Strip-tillage: Positive move from conventional tillage12/18/2018 | Crop Production Research, Soil Health, Water Quality
By Scott Nelson, On-Farm Network Director
Declining soil health and soil erosion are intergenerational issues in Iowa. Average soil loss due to erosion in Iowa is estimated to be 6 tons per acre per year, according to the Iowa Natural Resources Conservation Service (NRCS). At this rate, each generation over a typical 40-year farming career will hand down one inch less topsoil to the next generation of farmers.
To increase farm profitability, every input to a cropping system must be examined including tillage. A lower-cost tillage system, such as no-till or strip-till, can be more profitable even if it may be lower yielding. According to Mahdi Al-Kaisi, professor of Agronomy at Iowa State University, conservation tillage reduces costs associated with tillage by nearly 17 percent. Additionally, these conservation tillage systems can be used to retain soil cover for the prevention of soil erosion by wind and water.
However, a no-till system is not necessarily applicable for all Iowa farms. Some farmers who have tried no-till may have experienced slower drying of the soil in the spring as well as yield losses when compared to conventional tillage. Strip-tillage systems could be a happy medium between no-till and conventional tillage.
In 2017, the Iowa Soybean Association (ISA) On-Farm Network® established a series of farm strip-tillage research trials with non-checkoff funding. The study compared strip-tillage against conventional tillage or no-till.
With strip-tillage, the soil is tilled in rows of 6- to 10-inch strips in the fall or spring, leaving areas of crop residue in between the exposed rows. Because the crop residue has been moved away from the rows, this system has the advantage of faster soil drying in the spring. Less residue in the tilled strips reduces issues that may impair planting. In many cases, strip-till allows placement of nutrients around six inches below the strip of planted seeds.
Strip till represents a system less conducive to soil erosion as residue cover is maintained on 66 percent of a field area. In addition to reduced erosion, keeping residue cover on the field improves soil health by improving aggregate stability, water infiltration and reduces bulk density.
In most of the On-Farm Network trials, a Soil Warrior manufactured by ETS (Figure 1) was used to till the strips. To simplify the comparisons, there was no deep placement of fertilizer in these trials. At each trial site (Figure 2), field length strip-tilled rows were replicated four times and compared with conventionally tilled or no-till rows.
Early stand establishment was monitored in the spring. At harvest, effects of the tillage systems were estimated with a commercial yield monitor, from which the data was cleaned and calibrated for best comparisons. Additionally, aerial images captured in August were used to remove field areas that experienced flooding or other terrain attributes.
Research trial results
Individual location responses are represented in the bar graphs in Figure 3A-F. Each comparison contains a standard error bar. This reflects the variation in yield around the mean. These error bars can be used as a guide to decide if the difference was significant and greater than what would be observed by chance alone.
Strip-till was compared to no-till at four locations. On average there was a 5-bushel yield advantage for strip-tillage when compared to no-till, but the locations responded differently to tillage systems.
At the two locations where strip-till was compared to conventional tillage (Figures 3E-F), there was an average yield advantage for strip-till of 11 bushels per acre. However, all locations did not respond similarly. One site showed a 20-bushel yield advantage while the yield advantage at the second location was not significant. The site that showed the large yield advantage for strip-till (Figure 3E) was tilled in the spring when field conditions were likely too wet.
At most locations strip-tillage proved to be higher-yielding than conventionally tilled soil and no-till. Fuel costs will be slightly less than conventional tillage but more than no-till, as there are fewer passes in the field. Considerations such as fuel and equipment costs need to be included in management decisions to find which tillage system works best economically and environmentally for each farm.
This study was partially sponsored by Bayer Crop Science and Environmental Tillage Systems.
Scott Nelson can be reached at firstname.lastname@example.org.
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©2018 Iowa Soybean Association On-Farm Network®. All rights reserved. On-Farm Network® is a registered trademark of the Iowa Soybean Association, Ankeny, IA.Portions of some On-Farm Network trials are paid for in total or in part by the soybean checkoff.