Our spring in northeast Nebraska was similar to the spring of 2009 where cool, moist (not really wet) weather kept me from killing the cereal rye cover crop in the soybean stubble at an optimal time. A virtually dry last quarter of 2010 didn’t provide much moisture for the aerial-seeded cover crop to get a good start at growth going into winter. Some good snowfall in January and February helped the rye stay viable until 2.5 inches of rain fell in mid-April and got it going.
The 2.5 inches of rain was followed by very cool, moist (but not wet) conditions for 2 weeks that precluded the spraying of glyphosate to kill the cover crop. It wasn’t until May 4 that the weather gave me a shot at it. I applied 36 ounces of 5.4-pound glyphosate (Durango) and 1.125 pints of Surpass (acetochlor), along with a 1.5x rate of water conditioner because of the tough conditions.
My goal is to terminate the cereal rye at 8 inches. Knowing that I was facing 8- to 14-inch-tall rye made me aware of the fact that allelopathy and soil moisture depletion were going to be more of an issue.
I had read on a no-till cover crops listserv over the winter that allelopathy is more severe when the ground conditions are cool and wet. The gentleman blogging said that warm soil temperatures and in-furrow, pop-up fertilizer help corn plants overcome allelopathy.
Having had that experience in a low, wet area that I sprayed in spring 2010 and planted the next day — which was followed by 2 weeks of wet, cool soil conditions, I decided to wait until the soil temperatures warmed up to plant corn this year. The cold, wet soils did seem to exacerbate allelopathy and the corn in that area was behind the rest of the field in maturity and yield.
The area stayed wet through mid-July, so I believe the extended wetness was a factor as much as the rye allelopathy. Had I not been planting non-GMO corn, I would have considered planting and killing the rye after it had taken up more moisture.
I decided I’ll just take the planting season in the order Mother Nature gives it to me. It was already April 29 and I knew I’d have to plant soybeans sometime, so I no-till drilled 250 acres of soybeans, some into a rye cover crop on dryland sand corn stubble that I had aerially applied last fall. Having a GMO crop in the ground makes the cover-crop management a lot easier.
The soybeans are emerging as I write. I drilled them 2 inches deep and got 0.2 inches of rain that night. Monitoring the moisture depletion and the weather forecast, I decided to terminate the rye on May 4. It’s a good thing I did, as heat and wind on May 9 and 10 may have compromised the soil-moisture situation. The sandy soils did not dry out and the beans would have emerged even without the nice 2 inches of rainfall received over the last two nights.
So, back to corn planting we went on May 6, taking it in the order Mother Nature led us. The silty clay loam soils had dried out pretty well with 6 days of warm, windy weather. The soil temperatures were warm and it was time to plant. Knowing it was dry and with no good chance of rain in the forecast, I set the planter deeper to get a minimum 2.5-inch seed depth.
In an area where the helicopter had doubled up the rye seeding and it was 14 to 18 inches in height and very soddy, I kept the saddle tanks on the planter and the seed boxes on the upper half of capacity to ensure that I had adequate weight to cut and penetrate, place the seed at 2.5 inches, get good seed-to-soil contact, and optimally close the seed furrow.
Following 2 days of 90-degree temperatures and wind on May 9 and 10, we went out on May 11 to check for germination. The seed had germinated, with a 2-inch-long radicle and half-inch long mesocotyl. It appears planting would have been successful at typical seed depth, but a nice rainfall of 2.45 inches on two successive nights May 12 and 13 should ensure a nice even stand of corn. The half rate of acetochlor should activate and provide weed control until the floater comes with 35 gallons of 32-0-0, 6 pounds of sulfur and 1 pound of atrazine.
The post herbicide program in the non-GMO cornfield will be Steadfast, Callisto and atrazine. In the areas where the cereal rye was well established, I will look for the opportunity to take advantage of the allelopathic effect and use less or hopefully no post herbicides.
Rain makes us all good farmers. No doubt, the venture would have been more challenging with the cover crops drying out the soil to the extent they did. Now we will sleep easier.