As spring planting time approaches, many farmers are discussing and debating the pros and cons of various crop rotations, and the impact that fall tillage systems and winter cover crops may have. Balancing these 3 elements, among many others, will have an effect on soil erosion, soil nutrients and overall health, inputs, yield, and of course, overall economic return. As you prepare to plant, we want to give you a quick overview of a few articles, conference presentations, and study results that we found relevant and interesting. While the farms in question are located in the States, which obviously have different soil and weather conditions, many of their techniques and findings still have relevance up here in Canada as well.

Crop Rotation: How does it impact yield and economic return?

Results were recently published from a 10-year study (2003-2013) by Iowa State University of tillage and corn-soybean rotations in seven locations across the state, with five different tillage systems. The overall findings were that:

  • Overall corn yield was highest in a corn-soybean rotation in all five tillage systems (compared to continuous corn or a corn-corn-soybean rotation).
  • Overall economic return was also better in a corn-soybean rotation than in continuous corn.
  • Regardless of tillage system, continuous corn caused a “yield drag” of 11-28% (compared to a corn-soybean rotation).
  • Soybean yields were about the same for all tillage types, but economic return was better for no-till over conventional tillage.
  • Corn yields and economic returns with no-till and strip-till systems were competitive with conventional till systems for well-drained soils. [Note that results for no-till were generally best for the more southern locations in Iowa, due to better soil drainage on those plots, so this finding may not translate to conditions in Ontario, Quebec, or the Maritimes. ]
  • There was no discernible increase in corn yields over the 1-year study period.

The bottom line: When all inputs and costs are considered, the best net return on investment (ROI) was seen in a corn-soybean rotation. The lowest return was observed on continuous corn.

The hard numbers: Averaging the return at all seven study locations, the economic return per acre for corn-soybean rotations was 14% higher than for corn-corn-soybean, and 41% higher than for continuous corn. The location with the poorest soil lost money on continuous corn over the years, regardless of tillage system used.

Note that there were significant variations in yield and economic return between the locations, with corn yields varying between 108 bushels (bu)/acre and 204 bu/acre and economic returns spanning from $153/acre to $485/acre. Year-to-year variability of corn yield was shown to be 28% overall across all rotations, tillage types, and geographies. Soybean yields varied from 22 bu/acre to 74 bu/acre, with a number of regional variations demonstrating an impact – including weather, soil temperature, soil drainage, residue breakdown, and weed pressure in wet seasons.

Tillage Systems: How do they affect input costs and soil health?

In the Iowa study, five different tillage systems were randomly assigned to the various plots, with the same tillage operations conducted for each tillage treatment every fall at each location for the duration of the 10-year study. The tillage types studied were: no-tillage (NT), strip-tillage (ST), chisel plow (CP), deep rip (DR) and moldboard plow (MP). Details on the tillage treatments can be found in the Corn & Soybean Digest article about the study.

PROSeeds-corn-field-strip-till-tillage-GettyImages-10042123Image credit: Francisco Caravana / Hemera / Getty Images Plus 100421230

The study found that input costs for tillage systems (CP, DR, and MP) were 7.5% and 5.7% higher than those for no-till and till-plant, respectively, over all 7 locations and all 3 crop rotations. However – even with the lower input costs – typically, the economic return was lower for no-till in a corn-soybean crop rotation. The corn yield was about the same for the tillage systems (CP, DR, and MP) as strip-till, but no-till yield was only competitive at the more southern locations with good soil drainage; otherwise, no-till corn yields were poor.

Soil Health: How does it factor into overall yield and economic return?

While getting high yields and a strong economic return is obviously crucial for the farm, experts who ran the study did caution that soil health needs to be factored into your long-term considerations as well. Continuous corn destroys microbial populations, and tillage depletes organic matter in the soil. Soil with more organic matter in it holds much more water – combined with the nutrients it provides, this has a big positive impact on your yield. So before you throw the idea of no-till out the window, consider the benefits of using it to allow build-up of organic matter and improved soil conditions over time.

And it’s not just nutrients and water retention that bear thinking about. According to a presentation given at a November 2016 conference (Ag Data) and summarized in Corn & Soybean Digest in mid-March – soil erosion has a huge impact on yield potential, and most farmers significantly underestimate their soil loss. An on-the-spot survey at the conference showed that most growers (80%) estimated their annual soil loss to be 1 ton per acre or less, with over half of them guessing it to be less than ¼ ton. In fact, the presenter (from the Land O’ Lakes Sustain program) said that the average soil loss rate is 5.8 tons per acre per year. This translates into as much as 15 bushels/acre in lost potential corn yield.

An example given in the conference presentation takes it a step further: For a 40-acre farm with tillage before each crop and no cover crops, the measured soil erosion was 0.37 inches of top soil lost over the 10-year period. While this may not sound like much, it actually amounts to 5.46 tons/acre/year loss and results in $12,225 in lost yield and nutrients over 10 years.

With no-till and aerial seed rye cover crops, the conference presenter estimated the cost of erosion to drop to about $500 on 40 acres over 10 years. With a bigger farm with more acreage, that adds up fast. New tools and software offer a way to measure soil erosion – something that was not possible before – and therefore to estimate its effect on your yield and your economic return.

PROSeeds-rye-field-cover-crop-GettyImages-494712224Image credit: DarcyMaulsby / iStock / Getty Images Plus 494712224

Another example: In a panel session at Iowa State University’s second annual Soil Health Conference, an Iowa farmer described his experimentation with tillage and cover cropping. His objectives were conservation and soil health improvement, as well as added profit and increased family time. Over the years, he implemented no-till for his soybeans (1992) and strip-till for his corn (2001), which gave him a savings of $92 per acre in reduced labor and equipment costs. He achieved a yield equal to or better than his neighbours using conventional tillage. He has documented an increase to 6.1% organic matter, up from the 2.2 to 3.2% range on the same fields in his conventional tillage days, and has also seen a notable increase in the water-holding capacity of his soil.

This same farmer then started doing strip tests of cover crops in 2011, and after finding that he was able to get rid of them when he wanted and that he suffered no yield loss, he now uses cover crops in all his fields. He has measured a 70% reduction in nitrate loss with his cereal rye cover crops from 2014 to 2016 as a result. Overall he loves his system of no-till soybeans, strip-till corn, and cover crops.


Are you or any of your neighbours trying out different crop rotations, tillage systems, or cover crops? We’d love to hear more about what has (or hasn’t) worked on your farm! Send us a tweet @Sevita_PROSeeds or visit us @Sevita.PROSeeds on Facebook and share your experiences.  You can also reach out to our expert regional sales managers for help in selecting the right soybean varieties or corn hybrids for your trials and your fields.


Feature image credit: wakr10 / iStock / Getty Images Plus 619982486



Results of 10-year US tillage & crop rotation study:

The full study:

Article on economics of soil loss:

One farmer’s experience with no-till, strip-till, and cover crops: