Extension Update by Jenny Rees

Corn observations: It seems amazing to me to be where we’re at with harvest, and it’s only October 4^th as I write this! Many farmers finished beans last week and started on corn. It’s a good feeling to be at this point; can also appreciate there’s been no rain and not a lot of breaks either. Please be safe!

This past week was spent taking corn notes and starting to harvest corn studies. Besides harvest stand counts, I also like to look at percent stalk rot in fields. This gives an idea regarding standability and harvest priority. To do this, I use a pinch test using my thumb and first finger to pinch the elongated first or second internode above the soil line on 20 plants in an area of the field. Stalks that are compromised will “give” or “crush”. Obtain a percentage for the number of stalks that do so. Quickly doing this in five areas of the field provides a better idea of stalk health and harvest priority. Stalk quality pinch test video at: https://youtu.be/7z75VN1c51Q. So far, much of the corn is standing well. I’m mostly finding compromised stalks on plants that had premature ear droop. It will be especially important to assess stalk rot for fields that had high southern rust pressure and weren’t sprayed with a fungicide.

Another observation is some weakened ear shanks, although I can’t say this is a problem yet or even widespread. Weakened shanks makes sense on ears that prematurely drooped as that ear shank collapsed. Things we know cause weakened ear shanks and ear drop include stresses like high heat and/or moisture stress around pollination, large ears after this type of stress due to long grain fill, fungal disease like Fusarium infecting the shank, and to an extent, genetics (regarding shank diameter size). As we think of this year, we had the July 8^th wind storm shortly before tassel which caused additional stress on plants. Corn also had a long fill period creating larger ears. So again, not saying this is a problem, just something to watch.

Stress cracks and broken kernels are another thing to watch for and seek to minimize. We know this can occur during the grain drying process in the bin when high moisture corn is dried with high heat followed by rapid cooling. In one conversation this week, a farm family was wondering if there were conditions that led to more stress cracks to corn in the field this year. I really don’t know. Found one publication that said internal, invisible stress cracks can also occur during kernel fill as a result of high temperatures and/or high moisture. However, the focus of the publication was viewing cracks with other types of imagery instead of the physiology, so I don’t have more to share on that. Broken kernels can also occur with harvesting higher moisture corn (above 20%), particularly with too high of rotor speed. A handful of guys have mentioned seeing broken kernels as they’ve been harvesting above 20% and shared the combine adjustments they’ve made to minimize them, so thought it may be something to mention. Combine setup is not my expertise but with a quick search, there’s a number of YouTube videos and websites regarding reducing broken kernels that may be helpful.

Corn Drydown Calculator: If you’ve never seen it or used it before, Iowa State University has a neat tool that estimates corn drydown in the field based on weather forecast for a particular area. It’s called the corn drydown calculator and you can find it at: https://crops.extension.iastate.edu/facts/corn-drydown-calculator.

Land Leasing for Solar Development Oct. 9th: Just a reminder of this virtual seminar to be held October 9^th from 11 a.m. to 1 p.m. You can register at https://go.unl.edu/solarleasing. This seminar is open to the public. Farmers, landowners, and their families in areas with potential solar development have much to consider and should consider attending. This webinar will give an overview of solar development and touch on major issues to consider when negotiating a solar lease agreement. More info. on this topic at: https://cropwatch.unl.edu/2020/considerations-leasing-land-solar-development.

Bean harvest was rolling this week. Hearing non-irrigated beans in the area ranging from 40-60 bu/ac and irrigated beans going 70-90+. Regarding solar radiation and some wondering about smoke impact on drydown, I ran data from 9/1/20 though 9/26/20 for Harvard and York weather stations. Then looked at long term average for this same September time-frame from 1996-2020. Both stations showed slightly higher solar radiation in 2020 compared to the long-term average for September (York: 379 and 372 langleys respectively) (Harvard: 383 and 376 langleys respectively). And, it was higher yet for 2020 when I queried Sept. 10-26 for same time periods. So, unsure solar radiation was the factor impacting drydown for this part of the State?

Small Grains and Weed Control: Been watching weed control particularly in soybean fields. For future columns/winter programs, I’d like to hear from you. What weed control approaches have worked in your soybean and corn fields? I’m curious about all systems and all types of weed control options. Please share at jrees2@unl.edu or give me a call at the Extension Office. Thanks!

In the past, I’ve shared weed control begins at harvest by not combining patches of weeds or endrows full of weeds. I realize that’s difficult to do, and for many fields, we’re past this point. From a system’s perspective, another option to aid weed control is to plant a small grain such as wheat, rye or triticale this fall. We had a whole edition of CropWatch devoted to wheat production here: https://cropwatch.unl.edu/2020/september-4-2020. Wheat provides an option for both grazing and grain. Rye provides the best option for earliest green-up/growth in the spring and longest seeding time as it can be seeded into December. Triticale provides the most biomass but produces the latest into late May/early June. All keep the ground covered from light interception penetrating the soil surface which allows weed seeds to germinate. While I’ve observed this in farmers’ fields, there’s also recent research from K-State that supports the impact of a small grain in rotation for weed control.

One study looked at marestail (horseweed) and palmer amaranth control from 2014-2015 in no-till soybeans at six locations in eastern Kansas. They also found the majority of marestail emerged in the fall (research from UNL showed up to 95% does). They compared five cover crop treatments including: no cover; fall-sown winter wheat; spring-sown oat; pea; and mixture of oat and pea. Cover crops were terminated in May with glyphosate and 2,4-D alone or with residual herbicides of flumioxazin + pyroxasulfone (Fierce). Ten weeks post-termination, palmer amaranth biomass was 98% less in winter wheat and 91% less in spring oat compared to no cover crop.

Another study in Manhattan from 2015-2016 compared fall-seeded rye; a residual tank-mix of glyphosate, dicamba, chlorimuron-ethyl, tribenuron-methyl, and AMS; and no fall application. Four spring treatments included no spring application or three herbicide tank mixes: glyphosate, dicamba, and AMS alone or with flumioxazin + pyroxasulfone (Fierce) as early preplant, or as split applied with 2/3 preplant and 1/3 at soybean planting. They found the fall rye completely suppressed marestail while fall herbicide suppressed biomass by 93% and density by 86% compared to no fall application. They also found rye to reduce total weed biomass (including palmer amaranth) by 97% or more across all spring applications. In both studies, soybean yields were best with the combination of cover crop + herbicides or the combination of fall + spring herbicides compared to no cover and no herbicides.

The way I think about this for conventional systems is that the use of a small grain in the system reduces the pressure on the chemicals for having to provide all the control. It also buys some time for chemical control, perhaps even removing one application (based on these studies, small grain delayed at least a month till 50% palmer germination). Economically, while there’s the expense of seeding and purchasing the small grain seed, what are the other economics to consider? What could the small grain provide by reducing an additional chemical application, adding a forage crop after harvest, selling seed (if there’s a market), selling straw (depending on location for moisture savings & ability to get a cover back in for weed control), etc.? Just some considerations this fall looking at weed control by adding a small grain.