Soil microbes & crop fertility: the missing link?Craig Dick, Director of Wholesale at Midwestern BioAg, explains how soil microbes hold the key to organic matter formation and enhanced nutrient retention and efficiency.
When formulating a fertility plan, growers take many factors into consideration. These may include crop removal, soil tests, yield goals, cropping rotations and more. The process can be complex, especially since some of the largest impacts on crop performance – weather and soil health – are challenging to manage, at best. What recent soil science has taught us, however, is that soil health is a key driver of fertility and profitability. While growers cannot plan for floods or drought, good soil management can help all farms improve soil health, nutrient efficiency and plant uptake.
Fertilizer Solubility & Availability
In most states, NPK crop fertilizers are labeled using the percentage of total available nutrients in blends. This is the percentage of applied nutrients that are water-soluble, and immediately plant-available, upon application. Soluble nutrients are necessary to support early crop growth and yield potential, but additional nutrients are also needed throughout the season to
maximize crop yield potential.
“When we apply nutrients in soluble forms to the soil, the risk of nutrient loss and leaching increases,” said Craig Dick, Director of Wholesale at Midwestern BioAg. “However, what we’ve learned is that soil management with a focus on improving soil life and structure can help us capture more applied nutrients and boost profitability.”
When fields are managed for optimal soil conditions, soil porosity and aggregation improve. These are the conditions that allow beneficial soil life to flourish. “Deep tillage and harsh crop inputs can damage soil life,” said Dick. “When this occurs, we miss the opportunity to use soil microbes to our benefit.”
Soil Organic Matter: Your Nutrient Bank
Soils are often rich with nutrients stored within soil organic matter (SOM). Other nutrients can be bound to soil calcium, aluminum or iron, unavailable for plant uptake. Unlike soluble nutrients listed on fertilizer tags, these nutrients are not accessible to plants. However, when soil conditions allow for thriving microbial populations, microbes can cycle nutrients from organic matter into plant-available forms and release nutrients that are chemically bound within the soil.
“Think of soil organic matter as your farm’s nutrient bank,” said Dick. “Just like how bank tellers can deposit a personal check and return with cash, soil microbes can turn organic matter deposits into plant-available nutrients. Banks are only as good as their systems and staff. Soil works much the same way.”
Emerging Research Suggests Microbes Build Soil Organic Matter
It’s well understood that when present, soil microbes break down SOM and release valuable crop nutrients. However, emerging research indicates that the relationship between SOM and microbes may be more complex than previously thought. “Established soil science suggests soil organic matter is formed from decaying plants and residues,” said Dick. “However, recent findings from the University of New Hampshire show organic matter is formed as microbes breakdown plant residues – not directly formed from plants residues themselves.”
In the study, soil microbes generated SOM in the absence of plant residues. Even when fed only table sugar, SOM created by microbes was nearly identical to naturally formed SOM from the field.
“This research may revolutionize how farmers build organic matter, and stored nutrients, in their soils,” said Dick. “However, many of the same management practices that build organic matter also support soil life. When we focus on preserving and rebuilding soils through reduced tillage and careful input selection, healthy soils will follow.”
Research will continue to build on the industry’s understanding of soil health, but the benefits of healthy soils remain the same. When soils are managed for optimal soil conditions, growers can optimize SOM formation, crop yields and plant resiliency.
- With this week’s forecasted low temperatures projected to dip into the high 30s (°F) with potential rain events, growers have asked if/how germination will be affected for corn and soybean planted this week.SummaryImbibitional (fast) water uptake occurs within the first 48 hours after a seed is planted. Once planted, corn seeds need a two-day (48-hour) window and soybeans need at least a 24-hour window when the soil temperature at planting depth does not drop much below 50°F. When the soil temperature drops much lower than 50°F within that time frame, there is potential for chilling injury to affect seed germination and seedling growth. Soil temperature decreases after this time are less likely to affect seed germination.Key ConsiderationsCheck the weather forecast and soil temperatures for your area. It’s also important to check the soil temperature of each field the morning you intend to plant. (This can be done with a meat thermometer.)Second, check on your seed tag or with your seed dealer regarding the cold tolerance of your corn hybrids/soybean varieties. Hybrids and varieties vary in cold tolerance and company rating scales differ. However, be aware that imbibitional chilling is a physical phenomenon that can override genetics.An inexpensive meat thermometer is being used to check soil temperature in an individual field.Cold Stress in CornWhen corn seeds imbibe (take up) water, cell membranes stretch and cells expand. When a damaged cell membrane rehydrates, it may not return to its normal shape and size. This can create a “leaky” cell. Water is at its densest at about 39°F so when cold water is imbibed, it may result in additional membrane damage. These ruptured membranes may occur in the cell walls and in the mitochondria. In the plant this action may disrupt the embryo/endosperm enzymatic conversion to energy, but mostly results in leakage of cell solutes and sugars. This, in turn, is likely to reduce growth rate and interfere with growth of the emerging seedling.
Cold Stress in SoybeanSoybean germination consists first of a very fast uptake of water (imbibitional phase) followed by a much slower uptake of water (osmotic phase). Chilling during the first phase can cause severe problems because the imbibed water is needed to rehydrate the cotyledons and embryo to the point that cell membranes become functional. Cold temperatures interfere with proper hydration of those membranes.
- Debate exists about what specific temperature and timing causes imbibitional chilling. However, corn plants that imbibe cold water (in the low 40s) in the first 48 hours after planting undoubtedly are affected.
- Planting when soil temperatures are above 50°F alleviates concerns of imbibitional chilling affecting corn emergence. Some scientists suggest that corn will not be injured at soil temperatures as low as 41°F; however, there is certainly some risk of injury from imbibitional chilling at those low temperatures.
- For best results, begin planting corn when soil temperatures are in the high 40s and the short-term forecast calls for warm days that will continue pushing soil temperatures higher. If soil temperatures are in the high 40s and the weather forecast calls for cold wet conditions within the next 48 hours, soil temperatures will likely drop and planting should be delayed until temperatures warm.
- The imbibitional phase is typically not very long (usually less than 24 hours) and can occur with relatively little soil moisture since the seed is dry at planting. Thus, getting a cold rain within 24 hours after planting can lead to soybean chilling injury and thus lower stands.
- Chilling injury is likely greater if soil temperatures were cold (less than 50° F) at planting rather than becoming cold 24 or more hours after sowing. Chilling injury occurs with temperatures of less than 50°F within 24 hours of planting; germination failure and seedling death occur at soil temperatures around 40°F. The longer the seed is in the ground at warm soil temperatures before cold temperatures occur, the less chance there is for chilling injury.
- Saturated soil with cold temperatures significantly reduces germination rate, thus fungicide seed treatments are recommended if planting in April or early May.
- Bottom line: Plant your soybeans if you think the soil temperatures won’t get cold (less than 50°F) for at least 24 hours. If you planted two or more days before the cold rain, there should be no imbibitional injury due to cold temperature.
During the second phase of germination, the fully functional membranes (after imbibitional hydration) create an osmotic situation in which water diffuses into the living cells. Osmotic water uptake is slow with cold temperatures. Chilling during this phase causes little direct injury to the germinating seedling. Cold temperatures will, however, slow emergence.In conclusion, check the weather forecast, soil temperature, and hybrid/variety cold tolerance before planting. The first 24- and 48-hour periods are critical for soybean and corn, respectively, if soil temperatures dip much below 50°F. Monitor your fields based on planting date throughout the year to determine any affects on plant stand and yield.
This week I received phone calls from several growers asking about the planting intervals for corn and soybean following 2,4-D/dicamba applications in a burndown program. With cold, wet conditions in March, many producers may be facing a smaller than expected window for making their herbicide burndown applications in April. This makes timely applications now even more important to provide for a proper interval before planting this year.
Dicamba and 2,4-D are commonly used burndown herbicides for control of winter annual broadleaf weeds such as dandelion, field pennycress, henbit, tansy mustard, etc.
Additionally, several summer annual weed species in Nebraska emerge early in the season, prior to planting corn and soybean, and need to be controlled before they grow too large to be effectively controlled.
Of particular concern are giant ragweed, kochia, and marestail; we believe there are numerous populations of these species in Nebraska that cannot be controlled by glyphosate because they have evolved resistance to glyphosate. Therefore, use of 2,4-D/dicamba has increased in recent years, particularly for control of glyphosate-resistant marestail and giant ragweed. Based on observations in our giant ragweed research studies, we have had success controlling glyphosate-resistant giant ragweed with any herbicide program containing 2,4-D as a component of a burndown program.
If you apply 2,4-D prior to planting, be sure to adhere to the planting interval specified on the label. Several 2,4-D products have different planting intervals for soybean, somewhere in the range of 7 to 30 days depending on application rate.
As a general guideline, the following planting intervals should be maintained for corn and soybean after applying 2,4-D/dicamba
- If soybean is to be planted this year, do NOT apply dicamba. XtendiMax, a new dicamba product with VaporGrip Technology, can be applied in burndown application, but only if planting Roundup Ready 2 Xtend Soybean this season.
- If 2,4-D is applied at 16 fl oz/acre in a burndown program, the planting interval should be seven days for corn and soybean
- If 2,4-D is applied at a rate above 16 fl oz/acre in a burndown program, the planting interval should be 14 days for corn and 30 days for soybean
- If dicamba is applied at 4 oz/acre in a burndown program, the planting interval for corn should be five days. If dicamba is applied at 8 oz/acre, the planting interval for corn should be seven days. DiFlexx and DiFlexx DUO are dicamba products with CSI safener; therefore, corn can be planted any time after application of these products, which may be particularly helpful in a replant situation. Care should be taken, however, so that corn seed does not contact the herbicide.
Source: Amit Jhala, University of Nebraska CropWatch
ProAg Soltuions welcomes two new employees to our team!
We are excited to have added Jacob Haugen and Jodie DeVries!
Jacob Haugen will be customer service, delivery, warehouse, and application. Jacob is a 2016 DMACC graduate.
Jodie will be office assistant, sales, and precision ag. Jodie came to us as a 2017 ISU graduate.
Fungicide on corn is not only used to treat disease, but also for plant health. Fungicide increases standability and keeps the plant alive longer during the grain fill stage. Fungicide continues to prove itself as a great return on investment as it increases yield 12+ bushels year in and year out. Watch this quick video to see the benefits of fungicide for yourself!
Cant save your way into prosperityData collection can lead to a customized fertility approach to your farm rather than using a “state average” ratio.
Sometimes life events leave a mark for generations. The Great Depression created generations of frugal farm family survivors. Feeding a family was a challenge – holding on to a farm was almost impossible for many. The “frugal stamp” wasn’t just left on the parents but their children and many times passed on to another generation.
Did your grandmother save everything? Save leftovers – not in Tupperware but in leftover butter or other plastic food containers? Save old jeans to have material for future patches. Did your grandfather save pieces of old lumber for the next project? One of the most popular radio talk shows, hosted by Dave Ramsey, encourages being frugal to climb out of debt.
In tight economic times, it’s easy to want to take a frugal approach on crop inputs. In the November issue of CSD, an article highlighted DuPont Pioneer’s findings that many fields sampled have below optimum soil test P and K levels, with their expert calculating over $4 billion in lost revenues for growers.
The elephant in the room is the negative impact that high cash rents can have on maintaining the productivity of many farms. In most markets, the competition for land is so fierce that growers resort to penny-pinching on P and K applications. Many don’t want to leave any nutrients for the next renter if they get out-bid.
The article also highlighted the new higher-yield reality of how much has to be applied to keep up with nutrient removals. The “old” shotgun of 400 lbs. of dry fertilizer every other year can mine soil test levels quickly.
I believe the yield loss associated with being frugal is far more significant than most agronomists and growers realize. I believe that for many growers the “optimum” soil test level is even higher than university definitions of “optimum.” This chart shows one way to analyze data across a grower’s 1,700 acres of soybeans – examining the relationship between low to high yield acres and the corresponding soil test P and K levels.
If these were your yield results, what would consider your optimum soil test levels? That’s the power of your data – it can lead you to customize your approach to what is best on your farm versus a state-wide average.
There are many strategies to address the fertility needs of the crop. Strip tillage and deep banding of nutrients is a great way to compensate for low fertility fields and maximizing return for nutrient dollars invested. Irrigated sand requires that we spoon feed nutrients.
For most nutrients, feeding the crop is a combination what we apply, including manure, and what the soil supplies. We shouldn’t measure our success by whether we raised soil test levels but by our yields and cost/bushel. I believe your data will lead you to find the balance in your approach to input decisions. In corn and soybean production, you can spend yourself poor but you can’t save yourself into prosperity.