Written by Ellen Essman
Despite the fact that “pumpkin spice” everything is back in stores, it is still summer, and if you’re anything like me, you’re still dealing with weeds. In fact, we have been receiving many questions about noxious weeds lately. This blog post is meant to be a refresher about what you should do if noxious weeds sprout up on your property.
Continue reading Noxious weeds on your property: what is your responsibility?
In this Grazing Management Minute, the conversation revolves around the benefits of planting warm season annual grasses and working them into a comprehensive forage management plan for Ohio livestock producers.
Source: Alyssa Essman, Mark Loux, OSU
Herbicides with residual that are used in corn and soybeans can affect the establishment of fall-planted cover crops, and should be taken into account when planning cover crop practices and selecting species. Soil characteristics and weather also play a role in the persistence of residual herbicides, which can vary by field and year. More information is needed on rotational intervals for many cover crop species, and this information is often not included on herbicide labels. University weed scientists have studied the effect of residual herbicides on some of the most popular cover crop species in order to provide this information to growers. In general, residual herbicides that control grass weeds can hinder establishment of grass cover crop species. Broadleaf cover crop species are most impacted by group 2 (ALS inhibitors), 5 (PSII inhibitors), 14 (PPO inhibitors), and 27 (HPPD inhibitors) herbicides (Purdue University).
A multi-state study found that the general order of sensitivity of cover crops to herbicide carryover, from greatest to least sensitive, is:
Soybean herbicides that tended to be most injurious were:
Corn herbicide treatments that were most injurious to cover crops were:
(University of Missouri).
Below is a table of commonly used corn and soybean herbicides, the fall cover crops that are safe to plant in rotation, and cover crop species that may be injured following these herbicides (Adapted from Lingenfelter D. and Curran W., Penn State University).
Cover crops provide a multitude of benefits and their use is becoming an increasingly popular practice in Ohio. Including cover crops in rotation with agronomic crops to realize these benefits costs time and money. It is important to evaluate the potential risk of herbicide residue on the establishment of cover crops in order to ensure success. Residual herbicides applied at the time of planting typically interfere with cover crop establishment less than those applied POST. Weather can affect the persistence of herbicides also, especially rainfall in summer. The risk of residual herbicides affecting cover establishment will be higher in areas that have been dry since herbicide application. Risk will be lower where the herbicide application was followed by some wet weather to get herbicide degradation started, compared with an application during prolonged dry weather. One of the least problematic cover crop species is cereal rye, which can be successfully established following a late corn or soybean harvest, and is tolerant to a most of the most commonly used corn and soybean herbicides. Weed control should continue to be the priority in selecting herbicides, and cover crop species selection should be based on potential injury and goals for the use of cover crops. The introductory section of the “Weed Control Guide for Ohio, Indiana, and Illinois” has some of the same information presented here, and OSU weed scientists also summarize this in a video: https://www.youtube.com/watch?v=ylr0zGnXMfs
The following resources contain information on residual herbicides and cove crops also:
https://extension.psu.edu/corn-herbicides-and-rotation-to-cover-crops https://extension.psu.edu/soybean-herbicides-and-rotation-to-cover-crops
https://ipm.missouri.edu/IPCM/2020/3/coverCropTermination-KB/
https://ag.purdue.edu/btny/weedscience/Documents/covercropcarryover.pdf
Source: Jim Noel
The cooler than normal blob of water in the eastern Pacific Ocean near the equator tends to push the first autumn freeze later than normal in our region. Therefore, there is no indication of an early freeze in September this year. It appears the first freeze for Ohio will not come until October either on schedule or a bit later than normal.
September looks to have the first half start cooler than normal followed by a return to normal temperatures for second half of the month. Precipitation will be normal or sightly above normal for September. Normal rainfall is currently 1-1.5 inches per two weeks dropping to about an inch per two weeks for the second half of September. Even though we expect rainfall at or slightly above normal in September, there is a great deal of uncertainty due to the tropics and where those systems will travel. So you will want to pay attention to later outlooks at: https://www.cpc.ncep.noaa.gov
Rainfall for the first half of September will average 0.50-2.00 inches. The heaviest rains will likely surround the state of Ohio in most directions.
October into part of November looks to resume the above normal temperatures which should create an extended autumn this year. Rainfall remains highly uncertain but it appears near normal is the most likely outcome for October and November as we have some climate models showing above normal and some below normal rainfall.
The early outlook for winter calls for above normal temperatures first half and below normal temperatures second half. Precipitation is likely to become above normal with potential influences from the tropical Pacific Ocean.
Source: Peter Thomison, Laura Lindsey, OSU
Have very dry soil conditions increase the potential for toxic levels of nitrates in corn harvested for silage? Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins, and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in the growing leaves. Under unfavorable growing conditions, especially drought, this conversion process is slowed, causing nitrate to accumulate in the stalks, stems, and other conductive tissue. The highest concentration of nitrates is in the lower part of the stalk or stem. For example, the bulk of the nitrate in a drought-stricken corn plant can be found in the bottom third of the stalk. If moisture conditions improve, the conversion process accelerates and within a few days, nitrate levels in the plant return to normal.
The highest levels of nitrate accumulate when drought occurs after a period of heavy nitrate uptake by the corn plant. Heavy nitrate uptake begins at the V6 growth stage and continues through the silking stage. Therefore, a drought during or immediately after pollination is often associated with the highest accumulation of nitrates. Extended drought prior to pollination is not necessarily a prelude to high accumulations of nitrate. The resumption of normal plant growth from heavy rainfall will reduce nitrate accumulation in corn plants, and harvest should be delayed for at least 1 to 2 weeks after the rainfall. Not all drought conditions cause high nitrate levels in plant. If the soil nitrate supply is low in the dry soil surface, plant roots will not absorb nitrates. Some soil moisture is necessary for absorption and accumulation of the nitrates.
If growers want to salvage part of their drought damaged corn crop as silage, it’s best to delay harvest to maximize grain filling, if ears have formed. Even though leaves may be dying, the stalk and ear often have enough extra water for good keep. Kernels will continue to fill and the increases in dry matter will more than compensate for leaf loss unless plants are actually dying or dead. Moreover, if nitrate levels are high or questionable, they will decrease as the plant gets older and nitrates are converted to proteins in the ear.