By Brian Caldwell, Jeff Liebert, and Matthew Ryan
Soil and Crop Sciences Section, School of Integrative Plant Science, Cornell University
Interest in no-till planting soybeans into a rolled-crimped winter cereal cover crops is increasing among New York State organic grain farmers. This approach is also called “organic rotational no-till” because tillage is used to establish the cover crop in the fall. The rolled-crimped cover crop acts as mulch and helps suppress weeds in the summer. In addition to soil health benefits, this system has potential to save time and fuel by eliminating mechanical inter-row cultivation for weeds in organic soybean production.
In September of 2013, cereal rye, winter barley, and triticale were planted at an organically managed farm in Penn Yan, NY in anticipation of rolling-crimping them for no-till soybean planting the following spring. Two cultivars were planted per species: ‘Aroostook’ and a variety not stated (VNS) rye, ‘McGregor’ and ‘Verdant’ barley, and ‘TriCal 718’ and ‘TriCal 815’ triticale. The six cultivars across three species were arranged in a randomized complete block design with four replications, and plots were 15 x 15 feet to accommodate farm-scale equipment. Immediately prior to rolling-crimping, cover crop biomass was sampled from each plot. Cover crop biomass was determined by clipping the plants at the soil surface within a 5.4-ft2 (0.5-m2) quadrat, oven-drying the vegetation at 122°F for one week, and then weighing the dried samples. Weed biomass samples were collected approximately 15 weeks after soybean planting, which corresponds to the maturation of one of the most dominant weeds in the experiment, common ragweed (Ambrosia artemisiifolia L.). Weed biomass samples were collected, dried, and weighed as described for the cover crops, except 2.7-ft2 (0.25-m2) quadrats were used.
Soil types in this field were Cayuga silt loam and Honeyoye silt loam with 3-8% slopes. Soil test results showed the field was low in pH (5.7), P (3.8 lb/acre), and soil organic matter (2.0%).
This was an on-farm trial in conjunction with a series of experiments at the Musgrave Research Farm in Aurora, NY and the USDA Beltsville Agricultural Research Center in Beltsville, MD, which explored how different cultivars and termination timing of these three rolled-crimped winter cereal species affected weed suppression and soybean crop performance. Previous research suggested that optimal termination timing with a roller-crimper occurs when winter cereal cover crops have reached anthesis (flowering, Feekes growth stage 10.51), which is typically between late May and early June in the Northeast, depending on the winter cereal cover crop species. With anthesis signifying the transition from vegetative to reproductive growth, cover crop termination with a roller-crimper can be as effective as termination with synthetic herbicides (Ashford and Reeves, 2003; Davis, 2010; Mirsky et al., 2009).
Termination timing is particularly important for multiple reasons. If the cover crops are rolled prior to anthesis, termination can be incomplete and the cover crops will continue to grow, competing with soybean seedlings for light, water, and nutrients, and eventually producing seed that can become a weed later in the rotation. However, if termination timing occurs well past anthesis (i.e., too late), the winter cereal cover crops might similarly produce viable seed that can become a weed the following year, and late rolling will delay soybean planting, possibly reducing yield potential.
Winter cereals were planted with an Amazone Airstar Profi combination drill-power harrow on September 16, 2013, and terminated in 2014 on May 30 and June 5 with a 10-ft front-mounted roller-crimper (I & J Mfg., Gordonville, PA; Figure 1). The cover crops were drilled 1 inch deep in 5-inch wide rows with an Esch No-Till 5507 on the same day, and immediately after, rolling-crimping (Figure 2). Cereal grains can mature quickly in mid-May, which makes frequent growth stage scouting particularly important during that period of time. Feekes growth stages were 10.5, 10.54, and 11.1 for triticale, rye, and barley at the early termination date (May 30) and 10.54, 11.1, and 11.2 at the later date (June 5), respectively. These stages correspond to the onset of flowering (anthesis) through milky ripe for the early termination date, and the end of flowering through soft dough for the later date.
Cover crop biomass. Winter cereal biomass production at this site was relatively high, with over 8000 lb/acre for rye, 7000 lb/acre for triticale, and 5000 lb/acre for barley across both dates (Figure 3). After being rolled, the cover crops form a thick layer of mulch (Figure 4), which serves as the primary source of weed suppression in this system.
Based on work by Teasdale and Mohler (2000), achieving at least 7000 lb/acre of cover crop biomass at termination is likely to result in good weed suppression when rolled-crimped in this system (Mirsky et al., 2012; Mirsky et al., 2013). Thus on both planting dates, the rye and triticale cover crops produced enough biomass to exceed the recommended threshold, but barley did not. However, too much cover crop biomass can also be a problem. Lodging of up to 60% of the plants in a given plot was observed in rye terminated at the late termination date. As coulters on no-till planters and drills are not typically designed to cut through large amounts of residue, lodged plants that lay diagonally or perpendicular to the direction of rolling-crimping and no-till planting can impede adequate soybean seed placement, which can reduce germination and potentially decrease soybean yield. Also, if hair-pinning (i.e., residue forced into the furrow) is particularly problematic, poor seed-to-soil contact can result in gaps in the canopy, which can reduce late-season weed suppression.
Cover crop bounce-back was relatively low across all treatments with less than 20% of the barley plants “standing back up” after rolling-crimping, and less than 15% of the triticale and 10% of the rye plants doing the same. It is unlikely that the incompletely-terminated cover crops—most of which stood at a 45° angle and simply died at a slower rate than their flattened counterparts—impacted soybean yield. However, the resulting seed some cover crop plants produced might have resulted in volunteer cover crops in the following year.
It is worth noting that no-till drilling soybean seed into rolled cover crop mulch is not the recommended practice for most situations (Mirsky et al., 2013). Drilling can require adding a considerable amount of additional weight to the drill units to achieve acceptable, uniform planting depth if soil conditions are dry. Instead, a no-till planter set at 15- or 30-inch rows tends to perform better over a wider variety of soil conditions and biomass levels. We used a drill for the on-farm trial because it was the only no-till equipment available. Similarly, rolling-crimping and no-till drilling would ideally be completed in a single pass, but two operations were required in this experiment because the no-till drill width did not match the width of the roller-crimper.
Weed biomass. Across all treatments, weed biomass in early fall (September 15) tended to be lower in plots with greater cover crop biomass (measured before rolling-crimping). We observed lower weed biomass in late-terminated rye and triticale compared with early-terminated barley (P < 0.05), but weed biomass was not statistically different between the two termination dates within each species (Figure 5).
The perennial weed quackgrass (Elymus repens [L.] Gould) comprised 44% of the total weed biomass across all treatments. Across all species, mean quackgrass biomass was 512 lb/acre at the early termination date and 294 lb/acre at the late termination date (P = 0.08). This is an important consideration, since perennial weeds tend to proliferate in the absence of tillage. Common ragweed was the other dominant weed species in the experiment at 42% of the total weed biomass across all treatments. Similarly, mean common ragweed biomass was lower (P = 0.09) in the cover crop treatments terminated later (220 lb/acre) compared with the earlier termination date (541 lb/acre).
Soybean yield. Soybean yield was relatively high across all treatments, averaging 40 bu/acre (Figure 6). Even if weeds do not reduce crop yield, they can produce seeds and cause problems for future crops in the rotation. In this trial, late-terminated rye and triticale produced similar results, with high cover crop biomass, minimal cover crop bounce-back, low weed biomass, and relatively high soybean yields. Although soybean yield was not statistically different, early-terminated barley had the lowest cover crop biomass and greatest weed biomass (Figures 3 and 5). Thus, our results indicate that rye or triticale perform better than barley in this system, and terminating the cover crops at a slightly later date can be advantageous for reducing weeds (especially quackgrass and common ragweed) without sacrificing soybean yield.
Watching the weather. Soil moisture conditions are also very important to consider. In an extremely dry spring, such as in 2016, transpiration from a dense cover crop stand can reduce soil moisture, which can inhibit soybean seed germination and reduce yield potential. When the soil is this dry, the best option might be to forgo planting soybean entirely. Instead, it might be advisable to allow the cover crop to grow to maturity, harvest it, and plant a different crop afterwards. In most years in New York, however, limited spring rainfall is not a problem. Still, winter cereal cover crops can dry out the surface of the soil, making seed placement difficult. In this situation, we have found that adjusting planting dates based on rain events can be helpful to ensure the planter can penetrate the soil and achieve good seed-to-soil contact. In addition to no-till planting right after a rain, another trick that we have used is to add weight to the planter to increase the down pressure on the front coulters.
Conclusions. This on-farm trial augmented our research farm experiments in several ways. We had high cover crop biomass production at this site, and we were able to observe the results from different types of equipment than were used at the Musgrave Research Farm or Beltsville Agricultural Research Center. Perhaps most importantly, the good yields on this small field gave the farmer confidence in using this method on more soybean acres, and he has since advocated this approach at farmer meetings. However, our on-farm results were only from one year, so trials on more sites and over more seasons are needed to refine our management recommendations.
This work was supported by a joint research and extension program funded by the Cornell University Agricultural Experiment Station (Hatch funds) and Cornell Cooperative Extension (Smith Lever funds) received from the National Institutes for Food and Agriculture (NIFA) U.S. Department of Agriculture (Project: 2013-14-425). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture.
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