Crop Updates: It’s been interesting seeing growers sharing pics comparing crops on the same dates in 2018 to 2019. They are behind in many cases compared to last year. Yet, we can be thankful for every field that we’ve been able to plant in Nebraska this year! Weed control is something on many minds right now. On corn, please be sure to count collars to determine growth stages. First leaves are sloughing off on V5-V7 plants right now, so slitting open stalks to aid in counting collars is important as we think of herbicide applications. Bob Nielsen from Purdue has a nice recent article with photos to help you with this: http://www.kingcorn.org/news/timeless/VStageMethods.html. When it comes to beans, I’m concerned how much longer the PRE’s will hold. I share this every year in pesticide training to have the POST with residual on a week before you think you need it, even if you don’t see weeds in the field yet. So assess each field as to when your PRE went on, current weed emergence, and plan on your POST a week earlier to overlap when your PRE residual should be running out. Also, with palmer amaranth on people’s minds, consider attending a glyphosate resistant palmer amaranth field day July 10th near Carleton, NE. Dr. Jason Norsworthy from the University of Arkansas will be the featured speaker. For those who’ve heard me speak on palmer or at my pesticide trainings, much of what I share has been what I’ve learned from his presentations and research papers. You can learn more and register at: http://agronomy.unl.edu/palmer. Adding a small grain and diversifying our cropping systems is one way to aid in palmer/waterhemp management. There are several upcoming wheat and pulse crop field days occurring throughout Nebraska in the next two weeks and you can read more about them at: https://go.unl.edu/b65e.
At some point, irrigation may be needed again. Installing irrigation scheduling equipment now allows you to watch your soil moisture profile as your crops grow, gain better confidence in your readings, and it’s just easier to install them at earlier growth stages when there’s moisture in the profile. Here’s some tips for those using watermark sensors. (As I walk through this, I’m using kilopascals (kpa) for the sensor readings but the same numbers apply to centibars (cb)). First, be sure to prime the sensors to ensure they’re working correctly. Do this by soaking the sensors for at least 24 hours in water. If you still have mud on the sensors, gently remove with your fingers, not with a brush. Then check the readings to ensure they read 10 or less. If they don’t, I allow them to soak another 24 hours and recheck; replace any that don’t read 10 kpa or less. Allow the sensors to dry out to 199 kpa again by setting out in the sun/wind/blowing fans. (Note that water will move into the PVC tube during soaking, so you’ll need to remove the cap and dump the water out if you don’t have a hole drilled at the bottom of the PVC tube. This is also true during the installation process.) When you’re ready to install the sensors, they need to be soaked again, but it should only take them 1-5 minutes to read 10 kpa or less prior to installation. There’s a couple things I’ve learned with installations that help me. First, use an ag consultant’s tube on soil probe to dig the foot wherever the sensor is installed. This allows for a better fit with no air gaps along the sensor. I use a regular soil tube to dig the hole the foot/feet above that to aid in pushing the sensors. In wet, clayey soils, it can be difficult to push the PVC pipe into the ground, so digging the upper holes with a bigger tube helps me with that. The other thing I do is carry my bucket with water for the sensors to the field with me with the sensors. To aid with pushing the sensors in the ground, I wet the PVC tube with water from the bucket prior to installing it. NEVER pour water into the holes and don’t make a slurry mix. I’m hearing several were taught to do this, but it’s not what Nebraska Extension teaches based on Dr. Suat Irmak’s research as it will change the soil moisture of the holes compared to the surrounding soils. Make sure the sensors hit the bottom of the hole and fill in soil where the PVC pipe meets the soil line. Suat shared how he used rubber washers around the top of the PVC pipe at the soil line to aid in water not running down the PVC tube when soil cracks at the surface. For those installing ET gages, a reminder to remove the stopper from the ceramic top and fill the ceramic top with distilled water in addition to the main tube of the ET gage. I fill the ceramic top, allow it to soak into the ceramic plate a little and refill it. Then prime the inner tube with stopper ensuring there’s no air bubbles in the small tube after placing it into the ceramic top. You can also double check for air bubbles by gently removing the glass site gage (by pressing down on the rubber tubing at the base of the site gage), allowing some water to cycle through, and then replacing it.
Maple seedlings: Maple trees have now leafed out and the rain has allowed the abundance of seeds to produce seedlings in people’s lawns and gardens. I know they look bad because they do at my place too. Mowing is the best way to take care of them in your lawn and it will take several mowings to do so. Don’t lower your mowing height as you want to maintain a healthy grass canopy. Eventually the seedlings will continue to grow to where the mower blade cuts off below the growing point and the seedlings will die. In the flower beds, they are very easy to pull right now. It takes some extra time, but that’s the best way to rid them there.
What a blessing last week was for many to be in the fields to either finish or start planting! And, while some may not want it, we could also use some rain to help with the crusting issues that have been developing in various fields due to the warm temperatures and wind. As you assess stands, the following article provides some guidelines on what to look for and any replant considerations for corn: https://go.unl.edu/j727.
For those who planted soybean earlier into cooler soil conditions, Dr. Jim Specht also did so on different dates this year and monitored air/soil temperatures at the former ARDC near Mead. Air temperature daily lows were less than 36°F on eight days (five of which were 32°F or lower), were less than 40°F on 17 days, were less than 44°F on 23 days; and notably, were less than 48°F on 31 of the 37 days. I’ve talked about desiring a 24 hour window of near 50F temps for avoiding potential seed chilling of soybean. It’s based off some Canadian research that showed soybean completing the imbibitional (water uptake) phase in as little as 8-24 hours. Jim had a demo study this year in which he placed water into furrows and planted soybean seed 1.25” deep into the furrows on various days in April at 2:30 p.m. Adding water to the furrow was to hasten the imbibitional phase. There’s a slideshow with the full article in this week’s CropWatch at: https://go.unl.edu/yu2m. The article shows the seeds in this demonstration did not appear to be impacted by chilling injury in spite of low air/soil temperatures on some of the days including within a 24 hour period. The hypothesis is that planting in a warmer part of the day with good soil moisture allowed the imbibitional phase to complete more rapidly before the cold snaps occurred in the evening/following day. While this was only a demo, it spurs many questions. Further research to better document chilling injury and imbibitional period for different soil temps/moisture contents would hopefully help growers planting soybean in April.
Silver and Red Maple Trees: While back home helping with planting, I was also receiving numerous tree questions. For those with malformed leaves or various leaf coloration, I’m thinking that’s mostly due to the cool temperatures we’ve experienced. Malformed leaves can also be due to growth regulator herbicides such as 2,4-D (from weed and feed products or sprays) being applied to lawns when trees are beginning to leaf out.
For the past few weeks, I was observing the slow leaf-out of silver maples in town…even where portions of trees were leafing out and other portions seeming bare. Now, if your maples look like mine, they look brown and bare with huge seed production and minimal leaves. This can also be seen in red maple varieties such as the popular ‘Autumn Blaze’ maples from my observation. For everyone who called or texted, I told you I was assuming it was due to the cold snaps and frosts affecting trees leafing out. It also could be a result of the hard winter. Trees are interesting as stresses from previous years can also affect them several years down the road. While all that’s true, what I didn’t realize is that based on information from Ohio and Michigan State, frost at specific times trigger whether a tree goes into seed or leaf production. Maple trees produce very small flowers that turn into seeds every spring. Frost will kill some of the blossoms if received at the right time which leads to less seeds and more leaves. Even though it was a cold spring, perhaps fewer blossoms were killed than normal at the right time? It could also just be the natural cycle of heavy seed production this year? Regardless, the trees can’t support both massive seed production and leaf production, so many opted for seed production. The good news is that shade trees in general have an ability to shoot new leaves after being stressed. I see this every year after trees lose leaves due to herbicide damage, insects, diseases, or environmental conditions. So, give the trees a couple of weeks and you should begin to see new leaves developing. Don’t add fertilizer or other products to them as it’s not necessary and can actually stress trees that are stressed even more. By summer, the trees should look fairly normal. If they don’t, perhaps there’s another stressor occurring with your tree? The biggest culprits I see are roots that girdle (choke) the tree by wrapping themselves around the trunk or damage to the trunk from weed whackers.
What about those seeds in lawns and gardens? Some pre-emergent lawn herbicides will keep them from sprouting. Pulling them is time consuming, yet a valid option that’s best done as soon as seedlings emerge. Mowing may help keep some of them at bay. Weed and feed products for lawns often contain 2,4-D so using that or lawn care products with 2,4-D can be an option (just be sure to read the pesticide labels). Products like Preen can be pre-emergent options for flower beds/gardens.