By Jenny Rees
This article will focus on residue removal via baling and the resulting yield impacts, sharing data from multiple research studies.
Like anything, residue removal has both positive and negative effects. Positive effects include:
- reduced disease pressure from residue-borne pathogens,
- increased soil temperature leading to increased microbial activity and reduced nitrogen immobilization,
- increased germination and uniform plant emergence due to warmer soil temperatures.
Figure 1. Where moisture is not limited, research shows that removing some corn residue from a field may benefit yield in the following crop. However, if residue is removed for more than three years, research showed longer term impacts to the soil.
Negative effects of residue removal include
- increasing the potential for wind erosion (increased wind erodible fraction of <0.84 mm aggregates by 0, 27%, and 37% in first, second, and third year of a Nebraska study (Blanco-Canqui, et al., 2017) on sandy loam soil),
- water loss to evaporation (2.5-5 inches/year in North Platte study),
- soil loss through heavy rain events in the spring on sloping fields,
- increased raindrop impact and reduced soil water infiltration rates leading to more water runoff,
- increased potential for weed pressure, and
- nutrient removal from the field.
Usually more than 30% residue is left in the field after baling with many striving to leave at least 50% residue in place. Research has shown a minimum of 2.4 tons/acre of residue is necessary to maintain soil organic carbon in no-till systems (Wilhelm et al., 2007). A study conducted in eastern Colorado found that in a no-till, continuous corn system with 66% residue removal and adequate nitrogen applied for crop needs, soil organic carbon at the 0-6 foot depth in a clay loam soil decreased over the seven years of the study compared to its increase in the check where no residue was removed (Halvorson and Stewart, 2015). Residue removal did result in yield increases in the study (mostly within the first three to four years) with the researchers recommending residue removal every other year to every third year in this type of system to negate losses in soil carbon while potentially increasing yields.
A non-irrigated study in no-till continuous corn receiving treatments of 0 or 50% residue removal with 54, 107, and 160 lb/ac nitrogen application to the successive crop was conducted for 10 years at the Agricultural Research and Development Center (ARDC) near Mead. Results found corn yield reduction of 1.9 bu/ac when residue was removed over the 10-year period versus when residue was retained. It was speculated the yield reduction was due to evaporative losses of water in the non-irrigated environment. Yields were significantly less with only 54 lb/ac of nitrogen applied to the corn crop and there were no significant yield differences with 107 or 160 lb/ac nitrogen applications.
An irrigated study in both no-till and conventional till continuous corn with 0, 40%, and 80% residue removal was also conducted for 10 years at the ARDC near Mead with 180 lb/ac of nitrogen applied to all treatments. Soil samples were also collected at one-foot increments to a total of five feet to measure any changes in soil carbon. Results showed grain yields were greater in the disk-till compared to no-till study regardless of percent residue removed. A 40% residue removal resulted in a 5.8 bu/ac average yield increase in disk-till and 15 bu/ac yield increase in no-till. However, soil organic carbon over the 10- year study in the top foot of soil (originally >3% soil organic matter) decreased significantly for all treatments except for the no-till, no residue removal. It remained similar for all treatments in all depths below the top foot.
Analysis of 239 site-years across 36 research studies, mostly in the U.S. Corn Belt, found an average 3% yield increase with residue removal versus no residue removed. They also found a 20% yield increase in tillage vs. no-till systems where no residue was removed. There was no tillage effect on grain yield with moderate and high residue removal. This suggests that incorporating some residue removal into a cropping system could aid application of reduced tillage systems across more acres in environments where water deficits are not limiting to crop productivity.
A soil erosion study was conducted in a field near York from 2006-2009 where portions of the field contained 8% slopes. Treatments included strips with 0 and 53% residue removal following grain harvest. Within these treatments were subplots where cobs were retained or removed. Simulated rainfall of 1.7 inches in 30 minutes was then applied to these plots under a known soil moisture content and then applied again the following day under saturated moisture conditions. Runoff from the simulated irrigation occurred within 196 seconds where residue was removed compared to 240 seconds where it was not. Sediment loss was 30% greater when residue was removed and cob removal had no effect on runoff or sediment loss.
Summary
These and other studies show that where moisture is not limited, residue removal can result in no yield reduction to yield increases for the subsequent crop. Most often it was speculated or correlated to warmer soil temperatures allowing for more uniform seed germination, emergence, and plant stands. Residue removal doesn’t come without cost, though, as continuous removal beyond three years has shown negative impacts on soil carbon. Sediment loss has also been shown to occur on sloping soils or sandy soils via wind erosion. Considerations should include residue removal on fields with low erosion potential and, even in these conditions, it’s suggested that an annual average of 2.4 tons/acre of residue be left in the field. Growers may also want to consider reducing impacts on the soil by planting cover crops, reducing tillage, and adding manure on fields where residue has been removed. Research results on these types of amelioration practices are discussed in Amelioration Strategies after Corn Residue Removal.