In 2017, we dropped our starter fertilizer application in the furrow at planting. The past 4 years we purposely ordered short on 10-20 acres so we didn’t carry over any starter to the next year.
My wife, Nancy, runs our combine and yield monitor, and she is a stickler on calibration. We found no corn yield difference without the starter application. We apply approximately 40 pounds per acre of nitrogen (N) in the spring with our monoammonium phosphate (MAP), diammonium phosphate (DAP) and sulfur.
We are at a total application of 140 pounds per acre of total N with the 100 pounds per acre of sidedressed liquid N. Our yields are averaging about 200 bushels per acre.
The past few years we have interseeded our cover crops into corn starting at V3 to V4 stage when sidedressing. We terminate the cereal rye that was aerial seeded into the soybeans at 20% leaf drop the fall before with 2,4-D and Roundup at 10-12 inches so it started releasing the N that it scavenges in 30-45 days.
We then interseed with a 4-5-way mix of cover crop seed and apply no more herbicide. In 2017, our co-op agronomist called to have me meet him at a 100-acre corn field. He questioned whether I wanted to spray as there were only a few ½-inch weeds.
I decided to spray, but in retrospect we should have saved our money. We had a friend come over with his new Hiniker 12-row cover crop seeder, but one of the electric motors was not working so there were 4 rows that didn’t seed. We decided to not re-seed this area and use it as a test plot.
By harvest, those 4 rows were full of water hemp. No other weeds were in the field where the cover crop was seeded. So in 2018, we eliminated that herbicide application.
We are also seeing other benefits from interseeding. We had no stalk rot a couple years ago when everyone else in the area did.
Our agronomist determined that it was probably due to the cover crop preventing the rain drops from splashing the spores causing stalk rot on to the corn stalk. The following year, when attending field days, all the husks were pulled back on the different numbers of corn revealing major tip-back caused by stress at pollination.
We had no tip-back and knew we had enough population and N, as our prescriptions are done by our agronomist. We determined that the cover crop had kept the soil cooler during pollination so the plants weren’t as stressed.
When visiting with Jeff Coulter, professor and extension agronomist from the University of Minnesota about our theory, he suggested we buy a couple soil thermometers and do our own tests. We tested our field with the interseeded covers and neighbors with the same number of corn and no covers.
On the hottest days in the 90-degree range, the soil in our field was 10-20 degrees cooler. On cooler days, there was only a 6-8-degree difference. Jeff indicated that was a big difference when eliminating stress on pollinating corn.
In 2018, we had a Minnesota Department of Ag grant with our local watershed. We installed a weather station on one of our farms with the interseeded covers and on a neighboring farm with conventional tillage and no interseeding. They had soil probes at 4 and 8 inches monitoring moisture and a separate probe monitoring temperature. This will be a 3-year study.
When the watershed was doing our water infiltration test in fall 2017, we found our soils could hold 11 inches per hour with no runoff. Right before soybean harvest, we received 5 inches of rain.
We had flown on our cereal rye at 20% leaf drop into the soybean field. We had a nice stand started by harvest, which was able to help carry our combine at harvest, even through some standing water.
Our neighbors who don’t have cover crops had deep tracks from trucks and had to leave large patches in the field, coming back after it dried some to finish combining.