Cover Crop Selection and Use in Organic No-Till Farming

Cover Crop Selection and Use in Organic No-Till Farming

Summary

Austrian winter pea, hairy vetch, winter rye, winter triticale and other selected cover crops (CC) were seeded in IA, MN, ND, and WI during the 2010-11 growing season, as had occurred in 2009-10. The fall seeded CC were killed the following spring by rolling and crimping at all four locations, by mowing at three locations, by disking at two locations, and by undercutting with a blade plow at one location. Vegetative mulch produced by CC at termination ranged from 0 (winter killed Austrian winter pea in MN and ND) to over 10,000 kg/ha for winter rye in WI. Hairy vetch produced significantly less vegetative mulch compared with winter rye across termination methods and locations except in ND, where similar amounts were produced by both CC. Silage yields when corn was seeded into rolled and crimped CC averaged less than 1 Mg/ha in ND to 30 Mg/ha in IA; however, harvestable grain yield was not produced by corn at either location. Relatively low corn grain yields were produced in MN across all treatments (1860 kg/ha), but corn seeded into rolled and crimped hairy vetch plots produced a comparable yield (3640 kg/ha) to that produced in weed free plots (3420 kg/ha). Soybean was seeded during 2011 in WI because of poor corn performance in 2010, and significant differences in soybean seed yield were not detected between plots where rye was killed by rolling and crimping (3225 kg/ha) compared with weed free control plots (3480 kg/ha). In a second study in MN and ND, corn and bean (soybean in MN and pinto bean in ND) were seeded into rolled and crimped hairy vetch and winter rye, along with flax in MN and buckwheat in ND. Corn grain yield was similar across CC and averaged 2690 kg/ha in MN; corn failed to produce grain in ND. Soybean seed yield was significantly greater in rye plots (2580 kg/ha) than hairy vetch plots (1290 kg/ha) in MN; differences were not detected in pinto bean yield between rye and hairy vetch plots in ND but overall yield was low (250 kg/ha). Likewise, buckwheat yield across plots was low (385 kg/ha) in ND, and flax yield in MN ranged from 0 in hairy vetch plots to only 690 kg/ha in rye plots. Results of these field experiments demonstrate that refinement in the use of rolled and crimped CC for weed suppression when growing grain and seed crops is needed before this practice can be recommended for widespread use on organic farms in the north central region.

Objectives/Performance Targets

1. Identify crops and cultivars that are suited as cover crops in organic zero-till systems within the north central region.

   Refine methods for managing cover crops in certified organic fields that are viable, effective, and do not involve tillage.

   Determine the impact of organic zero-till farming using cover crops on economics, energy balance, nutrient cycling, pests, and soil quality.

   Coordinate outreach activities with others involved or interested in organic zero-till farming systems.

Accomplishments/Milestones

Austrian winter pea, hairy vetch, winter rye, and winter triticale were seeded in late summer during 2010 and maintained in plots, along with no cover crop checks, arranged in a randomized complete block at the ISU Neely-Kinyon research farm in IA, the UM Southwest Research and Outreach Center in MN, the NDSU Dickinson Research Extension Center in ND, and the UW Arlington Agricultural Research Center in WI. There were other cover crop treatments included at three of the locations (winter rye plus hairy vetch polyculture in IA; fababean, spring rye, spring triticale, sudangrass, a spring seeded polyculture [field pea, oat, mustard, and radish], and a fall seeded polyculture [buckwheat, proso millet, soybean, and sunflower] in ND; and winter barley in WI), but their impacts were unremarkable for any variable considered (e.g., dry matter [DM] production) and so are not discussed further.

Significant to complete winter kill of Austrian winter pea occurred across all locations; winter injury also occurred to winter triticale at two locations (MN and WI). Some winter kill (25% of initial plant stand) of hairy vetch occurred in ND, but the surviving plant stand (32 plants per sq. m.) was adequate for production of thick vegetative mulch based on previous research (unpublished data).

Above-ground DM production by CC ranged from 0 (winter killed Austrian winter pea) to 10,326 kg/ha (winter rye in WI). Dry matter production was similar across rolled and crimped CC (2016 kg/ha) and disked CC (2050 kg/ha) in IA, while significantly more DM was produced across rolled and crimped CC (5346 kg/ha) than disked CC (3983 kg/ha) in ND. Winter rye was very effective in suppressing weed growth in a subsequent corn crop seeded at or shortly after CC were terminated by rolling and crimping. No observable weed growth was detected in rolled and crimped rye plots in WI during September, 2011, and less than 300 kg/ha in ND. By comparison, weed DM production in check plots was over 8600 kg/ha in WI and over 2000 kg/ha in ND. Weed DM production was 875 kg/ha in rolled and crimped rye plots in MN but still less than the 1550 kg/ha in check plots. Likewise, weed density was significantly less in rolled and crimped rye plots compared with check plots in IA. Rolled and crimped rye mulch suppressed weed growth in a subsequent corn crop for the remainder of the growing season at all locations in 2011.

Winter triticale and winter rye CC produced comparable amounts of DM, except in WI where significantly less DM was produced by triticale (6384 kg/ha) than rye (10,326 kg/ha) across termination treatments. Similarly, hairy vetch produced less vegetative mulch at all locations except in ND, where similar amounts of DM were produced by hairy vetch (3212 kg/ha) and rye (3957 kg/ha). Rolled and crimped hairy vetch produced less DM than rye CC in IA (157 vs. 4032 kg/ha). Similarly, hairy vetch CC produced less DM than rye CC across no-till treatments (mowing along with rolling and crimping) in WI (4995 vs. 10,326 kg/ha), and also in MN. In ND, hairy vetch produced comparable amounts of DM (3212 kg/ha) to winter rye (3957 kg/ha) across all CC treatments, although mean DM production was greater arithmetically for rolled and crimped rye (5920 kg/ha) than hairy vetch (4166 kg/ha). These data suggest that winter rye is a good choice for organic growers wanting to optimize DM production by CC in the north central region.

Grain yields were inconsistent when corn was seeded directly into rolled and crimped CC at or shortly after termination treatments were imposed. Corn failed to produce harvestable grain in IA and ND because of the need to delay rolling and crimping until CC reached reproductive growth stages for effective termination. Corn silage yield averaged 28.6 Mg/ha in rolled and crimped rye plots and 27.7 Mg/ha in rolled and crimped hairy vetch plots in IA, and 29.6 Mg/ha across all rolled and crimped CC. Corn silage yields were much lower in ND, averaging only 800 kg/ha across all rolled and crimped CC treatments, 1.1 Mg/ha in rolled and crimped rye plots, and 1.5 Mg/ha in rolled and crimped hairy vetch plots. Grain was produced when corn was planted into rolled and crimped rye in MN (1317 kg/ha), but yield was only 38% of the weed free check (3418 kg/ha). Corn grain yield was comparable in rolled and crimped hairy vetch CC plots (3625 kg/ha) to that in weed free check plots in MN, even though weed DM production was over 1800 kg/ha in the hairy vetch plots. Soybean was seeded into killed CC in WI rather than corn because of poor corn performance in 2010, and soybean seed yield in rolled and crimped rye plots (3226 kg/ha) was comparable to that produced in control plots (3481 kg/ha), and significantly greater than that in rolled and crimped hairy vetch plots (2238 kg/ha).

Corn, soybean, and flax were seeded into rolled and crimped winter rye and hairy vetch in MN, while corn, pinto bean, and buckwheat were seeded into the same two CC at termination as well as spring rye that had been rolled and crimped the previous year, in 2010. No differences in plant stand were detected for the three following crops in rolled winter rye compared with hairy vetch plots in MN and ND. Fewer plants occurred in rolled winter rye plots than rolled spring rye plots in ND. However, grain yield across buckwheat and pinto bean was significantly lower following spring rye (40 kg/ha) than winter rye (285 kg/ha) and hairy vetch (626 kg/ha), probably because of greater weed growth in spring rye plots (1945 kg/ha) compared with hairy vetch (363 kg/ha) and winter rye (474 kg/ha) plots. Corn failed to mature and produce grain in ND because of the delay in seeding required so rolling and crimping was effective in killing fall seeded CC, preventing late seeded corn from reaching maturity. Corn did produce grain in MN but yield was relatively low (2688 kg/ha) and similar across cover crop treatments. Soybean in rolled rye plots produced significantly higher yield (2580 kg/ha) compared with rolled hairy vetch plots (1290 kg/ha) in MN. While flax seed yield in rolled rye plots was only 690 kg/ha, no seed was produced by flax in rolled hairy vetch plots in MN. Conversely, broadleaf weed DM production was higher in flax (5038 kg/ha) than winter rye (1370 kg/ha) plots.

Impacts and Contributions/Outcomes

Preliminary analyses of data collected during the first two years of this three year project indicate that seeding corn into rolled and crimped hairy vetch and other CC is a risky practice in the north central states of IA, MN, ND, and WI. The need to delay corn planting so that rolling and crimping kills CC effectively can result in a failure of corn plants to reach maturity and produce grain. Greater success has resulted when soybean is seeded into rolled and crimped winter rye cover crop, with grain yield sometimes approaching levels produced under conventionally tilled organic management. However, grain yield also can be depressed when seeded into rolled and crimped hairy vetch and other CC, sometimes exceeding 50% depending on the cover crop species and the environment. An effort to select for rapid growing and maturing cover crop species and cultivars should improve the ability to grow grain and seed crops by direct seeding into killed CC mulch in the north central region. Doing so will allow organic farmers to take advantage of the weed suppressive ability of flattened cover crop mulch in subsequent crops within a rotation, particularly that produced by cereal crops.

Collaborators: