Yuma Ag and You: Healthy Soils

Bobbi Stevenson McDermott     September 13, 2015

Farmers manipulate the soil quality to improve soil health and maintain or improve crop production.

Soil health depends on several factors. The soil quality indicators are physical, chemical and biological properties, processes and characteristics that can be measured to monitor the changes the soil. Soil has many different jobs, some of which are providing a home for living organisms; regulating and distributing water flow; storing nutrients and other elements; filtering, buffering, degrading, immobilizing and detoxifying organic and inorganic materials and providing a foundation for people and their structures.

Visual indicators of soil quality include exposure of subsoil from erosion; change in soil color; ponding of water or runoff; plant growth and quality; weeds, or blowing soil. Visual evidence can be a clear indication that soil quality is threatened or changing.

Physical indicators are related to the arrangement of soil particles and the spaces between them (pore space). Soil texture, amount of sand, silt and clay; topsoil depth; compaction; crusting and soil stability primarily reflect limitations to root growth, seedling emergence; infiltration, which is the rate that water enters the soil; and permeability, the rate that water moves downward through the soil.

All of these factors affect the ability of growers to produce the type and quality of crops they want, and the effects of chemical and biological indicators have yet to be considered.

The soil’s chemical condition, pH, organic matter content, nutrient levels, and soil contaminants all affect soil-plant relationships, water quality, availability of nutrients and water and plants and other organisms and the productivity of the soil.

The biological indicators vary with the type of soil and the area of the country being farmed. In the areas that have four seasons, soils tend to be rich in organic matter and microorganisms. Desert soils have less than one-half percent organic matter, while Eastern and Southern soils have as much as six percent organic matter. The organic matter, which may be crop residues, composted manures or crops grown and turned under before harvest, are extremely important to all farming. Essential plant nutrients needed for growing plants are released as the organic matter is broken down by soil microorganisms, fungi and bacteria. The material left after the nutrients are gone helps to build the soil structure and buffer the soil particles from one another so that air and water move through the root zone. All plants need as much water as they do air, so it is vital to maintain a healthy soil.

As field preparation goes on for the fall growing season, you will see fewer tillage operations ongoing, as farmers work to combine different equipment to reduce the number of times tractors are in the field. Not only does this save time and labor, but it reduces the potential compaction of the upper layers of soils, essential for water and air penetration. Mechanized thinning and transplants will further reduce foot traffic in the fields. Healthy soils are more disease resistant, provide better root support improve and conserve the wonderfully productive soils in Yuma County.

Bobbi Stevenson-McDermott is a soil and water conservationist. She can be reached at rjsm09@msn.com.