Yuma Ag and You: Soil as a living organism

Bobbi Stevenson-McDermott                   June 5, 2016 publication

June, the kids are out of school, weddings are being held, vacation trips being planned and the wheat stubble in Yuma farm fields is going up in smoke! Soil biodiversity reflects the mix of living organisms in the soil. These organisms interact with one another and with plants and small animals forming a web of biological activity. Soil is by far the most biologically diverse part of the Earth. The soil food web includes beetles, springtails, mites, spiders, worms, ants, nematodes, fungi, bacteria and other organisms. These organisms improve the entry and storage of water, resistance to erosion, plant nutrition and breakdown of organic matter. Soil organisms decompose plant residue, Each organism in the soil plays an important role. The lager organisms in the soil shred dead leaves and stems. This stimulates cycling of nutrients.

Organic matter is an essential component of soils because it: provides a carbon and energy source for soil microbes; aids growth of crops by improving the soil’s ability to store and transmit air and water; stores and supplies nutrients such as nitrogen, phosphorus and sulfur which are needed for the growth of plants and soil organisms.

Soil organic matter also improves the health of the top layer of soils, reducing crusting, increasing the rate of water infiltration and helps root penetration.

With $400 to 500 dollars in growing costs for Durum wheat, why would you burn up the remaining nutrients as well as the organic matter in the wheat stubble. If the stubble is baled there is still significant organic matter to be returned to the soil. Yes, it will be necessary to apply nitrogen to facilitate the soil microorganisms in the breakdown of the residue but how many growers burn their fields, then apply composted manure or other materials? As more and more crops are being transplanted, why not set up a trial where the wheat residue is turned under, nitrogen applied and then the produce crop grown as usual.

The additional benefits of the organic matter on your soil include less crusting, increased infiltration of water and air, easier root penetration, less compaction and of course, the nutrients released by the breakdown of the stubble. The soil is a renewable resource but it can only be overworked for so long before it is subject to disease or production problems. Every farmer understands the value of crop rotations, alternating shallow rooted crops and deep rooted crops, and breaking weed and insect cycles.

Some growers this year have alfalfa seed growing. Alfalfa and other legumes (beans, peas) are wonderful rotation crops. Alfalfa develops an extensive root system and after harvest, as the roots decay, there are passages for air, water and the next crops roots. Legumes also can take nitrogen from the air and it is fixed in the soil by microorganisms, available for the next crop.

Soil is a living, dynamic resource that supports plant life. It is made up of different size mineral particles (sand, silt, and clay), organic matter and numerous species of living organisms. Soil has biological, chemical and physical properties that are always changing. While we discuss and debate water issues, the soil needs equal time in the discussion. Without healthy soil, the wonderful agriculture that is the lifeblood of Yuma County will suffer.