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| Hi AgTalk community,
This post is paired with another that details grain yield response to tillage management in kura clover living mulch, so if you read that, some of this information will be the same.
My work focuses on N cycling and agronomic management for intercropping corn with kura clover, a perennial forage legume, and today I will be sharing the 2020 results from an experiment conducted at the University of Minnesota’s Rosemount Research and Outreach Center in collaboration with the USDA Agricultural Research Service.
I introduced my work with kura clover living mulch systems in a previous post, but for those who are unfamiliar, I’ll give a brief description.
Kura clover is a cool season legume forage crop that spreads by underground stems to re-establish itself after intensive management. The robust root system anchors the soil and immobilizes nutrients in the early spring when soils under conventional management are fallow or row-crops are not well established. Previous research has found that corn production in kura clover living mulch (KCLM) can reduce soil erosion and nitrate loss by 70%. More recently, my work has focused on fertilizer N management for continuous corn production in KCLM. Results from the 2017 and 2018 growing season suggested that KCLM could reduce fertilizer N requirements while increasing profitability due to increased harvest income from stover removal. While we were researching other agronomic changes to this system, we decided to re-test this finding with a small fertilizer N rate trial and compare yields with a conventionally managed corn-soy rotation adjacent to our study site.
The site was a newly established kura clover stand on a Waukegan silt loam. Clover was mowed on May 11, strip tilled using an Orthman 1tRIPr on May 12, fertilized with 0, 70, or 140 lb N/acre as SuperU banded at ~2” depth, corn was seeded on May 14, and 1 qt/acre of glyphosate was applied on May 30.
This experiment was conducted on a subset of plots from a larger experiment and detailed measurements of clover biomass, biomass decomposition, soil N, and nitrous oxide emissions were made throughout the growing season. Today, I’ll present grain yield results.
As mentioned in the other post, the weather turned cold and wet following planting. This slowed down corn emergence and development and favored clover growth. The clover became quite competitive with the seedlings and I was afraid that all the treatments were set too far behind to catch up. The growing season continued, and N deficiencies hit the unfertilized plots hard, however, the high heat and humidity of August helped the fertilized plots catch up. In the end the fertilized KCLM plots out yielded the conventional comparison. While this finding is positive, it goes against previous findings that KCLM reduces N requirements for corn production. At this point I will not continue the narrative that KCLM reduces fertilizer N requirements until I have a better understanding of the factors that influence in-season N credits and can reliably reproduce those results. Whether it has to do with weather conditions, spring clover growth, tillage tools, or stand age, is up for debate, so I’ll keep working on it and keep you posted.
Final results:
KCLM - 0 N: 117 bu/acre
KCLM 70 N: 194 bu/acre
KCLM 140 N: 235 bu/acre
Conventional 180 N: 221 bu/acre
 (Capture (full).PNG)
Attachments
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 Capture (full).PNG (100KB - 51 downloads)
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N rate trial kura clover living mulch
