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JenREES 5/23/22

This past week was a tough one on some crops. We’ve seen crusting, hail, wind, and frost cause damage to crops throughout the State. The following are considerations for plant recovery and replant.

Recovery: For any situation, while it’s hard to wait, waiting 3-5 days does help when assessing any regrowth potential. We may need closer to 5 days with the rain and cool nights forecasted. Some may have experienced plants in your field that have burnt leaves and appear to be very dry. When you dig up the plants, check the roots and see if they appear white and healthy. If they appear stunted or burnt back, that may still be ammonia burn occurring. Most of what I’ve seen this week was due to wind damage from the amount of soil moving, ridges of dirt, and plants ultimately being ‘sand-blasted’ minus the sand. In cutting open plants, look to see if the growing point is white/cream in color and firm. That would indicate it is healthy and should survive. Often one can see the newer green leaves under the dying brown ones that were exposed to wind. The brown, drying leaves may do some wrapping. Often the wrapped leaves are removed by wind as regrowth pushes through, depending on severity of wrapping.

Similarly, if the corn experienced hail and/or freeze damage, digging plants and splitting stems to check for healthy growing points are part of the assessment.

For soybean, the growing point is above ground. The most critical point for new soybeans is when they’re emerging with hypocotyl hook exposed. Anytime the hypocotyl gets pinched (whether from crusting, frost at soil surface, some PPO inhibitor damage), the soybean won’t survive. Soybeans can survive the cotyledons being stripped and/or burnt off. Soybeans at the true VC stage (unifoliolates unfurled) can have 4 growing points below the main growing point (due to the axillary buds) which can shoot new petioles. What was cool for me was watching this in an organic field where the farmers flame for weed control. The soybeans after flaming can look similar to frost damage, yet a few days later, new shoots formed from the axillary buds. I haven’t experienced frost damage past the true cotyledon (VC) stage so I can’t say for sure how they will recover in fields that were hit hard. I’m hoping they could react similar to the flaming situation, depending on how badly the hypocotyl was damaged. The hypocotyl is the stem portion below the cotyledons.

Replant Considerations: For corn, the following chart from Iowa State University by Roger Elmore and Lori Abendroth, is the standard for consideration regarding populations.

For soybean, I have left stands as low as 50,000 plants/acre, particularly the closer to mid-June we get. I realize that’s hard, especially when one considers weed control. University of Wisconsin found only a 2 bu/ac yield increase when replanting early soybeans between 50,000 and their optimum stand of 100,000-135,000 plants/acre. A York County irrigated field in 2018 comparing 90K, 120K, and 150K became final plant stands of 60,875, 88,125, and 121,750 plants/acre with yields of 93, 94, and 97 bu/ac respectively.

As you assess plant stands, keep in mind that a gap in one plant row will be compensated by plants in the adjacent flanking rows. They will form extra branches to take advantage of the sunlight. Thus single-row gaps may not be as yield-reducing as you might think, especially in narrower row spacings.

If one replants at this time of year, it’s best to use a similar maturity as what one started with. We can still use full season maturities to mid-June. For stands less than 50,000 plants per acre, plant a similar maturity into the existing stand; don’t tear out or kill an existing stand as early planted soybeans have a higher yield potential. And, you can also test this for yourself via an on-farm research study! Simply leave a planter pass of your existing stand, plant into your existing stand for a planter pass, and alternate this across your field. Please see this protocol for more information.

JenREES 5-12-19

Crop Update: It is really nice to see crops emerging! The corn, soybean and wheat I When estimating whether severely injured plants will survive, check the growing point. Healthy growing point is yellow/white and firm as is shown in this picture. Unhealthy growing point is discolored and soft to the touch.looked at didn’t seem too impacted by the frost. There may be places where crops were more affected. For corn and wheat, it’s important to look at the growing point and make sure it’s white/yellow and firm and not discolored and soft. Impacts to wheat later on can also be seen at heading in white awns. Soybean are more susceptible to frost when those hypocotyls are just emerged at soil level or above and exposed when frost occurs. Soybean with hypocotyls that are pinched and brown will probably not survive. Soybean that have light scarring of hypocotyls and cotyledons most likely will survive. Look for the plumule (first true leaves from the shoot) within 7 days post-frost to ensure the growing point wasn’t injured. (You can see the plumule between the cotyledons in the upper right-hand picture below).Frost on soybean.PNG

Hopefully we don’t have to deal much with replanting. As we assess stands, this week’s UNL CropWatch at http://cropwatch.unl.edu has an article regarding stand and replant considerations for corn. It’s important to take stand counts in several areas of the field. There’s a table on the CropWatch website which shows original planted stands with planting date and what can be expected for potential yields based on stand counts and replanting at a later date. Roger Elmore shared the following example, “If the original planting date was April 30, a population of 35,000 plants/acre is expected to provide maximum yield. If the population is only 20,000 plants/acre, yield potential is 89% of the maximum for the April 30 planting date. If several 4- to 6-foot gaps occur within the row, yields will be reduced an additional 5% relative to a uniform stand. Stand gaps of 16 to 33 inches will only reduce yield by 2%. Estimate replant yield with Table 2. Use planting date and target plant population to estimate the yield potential of the replanted field. Replanting on May 20 at 35,000 plants/acre will result in approximately 87% of the maximum yield. Compare the replanted crop to the original crop which was planted on April 30 that now has a population of 20,000 plants/acre, and consider the costs of replanting. Expected yields are 89% for retaining the old stand versus 87% for a replant. Remember though, there is no guarantee of getting a good stand with replanting. Insect and disease pressure may be greater in replanted fields.” You may also be interested in checking out a new CropWatch podcast on corn seedling diseases at: https://go.unl.edu/a5zf.

Interseeding Cover Crops: The past four years, some growers have shared with me an interest in interseeding cover crops into corn or soybean. The growers have different goals which may include fall grazing, additional nitrogen from the cover, or soil health impacts such as increasing soil organic matter. Because cover crop establishment after corn and soybean is more difficult and inconsistent year to year, there’s been an increasing interest in interseeding. Basically, the thought is to plant the cover before the corn or soybean crop reaches canopy closure. The cover emerges and then essentially doesn’t grow much during the growing season due to minimal light interception. After harvest, the hope is the cover has greater biomass production since it’s already established. Research in general from other states hasn’t shown yield reduction in corn when the cover was planted after V4…typically from V5-V7. When the cover was interseeded earlier, some states have found yield reductions as the cover basically competes like a weed with the corn for resources. A question we often receive is regarding herbicides.  Wisconsin shares that Sharpen and Resolve for herbicides allowed for greater success with short half-life. They planted radish, oat, pea, rye, red clover in their trials. A family conducting on-farm research in Merrick County has been interseeding the past three years. In their 2018 trial, they used 32 oz glyphosate + 5 oz Status per acre post on 6/1/18 (planting date 5/17/18). They interseeded on 6/26/18 with 6 lb cowpea, 6 lb soybean, 0.5 lb crimson clover, 5 lb sunhemp, 2 lb hairy vetch, 3 lb buckwheat, 0.5 lb chicory, 0.5 lb flax, 0.5 lb rapeseed/canola, 6 lb Elbon cereal rye, 6 lb spring oats per acre. From conversation they were happy with cover emergence after Status application but I failed to ask which species looked the best. They will continue the study for several years.  Outside of this, we have very little research from Nebraska and my hope is to obtain more research via on-farm research this year! We’ve created a 2 treatment and 3 treatment protocol which can be found at: https://go.unl.edu/kvjf. The three treatment protocol can be altered a number of ways: including looking at 2 different mixes compared to a check, looking at different ways of seeding the cover crop vs. check, and looking at different interseeding timings vs. check. Please contact me if you’re interested in trying this!

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