Integrated Crop Management

Time to check the terraces

Now that the June rains are over, how did your terraces fare? No matter what kind of terrace you have in your operation, terraces are a critical water and soil management tool, so it is important to check them every year for weak spots and needed maintenance.

If you notice a problem with your terraces, it's best to plan to address it now to avoid future problems. Below are the things you need to check when assessing the condition of your terraces, and some possible remedies for problems.

Check the inlets

Make sure inlets are clear of crop residue and other foreign material. If they are plugged, reestablish the integrity of screen by clearing it of sediment and crop residues. Also check for damage from machinery and livestock and repair or replace broken and bent intakes. Set up a warning flag or paint inlets to make them visible to machinery operators. Also, if livestock have damaged an intake, consider constructing a temporary fence around the intake to keep livestock away and prevent additional damage.

Check for excessive erosion

Take action to control erosion between terraces to reduce maintenance needs. Things to look for include sediment deposits in the terrace channel and noticeably lower water storage capacity due to sediment buildup. If a lot of topsoil has already washed in, now is the time to line up a contractor to clean out the terrace channel after harvest.

Check the stand pipe

An additional result of erosion that producers may notice is a shrinking or buried inlet or drainage stand pipe. Clear the inlet, or if the terrace was designed for some sediment buildup, the stand pipe can be extended.

Terrace ridge

The height of the terrace ridge may have been affected by tillage operations. Conduct a visual inspection to see whether tillage has inadvertently disturbed and lowered the ridge of the terrace. Plan to replace any low spots in the ridge and reestablish grass and vegetation. Practice good tillage techniques and avoid the ridge of the terrace in the future to prevent damage.

Check for slow drainage and standing water

After a normal rainfall event, terraces should completely drain in about 2 days or less (except in cases of very heavy rainfall). If drainage is slow, check the conditions around the inlet and outlets for plugged tile. If you don't see or cannot clear an obstruction, you may have to line up a contractor to help resolve the problem after harvest.

Look for evidence of burrowing animals

If an animal burrow is noticed in the terrace, trap and remove the burrowing animals to prevent damage to the terrace.

Inspect the vegetation on the terrace back slopes and stand pipe. Has a healthy sod been established, and is it free of weeds, trees, and brush? Is the grass working to maintain the integrity of the bank? Maintaining a good grass cover means you'll have to keep an eye on the terraces. Control or eliminate undesirable species and keep grass growing with weed control and fertilization. A little grass near a stand pipe can help settle out suspended sediments before they can enter the tile, but if it's too thick near the intake, the grass may become a detriment and plug the inlet. Consider establishing a small buffer strip around the stand pipe area to help settle out sediments and herbicides before they get to the stand pipe and enter the tile.

Check for overtopped terraces

Most terraces are designed with enough capacity to handle (at a minimum) the rainfall from a 10-year storm, but some producers may find that this year's June and July rains have overtopped their terraces. With properly established grass backs, most terraces can handle a little overtopping. However, if severe overtopping or erosion of the terrace has occurred, you may need to plan for extensive repair or reestablishment in the fall.

Now that your terraces have been inspected and plans have been made to get the work done after harvest, make certain that activities around terraces are designed with terrace maintenance in mind. It's OK to perform tillage operations on terrace slopes, but take care to stay off the ridge. Don't till steep back slope or narrow-based terraces; maintain a good grass cover. And make sure that you maintain any broad-base terraces and terrace channels with proper tillage practices.

Soil types, grades, and tolerance for in-field erosion and terraces vary throughout the state. If you have questions, talk with your contractor or local Natural Resources Conservation Service office for more specific information about maintaining the terraces on your operation.

This article originally appeared on pages 135-136 of the IC-484(18) -- July 17, 2000 issue.


Source URL:
http://www.ipm.iastate.edu/ipm/icm//ipm/icm/2000/7-17-2000/terraces.html