You Have Met T Values. What Now?

By Sjoerd Duiker and Jennifer Weld

Developing a soil conservation plan is a first step to minimizing erosion on your farm. During plan development, you will work with soil conservation personnel to evaluate and inventory your cropping and tillage practices and to calculate soil loss for your fields. As soil loss is calculated, you may need to make changes to cropping and tillage practices to reduce soil loss so that it is less than or equal to the tolerable soil loss value (T value). The final plan includes practices that meet the T value for your fields and that meet your farm management goals. For more information on T values, see our article A Values and T Values: What is That All About? 

Developing your plan was the first step, the next steps are plan implementation and plan evaluation. Implementing your plan will require following the steps outlined in your plan. While your plan reflects decisions made at the time of development, farm management is dynamic. Changes to farm management goals, fluctuating fertilizer and commodity prices, and variable weather patterns may mean that your plan needs to be re-evaluated. Evaluation of soil conservation plans is an important step to ensure that current farm management goals and erosion targets are met.

Field observation is part of soil conservation plan implementation and evaluation and can identify erosion not considered when developing your soil conservation plan. When a conservation plan is developed, sheet and rill erosion are evaluated, but not ephemeral gully erosion. Nonetheless, a lot of soil can be lost through ephemeral gully erosion. Reviews of studies showed that 10-95% of the erosion from a watershed was due to ephemeral gully erosion, with a median value of approximately 40%. Additionally, according to the Food Security Act Manual Section 512.0 C2 farmers are required to address ephemeral gully erosion on Highly Erodible Land.

Ephemeral gullies have several important characteristics. Typically, ephemeral gullies are:

• less than 1.5 feet deep
• farmable and can be erased with tillage, but they do not disappear in no-till fields
• formed in the same positions where runoff concentrates on the landscape
• important to identify because if left unmanaged can become classic gullies

Ephemeral gullies are different from rills. Typically, rills are:

• less than 4" deep
• usually parallel on the slope until they converge
• obliterated by normal tillage
• formed in different locations from year to year

Ephemeral gullies are different from classic gullies. Typically, classic gullies are:

• more than 1.5 feet deep
• not easily driven or tilled across
• lead to disfigurement of the landscape making it unfit for crop production

If you see ephemeral gullies on your farm, it is important to talk to a soil conservation professional. You need to evaluate management options that are consistent with your soil conservation plan and that will work to manage the ephemeral gully over the long-term.

Tillage might seem like the best management approach; however, tillage compounds the problem. Soil from surrounding areas fills in the gully, and this unconsolidated, loose soil is easily washed away in the next big runoff event. Instead, you should focus on soil health principles to manage the ephemeral gully and soil compaction.  These practices include reducing tillage, increasing organic cover, increasing crop rotation and crop associations diversity, and increasing the period of active root growth to increase soil infiltration.

When concentrated runoff entering the field from a seep, spring, road, culvert, or development causes an ephemeral gully, approaches to stabilize the concentrated flow area, and repair the ephemeral gully are needed. Management approaches can combine structural drainage management such as a terrace with inlet, diversion, lined grassed waterway, or outlet with non-structural practices that complement the soil health practices mentioned above, such as strip cropping, contour planting, contour buffer strips, field borders, vegetative filter strips, or vegetative barriers.

Soil conservation plan development is the first step toward minimizing erosion on your farm. The next steps of plan implementation, plan evaluation, field observation, and continued communication with a soil conservation professional are critical to integrating soil loss goals into your farm management. We challenge you to observe your fields to see where soil loss may be occurring.