Mid-summer is a good time to evaluate and perform maintenance on terraces if fields are in wheat stubble.
In Kansas, over 9 million acres of land are protected by more than 290,000 miles of terraces, making Kansas No. 2 in the U.S. for this soil and water conservation practice.
To accomplish the goal of erosion control and water savings, terraces must have adequate capacity, ridge height, and channel width. Without adequate capacity to carry water, terraces will be overtopped by runoff in a heavy storm.
Overtopping causes erosion of the terrace ridge, terrace back slope, and lower terraces and may result in severe gullies. Terraces are typically designed to handle runoff from a 1-in-10-year storm. The rainfall amounts for such a storm are approximately five inches for eastern Kansas, four inches for central, and three inches for western Kansas during a 24-hour period. Kansas producers have seen their fair share of these intense storms in the spring and summer of 2019.
Terraces need regular maintenance to function for a long life. Erosion by water, wind, and tillage wears the ridge down and deposits sediment in the channel, decreasing the effective ridge height, and channel capacity. The amount of capacity loss depends on the type and number of tillage operations, topography, soil properties, crop residue, and precipitation.
Terrace maintenance restores capacity by removing sediment from the channel and rebuilding ridge height. Typically, more frequent maintenance is required for steep slopes and/or highly erodible soils. Annual maintenance is necessary for intense tillage operations and heavy rainfall runoff. Less frequent maintenance is often adequate with high residue levels or where lower rainfall occurs and runoff intensity is low.
— Ryan Flaming is a Kansas State Research and Extension Agent for Harvey County. Agriculture is his specialty. The Harvey County Extension Office can be contacted at 284-6930.