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What’s Your Cover Crop Goal for 2020?

Have a plan for seeding cover crops into corn, soybean, or sorghum fields. 

The benefits of cover crops as part of a crop rotation are compelling: nutrient cycling, improved soil tilth, and weed suppression, to name a few.  

It’s easy to get excited about planting covers after fall harvest, but before you do – have a plan of action, says Ryan Moore, small seed product manager for Beck’s Hybrids, of Atlanta, Indiana. 

Moore has heard stories from farmers who have experienced difficulties from cover crops: they were too expensive, they selected the wrong covers to plant, or the farmers had difficulty getting a cash crop planted the following spring. The common denominator, however, was that growers who had a bad experience one time typically never planted cover crops again. 

Planning, Moore says, is vital. 

What cash crop do you plan to plant in 2020? 

Ahead of soybeans, cover crop selection is pretty simple. Cereal rye planted after corn harvest “…is like bread and butter,” he says. “There are so many benefits, including weed suppression and erosion control.” 

Moore says any grass species planted behind corn – and he prefers using a grain drill to apply the seed, rather than spread it on and wait for rain to activate the seeds – can work. “To a newcomer, planting corn into a field that has biomass from 50 to 60 pounds of fall-planted seed can be pretty daunting,” he explains. For first-timers, he recommends planting 25 to 30 pounds of rye or winter oats in the fall. That cheapens up the mix, still offers benefits to the soil, and creates an easier learning curve. 

Ahead of corn is a bit more difficult, Moore says. 

“This is the one everyone struggles with,” he explains. “You don’t want to plant something that will be competition in the spring and dry out the soil.” Therefore, he suggests a blend of oats and/or rye, combined with crimson clover and/or rapeseed, plus maybe some radishes. This gives the benefit of winter and spring cover, but it can easily be tilled lightly in the spring, or seeded into directly. 

It’s All About Biomass

Research at the University of Nebraska-Lincoln suggests that a minimum of 1,000 pounds of biomass per acre is needed in the spring to effectively reduce erosion and soil nutrient loss, suppress weeds, and supply forage. More than 1,000 pounds is certainly better. 

The trouble is, there is little time for cover crops planted after corn harvest to grow. That looks to be particularly true in 2019, when a late harvest is expected in much of the Corn Belt. 

UNL researcher Katja Koehler-Cole led a research project that used two types of cover crops to evaluate biomass establishment in three Nebraska locations: east, northeast, and south-central. The trials were conducted over four years, 2015-2018. 

The cover crops were:

  • cereal rye (planted at 60 lb/A) 
  • a mix (30 lb/A of rye, 20 lb/A of winter pea, 8 lb/A of hairy vetch, 4 lb/A of brassicas), planted either pre-corn harvest or post-corn harvest, would achieve the biomass threshold of 1,000 lb/A. 

The pre-harvest planting was carried out by spreading seed by hand into corn stands in September to simulate broadcasting either by high-clearance equipment or aerial seeding. The post-harvest planting was carried out with a no-till drill between mid-October and late November. 

In eastern and northeast Nebraska, the pre-harvest planting achieved the biomass threshold, producing on average 1,900 to 2,500 lb/A of biomass by late April to early May, whereas the rye planted post-harvest produced approximately half of that amount. Pre-harvest planted cover crops had lower emergence than post-harvest planted cover crops, but had more time to grow and tiller, compensating for low populations. In south-central Nebraska, both planting times reached the threshold, but the post-harvest planting produced more biomass. This site receives less rainfall in the fall, restricting the emergence of pre-harvest cover crops.

Overall, the mix biomass was lower than the rye biomass. The brassicas in the mix winterkilled, and hairy vetch and winter pea produced very little growth. Thus, the mix can be thought of as rye planted at 30 lb/A. Despite this low seeding rate, the mix produced more than the threshold biomass at the south-central sites in both planting times, and at the northeast site in the pre-harvest planting.

Cover crops will only achieve their purpose and be successful if they produce sufficient biomass. 

In northern climates, it may be best to plant rye, pre-harvest, using a broadcast seeder or aerial application. South of I-80, you may be better off planting post-harvest and using a mix to obtain maximum biomass. 

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