Applied no-till for carbon-positive farming

By Christine Ziegler-Ulsh and Rita Seidel

In the fall of 2008 the Rodale Institute partnered with Iowa State University, Michigan State University, North Dakota State University, University of Wisconsin, University of Minnesota and select farmers on a project to develop carbon-positive organic systems through reduced tillage and cover crop-intensive crop rotations. The long-term goals of the project are to enhance soil quality in organic systems by maximizing cover, minimizing erosion, and improving soil ecology and biological processes with the aim of reducing environmental and economic costs, and optimizing yield stability.

No-till corn.

The selected method of reduced tillage is Rodale Institute’s cover crop roller/crimper, which has been used in a number of organic no-till research projects since 2002. Some of the known benefits of rolling cover crops for organic no-till are:

• Reduced number of tractor passes over the field, which saves time, fuel, and money
• Covered soil, which reduces erosion and weed growth at vulnerable times
• Moisture retention and cooler soil in mid-summer
• No need for herbicide

Tilled soybeans, tilled corn.



But there are challenges. The cover crop can keep the soil too cool in the spring, can allow weed growth if the cover crop stand is poor, may provide habitat for plant-damaging pests, and requires later planting and well-timed rolling in order to be fully effective. This project, funded by the USDA Organic Research and Extension Initiative (OREI), gives us the opportunity to see if we can overcome some of these challenges.

The rotation for the project, being planted in all six research regions, began with spring wheat in the spring of 2008, followed by rye and vetch cover crops in the fall of that year.  Then in the spring of 2009, the rye was either rolled or tilled (depending on the experimental treatment) to plant soybeans, and the vetch was either rolled or tilled to plant corn.  After harvest in the fall of 2009, the field lay fallow until March of this year, when oats were planted.  The oats were just harvested last week, and in late August and early September, rye and vetch will again be planted for rolled or tilled corn and soybean crops in 2011.

Now that the data are tabulated, we’re excited to share some of the highs and lows of the 2009 season!

2009 Rye/Soybeans

The no-till beans were planted first on May 21, 2009 and had to struggle from the beginning because the they had to compete with “escaped” vetch (perhaps due to contaminated rye seed) that was unintentionally growing in the rye and survived the rolling. The tilled beans were planted much later, on June 25, due to the wet spring. The late planting date and the fact that we had enough breaks in the rain to do early weed control at timely intervals seemed to have a very positive effect on weeds in 2009: weed biomass in the tilled plots was significantly lower than in the no-till plots, at levels that probably did not impact yields.

Yields reflected those observations. The tilled beans produced significantly higher yields than the no-till beans: 41.6 bu/a, just above the 40 bu-yield goal for our soils, whereas the no-till yields were almost 50% less (23.3 bu/a).

And as suspected, weed biomass and soybean yields were highly correlated (R2 = 0.93).

2009 Hairy Vetch/Corn

The tilled corn was planted first on May 28, and then three tine weeding treatments (June 1, 4 and 15) and four cultivations (June 8, 25, 30, July 6) were performed in the tilled plots. In the no-till plots, vetch was rolled and corn was planted on June 17. Vetch was not at full bloom at that time, but we did achieve sufficient kill, and no re-rolling was necessary. No weed control was performed in the the no-till plots. Both treatments were planted with the same corn variety, Blue River 41R00 (99-day relative maturity).

Throughout the growing season, both the tilled and no-till treatments did well in terms of crop establishment (population), vigor and ability to compete with weeds. Overall, soil samples taken for a PSNT at the V6 growth stage of the corn showed lower nitrate levels for the no-till plots compared to the tilled plots (22.3 ppm vs. 33.7 ppm), but only Rep 1 and Rep 4 were below the recommended level of 21 ppm. All other plots had sufficient nitrate levels.

Corn yields were strongly correlated to the PSNT nitrate levels (R2=0.49), with the lowest yields (100 and 111 bu/a) in the plots that had the lowest soil nitrate results.

The tilled corn had adequate N inputs (175 kg/ha) and produced yields that were very close to the 150 bu-yield goal for Rodale soils (149 bu/a). The no-till yields, on the other hand, were significantly lower at 117 bu/a, despite a higher N input from the greater vetch biomass (206 kg/ha).

Weed biomass was not a limiting factor in the no-till plots, since both treatments had the same level of weed pressure (~1,600 kg/ha), a level that is often observed in our fields. In addition, the correlation between weed biomass and yields was very low (R2=0.08). The lower yields in the no-till plots most likely were due to the late planting date and insufficient growing degree days (see table below), and to less available N from rolled vetch vs. plowed vetch (see PSNT results).

PSNT tests revealed no significant differences in nitrate-N between the two treatments.

Only two of the no-till plots drew recommendations for N additions (suggesting 100 lbs and 110 lbs).  The other plots required no additional N, and, of course, none was added to any of the plots, in keeping with study protocol and organic management.

The other five IOP project research stations are in the process of summarizing their 2009 data, so comparative information that relates our findings to the bigger picture of no-till in the northeast and north central parts of the country will be available in early fall.  Meanwhile, data on our 2010 oat and weed crops is finally all collected and will be fully processed and analyzed in a few months.  We’re looking forward to sharing this information with you, along with updates on our fall cover crop planting and growth, later in the fall.

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