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Soil conservation and weed control - Part 1
Dr. Victor Martin

This is written last Thursday so by now the warnings for severe weather and heavy rains may have happened. Hopefully, the forecasts were wrong.  The past week did allow for some drying and with warmer temperatures, field work was picking up, especially south of the river on the sandier soils. Wheat is heading out and some fields look to have excellent yield potential, especially considering all the challenges of the last seven months. Wheat benefitted greatly from the moisture and cool temperatures. The downside is the appearance of leaf diseases which from K-State reports haven’t reached the flag leaf in our area yet and aren’t severe. However, if producers are considering applying a fungicide, time is short. The decision is more challenging with the price of wheat. The decision would be much easier with six or seven dollar wheat. All the rainfall across the area resulted in soil erosion and that is the topic of today’s column.

From the 1990s up until the last several years, acreage in some type of conservation tillage, especially no-till and strip till, had increased dramatically across the nation and in Kansas. Two major factors contributed to this increase. First, the development of planting equipment improved dramatically allowing for effective no-till planting. Strip till combined the advantages of no-till with the benefits of till a small strip for seed planting for row crops. 

The advent of auto-steer allowed for the practicality of the strip till system. Second, herbicide efficacy improved dramatically, both from the development of new herbicides technologies, and modes of action, especially the development of Roundup Ready ® crops. However, as anyone in the industry knows, the overuse of glyphosate led to the development of weeds resistant to the herbicide, hundreds of them across the world. Herbicide technologies existed and new ones developed, that could address this issue but they are pricier and may involve specially developed seed, a further expense. The result, especially those producers dealing with resistant weeds such as pigweed species, was a return to tillage to control weeds. The result of this, as demonstrated with the wet weather this spring is an increase in soil erosion due to water. In addition, especially for producers on sandier soils, an increase in wind erosion.  

There are three basic types of water erosion: sheet, rill, and gully. Remember, it only takes a minor slope for soil erosion to take place. A one percent slope, i.e. a one foot change in one hundred feet is all that is needed.  Sheet erosion is the removal of a fairly uniform layer of soil downslope. Rill erosion occurs when the water concentrates and forms small channels. These can be addressed with tillage. The sheet erosion between the rills is termed inter-rill erosion. Finally, as rill erosion increases it forms deep channels termed gullies. Gullies are defined as difficult or impossible for equipment to cross and cannot be repaired with normal tillage equipment.

While rill and gully erosion are more visible and gully erosion often quite dramatic, most soil is lost through sheet erosion. Sheet erosion is subtle and can go unnoticed but results in the loss of the most productive, valuable soil separates, silt and especially clay and organic matter. Under ideal conditions, it takes hundreds of years to form an inch of topsoil. So what can we do to stop this loss and start to repair the damage? This is addressed in next week’s column.

Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.