If soils could talk, what would they say?

Cold nights, rain, fog, wind and sunshine and all on the same day! Yuma weather has been anything but predictable.

As we head for the middle of February, many of the early fields of produce are being planted into wheat. The early produce planting and harvest schedules were disrupted by our weather, but I understand prices of our winter crops have been good this year.

As the fields transition to rotation crops, my first concern is the soil condition of the harvested fields. With almost an inch of rain this week, the fields are really wet for tillage, particularly any deep tillage.

The roots of the vegetable crops are typically shallow, 1 to 2 feet deep, compared to wheat, cotton, Sudan grass, silage corn and other rotation crops. With the shallow root systems, the soil below 2 feet is generally saturated because water is not being used by the plants.

To do anything beyond surface discing risks disrupting the soil’s ability to absorb water into the surface and destroys the soil structure in the saturated layers.

Plants need as much air as they need water to grow, whether in a flower pot, garden or farm field. Air and water are carried into the soil through the tunnels or pore space left behind after the roots die. These spaces between the soil particles are fragile and need to be protected from destruction.

Rippers are a type of tillage equipment like giant knives that are pulled through the soil at a 2 or three feet depth. When the soil is dry after wheat, Sudan grass and cotton, the compaction caused by the intense vegetable production operations is effectively shattered, creating new pathways for air and water to get to the soil depths.

If done while the soil is wet, ripping is like pulling a fork through butter, the soil comes up in chunks and most of the pores are crushed. As the ripper shanks go through the soil, they compact and slick the sides of their path, actually causing compaction rather than opening it up.

Part of the answer is to never work wet soil. This is often not possible due to crop planting patterns but it is possible to use the least disruptive tillage method you can.

Coming out of a row crop, it is possible to lightly disc the rows down so the field is essentially cloddy then seed your wheat or Sudan grass and apply a light irrigation which reduces the clods and germinates the seed. Since most of the irrigated cropland is leveled to flat basins, the high irrigation efficiencies can be maintained with flood irrigation. Some growers prefer to string out the irrigation pipe and sprinkle the crop up.

Wheat, cotton, corn and Sudan grass fields are all allowed to dry down while getting ready for harvest. This allows the deep roots of these crops which reach 3 to 4 feet or greater into the soil to suck out all the available water and then when ripping or plowing occurs, the soil breaks up, creating new paths for air and water.

Plowing is not as common in Yuma County soils as it is in other parts of the country. The soils in Yuma County were transported into our area by the Colorado and Gila rivers. The three basic soil particles are sand, the heaviest, silt, like flour, and clay which is very fine grained.

As the water from the rivers overflowed the banks, the heaviest particles, sand, fell out first, then the silt and then the clay. Over millions of years the layers of different particles became deep enough to support plants.

The best fields were those that received an equal mixture of sand, silt and clay. Much of the soil in North and South Gila Valleys are this type of loam soil. Other areas of Yuma counties have soils that are not mixed but instead layered, dependent on the soil the rivers were carrying when they overflowed.

With layered soils, if the best soil is in the top layer, farmers do not want to disturb it by mixing it with lower soil layers that are not as productive so plowing is not done, rather the ripper which shatters but does not turn and mix the soil is used for tillage.

Yuma County has very unique and productive soils, but they must be managed properly. It is logical that much of the soil we farm was once part of the Grand Canyon before it was created. If only the soils could talk!

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