Studies such as this will be shared by area farmers starting this week at On-Farm Research Updates (Feb. 15 at Holthus Conv. Center in York)! RSVP at: go.unl.edu/2023ofr. Since 2019, a group of area farmers have been interseeding cover crops into early season corn (V3-V4) and soybean (VE-V2). The goals for interseeding cover crops into cash crops include: providing nutrients for the cash crop, weed control, erosion control, diversity, reducing inputs such as fertilizer and chemicals, and providing forage for grazing after harvest. Interseeding of cover crops can also occur at other growth stages, such as at male row destruction in seed corn or at senescence in late-season corn and soybean. This article will focus on our results from early-season interseeding of cover crops into corn and soybean.

In 2019, two farmers interseeded cover crops (one drill interseeded and one broadcast) into corn in York and Seward counties. Both got establishment and showed no yield differences between interseeded and check. In 2020, a partnership formed between The Nature Conservancy, Upper Big Blue NRD, Extension, Kelloggs and area farmers. A four row interseeder was purchased. Six farmers chose to conduct studies via on-farm research where they maintained the same field-scale strips of interseeded cover crops and check treatments for 3 years. The different cover crop mixes and rates can be viewed at jenreesources.com.

From 2020-2022, fields were impacted by July 9, 2020 and 2021 wind events and June 14, 2022 hail. We had 12 site-years of corn studies and 2 site-years of soybean studies. Biomass samples of the cover crops and also weeds were taken each September. Cover crop biomass ranged from 200 lb/ac to 4 tons/ac depending on the location, hybrid, irrigation, and storm events. In 10 of 12 site-years, interseeded cover crop had more biomass than the check treatment (weeds).

Yield: No corn yield difference between check and interseeded in 6 of the 12 site-years. Yield losses ranged from 2-10 bu/ac in the remainder. No soy yield difference between the interseeded and check.

Net Return: In 10 of the 12 corn site-years, and 1 of the soybean site-years, the check treatment had a higher net return. (However, no benefit to grazing, reduced inputs, etc. was given to interseeding).

Soil Health Values (PLFA & Haney): Large numerical increases in soil health numbers when all 6 sites were combined (as well as some individual sites). Significant increase in the Check from 2020 to 2022. Significant increase in the Interseeded from 2020-2022. However, because this happened for both treatments, when comparing Check vs. Interseeded from 2020 vs. 2022, there is no difference. Why? All farmers were incorporating additional soil health practices across their entire fields (planting rye each fall, grazing, adding biological products, etc.) that would have impacted both cover crop and check treatments. Good news: all increased their overall soil health (soil microbial pops and scores) in 3 years.

Soil Nutrient Values: There were no differences between OM, pH, P, S, K, and base saturations between Check and Interseeded from 2020 to 2022 across sites. Numerical changes occurred at individual sites.

Our studies proved that drill interseeding of cover crops into early season corn and soybeans can be achieved for establishment that lasted after harvest with regrowth of perennial covers into the spring. We also showed this in spite of a number of PRE- herbicides used. We increased beneficial insects and saw pest insects feeding on cover crop instead of cash crop. We increased diversity in the fields and had additional cover aiding erosion control. We also showed reduced water use in the corn where the diverse cover crop was used compared to the check treatment. The disappointment to me was the low amount of forage for those desiring to graze after harvest and the spotty survival of perennials in the spring. However, those who grazed said there was value in the amount of green material present at harvest coupled with the corn residue. Additional challenges can include the fact that it does look ‘messy’, one needs to think through herbicide options ahead of time, and we need to put dollars to additional benefits that are harder to calculate (soil erosion, etc). Next week I’ll share our next steps in where we’re headed.