Iowa State University annually evaluates the agronomic performance and nematode control of hundreds of soybean varieties that are resistant to the soybean cyst nematode (SCN). A limited number of SCN-susceptible soybean varieties are included in the research to serve as a reference point for comparison. The work is supported by the soybean checkoff through the Iowa Soybean Association. The experiments are conducted in each of Iowa’s nine crop reporting districts.
The results of the experiments conducted in 2018 were compiled in a report that will soon appear in an issue of the Iowa Farmer Today in January 2019. The report currently is available online for free.
A summary of the basic information about yields and SCN populations for eight of the nine experiments conducted in 2018 is given in Table 1. One of the experiments, in southwest Iowa, was not harvested because of wet soil conditions.
Low SCN population densities at planting, but high reproduction on PI 88788
Table 1. Basic yield and SCN population information for eight variety evaluation experiments conducted throughout Iowa in 2018.
In all but one of the experiments, the initial (at-planting) SCN population densities were low (Table 1). The exception was the experiment near Newell (northwest Iowa), which was in a field with a moderate SCN population density. The SCN infestation categories are explained in a publication available online for free.
The ability of the SCN populations in the fields to reproduce on the Peking and PI 88788 sources of resistance also is shown in Table 1. The SCN populations in all of the fields where the experiments were conducted had 10 percent or less reproduction on Peking. But reproduction of the SCN populations on PI 88788 was more than 10 percent in all fields and ranged from 11 percent to 53 percent. Ideally, levels of reproduction should be less than 10 percent. PI 88788 is the source of resistance genes for more than 95 percent of resistant varieties in Iowa whereas currently, Peking resistance is available only in 35 varieties (see previous ICM News article).Low initial SCN population densities build up to cause yield loss
Even though initial SCN population densities were low in all but one experiment, differences in yield between resistant and susceptible varieties occurred in all of the experiments and ranged from 3.8 to 19.3 bushels per acre (Figure 1). For example, the initial SCN population density in the experiment near Urbana, in east central Iowa, was 448 eggs per 100 cc of soil. And the average yield of resistant varieties was 14 bushels per acre (or 35 percent) more than yields of the susceptible varieties in that experiment. This large yield difference shows the potential for low population densities of SCN in the soil to reduce soybean yields.
Figure 1. Overall mean yields of SCN-resistant and susceptible soybean varieties in experiments conducted in 2018. The Pi numbers in the column on the left are the initial SCN population densities in the plots when the experiments were planted. Significant soybean sudden death syndrome (SDS) occurred in the experiments near Arlington, Moorhead, and Urbana.
The population density of SCN in the soil increased 3- to 22-fold over the course of the growing season in the experiments on both SCN-resistant and susceptible varieties (Figure 2). The experiment conducted in the field near Ames, in central Iowa, had the lowest initial SCN population density of 218 eggs per 100 cc of soil. End-of-season population densities at harvest in the Ames experiment averaged 1,618 for the resistant varieties and 4,975 for the susceptible varieties. The largest increase in SCN population densities was seen in the experiment in southeast Iowa, near Fruitland, where the initial SCN population density was 372 eggs per 100 cc of soil and end-of-season population densities averaged 7,968 for the resistant varieties and 6,392 for the susceptible varieties.
A wide range of yields among SCN-resistant soybean varieties
Figure 2. Mean end-of-season (final) SCN egg population densities for SCN-resistant soybean varieties compared to susceptible soybean varieties in experiments conducted in 2018. The Pi numbers in the column on the left are the initial SCN population densities in the plots when the experiments were planted.
There were some large differences in yields and in the season-long increases in SCN population densities among the SCN-resistant soybean varieties in the experiments. Differences in yields of individual SCN-resistant varieties ranged from 10.6 to 35.6 bushels per acre in the experiments (Table 1). Some differences in yields and in season-long changes in SCN population densities were not significantly different (i.e. were not true differences among varieties but due to various other sources of variation). However, there were many significant differences among varieties studied in the experiments.Soybean sudden death syndrome in three experiments
SCN is never the sole pathogen or pest within a field. Efforts are taken to not use fields with a history of other diseases to conduct the SCN-resistant soybean variety evaluation experiments. Also, substantial efforts are put forth to control weeds and insects (if warranted). However, disease levels sometimes reach the extent that they likely affect the yield results of the experiments. Such was the case with soybean sudden death syndrome (SDS) in 2018.
Significant SDS occurred in the experiments conducted in northeastern, west central, and east central Iowa. For those three experiments, SDS incidence and severity were rated for each plot, and an SDS disease index was calculated and included in the tables in the report with the other data for those experiments.Summary
The results of these experiments show that even low SCN soil population densities in the spring can increase greatly throughout a growing season and cause substantial yield loss. The yield benefits of SCN control provided by good resistant varieties are apparent in the research.
The data from these experiments represent a limited number of locations and should be used only as a beginning point for developing a SCN management program for a specific field. Performance of individual SCN-resistant soybean varieties in SCN-infested fields will vary among locations and years. Farmers and those who advise them are encouraged to evaluate several SCN-resistant soybean varieties at their own locations to determine the best varieties for their local conditions.Learn more about managing SCN from The SCN Coalition
SCN continues to reduce the productivity and profitability of soybean production throughout Iowa and the Midwest. Yield losses due to SCN occur in every infested field. The best approach to managing SCN is through integrated use of multiple management strategies including growing nonhost crops and resistant soybean varieties with different sources of resistance. Nematode-protectant seed treatments also are available to use in an integrated management plan. And fields must be monitored regularly to assess changes in population densities. Consult the SCN Coalition for more information at www.TheSCNCoalition.com.Crop: SoybeanCategory: Plant DiseasesTags: SCN; SCN resistance; SCN Management
With this year’s harvest of soybeans delayed beyond what is considered an ideal window of time, the opportunity for diseases to infect seed pods and in some instances, to the seed itself, was greatly increased. Across the state and the north central region, seed suppliers have reported that this year’s crops of seed soybean are frequently testing positive for the Diaporthe fungus (Phomopsis seed decay), which is resulting in lower than normal germination rates of seed. Seed decay is characterized by cracked, shriveled seed with white chalk-colored mold on the seed surface.
Diaporthe infection on a soybean pod and seed. Daren Mueller
The large amounts of rain that occurred throughout August and September set up this year’s soybean crop to be at a disadvantage to the Diaporthe fungus, which typically infects soybean pods between the R5 (early seeding stage) and R6 (fully seeded pods) growth stages. This is important because only infections initiated in the pods can infect seeds and cause seed decay. As soybean plants reach the R7 growth stage (beginning to mature and dry out), pod colonization declines drastically. Seeds will not become infected once moisture is below 19 percent. However, during periods of wet and warm weather, seed infection and colonization can continue or resume if seed moisture increases to more than 19 percent.
Infected seed will have a lower probability of germination in the following season, when planted. If soil conditions are wetter and cooler than normal, this could drastically impact both the survival and stand count of plants. Diminished seed quality and reduced seed vigor, germination and emergence are all consequences of seed decay. Seed decay can also reduce seed test weight and oil content.
Many dealers will want to have their seed treated with a fungicide to increase the chances of germination and prevent seedling diseases. The Iowa State University Seed Lab is able to test the germination rate of seeds to verify if and what percentage of seeds are infected with the Diaporthe fungus. Depending on the germination rate and incidence of infection, the use of a seed treatment may be warranted.
Decaying seed as a result from Diaporthe infection.
According to past Iowa State University research, appropriate seed treatments can increase germination rates by 10-15 percent. Given the progress and development of fungicides, germination rates could be further improved, given the right mix. However, winter storage of seed can also increase germination rates, due to the fact that under dry storage conditions, the mycelium of the fungus will die, improving the seed quality. A suggested practice is to dry-store low germ-seeds over winter and re-test the seed in February.
When deciding on which fungicides will be the most effective, consult the Crop Protection Network's guide on seed treatments, which includes a chart rating the efficacy of fungicides for several diseases (consult the Phomopsis section for combating Diaporthe).
It is recommended to not use seed lots with more than 20 percent Diaporthe infection because severely infected or moldy seed will fail to germinate even after being treated.
To be proactive with seed production next year, foliar fungicide applications to protect from seed infection between R3 (beginning pod) and R5 (beginning seed) may reduce seed infection especially in seed production fields. Although fungicide applications may reduce disease and improve seed quality, yield may not be impacted.Category: Grain Handling and StoragePlant DiseasesTags: Diaporthephomopsis seed decaySoybeanseed treatments
On October 31, 2018, the EPA made the long-awaited announcement regarding dicamba registration for use on dicamba-resistant soybean. I suspect opinions regarding the EPA actions are as varied as people’s views of the technology. Following are pertinent changes on the dicamba labels:
- People under the supervision of a certified applicator are no longer allowed to make applications.
- Applications are allowed only from 1 hour after sunrise to 2 hours before sunset (previously the restriction was between sunrise and sunset).
- Applications are restricted to 45 days after planting or prior to R1 stage of soybean, whichever comes first (previously the restriction was up to and including the R1 stage).
- Applications cannot be made if rain within 24 hours may result in soil runoff (previously the label stated not to apply if rain is expected to occur within 24 hours).
- The label clarifies what constitutes sensitive areas and where downwind buffers are required. The applicator must survey the area for sensitive crops and residential areas, and then not apply the product when wind is blowing towards these areas. It is up to the applicator to determine the appropriate distance between the target site and sensitive area. One of the more important changes is that the label states that managed or mowed areas adjacent to fields are now considered a non-sensitive area. Thus, the road right-of-way can be considered part of the 110 ft downwind buffer.
- There is a new restriction regarding buffers around the entire field in counties with endangered species. The specifics have not been posted at this time, but this probably won’t impact applications in most of Iowa. EPA has a website identified on the label that will have bulletins related to this restriction.
- Dicamba specific training will again be required for all applicators using the registered products on dicamba-resistant soybean.
I still have reservations about the ability to use dicamba postemergence in soybean with an acceptable level of risk to sensitive vegetation (Table 1). Restrictions related to wind speed, rainfall, and hours during the day when applications are allowed, provide few hours that are appropriate (legal) for application. The label changes for 2019 do little to reduce the risk for volatility; experience indicates that volatilization has played a significant role in off-target movement and injury. Preemergence applications of dicamba greatly reduce the likelihood of injury compared to postemergence applications, and this is our recommendation for the technology. However, I recognize preemergence applications reduce the value of dicamba on weeds with prolonged emergence, such as waterhemp. The potential for off-target movement increases as postemergence applications are delayed. When using the new dicamba products postemergence, the goal should be to complete applications by the V2 – V3 stage of soybean. Avoiding applications when temperatures are forecast to exceed 85°F within 24 hours after application will reduce the potential for volatility losses. Combining dicamba with a Group 15 herbicide (Dual, Warrant, Zidua, etc.) when it is applied early postemergence will prolong activity on late-emerging waterhemp.
Table 1. Pesticide misuse cases handled by IDALS
Total Group 4
The spread of multiple resistance weeds has greatly complicated weed management, creating the demand for new tools. Dicamba requires a much higher level of management than any other herbicide to be used safely. It is the applicator’s responsibility to follow all label requirements, and know what sensitive plants are in the vicinity of any Xtend field being sprayed with dicamba.Crop: SoybeanCategory: WeedsTags: dicambaXtend soybeanEPA
As the season approaches its conclusion and harvest conditions are most challenging, there are few things worth remembering to protect and sustain soil health. At this time, soil is susceptible to compaction due to rain and saturated soil conditions. Soils remain saturated longer at this time of the year since water use by crops is negligible and there is low water evaporation due to cool temperatures. Conventional tilled soil remain saturated longer than fields under conservation tillage since intense tillage destroys soil aggregates, resulting in reduction in water movement through the soil profile. A no-till system provides better, stronger and more stable soil structure, which allows water percolation deep into the soil profile to mitigate wet fall conditions.
Building soil health is a long-term effort which requires multiple practices to rejuvenate soil. Consider the following practices this season to improve your soil health to sustain yield, reduce soil erosion, and improve water quality:
- Monitor soil moisture conditions to make sure it is below field capacity before conducting any field operation, such as applying nitrogen, spreading or injecting manure, seeding cover crops, or attempting tillage. Soil at field capacity, where a handful of wet soil leaves noticeable moisture on your palm, is highly susceptible to soil compaction, reduction of water infiltration and an increase in surface runoff.
- Consider the use of cover crops to protect soil during the off-season. Cover crops have multiple benefits by physically protecting soil from water erosion, they stabilize soil structure through organic carbon input from the root system, and the extraction of residual nitrogen from the soil profile reducing its leaching potential to water bodies.
- Consider no-till or reduced tillage, such as, strip-tillage to keep residue on the soil surface as another measure for protecting soil and enhancing soil biological properties as an essential mechanism for healthy soil and efficient nutrient cycling.
- Lastly, consider updating your skills and knowledge on how to protect soil as your main capital or investment. Consider attending the 2019 Soil Health Conference held on February 4-5. This conference will offer a wide range of training, learning sessions and panel discussions by experts from several universities, the United States Department of Agriculture, as well as agronomists, farmers, and industry leaders.
Soybean varieties that are resistant to the soybean cyst nematode (SCN) have been a critically important tool for managing this pest. These SCN-resistant soybean varieties have allowed farmers to keep SCN numbers in check while producing profitable soybean yields.
The number of SCN-resistant soybean varieties that are available for Iowa soybean farmers has increased from less than 30 in 1991 to more than 1,000 in 2017(see figure below). Iowa State University compiles a list of the SCN-resistant varieties in maturity groups (MG) 0, I, II, and III for Iowa farmers every year in a publication titled “Soybean cyst nematode-resistant soybean varieties for Iowa”. The updated 2018 list has just been released and is available to download for free here.
There are 820 soybean varieties in the 2018 edition of the publication. That is 182 fewer than there were in 2017 (see figure below). And there are nine fewer brands offering SCN-resistant soybean varieties in the list than last year (28 in 2018 versus 37 in 2017). This is the fewest brands of SCN-resistant soybean varieties represented in the list since the 1990s.
Since 2006, about 97% of all SCN-resistant soybean varieties available for Iowa have had resistance genes from a breeding line called PI 88788. Prolonged, widespread use of varieties with PI 88788 SCN resistance has resulted in Iowa SCN populations developing elevated reproduction on varieties with PI 88788 resistance. There is great need for SCN-resistant soybean varieties with resistance from other breeding lines to slow the buildup of SCN populations that can reproduce on varieties with PI 88788 SCN resistance. The second-most common breeding line used to develop SCN-resistant soybean varieties is Peking.
Despite having fewer varieties and brands in 2018 than the past several years, the number of SCN-resistant soybean varieties with a source of resistance other than PI 88788 has increased in this year’s list. There are 35 varieties in this year’s list with SCN resistance from Peking, which is 4.3% of the total number of varieties and 7 more varieties with Peking resistance than were available in 2017.
Nine varieties in the 2018 list with Peking resistance are in MG 0-I, 23 in MG II, and 3 in MG III. This is the first year since 2000 that there has been more than one variety with Peking SCN resistance in MG III.
Number of SCN-resistant soybean varieties in maturity groups 0, I, II, and III for Iowa farmers – 1991 to 2018. The blue line represents varieties with resistance from PI 88788; the red line represents varieties with resistance from sources other than PI 88788 (primarily Peking).
Successful, long-term management of SCN requires an active, integrated approach that includes growing nonhost crops such as corn in rotation with SCN-resistant soybean varieties. Also, farmers should seek out and grow soybean varieties with different sources of resistance to grow in different years. And nematode-protectant seed treatments now are available to bolster the performance of SCN-resistant soybean varieties. Fields should be sampled in the fall prior to every second or third soybean crop to monitor SCN population densities. For more information about the biology and management of SCN, visit www.soybeancyst.info and www.thescncoalition.com.Crop: SoybeanCategory: Plant DiseasesTags: SCN managementresistant varieties
Late harvest and the rush to get grains out of the fields may present an opportunity to rethink the need for tilling fields this fall or not. The question to ask is, “Do I need to till this fall?” Given the economic and environmental challenges farmers are facing, the answer in most cases is no. With harvest under way, now is a good time to start thinking about this decision. Take into consideration your specific situation, and whether tillage will provide economic and environmental benefits. Be sure to consider the costs associated with tillage and the impact tillage has on soil health and water quality. Even though you may think tillage may be needed in certain situations and field conditions, a well-managed field and proper crop rotation may not call for tillage.
Two main considerations for making any tillage decisions:
- Soil conditions: It is important to take into consideration natural drainage, top soil depth, soil slope, organic matter, and soil texture. These factors have significant effects on how tillage affects soil health, productivity, and water quality.
- Management considerations: These include residue management, crop rotation, equipment availability and efficiency (planter suitability for different tillage systems, calibration of combine to ensure uniform residue distribution, etc.), drainage tiles for managing excess soil water, soil test and fertilizer management, suitable varieties for your area, and insect and disease control. These management decisions are equally important to determine the success of crop production.
Over the past 16 years, long-term tillage and crop rotation studies were conducted across Iowa. The studies document the most effective tillage and crop rotation combination for each region. Results showed a wide range of yield responses in corn and soybean for different regions, which reflect soil and climate conditions across the state. Also, the research shows that tillage systems did not affect soybean yields after corn. Soybean in no-till performed as good as or better than conventional tillage systems. Also, the research shows a reduction of $15-30/acre in input costs with no-till compared to conventional tillage systems (chisel plow, deep rip, and moldboard plow).
The choice of tillage for corn is more complex; careful consideration should be given to the soil’s long-term health and productivity as decisions are made. Research demonstrated that no-till and strip-till are as competitive as any conventional tillage system in well-drained soils or where field drainage is available to remove excess water in poorly-drained soils with corn after soybean (C-S) or continuous corn (C-C) rotation.
Benefits of No-till
Figure 1. No-till field after corn harvest
Conservation tillage systems such as no-till have a positive impact on soil health, productivity, and profitability under extreme weather events of wet or dry conditions. These systems protect soil, conserve energy and improve soil health by improving soil organic matter (0.17-0.23 ton carbon/acre/year increase with no-till). In addition, conservation tillage reduces costs associated with tillage operations by almost 17%.
Agricultural row cropping systems places significant stress on soil functions through tillage, chemical applications, and mono-cropping systems (i.e. continuous corn). Conservation practices, including no-till, cover crops, and extended crop rotations can mitigate the negative effects on soil health and productivity. A no-till system can restore soil health over time by improving soil infiltration, organic matter, microbial diversity, and soil structure. Extended crop rotations that include small grains, legumes, and cover crops will equally increase soil biodiversity, protect the soil surface physically during the off season, and provide organic carbon input.
There may be some challenges in managing corn residue, but tillage is not the answer. Modification of the planter to include residue cleaners, heavier down-pressure springs, or other residue management attachments are far more cost effective given the environmental cost and economic expense associated with conventional tillage.
The extended period of time when the soil has no living cover or residue in Iowa, presents a major environmental challenge that needs consideration when deciding on a tillage practice for this fall. Tillage can contribute to the acceleration of soil and nutrient loss given the uncertainty of weather events and their variability, as demonstrated yearly and most particularly this year from early wet season to late wet-fall.Crops: CornSoybeanCategory: Soil ManagementTags: no-tillSoil Managementconservation tillage
As of October 14, 2018, Iowa soybean harvest was only about 20% complete, making it the latest soybean harvest on record. This was caused by the prolonged heavy rains in September and early October. As a result, field losses, abnormally high harvest moisture content and moldy/weathered soybeans are all issues this year.Mold in the Field
Soybeans that have molded in the field have essentially lost their shelf life. They should be dried, preferably with air or very low heat addition, then marketed as soon as possible. Oil rancidity has started and likely will continue. An initial examination by shelling pods may look worse than justified, however. Often soybeans that have been weathered or molded in the field will appear somewhat better (lower visual damage) after a period of aeration. Surface mold and moldy pods may be removed by the combine. At an elevator or processor, most forms of mold or discoloration will Grade as Total Damage, for which 2% is allowed in US No. 1 soybeans and 3% in US No. 2 soybeans. Processors will discount at rates based on their markets for soybean meal and oil. River terminals (export) will probably adhere to the Grade limits because exported soybean will always be Graded by USDA-FGIS personnel. Each market may have an upper limit for acceptance. Crop insurance carriers can explain the effect of quality discounts and field losses on settlements. Be sure to get samples for adjustment purposes at the field, before placing in storage. The always needs to be clear proof of loss in the field.
Some examples of mold and related field losses:
Photo courtesy of Austin Miller.
Storage and Handling
Photo courtesy of Meaghan Anderson
Refer to the maximum storage time table for corn and soybeans below to estimate storability based on temperature and grain moisture content. Example, if soybeans harvested at 15% moisture sit at 60°F for six weeks, approximately one-half of their storage life is used up. If they are then dried to 13% moisture and held at 50°F, they have a maximum of (1/2 x 16) 8 months of storability remaining before they are likely to drop by one U.S. grade. Generally soybeans have storage properties of corn about 2% points wetter (15% moisture soybeans = 17% moisture corn in storage properties). The table values are reduced sharply if the soybeans have already molded in the field.
Air drying is best if possible. In Iowa, an airflow of 1 cfm/bu will dry to about 18% moisture soybeans. Normal October air conditions in Iowa will dry beans to 12-13% moisture. Addition of heat will dry to much lower levels; soybeans are very sensitive to air humidity. Because harvest is late, there is a possibility that air drying will not be completed in the fall. If this happens, either market the grain or cool it below 30F, with the expectation of resuming drying in the early spring.
For bin dryers, very little heat is recommended. Stirring devices that control overdrying in corn may create splits and remove hulls. In continuous dryers, limit the grain temperature to 120F or less. Heat causes cracking and removal of hulls. Gas fired burners are well known for fire potential in soybean drying. Hulls ignite easily; the soybeans are 20% oil, which then are very difficult to extinguish.
The potential for in-field drying is diminishing daily. At the same time, field loss will increase from split pods and molded soybeans. Field loss will not be captured in production records. It may be best to harvest soybeans as soon as possible regardless of moisture, and even if bins previously identified for corn have to be used temporarily. Also, estimate the cost of drying the wet beans on the farm and then delivering compared to the current price and shrink deductions at the local market.
For additional information on soybean drying, please see publication PM1636, Soybean Drying and Storage.Moisture Measurement and Shrink
Normally moisture testers and yield monitors are quite accurate in measuring soybean moisture. Moisture meter inspection data show that differences among tests are often less than 0.25 % points. However, wet soybeans are not often tested. The meters at an elevator or processor are checked annually by the State of Iowa. The new USDA meter technology that is widely used in trade is as accurate in high moistures as in lower moistures 13% and below. Check and correct your yield monitor or hand-held meter reading against the buyer’s meter on at least three samples of wet beans.
Since yield monitor data is now reportable as a measure of production for crop insurance, it is very important to recalibrate the weight measurement every year according the manufacturer’s instructions. Production records are subject to audit; documented moisture and weight calibration would be part of any audit. This year’s corn and beans have different characteristics than last year; including calibration data from this year’s crop will be especially important to ensure accuracy.
Soybeans are normally sold on moisture standard of 13%. In a normal year, most soybeans would be delivered at lower moisture than 13%, so moisture level would not influence either the price or the listed bushels on scale tickets, warehouse receipts, settlement sheets or insurance production records. In 2018, the weight adjustment for grain with moisture content over 13% will be important.
The weight loss for the water in drying to 13% is 1.15% percent moisture, regardless of starting moisture other quality conditions. Typically in any grain drying and handling situation about 1% of dry matter is lost due to breakage, dust, spillage and other sources. For example, 16% soybeans would shrink by (3*1.15+1.0) = 4.5% if dried to 13% moisture and placed in storage. Any shrink deduction larger than that is a discount or discouragement to delivery of wet beans. However, if the weight itself is reduced more than actually experienced, records that rely on accurate statements of bushels would be affected, such as warehouse receipts, crop insurance APH calculations, and the tariff compensation payments. Iowa grain dealers are required to post their weight shrinkage scale, and to use the same scale for all grains (eg corn and soybeans).
If you anticipate delivering significant amounts of wet or damaged soybeans, check closely with your soybean merchandiser about the specifics of their dried weight calculations, and about their damage discounts, which may change quickly due to processor response. Most farmers purchase multi-peril crop insurance on their soybeans annually. Three additional steps to take when soybean quality concerns emerge include:
- Contact your crop insurance agent within 72 hours. The insured could be eligible for a quality adjustment as a part of insurance coverage. The minimum damage for loss is 8% for soybeans, 10% for corn. These are levels that would make the grain Sample Grade (not within the numbered Grades). An adjuster will likely be assigned and/or samples will need to be collected in-field, in the bin and prior to delivery to the market. The in-field samples are the most critical is establishing settlement amounts. Consider using an Official FGIS grading agency for determinations.
- Keep good records at harvest. This includes yield monitor data (calibrated with documentation), scales on grain carts, or scale tickets. These records are deemed “soft records” by the Risk Management Agency. These same records can be used for the new Farm Service Agency (FSA) Market Facilitation Program (MFP) payment. Should a crop insurance loss occur, then “hard records” such as grain bin measurements, warehouse receipts, or settlement sheets would be required.
- The revenue protection crop insurance that most Iowa farmers utilize provides a guaranteed price for an insured’s Actual Production History (APH) bushels. For 2018, the guarantee is the insured’s APH bushels times the level of coverage elected times the spring projected price of $10.16. Provide production evidence to your agent as soon as soybean harvest wraps up so potential indemnity claims can be determined. This same information can be provided to the FSA when applying for an MFP payment. You need not wait until corn harvest wraps up to file production evidence for soybeans.
This is a stressful harvest that could have several issues needing resolution. Use good communication skills when working with your ag service providers.Summary
Conditions of the 2018 soybean crop are very unusual. Harvest went from potentially abnormally early to the latest on record in just over a month. In-field quality has decreased, harvest losses have increased, and high moisture beans present both a handling and marketing challenge. ICM News will provide updates as needed.Crops: CornSoybeanCategory: Grain Handling and StorageTags: soybean qualitymold damagemarketingcrop insurance
Above normal rains in September have slowed field crop dry-down. Coupled with early season drought in South Central and Southeast Iowa and above-average rainfall in the Northwest, there is high risk of reduced grain quality. Corn and soybeans remaining in the field are currently exposed to excessive moisture that encourages the growth of ear molds. Moldy kernels are counted in total damage, thereby affecting the overall grade of the corn. Additionally, if the fungus is capable of producing mycotoxins, affected grain may be subject to marketing restrictions.
Not all fungi produce mycotoxins. Ear rot identification is key to assessing if and for which mycotoxins you are at risk. Check out Crop Protection Network’s document CPN-2001 Corn-Ear Rots found in their online library. Generally, be watchful for vomitoxin (also known as deoxynivalenol or DON) and zearalenone in the northern half of the state—these two mycotoxins are produced by the same fungus. Aflatoxin and fumonisin are the predominant risk in the southern portions of the state. Sporadic risk exists in between with cool, wet growing conditions favoring vomitoxin and zearalenone and hot and dry conditions favoring aflatoxins or fumonisins. If weather hinders harvest, consider scouting fields to assess the presence, extent and severity of fungal-infected ears. Suggested scouting methods can be found in Section 6 of the document CPN-2002 Mycotoxin FAQs Crop Protection Network document and in the section “How to prevent aflatoxin in corn” found in the Aflatoxins in Corn document.
Harvest and Post-Harvest Management
Fusarium ear rot-fumonisin risk
Adjust combine settings to minimize damage to grain. High dewpoints are limiting storage aeration and mycotoxin levels can increase rapidly in high moisture corn. One research study reported a 77% increase in fumonisin levels in 25% moisture corn over seven days . When possible, utilize a dryer that will reduce moisture content rapidly prior to grain storage. Avoid overheating to the point that stress cracks develop in the kernels, as these are entry points for fungus through the seed coat and into the interior of the kernel. Recommended maximum limit for kernel temperature is 180°F. Mycotoxins will not decrease in the field or in storage, but they will get worse if grain is not maintained properly.
The maximum storage time table below provides estimates for grain storability at various moisture and temperature combinations. These recommendations are for sound, good quality grain; storage times for poor quality or damaged grain should be reduced by about half. Example, 18% moisture corn which has a high incidence of field mold would have a storage life of only 1.7 months at 50°F compared to sound, high quality 18% moisture corn which could be stored at the same temperature for about 3.4 months. Mold and mycotoxin issues tend to be worse on broken and damaged kernels and fines relative to sound, whole kernels. Core bins (without a spreader) to remove the majority of broken kernels and fines (the highest-risk portion) and to improve bin airflow. Document CPN-2004 produced by the Crop Protection Network is an excellent resource on best management practices from harvest to storage for at-risk grain. If aflatoxins are a significant issue in your fields, crop insurance adjusters will want to see the affected corn still in the field.Sampling and Testing
Mycotoxins tend to occur sporadically throughout a field and among kernels on an ear. The level of mycotoxin contamination also varies greatly among the individual kernels on an ear. Representative sampling is crucial to achieving an accurate mycotoxin test result. Ideally samples are comprised of kernels obtained from throughout the lot (e.g., from multiple locations/units, representing many ears) be it a field, a bin, or from a composite of multiple grain deliveries at an elevator. It takes relatively few kernels to contaminate a load at a level that would incite marketing restrictions, so enough grain must be collected to ensure you have a chance of sampling those affected kernels. Obtain at least two pounds of material and, ideally, 5-10 pounds if feasible. Larger samples of whole kernel material provide greater lot representation. A scoop of corn off the top of a truck will not accurately depict the whole load. Data from individual loads is notoriously more variable than a composite of multiple loads in a time period. Likewise, for bins, a composite acquired from throughout the bin will yield a more true result than a single probe taken from one location.
After a representative sample is collected, it can be prepared and analyzed in-house or sent to an external testing lab for analysis. Whole kernel samples can be submitted for analysis to a regional FGIS location or to a state-affiliated or private laboratory near you for analysis. The Iowa State University Veterinary Diagnostic Laboratory typically accepts submissions through veterinarians, but will run fee-for-service mycotoxin analysis samples for others after setting up a billing account. Mold growth and mycotoxin content may continue to increase in high-moisture grain samples between the time of collection and analysis. Ideally, take subsamples of grain from out of the dryer until a representative sample of sufficient size has accumulated. A variety of rapid test kits are available on the market for in-house analysis (some of which have gone through a FGIS rapid test kit evaluation program). One key step often misinterpreted is the sample size used for analysis—this is not the amount that is ground. After the two to ten pound sample is collected or received, that entire sample should be ground followed by subdivision using a divider to obtain the amount of ground sample needed to run the analysis. Remember that a test result is only as good as the sample from which it came. It does not matter if your sample is analyzed by the simplest or most complex analysis method—if the whole corn and ground analysis sample is not representative of the entire lot, your test result will be uninformative and useless.Summary
Wet conditions and lodged corn have created mold and sprouting issues in the 2018 corn crop still in the field. This may create mycotoxin issues in addition to moldy corn. It will be important to dry and cool corn as rapidly as possible. If mycotoxins are suspected, a well-planned representative sampling process will be needed to give useful information for processing and feeding.
Aside from those linked earlier in the article, some other mycotoxin resources include:
 Blandino, M., et al. Control of mycotoxins in corn from the harvest to processing operations. Purdue University.Crops: CornSoybeanCategory: Grain Handling and StorageTags: mycotoxinscorn quality
Rain events during September and October have created challenging conditions not only for timely harvest of corn and soybean crops but also for the impact harvest will have on the soil. These wet conditions coupled with a drop in air temperature will slow harvest operations. Soils are too wet for traffic from heavy equipment, making them susceptible to compaction during harvest operations. When soils are near saturated conditions, heavy equipment loads weaken soil structure where water works as lubricant, leading to the collapse of soil aggregates. This will cause significant surface compaction, rutting, and deep subsoil compaction.
Damage from soil compaction can have significant impact on water infiltration, root development, and ultimately grain yield the following season. It is generally estimated that yield loss due to soil compaction caused by wheel traffic ranges between 10-20% depending on the extent of soil compaction experienced. Over the past decade the size of Iowa farms has increased, leading to larger and heavier equipment. An axle load from a 12-row combine with full grain tank is estimated at 26 tons/axle and a single-axle fully loaded grain cart is estimated at 22 tons/axle.
Avoiding field conditions prone to soil compaction will likely be unavoidable this fall as farmers make an effort to get grain harvested without further field pre-harvest yield losses and worsening grain quality. Soil compaction will be worse the wetter the soil conditions are. Care should be taken to avoid wet and near saturated soil conditions; ideally, field operations would be delayed until soil water is below field capacity. Tillage energy, time, and costs could increase a hundredfold to remediate excessively compacted soils during harvest operations.
Tips to minimize soil compaction during and after harvest
Ruts made when harvesting soybean under saturated soil conditions.
- Dedicated travel lanes. Many combine operators use “on-the-go” unloading into a grain cart to speed harvest. In areas that have received excessive rainfall since Sept. 1, farmers may want to consider having dedicated travel lanes for the grain cart. It has been documented that 60-80% of soil compaction occurs from the first wheel passes, subsequent field operations account for a much smaller amount of compaction.
- Don’t run at full capacity. Reduce the axle loads of both the combine and grain carts by not loading them to full capacity. This may not be an attractive option in high-yielding cornfields and where harvest has already been delayed. This is much easier to implement in soybean where the grain volume is much less than corn. A compromise may be to try and keep axle loads lower in the far reaches of fields and achieve the highest axle loads (full capacity) nearest the end rows where grain will be transported out of the field.
- Tire size and inflation pressure. Use appropriate tire sizes for the conditions and adjust tire air pressure to match the axle load being carried. Larger tires with lower air pressure provide more surface area, allow for better flotation, and reduced pressure on the soil surface.
- Concentrate non-harvest field activates near the point of exit from the field. While it is tempting to move semi-trailers and tractors with wagons along the field edge as harvest continues, this practice increases compaction along the end rows.
- Harvest around the wettest areas. The wettest areas are the most at risk for soil compaction but are also an accident risk that ultimately could lead to longer harvest delays. Additionally, buried equipment may come with large financial penalties. Come back to these areas later in the fall once the soil conditions are drier or have frozen.
- Avoid or minimize tillage. Remember to hold off tillage operations until soil conditions are drier than field capacity. It is important to consider the soil moisture at the depth of tillage. Tillage in wet conditions results in further compaction and smearing of soil instead of the intended fracturing of the soil. If it is absolutely necessary to cosmetically fill in ruts, use a disk unless soil conditions are dry enough for fracturing of the soil through use of more aggressive implements.
In wet conditions, the best choice farmers can make is to stay away from the field and avoid traffic on wet soil to reduce soil compaction. How you approach fieldwork after a heavy rain event can impact your soil for future growing seasons. More consequences of soil compaction can be found in Top 10 Reasons to Avoid Soil Compaction.Easy test to check soil conditions for field operations
Most of Iowa's soils have medium textures. For these soils, a simple method of checking soil moisture is the "feel" method. Probing the top 12-18 inches with a hand soil probe to assess the field's soil moisture conditions is time well spent.
Check the soil moisture status by pushing a ribbon of soil from between the thumb and index finger. If it breaks off within one or two inches, the potential for creating compaction is less. However, if the ribbon stretches out to four or five inches, it is still too wet. The chances are good that being in the field under these conditions may cause more problems than it will solve.
Another soil consistency test is to roll soil against the palm of your hand to determine if it will clump and roll or if it is fragile and falls apart. Soil that clumps together is more prone to compaction.Additional Resources:
Crops: CornSoybeanCategory: Crop ProductionSoilsTags: soil compactionyield losstillage
This year continues the chain of years with unusual harvest conditions driven by rapid weather changes in the latter part of the growing season. In mid August, crops were significantly ahead of schedule in terms of maturity. Heat and moisture in May and June accelerated the pace of development, to the point that signs of maturity were evident by the 15th of August. Rains followed by above average temperatures began over Labor Day weekend, and have been repeated nearly every weekend to date. The forecast for the weekend of October 7 is more of the same – very heavy rains with intermittent warm, sunny and high humidity periods. The 2018 crop is now at a point where the wet conditions are affecting quality.
In some areas, flooded streams inundated mature crops. Please see this ICM News article written on September 27, for guidance in handling these crops.
Corn moisture contents vary widely but field mold is showing up. Most field molds grow on corn after blacklayer; rapid drydown normally prevents significant further problems. Fields should be scouted for molds because some species have the potential to produce mycotoxins. Those fields should be harvested as quickly as possible, and dried rapidly without a long period of wet holding. Field molds normally do not grow in storage after drying but wet holding and slow drying can cause growth and toxin increases before the corn is dry. The lower temperature and air drying systems will have difficulty in the weather conditions predicted to continue for the next 10 days. Run bin dryers as warm as manufacturer recommendations allow, and try to fill bins in stages to reduce depth and increase drying rates in individual bins. Rotating fills may require documentation for crop insurance purposes, to identify grain traceable to specific fields.
Good descriptions and photographs of field molds, mycotoxins and their impacts are available at https://cropprotectionnetwork.org/library, in the training modules section.
- CPN-2001 Corn Ear rots
- CPN 2002 Corn Mycotoxin FAQs
- CPN 2003 Corn Grain sampling and mycotoxin testing
- CPN 2004 Storing mycotoxin-affected grain
A two-part narrated presentation on mycotoxin effects on animals and on handling and management for toxin-affected grain is available on the Iowa Grain Quality Initiative website.
A recommended scouting/sampling procedure for mold identification is given below:
- Check at least 100 ears selected from throughout the field.
- If more than 10 percent of plants have an ear rot, harvest the field early.
- Dry and cool harvested corn quickly.
- Test moldy grain for mycotoxins before feeding to livestock
This year, the highest risks for mycotoxins are for vomitoxin (DON) in northern and SW Iowa, and for some aflatoxin in SE Iowa (where drought conditions prevailed until after Labor Day).
Photo on left: Aspergillus flavus (aflatoxin) on an ear, Photo on right: Giberella (vomitoxin) on an ear
The longer the wet weather persists the more risk of mold and toxins that there will be. The moderately warm temperatures forecast for the next 10 days will accentuate mold growth. Moldy grain does not automatically contain mycotoxins; some species are not toxigenic, and not all toxigenic species always produce toxins. This is why end users (ethanol plants, feed mills, wet mills) will be screening composite samples of early harvest deliveries to determine if there are concerns. The often-present “polka dots” from Cladosporium are an example of field mold, that will grade damaged but that does not produce a toxin.
Stalk strength is low; there will be increasing amounts of downed or broken stalks. Harvest downed corn first regardless of moisture content because mold growth is accelerated, and drydown rates are reduced. Consider cleaning this corn if possible because the larger mass of material through the combine will create more airflow clogging fines and foreign material. It is always recommended to remove the center of bins before long term storage. That need will be greater this year.
General corn quality is average at best, as indicated by test weights. The kernel fill was not as complete as last year; dry corn test weights probably will be around 54-56 lb/bu. This still meets grade standards but expect a shorter storage life than last year. Because of reduced fill and kernel size, protein contents will probably be below the 7.5% long term average. The critical management actions this year will be rapid drying without long holding periods and cooling as quickly as possible to preserve future storage life. Always, actions right at harvest are the most crucial in determining future quality the following spring and summer.
The table below shows the time-moisture and temperature relationship for safe storage.
Both temperature and moisture content are important in grain preservation, but often temperature control is the most immediately important if drying capacity is limited.
Soybeans experience fewer in field mold problems than corn, because field moistures are normally low (<13%). However, if the soak-dry cycles continue with more heavy rain, expect pod splitting and eventually grey colored beans. Freeze-thaw cycles would further accentuate the splitting but currently there are no forecasts for frost in the near future. Do not try to store field molded soybeans; the oil will become rancid and continued deterioration is likely. The grey beans will grade damage in the market, but likely will get worse in storage. Aerate them for cooling, then market them as soon as possible.
The same needs for removing the center core of bins and dropping the temperature as rapidly as possible apply to soybeans as corn. Notice in the storage time table above that soybeans spoil at a rate equal to 2% points wetter corn. Soybeans are normally 13-14% or less in the field.
Soybeans are often stored in unaerated bins or buildings; this removes both the cooling and drying capability of aerated bins. Wet fields and warm temperatures may require special handling to be sure that beans in unaerated bins are cool and dry.
None of these wet-conditions problems affect grain yield; that was established earlier in the growing season. The predicted high yields and corresponding long term storage will make at-harvest management very important this year. Future ICM articles will update these issues, and identify long term storage management needs as weather conditions develop.Crops: CornSoybeanCategory: Grain Handling and StorageTags: grain storagemoldwet conditions