Managing corn and soybean fields submerged by recent heavy rains |
The heavy rains have continued and what two weeks ago was isolated flooding has now progressed to cover the majority of the corn- and soybean-producing areas of the state. This problem has left growers struggling with the question of whether or not to replant water damaged stands and how to manage fields that have yet to be planted. Assessing plant and stand viability Generally, the time it takes for submerged soil to dry out enough to get equipment on for replanting is usually time enough to make a determination whether or not plants have survived. However, it can be difficult to determine survivability when plants are covered with soil and plant residue left behind by receding water. In these cases, split a plant lengthwise through the stem. The growing point should be relatively firm and white or cream-colored. Darkening or softening of the growing point indicates a nonviable (dead) plant. A step-by-step worksheet (MSUE Bulletin E-1961) to guide producers through a replant decision is available through local MSU Extension offices. How late into the year can I plant/replant
and still expect a reasonable chance of maturing grain? Considerations for replanting
into existing stands Other considerations for late
planting/replanting § Bt corn hybrids. For most Michigan corn production systems, economic benefits from the use of transgenic Bt corn hybrids resistant to corn borers are more likely to occur with delayed plantings, especially when there is earlier planted corn in the vicinity. Consequently, growers may want to consider switching some of their late-planted intended non-Bt corn acreage to Bt hybrids as insurance against the higher risk of infestation by late brood corn borers. § Previously applied herbicides and insecticides. Before replanting, review label restrictions associated with previously applied herbicides and insecticides. Please see the article on herbicide concerns in this issue by Jim Kells and Kathrin Shirmacher and a similar article on insecticide concerns by Christina DiFonzo for more details. § Seeding rates. There is no need to consider changing seeding rates for corn simply because planting is delayed. Optimum seeding rates for most growers' fields range from 28,000 to 33,000 seeds per acre. Lower rates (low to mid-20's) are suitable for fields with yield levels historically near or below 100 bushels per acre. Unlike corn, soybean has a great propensity to compensate or "flex" when plant populations vary. Therefore, the optimal planting population range is wider for soybean than corn. Determining the minimal scale of that optimal soybean planting population range will optimize profitability and still maintain yield. As a starting point, begin with a planting population of 175,000 seeds per acre for drilled systems and 130,000 seeds per acre for 30-inch rows, and then adjust down or up from there based upon field productivity, planting date, and planting conditions. When planting late, resulting soybean plants will be smaller than earlier planted soybeans. To compensate for the potential yield decrease of smaller plants due to late planting, increase your planting population by 20 percent. § Seeding depth. The key factor for determining seeding depth for corn is the importance of adequate and uniform soil moisture in the seed furrow. Some might say this is a moot point given the current soggy soil conditions. Remember, though, how quickly Mother Nature can change and how quickly shallow-placed seed can find themselves in bone-dry soil. A seeding depth of 1.5 to 2.5 inches for corn and 1.0 to 2.0 for soybean is acceptable over a range of soil conditions. Shallower depths for corn are risky if rains stop altogether and surface soils begin to dry rapidly. § Field tillage operations. Remaining pre-plant field operations should be scrutinized carefully to determine whether they are necessary. With today's modern corn planters, there is little reason to overly-prepare a field to create a picture-perfect seedbed. In delayed planting situations, every day wasted overworking a field is a day lost to planting and represents lost yield potential. Furthermore, unnecessary tillage operations on marginally wet soils increase the risk of creating tire and tillage compaction layers that can haunt root development and corn health later if excessively dry conditions suddenly become the norm. § Planter sidewall compaction. Another concern to watch for is the potential for significant root restriction by severe sidewall compaction when a rapid shift from wet to dry conditions occurs. If at all possible, avoid planting fields when soil moisture conditions favor the smearing of furrow sidewalls by the coulters or double-disc openers of the planter. The potential yield loss from planting in fields too wet far outweighs the potential yield loss from delaying planting until field conditions are suitable. Please see the article by Carrie Laboski and myself in this issue for more information on seed furrow sidewall compaction. § Nitrogen fertilizer applications. Because the recent flooding will likely delay planting until the end of May or early June, growers may want to consider backing off on their intended nitrogen fertilizer application rates due to the expected lower yield of the late-planted corn. Details on nitrogen management strategies for flooded soils can be found in Carrie Laboski and Darryl Warncke's article in this issue. The rule of thumb most commonly applied to lost yield potential for delayed planting is one bushel per acre per day after May 10, and up to two bushels per acre per day after June 1. Consider using a pre-sidedress soil nitrate test to further fine-tune your nitrogen application rates. (Information on calculating the most cost effective nitrogen rate can be found on my website at: http://www.msu.edu/~thelenk3/. Hit the "calculate optimum nitrogen rate for corn" hot button located in the Extension and Outreach section). § Starter fertilizer. Where soil phosphorus and potassium soil test levels are adequate or better and tillage is other than pure no-till, consider eliminating starter fertilizer use for the remainder of this season's corn planting. Soil temperatures at planting from here on (should) be more than adequate for rapid corn germination and early seedling growth, thus greatly diminishing the value of starter fertilizer. Eliminating starter fertilizer will not only reduce your costs, but will save some time during the planting operation. No-till corn, however, will likely continue to benefit from starter fertilizer applications, especially the nitrogen component, for planting throughout the remainder of the month. However, growers may want to consider applying some of the corn nitrogen requirement at planting. |
Aphanomyces on alfalfa
|
Because of wet conditions this spring, many newly seeded alfalfa fields may show poor growth in wet or slowly drained fields, which may be due to several diseases. Seedling diseases should be suspected when emergence is poor or there are stunted, discolored, or dead seedlings. Aphanomyces root rot can cause death and stunting of seedlings as well as more subtle disease of established plants that can result in significant yield reduction. Other diseases that occur in wet or poorly drained soils include Phytophthora root rot and Pythium seed and root rot. Plants infected with Aphanomyces usually become stunted and chlorotic (yellow) before they wilt and die, whereas Phytophthora and Pythium tend to kill seedlings quickly before plants become severely chlorotic. Another clue to a problem with Aphanomyces is root rot of an alfalfa cultivar that is highly resistant to Phytophthora. Although not much is known about Aphanomyces root rot in Michigan, it is known to be a serious problem in nearby states including Wisconsin, Indiana, and Iowa. We suspect this disease is also a problem in some Michigan fields. This disease is caused by the soil-borne fungal-like pathogen Aphanomyces euteiches. Perhaps because alfalfa disease that occurred in wet soil was attributed to Phytophthora, Aphanomyces root rot of alfalfa was not recognized as a serious problem until the early 1980s. Aphanomyces root rot is best managed by avoiding poorly drained soils and using Aphanomyces-resistant alfalfa varieties. However, this year, even well drained fields have been water saturated due to abnormally high rainfall in May. Fungicides are not available for control of Aphanomyces root rot of alfalfa. Phytophthora and Pythium root rots of seedlings can be controlled with fungicidal seed treatments, such as Allegiance-FL, ApronXL, or Apron-FL, but these seed treatments are not effective against Aphanomyces. Alfalfa varieties rated highly resistant (HR) or resistant (R) to Aphanomyces root rot should be planted where slowly drained soils occur and where Aphanomyces may be a problem. A list of varieties and their disease resistance can be found at the MSU Forage Information Systems web site at: http://web1.msue.msu.edu/fis/ Click on the Extension bar and then the Perennial Forage Legume and Grass Varieties for Michigan. Control of Aphanomyces root rot became more challenging when different races of this pathogen were discovered. Many commercial alfalfa cultivars are now available that have resistance to race 1, the first race discovered. Another race (race 2) of Aphanomyces was identified in the early 1990s that overcomes race 1 resistance. Alfalfa cultivars developed for resistance to race 1 are killed by the aggressive race 2 isolates. Race 2 isolates have been identified in a number of states including Wisconsin, Iowa, and Kentucky. Race 2 has not yet been confirmed in Michigan. Alfalfa varieties with resistance only to race 1 may be genetically vulnerable to Aphanomyces root rot in many regions due to the presence of race 2. Several commercial alfalfa varieties are now available that have resistance to both races of Aphanomyces. If resistance to race 2 is not specified for an Aphanomyces-resistant alfalfa cultivar, then you can assume it is resistant only to race 1. The overall distribution and impact of races 1 and 2 of Aphanomyces are uncertain, but Aphanomyces root rot should be considered as a potential problem in many parts of Michigan. If you have an alfalfa seeding that has failed this spring, it should be safe to replant with alfalfa again this year since compounds that cause autotoxicity do not accumulate in seedlings. A Phytophthora- and Aphanomyces-resistant varieties (treated with Apron XL) are recommended for replanting failed seedings. However, timing is a factor because alfalfa seedings done too late in the spring may fail because of inadequate moisture. If this occurs, one may wait until late summer for re-seeding alfalfa fields. For a photo of Aphanomyces
symptoms on alfalfa, please look at the following web site. |
Corn contracted for fall delivery but not yet planted |
With the wet weather, many producers may think they are trapped because of having corn contracted for fall delivery, but they don't have it planted and they want to switch to soybeans. Producers in this situation need to review their options and the risk management tools in place. First review "How many bushels per planted acre are contracted?" As of May 23, in Michigan 71 percent of the corn and only 36 perent of the soybean crop was planted. (Higher numbers were planted to the south and lower numbers were planted to the north and east.) Some crop insurance policies (CAT, Multi Peril, CRC and RA) have a "prevented planting" provision that will provide revenue from the prevented planting. June 5 is the corn planting deadline (June 15 soybeans) for full crop insurance coverage. However, there is a late planting option where the coverage level is reduced 1 percent per day (up to 25 days) past the planting deadline. The producer must notify the insurance agent within 72 hours if the decision is to not plant. If planted, the yield realized will be used in future established payment yields. Evaluate your decision carefully as the payout on prevented planting may or may not be more attractive than the projected return over variable cost from late planted corn or soybeans. The "Prevented Planting" payment is 60 percent of the bushel guarantee (Established Yield X Coverage Level) times a price of $2.45 for Multi Peril, or $2.83 for CRC and RA policies. Direct Payments and potential Counter Cyclical payments are not effected by prevented planting. Call your insurance agent before the crop planting deadline to get the particulars of your options. If you have contracts for fall delivery and you don't think you will be able to deliver on all the bushels, then you need to consider your options. There are many. Depending on the established forward contract price you may be in good position as prices have recently declined. Most grain buyers will work with you to either delay the delivery and roll the equity (or loss) into future bushels even if next year. They may be able to roll the position into a different commodity. For example, say you have 10,000 bu of corn contracted at 2.85 but you can't deliver. Suppose the current bid for fall delivery is $2.65. You are on the "good side" with the position and have $0.20 per bu or $2,000 "equity." The grain buyer may be able to roll the $2,000 "equity" into a soybean contract. With 5,000 bu soybeans this would be $0.40 per bu added to the soybean price above the current future price. Another possibility is to use the "equity" to buy a put. If you get the crop planted, the put would provide downside protection if prices continue to fall. If you don't grow the crop and prices go up, you would simply lose value in the put. If prices go down, you could still gain on the put even though you didn't grow the crop. Grain buyers will be very reluctant to just cancel the contact and give you the $2,000. A simple cancel of the contract will probably have a $.10 charge, or in our example, you would only get $1,000. You are probably better off to roll the contract to next year or, if available, to another crop. The most important point is to contact and talk with your grain buyer early. They want your business, and if you work with them early, they will do their best to give you the best value for your market position. |
Other articles to consider during heavy rains |
Considerations for replanting other crops after sugar beets in the May 13 issue of the CAT Alert and Importance of timely burndown applications in no-till soybean in the May 20 issue of the CAT Alert should both be reviewed because of the heavy rains. These articles and others related to spring conditions can be found through the calendar or search button located on the IPM Program website at: http://www.ipm.msu.edu/fieldCAT.htm |
Excessive rain and soil-applied corn herbicides |
The excessive rainfall over much of the state has raised concerns about soil-applied herbicides. The concerns relate to weed control and corn injury. Weed control Corn injury |
Herbicide considerations when replanting flooded corn |
The persistent, heavy storm systems that have passed through most of the state left many fields at least partially flooded. A likely consequence to this relentless wet weather is damage to earlier planted stands. This problem has left growers with the need to replant portions of fields. When replanting fields, herbicides applied previously this spring must be considered in the decision. If cornfields will be replanted to corn, most soil-applied herbicides present no problems for replanting (Table 1). However, replanting corn in fields treated with pendimethalin (Prowl or Pendimax) is risky, as the herbicide cannot be mechanically incorporated due to the risk of severe corn injury. In this situation, risk of corn injury can be minimized by replanting without reworking the field and with as little soil disturbance at planting as possible. Furthermore, the corn seed should be planted deep (usually two inches) to get the seed below the herbicide. The option of replanting cornfields to soybeans depends on herbicides applied previously this spring to the corn. Many of the preemergence herbicides on corn are also used in soybeans, and therefore, do not present a problem for switching the field to soybeans (Table 1). The field cannot be replanted to soybeans this year if atrazine or any premix containing atrazine has been applied to the field. Even with the heavy rainfall the past several weeks, the risk of soybean injury from atrazine is high. Where fields will be replanted to either corn or soybeans and a soil-applied herbicide has been applied, we recommend that no additional soil-applied herbicide be used. The best strategy is to monitor the fields and use postemergence herbicides or cultivation to control weeds after emergence, if needed. Table
1. Replant options with soil-applied corn herbicides.
*Replanting corn should be done without tilling and planting the
seed at least 2 in. deep. **Sorghum seed needs to be properly treated with an approved herbicide safener or severe injury may occur. See herbicide label for details. |
Postemergence herbicide application to large corn and weeds |
With the recent heavy rains across most of Michigan, many growers and custom applicators will be faced with weedy cornfields where the corn or weeds are past the recommended application window for herbicide application. This is not an ideal situation, but several options still exist. With herbicide use, there are two strategies that can be followed: (1) broadcast application and (2) directed application. If the weed population is low to moderate, cultivation may be the most economical option. With high weed populations, cultivation may also be needed following herbicide applications to control the weeds that the herbicide misses. Broadcast
applications Also,
consider corn stage and risk of injury. Some herbicides have little
injury risk and can be applied over a wide size range, such as Basagran,
Buctril, and Permit (Table
1J pdf). For others such as Basis, Banvel/Clarity, Distinct,
and 2,4-D, corn tolerance decreases as corn size increases. In general,
injury from systemic herbicides is of greater concern than injury
from contact (burn) type herbicides. Weeds under stress are more
susceptible to postemergence herbicide injury since they have less
ability to metabolize (deactivate) the herbicide. Crop safety will
be improved if corn has regained active growth before herbicide
application. Environment also plays a major role in injury risk.
Cool, cloudy weather results in plants with thin cuticles that rapidly
absorb herbicides. Hot, humid weather following several cool, cloudy
days is not the time to take chances with "hot" herbicide combination
or additives. Directed
applications With 2,4-D and Banvel, directed applications should be used when corn exceeds eight inches in height (as it stands in the field). The spray should be directed to avoid exposure of the corn, especially the whorl. The spectrum of weeds controlled will be the same as with broadcast applications. Gramoxone Extra is labeled for postemergence directed application in corn. Do not use before corn is at least 10 inches tall. Since any leaves exposed to the spray will be killed, extreme care must be taken to minimize exposure of the corn leaves. If the lower leaves are exposed to the spray, they will be killed but the corn will recover. Listed below are some general
guidelines for directed postemergence application 2) Drop pipes should be used that are
rigid (should not "flop around"), although some flexibility is desirable
to avoid breaking. Operate the sprayer slow enough to prevent the
boom from bouncing. 3) Applications should be made using a minimum of 20 gal/A of spray volume and a spray pressure of no more than 20 psi (to avoid fine spray droplets and "bounce back"). 4) For directed applications to be effective, the weeds must be small enough to allow adequate coverage without excessive exposure of the corn leaves to the spray. |
MSU Weed Tour postponed |
The persistent rain has delayed planting of our weed control trials in corn and soybeans. Therefore, the MSU Weed Tour, originally planned for June 30, will need to be rescheduled. Once our trials have been planted, we will be able to identify a new date for the 2004 Weed Tour. |
Nitrogen losses due to excessive rainfall |
Saturation of the soil by continual and excessive rainfall is causing significant loss of nitrogen from the soil. Plants that survive the standing water and saturated soil conditions will have little nitrogen available for them to use. Much of the nitrogen has been lost by either leaching or denitrification. Nitrate is the form of nitrogen vulnerable to these losses. Leaching Denitrification So how much nitrogen might remain in your soil? Well, that answer depends on when you applied the nitrogen. For applications prior to May 10, there has been sufficient time and warm enough temperatures for much of that nitrogen to be converted into nitrate and lost, regardless of the form of nitrogen applied. For applications of anhydrous ammonia, 28 percent N (urea ammonium nitrate), urea, or ammonium sulfate after May 10, some of the nitrogen will still be in the ammonium form and remain available to the crop. Some conversion (mineralization) of soil organic nitrogen to ammonium and then nitrate will have occurred thus far this season. However, the greatest amount of organic matter mineralization will occur during the month of June. This means that the soil's ability to supply nitrogen to your crops may be somewhat reduced but not eliminated. The best way to determine how much available nitrogen remains in the soil as it dries out is to collect samples and have them analyzed by a soil testing lab. For a typical pre-sidedress nitrate test (PSNT), collect 15 to 20 soil cores to a depth of 12 inches from representative field areas. Because some available nitrogen may remain in the subsurface soil, collect an additional sample from the 12 to 24 inch depth. In fields where anhydrous ammonia was knifed in prior to planting, collect 25 to 30 cores to get a better indication of the overall available nitrogen status. Samples should be dried and mixed as quickly as possible before sending them to the MSU Soil and Plant Nutrient Lab. You can also deliver them directly to the lab or have County Extension offices send them. Most commercial soil testing labs provide soil nitrogen testing and are able to provide results within 48 hours of receiving the sample. How should you interpret the nitrate testing data? First, keep in mind that for a regular PSNT sample, MSU determines the nitrogen credit by multiplying the ppm of nitrate-nitrogen by 6 to obtain a credit in pounds N per acre. The factor of 6 is based on the amount of nitrate measured in the top foot of soil plus an assumption that the amount of nitrate in the second foot (12 to 24 inches) is two-thirds of the amount in the top foot. This relationship was developed after sampling many fields over a period of several years. In general, it is a good relationship. This year, however, may be different. Because of leaching, the second foot of soil may contain more or less than two-thirds the amount of nitrogen as the top foot. This is why we are recommending sampling the second foot of soil. To determine the actual pounds of N per acre in each sample, multiply the ppm nitrate-nitrogen in the 0- to 12-inches and 12- to 24-inches samples by 3.6. Then add the pounds of N per acre in the 0- to 12-inch and 12- to 24-inch samples together to obtain the pounds of N per acre in the soil. The following is an example. The soil test report shows that the 0- to 12-inch sample has 3 ppm and the 12- to 24-inch sample has 7 ppm nitrate-nitrogen. The total amount of N in the soil profile would be: (3 x 3.6) + (7 x 3.6) = 36 pounds N per acre. For our current weather situation, this method will provide a better estimate of the amount of nitrogen available to your crops. In most areas of the state, corn is still relatively small and has only accumulated a minor portion of the nitrogen needed. If you applied all or most of your nitrogen at or prior to planting, you will want to consider applying sidedress nitrogen to compensate for losses. The amount to sidedress nitrogen would equal your planned nitrogen rate minus the amount of nitrogen measured by the soil test. For example, let's say I applied 150 pounds N per acre prior to planting and based on my soil tests from above, I have 36 pounds N per acre remaining in the soil. I would sidedress 114 pounds of N per acre (150 - 36 = 114). You can round the rate up or down to a rate that is convenient for your operation (perhaps 100 or 120 pounds per acre). In lieu of a soil nitrate test, applying at least 70 pounds of nitrogen per acre may be appropriate for many cornfields. The nitrogen can be broadcast by land or plane or knifed in once the soil dries out. Knifing or broadcast with cultivation will also provide the benefit of loosing and aerating the soil. |
Exercise restraint in resuming field operations |
As your fields begin to dry and you begin to anticipate field operations, remember that trafficking soils that are too wet can create short and long-term damage. Short term damage Long term damage |
Rill and gully erosion increases risk of tractor rollovers |
The heavy rains have caused deep rill and gully erosion in some sloping fields. These rills and gullies pose a safety risk to tractor operators by increasing the potential for rollover accidents. If the field has not already been planted, you can reduce the risk by repairing eroded areas using a light utility tractor and a three-point hitch mounted back blade prior to resuming normal field operations. Straddle the eroded area with the tractor and tilt and angle the blade. If the eroded areas cannot be repaired prior to continuing field operations, make sure to drive slowly when working in affected areas. Higher speeds increase tractor instability. Be especially careful when driving across steep slopes. If the downhill tire falls into a rill or gully before the uphill tire, the tractor may rollover. Take care when working up and down the slope as well. Some rills or gullies may be so deep that the tractor will rollover if one of the tires slips into the eroded area. If a tire does slip into a washout, steer the tractor into the gully and bring it to a stop. Don't try to quickly turn the tractor out of the gully as this can increase the chance of a rollover accident. Always wear your seat belt when operating tractors equipped with rollover protection. The tractor's rollover protection will not provide adequate safety unless the seat belt is worn and is properly adjusted. |
Update on wheat scab in Michigan and using the prediction models |
Because very little wheat, if any, is planted into corn residue in Michigan, the correct model to use for scab prediction is the no corn residue model. This model is predicting low to moderate probability of scab in areas where flowering is just now beginning. Although the model shows a high probability of wheat scab in the thumb, this would be true only if the wheat was just entering the flowering stage, which has not yet occurred and is still at least five to ten days from starting in the more central counties and north. It is important to consult the model when flowering first occurs, and for the first few days into flowering, to obtain an accurate estimate of the probability of wheat scab occurring in your area. High-risk predictions before flowering may not be accurate. The Folicur label states that Folicur can be applied through the beginning of flowering, and wheat that has been treated with Folicur cannot be harvested within 30 days. Therefore, Folicur should be applied between when flowering is first observed in a field and seven days later. This should keep applications within the label restrictions. Also, Folicur is more effective when applied early versus being applied later into flowering. |
Impact of the current weather situation on field crops insects |
Late planting § Several insects favor early-planted crops (the oldest fields in a region). Watch for first-generation corn borer in corn (ECB moths were reported in St. Joseph County on May 26) and bean leaf beetles in soybean. |