C.O.R.N. Newsletter: 2020-10
CFAES Ag Weather System Near-Surface Air and Soil Temperatures/Moisture
We are once again providing a soil temperature overview in the C.O.R.N. Newsletter through April-May 2020. The College of Food, Agricultural, and Environmental Sciences (CFAES) Agricultural Research Stations located throughout the state have two- and four-inch soil temperatures monitored on an hourly basis.
Our Western site in Clark County is now available. We have added this and Northwest Agricultural Research Station from Custar, Ohio as well. We are still supplementing additional data from western Ohio with data from Darke and Greene Counties. These sites (noted by an asterisk on Figure 1) report minimum (morning) soil temperatures. The other sites are reported on Figure 1 as a daily average.
Figure 1 shows that two- and four-inch soil temperatures have cooled significantly in response to air temperatures running 4 to 12°F below average for the week ending April 19, 2020. In general, average soil temperatures have dropped from the mid-50s/low-60s back into the 40s across the state. In fact, 2-inch soil temperatures at Northwest were in the upper 30s as of April 16, 2020. These soil temperatures are below their 5-year averages. The current weather forecast calls for seasonally cool air temperatures over the next 5-7 days with highs generally in the 50s and 60s, and overnight lows in the 30s and 40s. Soil temperatures are likely to slowly warm throughout the week.
Figure 2 (left) shows that lighter precipitation fell across Ohio this week, but some of this precipitation across the north came in the form of accumulating snowfall. Totals ranged from 0.1 inch in the northwest up to 2 inches in southeast Ohio. Calculated soil moisture ranking percentiles (right) remain above the 80th percentile with the greatest percentiles noted in southeast Ohio.
For more complete weather records for CFAES research stations, including temperature, precipitation, growing degree days, and other useful weather observations, please visit https://www.oardc.ohio-state.edu/weather1/.
How cold is too cold (for winter wheat)?
Overnight temperatures on April 15 and April 16, 2020 dropped into the low to mid 20s across a large portion of Ohio (Figure 1), and unofficial reports show a few locations briefly dropped into the upper teens! These temperatures were generally 12-20°F below average (1981-2010). A closer investigation at a few of the colder sites reveal temperatures remained below 32°F for 9-11 hours, below 28°F (hard freeze) for 7-9 hours, and below 22°F for 3-5 hours.
Injury to winter wheat depends primarily on three factors: 1) growth stage, 2) how cold, and 3) duration of cold temperature. Differences in freeze injury among cultivars can usually be attributed to slight differences in growth stage.
Although temperatures were low and there may be some yellowing/browning of leaves, the impact on wheat grain yield is likely to be minimal. In our research, at Feekes 6 growth stage, reductions in wheat grain yield began when temperatures fell to less than 20°F for a 15-minute duration. A 50% reduction in grain yield occurred at 12°F for a 15-minute duration.
Prior to Feekes 6 growth stage, the growing point of wheat is below the soil surface, protected from cold temperatures. However, at Feekes 6 growth stage, the first node appears and pushes the growing point (developing spike) up through the plant stem, and this developing spike can be damaged by low temperatures.
Damaged spikes can be observed by carefully cutting the wheat stem lengthwise to expose the developing spike at the first node. Damaged spikes will appear discolored and shriveled, which occurred at the 3°F temperature treatment (Figure 2).
At Feekes 6 growth stage, damage from low temperatures will cause yellow or browning (necrosis) of the leaf tissue, most likely leaf tips or edges exhibiting symptoms first (Figure 3). Death of leaf tissues and stems may result in the formation of tertiary (regenerative) tillers from surviving plant crowns (Figure 4). These tertiary tillers may produce seed, but often time do not fully mature, resulting in small, lightweight kernels. Overall, grain yield is reduced in these situations as primary and secondary tillers account for the majority of grain yield.
Freeze Potential in Ohio
Note: This article has been modified from an article originally published in VegNet Newsletter (https://u.osu.edu/vegnetnews/) on April 6, 2020.
Now that we are well into spring and turning a corner toward May, warmer temperatures are hopefully on the horizon. As we have already experienced, April can be a fickle month, with both warm spring rains and lingering cold nights that bring frost and occasionally, a late-season snowfall. Cold April weather can delay the warmup of soils (see CFAES Ag Weather System Near-Surface Air and Soil Temperatures/Moisture) jeopardizing early planted corn and wreaking havoc on horticultural interests, especially following early season warmth where phenological conditions may be advanced for this time of year. Winter (December 2019 – February 2020) averaged 2-8°F above average compared to climatological normal (1981-2010; Fig. 1). This warmth continued throughout March as well, with temperatures 4-8°F (west to east) above average.
Frost and Freeze Potential
With many areas in Ohio experiencing hard freeze conditions (air temperatures ≤ 28°F) last week (see How cold is too cold (for winter wheat)?), how unusual is an event like this in Ohio? What are Ohio’s typical expectations regarding freeze conditions in April and May?
On average, locations throughout Ohio experience their last seasonal freeze (temperatures ≤32°F) from mid-April (southern Ohio) through mid-May (northeastern Ohio). Figure 1 shows the climatological date of a late last hard freeze, meaning that only 1 out of every 10 years does a hard freeze occur after this date. Across southern Ohio, a 28°F day occasionally occurs as late as April 20, with much later dates (as late as May 10th) across northeast Ohio.
For a state analysis, we have selected 8 locations from around Ohio to compare typical last seasonal freeze conditions (Figure 2). Figure 3 shows the probability of experiencing a later freeze in spring than indicating by the line graphs. All locations show probability based on the most recent 30-year period (1990-2019) except for 7-Lancaster (1996-2019). For each location, five temperatures are displayed (20°F-purple, 24°F-blue, 28°F-green, 32°F-yellow, and 36°F-red). For the purposes of this article we will focus on 32°F and 28°F. The bottom (x-axis) shows the probability that each of these temperatures will occur after a given date (indicated by the left or y-axis).
For 1-Wauseon, we see that there is a 50% climatological probability of experiencing a 32°F temperature (yellow) after April 27, and this probability decreases to 20% by May 10. The colder, more damaging temperature of 28°F occurs 50% of the time after April 16, with only a 20% chance of seeing 28°F after April 27. For a southern location like 8-Marietta, these dates occur earlier in the season. Here, there is a 50% climatological probability of experiencing a 32°F temperature after April 18 with 28°F occurring 50% of the time after April 2.
Besides latitudinal (north of south) position, what other factors can influence springtime minimum temperatures? Colder air is more dense than warmer air, meaning it wants to remain close to the ground and will flow over the terrain like a fluid to settle in areas of lower elevation. If your location is in a valley or low-lying area, the climatological dates will likely be shifted later to account for more freeze potential later in the spring. Water bodies are typically colder than the surrounding land areas in spring which may keep temperatures in the immediate vicinity a little colder. For 2020, water and soil temperatures are above average, so they are likely to have a moderating impact this year. Cloud cover and higher humidity in the spring will keep air temperatures warmer due to their absorption of terrestrial (from the surface) radiational effects. Finally, late season snowfall combined with clearing skies overnight can also cause the surface to cool rapidly and lead to damaging freeze potential as well. All of these factors should be considered when comparing your location to those selected in Fig. 3.
Alfalfa Weevil Update
Last week we reported that peak alfalfa weevil feeding damage occurs between 325 and 575 heat units (based on accumulation of heat units from January 1 with a base of 48°F). The cool temperatures over the past seven days have slowed the accumulation of heat units and thus weevil development, though southern Ohio is now at the lower end of this range. For more details on alfalfa weevil scouting and thresholds please see our April 13 article https://agcrops.osu.edu/newsletter/corn-newsletter/2020-09/alfalfa-weevil-%E2%80%93-it%E2%80%99s-closer-you-think
Slight Frost Injury on ForagesAuthor(s): Mark Sulc
I have observed and received reports of only very slight frost burn on the tips of leaves of alfalfa and winter annual forage crops after the two cold nights last week in Ohio. On Monday, the alfalfa at the Western Agricultural Research Station looked excellent, with just scattered stems showing slight frost burn on the upper leaves. The 2019 late summer seedings also looked excellent. Italian ryegrass and winter wheat on the station showed just a little purpling on the upper leaf tips.
The situation could be a little more severe in certain pockets of the state, depending on the duration of the low night temperatures last week. However, reports from around the state indicate only slight damage to forage crops and they should grow right out of it with no significant effect on forage yields.
If more injury is observed in certain pockets, the recovery will be very dependent on the general health of the stand. The best recovery will be in younger stands where soil pH and fertility are in the optimal range, and the last cutting in 2019 was not taken by early September. If you have observed more severe injury, feel free to contact me with any questions you may have.
Worried about Fallow Syndrome? Assess the Risk with On-Farm Research
Wet weather conditions last spring prevented Ohio farmers from planting over 1.5 million acres. When fields are left unplanted or fallow, there may be a decline in beneficial mycorrhizal fungi, which is commonly referred to as fallow syndrome. Mycorrhizae are beneficial fungi that colonize plant roots. They aid plants in scavenging for soil nutrients, by extending the root system via thread-like structures called hyphae. In return, plants provide sugars produced during photosynthesis to the mycorrhizae.
Stunting and phosphorus deficiency are common symptoms associated with fallow syndrome.
The impact of fallow syndrome on crop yields is unclear and the extent that it will occur in 2020 remains a mystery. Ohio State eFields will be running a series of on-farm trials to investigate the yield impacts of fallow syndrome and the efficacy of potential remediation options, such as starter phosphorus applications and microbial inoculants. Information from this trial will be used to improve management recommendations for growers throughout the state.
At each field site, a starter phosphorus fertilizer treatment will be compared to a control with no phosphorus applied. Additionally, growers can include 3Bar Bio-YIELD® microbial inoculant and/or Valent MycoApply® EndoPrime® SC mycorrhizal inoculant in their trial.
If you have fields that were not planted in 2019 and will be planted to corn in 2020 and are interested in being involved in this trial, contact your local Agriculture and Natural Resources OSU Extension Educator. Fields with soil test phosphorus levels <30 ppm Mehlich-3 P, or ideally <20 ppm Mehlich-3P, are preferred.
eFields is a program at The Ohio State University program dedicated to advancing production agriculture through field-scale research. To learn more visit digitalag.osu.edu.
Cool weather to hang on for the rest of AprilAuthor(s): Jim Noel
The cold pattern that was expected last week dropped soil temperatures and put a hold on most activities. Improvement will occur but it will be slow for the rest of April. A progressive west to northwest airflow will keep weak or weak/moderate systems passing through Ohio about every 2 days over the next week with generally light or light to moderate precipitation. The flow pattern supports temperatures remaining at or below normal for the rest of April but not as cold as last week. Precipitation is expected to be close to normal. Warmer weather is expected as the calendar turns to early May with above normal temperatures expected which is some good news.
Temperatures will moderate for the rest of April with highs mostly in the 50s and 60s though northern Ohio may only see highs in the 40s Tuesday of this week. Low temperatures will be in the mid 30s to the 40s for the most part. For the rest of April temperatures will average about 5 degrees below normal. May temperatures will likely be near normal or slightly above normal but the start of May looks to be above normal temperatures by several degrees.
Excessive rain is not expected the next 2+ weeks but frequent lighter rain is. Rainfall will average 1-3 inches the next two weeks with normal being 1.75 to 2 inches. Therefore, rainfall is considered near normal overall. A few wet snowflakes can not be ruled out Tuesday or this week in the northeast corner of Ohio. May is expected to see rainfall normal to slightly above normal. The blocking pattern over Alaska and northern Canada in 2019 which drove the active storm track from Japan to the Ohio Valley does not look to occur in 2020. This will result in fewer overall moderate to strong storm systems into May and June of 2020. The pattern is still active bt just not as active as 2019.
We do see another freeze this Wednesday AM with lows in the mid 20s to lower 30s. Some additional frost and near freeze conditions can also be expected this upcoming Sunday into Monday mornings. Overall, the frost and freeze conditions going forward are considered pretty close to typical for Ohio in late April and early May. After this Wednesday the chances of hard freeze conditions begin to decrease.
Soil temperatures dropped below 50 in most areas last week and will slowly work back toward that level for the rest of April though it may not reach that level in parts of the north and northeast section of the state.
SUMMER GROWING SEASON
There is uncertainty in the summer outlook but currently above normal temperatures are favored with rainfall going from above normal to start to normal or drier than normal in the later portions of summer.
The latest NOAA climate information can be found at: https://www.cpc.ncep.noaa.gov
The lastest river and soil information can be found at: https://www.weather.gov/ohrfc/
The latest Water Resources Outlooks can be found at: https://www.weather.gov/ohrfc/WRO
Time to stock up on nozzles is now! But, do you know which ones to buy?Author(s): Erdal Ozkan
This is the time of the year you must complete shopping for nozzles because the spraying season is just around the corner. Although nozzles are some of the least expensive components of a sprayer, they hold a high value in their ability to influence sprayer performance. Nozzles help determine the gallon per acre. They also influence the droplet size, which plays a significant role in achieving improved penetration into crop canopy and better coverage on the target pest, both affect the efficacy we expect from pesticides applied. When I get a question like, “what is the best nozzle I can buy?”, my answer is: it depends on the job on hand. One nozzle may be best for a given application situation, but it may be the worst nozzle to use for another situation. Sometimes, the choice of nozzle may be determined by the requirements given on the pesticide label.
Selecting the best nozzle requires careful consideration of many important factors including: sprayer operation parameters (such as application rate, spray pressure, travel speed); type of chemical sprayed (herbicides, insecticides, fungicides); mode of action of chemicals (systemic, contact); application type (broadcast, band, directed, air assisted); target crop (field crops, vegetables, vineyard, shrubs and trees, etc.); and spray drift risk. I will briefly cover some of these topics in this article. For detailed information on nozzle selection, I strongly recommend you read a new Ohio State University Extension Publication, entitled “Selecting the Best Nozzle for the Job”. In this publication, you will see step-by-step guidelines for selecting the most appropriate spray nozzle for a given application situation. The publication is available online at following web site: http://ohioline.osu.edu/factsheet/fabe-528
Which nozzle type is best your situation?
Each nozzle type is designed for a specific type of target and application. For example, a nozzle designed for broadcast spraying is not good for spraying pesticides over a narrow band. While one nozzle may be best for a given situation, it may be worst choice for another. For example, we at Ohio State University have conducted field experiments to determine which nozzles to choose for two different application situations: soybean diseases such as rust and white mold, and wheat diseases such as head scab and stem rust. We included 6-8 different nozzles in the experiments. We found out that while a twin-fan pattern nozzle was best for controlling wheat head scab, the same nozzle turned out to be the worst choice to protect soybeans against rust and white mold when the soybean canopy is tall and dense. So, before buying the nozzles and putting them on the boom, check the nozzle manufacturers’ catalogs which have charts showing which nozzle type will be best for a specific job. Check the websites of nozzle manufacturers to reach their catalogs.
Once you determine the type of a nozzle you need to buy, you also must buy the right size of that nozzle which will satisfy the application rate (gallons per acre or gpa) you wish to use as you do your spraying at different travel speeds. Nozzle catalogs are filled with tables and charts showing application rates, given a nozzle’s flow rate (gallons per minute or gpm) delivered at various pressures (psi) and travel speeds (mph). However, the charts are only for a limited number of travel speed and nozzle spacing situations. Most nozzle manufacturers have developed Apps for smart phones that provide you the exact nozzle flow rate required for any given set of application parameters, and identify a specific set of nozzle recommendations for the given application parameters. To find these Apps, simply visit the App Store in your smart phone or tablet and do a search under “Spray Nozzle Calculator”, or some other key words related to nozzle size selection.
Keep several types of nozzles on the boom
Remember that one specific type of nozzle will not be best for all applications. For this reason, it is best to have several types and sizes of nozzles on the boom so that you can switch to the “best” nozzle choice for a given spraying job. As shown in the pictures below, there are various types of sprayer components and setups you can buy to configure your boom so the new set up allows you to easily switch from one nozzle to another instantly.
Keep spray drift in mind when selecting nozzles
Spray drift (movement of pesticides by wind from the application site to an off- target site) is a serious problem for many reasons. Extensive information related to factors influencing creation of spray drift, is provided in the Ohio State University Extension publication FABE-525 (http://ohioline.osu.edu/factsheet/fabe-525). After wind speed and other weather-related conditions, choice of nozzles is the second most influential factor affecting drift. Research conducted at The Ohio State University and elsewhere clearly indicate that nozzles labeled as “low-drift” significantly reduce spray drift. If drift is, or becomes a concern, it may be best to switch from a conventional nozzle to a “low-drift” version of the same type nozzle with the same flow rate. This is another good reason to have more than one type of a nozzle on the boom.
Give special attention to choice of nozzles when applying pesticides containing 2,4-D and Dicamba
The labels of 2,4-D or Dicamba herbicides include specific requirements on which nozzle or nozzles must be used when spraying these products. The requirements also include a range of operating pressures for each one of these nozzles. These strict requirements are put on the labels to avoid off-target movement (drift) of spray droplets. Simple interpretation of these requirements is: you would be violating the pesticide label, therefore the law, if you use any other type and size of nozzle and operate these nozzles outside the pressure ranges. Remember, the label is the law! So, it is your responsibility to comply with the requirements on pesticide labels. You can reach a list of currently approved nozzles and their operating pressure ranges on labels of the several commonly used 2,4-D and Dicamba products at this web site: https://pested.osu.edu/sites/pested/files/imce/ApprovedNozzles.pdf
The table at this site is provided mostly for information purposes and may not be up to date. So, check the manufacturers’ websites, and read the product label for the most current information. Do not assume that you do not have to worry about checking the label because you had applied the same product in a previous year. A nozzle required for the same product last year may not be on the label this year, or the operating pressures might have been changed.
Some final thoughts
Nozzles are typically the least costly items on a sprayer, but they play a key role in the final outcome from a spraying job: achieving maximum efficacy from the pesticide applied while reducing the off-target (drift) movement of pesticides to minimum. Pesticides work well if the rates on labels are achieved during application. This can be achieved only if the right nozzle type and the proper size of the nozzles are on the sprayer, and the sprayer is operated properly.
Managing stored grain into summer
If you are storing more grain on farm this spring than usual, you are not alone. Over the last few weeks, we have heard from more producers who are considering holding grain longer into summer months than they normal would. We have also heard a few reports of spoiled grain as producers fill April contracts. Carrying graining into summer has been done for many years successfully but requires much more intensive management than winter grain storage.
Key advice for long term grain storage
- If bins were not cored in early winter core bins now
- Verify the moisture content of stored grain is at or below recommended levels
- Monitor grain temperature every 3 or 4 weeks throughout storage paying special attention to insect activity and mold
- Monitor the roof area for signs of condensation
- Cover fans to keep the chimney effect from warming the grain
- Provide roof ventilation at two levels above the surface of the grain, one vent should be close to the peak of the bin
- Aerate bins on cool mornings every couple weeks as grain at the top of the bin becomes warm
The first management consideration is the moisture of your stored grain. If you plan to store grain into the warmer summer months, it is important to know the moisture content of your stored grain. Last fall some grain went into storage at a higher than ideal moisture content. If crop development was impacted by the unusual weather conditions in 2019, moisture tester readings can be off by up to 2 points. The recommended maximum storage moisture content for summer are shown below.
Maximum summer storage moisture %
If your stored grain is currently at a higher moisture content, you should consider moving it to market or drying to these recommended storage moistures using natural drying, if possible. Using high temperature drying now is not recommended because recooling the grain for summer storage will be challenging.
The second consideration for maintaining stored grain into the summer is temperature. Historically, it was recommended to warm grain in the summer as ambient air temperatures increase, but this is no longer considered a best management practice. It is now recommended to keep grain as cool as possible for spring and summer grain storage. Warming grain to average outdoor summer temperatures can lead to increased potential for insect infestation and mold growth. Keeping grain temperature below 70ºF lessens insect reproductive activity compared to 80ºF but keeping this temperature below 60ºF will greatly reduce insect activity. When grain temperatures are below 50ºF, most insects are dormant.
Monitoring stored grain temperature through the summer will allow you catch potential problems. Grain is an excellent insulator, so it can be challenging to detect pockets of warm grain. If summer grain storage will be common on your farm, using multiple temperature monitoring cables throughout the bin is recommended. Since the grain at the top of the bin is often the warmest, a two foot thermometer can be used to check temperatures if monitoring cables are not installed. Grain temperature should be checked every couple weeks in the center and around the edges of the bin. Often the south side of the bin warms up before other sections. Increased temperature maybe a sign of mold growth or insect activity.
Proper ventilation is also important when keeping grain in summer months. Solar radiation warms the roof of the bin and the air below. Natural convection air currents within the bin cause air to rise along the walls and be drawn into the center of the bin, warming the grain. Natural ventilation of the air space above the grain can be used to help keep this space cool. Having vents in two areas above the grain with either a vent or fan at the peak assists with this ventilation. This works similar to attic vents in a home. Air enters at the bin eave openings and leaves at the peak vent helping to keep the area above the grain cool.
The bottom positive pressure ventilation fans can also be used to help keep the grain at the top of the bin cool. Running fans every three or four weeks on a cool morning for a couple days in a row can cool the grain at the top of the bin. The air entering the bottom of the bin is cooled by the cold grain and then cools the grain at the top. It is very important to select mornings when air is cool and dry. While we often do not cover bottom ventilation fans during winter grain storage this is much more important for summer storage. Openings at the bottom of the bin create a chimney effect throughout the entire grain mass. Warm air enters the bottom of the bin and as wind blows past the top of the bin the air is drawn up through the grain mass warming it up. Fan covers can be as simple as a tarp fastened over the fan or there are more durable fan covers available.
Keeping stored grain in condition during summer months will take more management than winter storage and the risk of spoilage is higher. Remember that stored grain cannot be kept in condition indefinitely. We strongly recommend you have a grain marketing plan for any grain you are keeping in storage.
Crop Observation and Recommendation Network
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaesdiversity.osu.edu. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.