Bobbi Stevenson-McDermott Jan. 31,2016 publication
Soil, handle with care as we cannot live without it! This is the time of the year when there are many tractors and tillage implements being used in our farm fields. It is also the time of the year when the soil itself is most vulnerable to damage from equipment traffic. During the produce growing season, a percentage of the irrigation water used goes past the 1 to 2 foot root zone of the vegetable crop. As a result, the soil below the root zone is saturated, since no roots are using the water. This saturated layer of soil should not be disturbed with a ripper or plow, as it destroys the soil structure by compacting the soil, eliminating the pores between the soil particles that are needed for air and water movement. Once the soil is compacted, it takes crop rotations with deep rooted crops along with adding organic matter to restore the soil structure and it is not a rapid process.
For the soils benefit, after the first crop is harvested, growers should just shallow disc the fields to break up the crop residues and remove the rows. If the field is going back into produce, run the rows, shape the beds and plant, not doing any deep tillage. I have already seen fields with huge clods which will take time and fuel to break down to a farmable surface. If the field is going to wheat, Sudan grass, or other flat planted crop, just seed and water.
The water and fertilizer that is in the second and third foot of soil in produce fields will be utilized by the deeper rooted crops. As the roots grow downward, they help break up compaction caused during the growing of produce. Since the harvest of the rotation crops is done after the crop matures, irrigation is reduced as the crop approaches harvest, drying down the soil layers. After harvest is the perfect time to do deep tillage as the soil will shatter rather than slick, and the compacted layers will be broken up.
A healthy soil needs to have soil organisms, organic matter, pore space, air and water to reduce disease and other plant pests. Additional benefits of having good soil quality include improved soil structure; better infiltration of water into the soil; more water being held in the plant root zone; reduced crusting on the soil; reduced salt build up; better organic matter content and better drainage.
Soil management is particularly important on our valley soil, predominantly clays, silty clays, silt loams and loams. These highly productive soils need special care to keep them healthy.
When in the produce business, producing the same quantity and quality of crops is the name of the game. Weather normally is never the friend of the farmer, as has been seen this growing season. Contracts with the restaurants, grocery stores, institutions and exporters must be met with quality product, requiring harvest of crops in all types of weather and conditions. Just the normal ‘wear and tear’ on the soils in growing season stresses the soil health. Add in crop harvest in wet fields, need to use heavy equipment to move the harvest aids and trailers through the fields and weight on wet soils, any reduction of trips through the fields when growing rotation crops is a benefit.
Soil structure, permeability, organic matter content and soil microorganisms can all be restored to the soil, but it takes a plan by the grower to provide the inputs to keep their soil healthy and productive.
Bobbi Stevenson-McDermott is a soil and water conservationist. She can be reached at email@example.com.