especially hard to build up soil organic matter in the south because of our abundant rainfall and warm temperatures- ideal conditions for decomposition.,It is especially hard to build up soil organic matter in the south because of our abundant rainfall and warm temperatures- ideal conditions for decomposition.,

3. Soil Organisms Bacteria in soil have sticky substance on cell wall. This “glue” holds soil particles to bacteria and to each other. This binds soil particles into larger particles. Fungi produce thread-like structures called mycelia which bind soil particles and peds making larger particles. Two of the most important soil organisms are bacteria and fungi. They are extremely abundant in soil and hold the soil particles together into larger aggregations called peds.Two of the most important soil organisms are bacteria and fungi. They are extremely abundant in soil and hold the soil particles together into larger aggregations called peds.

4. Soil Colloids Very small particles with a weak electric charge. + o o- The charge causes water to bind to particles. As water evaporates, colloids and larger particles draw together, creating even larger particles.

5. Tillage Positive effect Creates air space in soil, allowing organisms needed oxygen Negative effect Disrupts the soil structure and kills the larger organisms such as earthworms. If done when too wet or dry, may destroy the soil structure of the tillage zone.

6. Freezing and Thawing As water in soil freezes it expands, pushing soil particles apart. This opens pore spaces for air. As water thaws, pore spaces tend to remain temporarily. This can be enough to encourage soil organisms, by allowing more oxygen. After a freeze the ground will feel spongy, due to the water pushing the soil particles apart. As you walk on the soil, it will compact.After a freeze the ground will feel spongy, due to the water pushing the soil particles apart. As you walk on the soil, it will compact.

7. Water Movement Positive + As water moves vertically through the soil some of the water is stored, and can be used by crops. Negative - Vertical movement of water can cause leaching of minerals. Vertical movement in soil freshly tilled may cause collapse and less pore space. Vertical movement in clay can result in a hard pan. Horizontal movement may cause erosion. Clay particles are easily picked up by water because of their charged nature and carried down the soil profile. When they hit a compaction zone they will fall out of solution and form an impermeable layer, called a hard pan. This property is used to seal ponds. It is not good in a field because it prevents the plant roots from penetrating.Clay particles are easily picked up by water because of their charged nature and carried down the soil profile. When they hit a compaction zone they will fall out of solution and form an impermeable layer, called a hard pan. This property is used to seal ponds. It is not good in a field because it prevents the plant roots from penetrating.

8.  This card was developed by the Georgia Conservation Tillage Alliance to help farmers monitor the quality of their soil from year to year.This card was developed by the Georgia Conservation Tillage Alliance to help farmers monitor the quality of their soil from year to year.

9. All of these criteria can not be answered at a glance, but gives you a quick comprehensive overview of what you should look for as you examine your soil.All of these criteria can not be answered at a glance, but gives you a quick comprehensive overview of what you should look for as you examine your soil.

10. pH pH is the measure of the concentration of hydrogen ions. It is measure on a logarithmic scale going from 1-14 with 1 being the most acidic (most hydrogen ions) and 14 the most basic (least hydrogen ions). pH of soil is important because certain chemical reactions only occur in certain range. Not as important for organic systems, because they depend on biological reactions more than chemical reactions. pH determines what chemical reactions occur. Blueberries and azaleas need a low or acidic pH because they need nitrogen in the form of ammonium, which is more available at a low pH.pH determines what chemical reactions occur. Blueberries and azaleas need a low or acidic pH because they need nitrogen in the form of ammonium, which is more available at a low pH.