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In Iowa corn-soybean production systems, cover crops are typically aerially seeded into standing crops around the time of physiological maturity or drilled immediately following corn or soybean harvest. Previous on-farm research conducted by Jack Boyer has shown that seeding cover crops earlier in the fall can translate to greater fall and spring biomass. This may present the opportunity for more diverse cover crop species selection. With this in mind, farmer-cooperator Jon Bakehouse wanted to investigate how he could seed cover crops earlier than normal in a corn-soybean system and more successfully include a diverse array of cover crop species. To accomplish this, Jon planted early maturing varieties of corn (104- or 105-day) and soybean (1.0 group) in an attempt to harvest earlier in the fall and seed cover crops earlier in the fall.
You can read the full research report here: Accommodating Cover Crops with Early Maturing Corn and Soybeans.
The table below shows how Jon conducted the trials in 2015 and 2016 on his family’s farm near Hastings in Mills County in southwest Iowa. The late maturity system includes corn and soybean varieties of typical maturity groups in the region. The early maturity system includes corn and soybean varieties that would mature and be harvested earlier than the typical varieties in the region. In both systems, a cover crop mix was seeded immediately after corn harvest and a cover crop of cereal rye was seeded immediately after soybean harvest.
Cover crops seeded after soybeans were cereal rye (30 lb/ac); hairy vetch (5 lb/ac); Austrian winter pea (8 lb/ac) in 2015 (ahead of 2016 corn). Cereal rye (55 lb/ac) was seeded after corn in 2015 (ahead of 2016 soybeans). In the fall of 2016, cover crops seeded after soybeans were cereal rye (25 lb/ac); hairy vetch (5 lb/ac); rapeseed (3 lb/ac). Cereal rye (55 lb/ac) was seeded after corn.
- Planting early maturing varieties of corn and soybean generally did not result in yield drag compared to the late maturing varieties typically grown in southwest Iowa. The exception was in 2015 when the early maturing soybeans yielded less.
- Cover crop biomass produced tended not to differ between the early and late maturity corn-soybean systems. Seeding cover crops earlier in the fall, following the early maturing corn and soybean varieties, proved to be a challenge. “The cover crop could have been planted on Sept. 22 following the harvest of early maturing corn in 2015,” Jon says, but rain immediately after harvest prevented this. “Also, the early maturing soybean was ready for harvest by Sept. 28, and the cover could have been planted as well if soil conditions would have allowed,” he adds. “My takeaway: drilling cover after soybeans in September is possible.”
Conclusions & Next Steps
“Can early maturing corn and soybean varieties facilitate cover crops?” Bakehouse asks. “I think the answer is, ‘probably not’ unless a grower is willing to get down to an 80-day corn variety. The early maturing soybean could possibly work, though I think we’ve confirmed that group 1 soybean grows better when planted in early to mid-May, at which point there probably isn’t going to be much difference in the fall between a late-planted group 1 and an early-planted group 3.”
“I also think letting the cover grow in spring is just as important (or maybe even more important) than a few extra days/weeks [in the fall] from earlier planting,” he says. “Earlier planting in the fall naturally facilitates better spring growth, but I think having soil cover during spring rains is essential.”
For more details on this trial, read the full report: Accommodating Cover Crops with Early Maturing Corn and Soybeans. This project was supported in part by the Walton Family Foundation and the Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation.