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Corn Newsletter : 2018-08
Wheat Growth Stages and Associated Management- Feekes 6.0 through 9.0
With below average temperatures and snow, wheat growth and development is slower this year compared to the previous two years. Last year, wheat in Pickaway County reached Feekes 6.0 growth stage the last week of March. Remember, exact growth stages cannot be determined by just looking at the height of the crop or based on calendar dates. Correct growth identification and knowledge of factors that affect grain yield can enhance management decisions, avoiding damage to the crop and unwarranted or ineffective applications.
Feekes 6.0, the nodes are all formed but sandwiched together so that they are not readily distinguishable. At 6.0, the first node is swollen and appears above the soil surface. This stage is commonly referred to as “jointing.” Above this node is the head or spike, which is being pushed upwards eventually from the boot. The spike at this stage is fully differentiated, containing future spikelets and florets.
Growers should remove and carefully examine plants for the first node. It can usually be seen and felt by removing the lower leaves and leaf sheaths from large wheat tillers. A sharp knife or razor blade is useful to split stems to determine the location of the developing head. The stem is hollow in most wheat varieties behind this node. Feekes 6.0 growth stage video: https://www.youtube.com/watch?v=iukwznx4DPk
Feekes 7.0- Second Node Becomes Visible: This stage is characterized by the rapid expansion of the head and a second detectable node. Look for the presence of two nodes—one should be between 1.5 and 3 inches from the base of the stem and the other should be about 4 to 6 inches above the base of the stem. These nodes are usually seen as clearly swollen areas of a distinctly different (darker) shade of green than the rest of the stem. Note: the upper node may be hidden by the leaf sheath; you may have to run your fingers up the stem to feel for it. If only one node is present, then your wheat is still at Feekes Growth Stage 6. Wheat will still respond to N applied at Feekes 7.0 if weather prevented an earlier application; however, mechanical damage may occur from applicator equipment. Feekes 7.0 growth stage video: https://www.youtube.com/watch?v=PZ7Lvsux1y8
Feekes 8.0- Flag Leaf Visible, but Still Rolled Up: This growth stage begins when the last leaf (flag leaf) begins to emerge from the whorl. This stage is particularly significant because the flag leaf makes up approximately 75 percent of the effective leaf area that contributes to grain fill. It is therefore important to protect and maintain the health of this leaf (free of disease and insect damage) before and during grain development. When the flag leaf emerges, three nodes are visible above the soil surface. To confirm that the leaf emerging is the flag leaf, split the leaf sheath above the highest node. If the head and no additional leaves are found inside, Stage 8.0 is confirmed and the grower should decide whether or not to use foliar fungicides to manage early-season and overwintering foliar fungal diseases.
This decision should be based upon the following considerations:
- Is a fungal disease present in the field?
- Is the variety susceptible or are weather conditions favorable (wet and humid) for rapid spread and development of the disease(s) found in the field?
- Does the crop yield potential warrant the cost of application of the fungicide in question to protect it?
- Is the crop under stress?
If a positive answer applies to the first three questions, and a negative response to the last, plans should be made to protect the crop from further damage. Check product labels and apply as soon as possible. In most situations, the greatest return to applied foliar fungicides comes from application at Feekes Stages 8 through 10. Nitrogen applications at or after Feekes 8.0 may enhance grain protein levels but are questionable with respect to added yield. Moreover, additional N may increase the severity of some foliar diseases, particularly the rusts.
Feekes 9.0- Ligule of Flag Leaf Visible: Stage 9.0 begins when the flag leaf is fully emerged from the whorl with the ligule visible. From this point on, leaves are referred to in relation to the flag leaf (i.e., the first leaf below the flag leaf is the F-1, the second leaf below is the F-2, and so forth). After the flag leaf emergences, army worms can seriously damage yield potential.
For more information on Wheat Growth Stages and Associated Management: https://stepupsoy.osu.edu/wheat-production/wheat-growth-stages-and- associated-management
Pattern Favors Only Slow Improvement - Challenging Weather to linger throughout April!Author(s): Jim Noel
The expected cold and wet weather pattern for spring that has been forecast since December continues. There will be some relief this week after a cold start to the week with temperatures 10 degrees below normal we will switch and see temperatures by the end of the week a good 10+ degrees above normal but when average out through Sunday April 15, we will return to about average temperatures for the week. Drying is expected as well through Friday with only minor precipitation events but another rain event is expected this weekend. There is a lot of uncertainty on amounts and placement so confidence is low but there is potential for some heavy rain in parts of Ohio.
The week of April 16-22 will return to a colder than normal pattern with temperatures several degrees below normal. Precipitation will be lighter next week after the weekend rain event. Though April 25, rainfall is forecast to average 2-3 inches with isolated 4+ inches across the state of Ohio. This is still above average. See the associated graphic from the NWS Ohio River Forecast Center.
Soil temperatures will also continue to be below normal with the risk of some late freezes in late April so early planting risk will remain elevated. Improvement will likely not fully come until May when temperatures may actually be slightly above normal. However, rainfall may continue to be at or above normal so challenges will likely linger this year into May for planting season. The summer growing season still looks to see a switch toward warmer and drier weather but it is not clear whether this will happen in later May, June or early July. We will keep you posted. In summary, thanks in part to La Nina, expect a challenging planting season in Ohio into May. Summer may also offer its own challenges as the pattern switches from the cold and wet period to a warmer and drier period but it is uncertain exactly when that will occur.
Avoiding CompactionAuthor(s): Alan Sundermeier, CCA
Heavy farm machinery compacts the soil, both on tilled ground and no-tilled ground. Compaction induced by agricultural machinery often affects soil properties and crop production. Axle load is the first factor that has to be considered in soil compaction, according to Randall Reeder, Ohio State University Emeriti and Dr. Sjoerd Duiker, Penn State Soil Specialist. Axle load is the total load supported by one axle, usually expressed in tons or pounds. Farm equipment with high axle loads on wet soil will cause compaction in the topsoil and subsoil, whereas low axle loads will cause compaction in the topsoil and the upper part of the subsoil only. Deep subsoil compaction can only partially be alleviated with subsoilers, and at considerable cost. Freezing/thawing and drying/wetting cycles have been shown not to remediate soil compaction at this depth. Finally, biological activity (such as cover crops) is concentrated in the topsoil except deep root crops (e.g. radish or annual ryegrass) and therefore also contributes little to alleviation of deep subsoil compaction. Therefore, avoiding deep subsoil compaction is critical. The key to eliminating deep subsoil compaction is to keep axle load low.
Research has shown that a 10-ton axle load almost always causes deep subsoil compaction (more than 20 inches deep) under wet to moist field conditions. If the soil is dry, deep subsoil compaction is less likely, even with high axle loads.
Contact pressure is the pressure that is exerted by a tire or track on the soil surface, expressed in pounds per square inch (psi). Reducing contact pressures will cause less topsoil compaction. In completely flexible tires, surface contact pressure is similar to tire pressure. Tires run at 35 psi caused higher stresses at 14 inches depth and created ruts that were more than twice as deep as tires run at 12 psi tire pressure. However, at 22 inches, no difference was noted in measured stress between both tires because the tire load was the same.
Deep subsoil compaction is permanent and should be avoided at all costs. This can be done by keeping axle loads below 10 tons, and preferably below 6 tons. Compaction in the topsoil can be avoided by reducing tire pressure, using flotation tires, doubles, radial tires, or tracks, and by employing large-diameter tires. Reducing the number of trips over the field and reducing the total area per acre actually traveled are recommended. Driving on soil that is wetter than the plastic limit (soil crumbles, ideal for tillage) should be avoided at all times.
More information can be found at https://extension.psu.edu/avoiding-soil-compaction
OARDC Brach Station Two Inch Soil TemperaturesAuthor(s): Greg LaBarge, CPAg/CCA
During our recent survey of CORN Newsletter users, one item suggested for addition was a chart of soil temperatures in the spring. The Ohio Agricultural Research and Development Center (OARDC) Agricultural Research Station located throughout the state have 2 and 4 inch bare surface soil temperatures monitored on an hourly basis. The chart provided here summarizes the average daily two inch bare soil temperature from several stations. More complete weather records for the just passed day as well as long term historical observations can be found at http://www.oardc.ohio-state.edu/weather1/ . Observations include temperature, precipitation, different measures of degree day accumulation and other useful weather measures.
About the C.O.R.N. Newsletter
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.
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