The death of a soybean plant follows a pre-determined path. You first notice a few yellow leaves on plants. Then several more yellow leaves follow with the leaves rapidly falling off the plant. At this time if you walk through a soybean field if you touch the petiole still attached to the stem it will break off the plant with just a light touch. Stems go next.
The plant is simply digesting all available starch and minerals remaining in tissue in order to maximize grain fill. When we hear complaints of green stem in beans at harvest this typically is associated with higher grain yield as the soil was able to mineralize more nutrition late season and provide beans a more peaceful end.
Later this summer, soybeans in their early reproductive stages will similarly march toward
self-destruction, believing the short-term goal of filling seeds is aligned with your broader production targets. Soybeans will sacrifice roots and abandon nodules at late V5 and V6, cutting off nitrogen supply. Leaves, unable to maintain protein, will lose photosynthetic capabilities and, in turn, be cannibalized to fill beans. Yields will retreat from what they could have been if they had better command of the plant’s resources.
Plant development must include a balance of resource allocations. Some resources should be used for immediate needs, while others maintained for future plant needs.
In the soybean plant at R3, a balancing act should occur with sugar. The plant has an immediate need to develop pods and nourish developing seeds. At the same time, the plant must invest in roots and nodules for nutrient uptake and nitrogen fixation to produce new leaves that make sugar to fill future pods and seeds.
However, too often at R3, a soybean plant fills the first seeds and invests in the future. It doesn’t maintain roots. It doesn’t make new leaves. It raids nutrients from existing leaves to move them to seeds. Early-setting seeds, seize all the sugar they can get, then release a barrage of hormones that force pods to abort.
A soybean plant exemplifies this poor strategy for two reasons. As a legume that requires far more nitrogen than corn for grain fill, it’s decision to prematurely stop support for the roots and nodules that supply this nitrogen has a dramatic effect on crop yield and quality. Secondly, soybean yield is not determined early, like corn. Late-season behavior continues to affect seed number and yield.
What can be done about it? As growers we may better command these processes with soybean finisher products that improve crop growth and seed production. Unlike many other yield-improving practices, these new technologies are deployed later in the season, instead of being crammed in with other early-season applications.
Our most fundamental tactic is to ensure soybeans have adequate nutrition. Potassium, manganese and boron are critical in maintaining leaf tissue and the adequate movement of sugars throughout the plants. Micronutrients are best fed through the leaf; in dry soils, foliar potassium is important.
Supplemental nitrogen can be used and may increase the amount of nitrogen as protein harvested with the crop. Beans use about 6# of N for each bushel produced. However, mid to late season N applications have been highly inconsistent providing return on investment.
Plant growth regulator gibberellin will help facilitate sugar movement to roots, while auxin and salicylic acid (aspirin) will suppress production of ethylene – a gas that triggers plant stress responses, including leaf senescence (death). Properly timed foliar fungicides have also demonstrated ability to reduce ethylene senescence as well.
In the future, the solution to soybeans that mature too soon may be to “apply two aspirins and call me when your bin is full.”
Progressive Crop Technology offers a late-season nutrient product, PCT Soybean Finisher to consider.
Learning about nutrient availability from tile linesAs wet weather continues this season, the positions of tile lines are abundantly clear. Crops over those lines are darker, larger and more robust than crops between the lines. This variation illustrates differences between the presence and bioavailablity of nutrients.
A soil test measures the concentration of available nutrients per unit of soil. Many (arguably, too many) years ago, the relationship between crop yield and nutrient concentrations were quantified; these relationships continue to be the basis of modern recommendations.
However, adequate nutrient test levels do not guarantee availability throughout the season. Compaction and dry weather can limit root growth, nutrient solubility or even movement within the plant.
This year we can see how excessive moisture is depriving plants of the oxygen and energy they need to concentrate nutrients in roots. With the exception of well-drained sections over tile lines, plants are pale, stunted and starving.
Presumably these fields received fertilizer at either a straight rate or a variable rate that matched fertility with production goals. Either practice should have ensured enough nutrition for plants across the field. But while nutrients are present in adequate amounts, they are not bioavailable to plants lacking in oxygen and energy.
When soil-based nutrients fail due to excessive or limited moisture, foliar feeding bypasses the soil so that nutrients directly enter the plant. While these few pounds or ounces of nutrition don’t replace the hundreds of pounds of soil-based nutrients consumed over a growing season, they buy time until weather returns to more normal patterns.
While wet fields may not be accessible with foliar fertilizers, this is a great time to reflect on the relative advantages of foliar- and soil-based nutrition.
The role of boron in plantsBoron is thought to play important roles in cell wall synthesis and sugar transport. As such, it affects cell wall strength and resistance to disease, as well as the efficiency of nutrient movement between sources (such as leaves) and sinks (either roots or grain). The latter has important implications for maintaining sufficient sugar movement into embryos to avoid abortion during grain fill. It may also explain why boron availability is associated with nodule formation in legumes.
Like potassium and manganese, boron is severely affected by drought conditions. Dry soils fail to support mass flow, whereby boron flows with moving soil water to the roots. Secondly, boron is not plant mobile meaning the plant cant move the nutrient from a leaf of higher concentration to new growth that may have a limited supply.
The dependency of boron on xylem transport may also explain why shortages are often more pronounced in flower and seeds than leaves and roots. Because reproductive structures are more poorly supported by vascular tissues and have lower transpiration rates, supply of boron may be more limited.
Foliar applications of boron are the most reliable form of application as the nutrient is used in very small quantities. With most soils receiving a variable rate P and K application it is very hard to adequately include Boron as a soil broadcast partner.
Because of its critical role in cell wall and cell membrane integrity and function, boron availability is also associated with other plant functions. This includes the establishment of nodules in legume roots, which requires the successful construction of cell walls and membranes around nodules following Rhizobium infection.
Cell wall and membrane integrity also affects uptake and retention of nutrients. Healthy membranes allow nutrient uptake and retain nutrients once absorbed. Adequate boron is associated with improved soil phosphorus uptake. Conversely, boron deficiency is associated with potassium leaching from excessively wetted leaves.
These characteristics, combined with the general challenges of efficiently delivering micronutrients to plants through the soil, shows how effective foliar boron can be, especially when used in combination with manganese and potassium.
The importance of foliar nutrition in soybeansFoliar fertilization of soybeans is a critical step in achieving greater yields. In recent years, we have burnt the proverbial candle at both ends when it comes to crop micronutrients. On one end, yields have increased and with each additional kernel or bean removed from the field, we have taken away more nutrients.
On the other end of the candle, we have not returned micronutrients to the soil as quickly as in past years. That’s right, we applied micronutrients for decades, long before they became a hot issue. The micronutrients were in the manure we spread, in the rain that fell downwind from factories and even in the N-P-K fertilizer that we used to apply.
Manure is now applied to fewer acres, and the Clean Air Act has resulted in cleaner air technology that has also removed trace elements like zinc, a critical micronutrient for root development and stalk extension. And finally, in formulating more concentrated N-P-K fertilizers, we have removed the micronutrient by-products in those fertilizers.
Another concern in recent years has been that glyphosate may alter the chemistry of micronutrients inside plants and the availability of micronutrients in the soil. However, this is not true as empirical research has shown no significant differences in manganese uptake in soybeans that are glyphosate tolerant. Rather, the specific variety of beans will show different manganese uptake from soil.
Therefore, we need to add micronutrients to our soybean program – especially manganese and boron. Broadcasting these nutrients in dry form, however, makes them more difficult for plants to intercept. Banding these nutrients in the root zone improves their availability, however, in-row starters are less common in soybean production.
The most efficient and common way to feed micronutrients to plants is through the leaves. Foliar application of micronutrients to soybeans allows us to bypass chemical reactions in the soil that may reduce micronutrient availability. It also allows nutrients to enter the plant during dry conditions, when soil moisture may be too low to move micronutrients toward plants.
Dry soil conditions not only threaten micronutrient availability to plants, but nitrogen, potassium and phosphorus availability as well. Potassium deficiencies are exacerbated by low soil moisture. Add to this a general reduction of K soil test levels across the region and we now have need for supplemental K along with critical applications of Mn and Boron.
Balanced nutrition is also important in a foliar program. Single-nutrient approaches can be dangerous. Too much of a single nutrient may block the availability of other nutrients to plant cells. In addition, supplying only one nutrient will provide a short-term solution until the next most-limited nutrient slows plant growth. Remember, micronutrients are required in very small amounts, so highly-concentrated single nutrient products that look like a bargain may supply that nutrient far in excess of what the plant requires.
Among the micronutrients recommended for soybeans are manganese, which is important in chlorophyll development and enzyme activation, and boron, which promotes reproductive growth and stem branching in soybeans. Plant growth regulators can also be added to the foliar mixture to more precisely shape soybean development.
Some foliar ingredients may trigger the plant’s immune system. This trigger gives the plant the advantage of manufacturing defense proteins before the attack of fungi and bacteria, thereby reducing the time required to contain an infection.
Finally, soybean foliar products should include a basic sugar such as sucrose, which has been shown to reduce leaf burn in soybeans. It is also thought to act as a humectant, raising moisture levels at the leaf surface so nutrients stay dissolved for uptake.
Foliar nutrition is an important step in taking good soybean management programs to a higher level.
PCT | Sunrise offers three foliars developed in-house: Soy Foliar BAM, Soybean Foliar LITE and Soybean Foliar EXTRA, along with a late-season foliar, PCT Soy Finisher.
The other livestock on your farmIn a healthy soil a small sample the size of the tip of your little finger or about 1 gram of soil contains about 10 billion microbes. That is not a misprint 10 billion. Soil microorganisms can be used for the good of a plant like breaking down residue and returning nutrients to your crop but can also be present in quantities that can overwhelm a plant like pythium and fusarium root disease.
As farmers and agronomists, we are often preoccupied with managing the physical and chemical aspects of crops: soil texture, chemical composition of soil, compaction, seedbed preparation, residue management and chemicals that directly suppress weeds, pest insects and disease. We often emphasize practices that directly manipulate these properties and pay less attention to cultivating microorganisms that surround our crop and dramatically impact its growth.
Science and industry understandably recognize the relative ease of perfecting inputs that directly affect crops and pests, in contrast to complex microbial systems that respond to a myriad of different factors. However, we know that microorganisms above and below ground have profound effects on plant growth and vice versa.
The practice of introducing and nurturing beneficial microbes – plant-growth promoting rhizobacteria (PGPRs) – has increased, especially where regulations or availability limits fertilizer use or where diseases are resistant to conventional fungicides. Some farmers even refer to these microbes as their livestock as these organisms account for thousands of pounds of living biomass per acre. In the Corn Belt, we are seeing more microorganism-based products, including our in-house Progressive Crop Technology (PCT) products.
Microorganisms:
• dissolve nutrients, making them chemically available to plants;
• release hormones to stimulate root growth;
• produce chelates that improve micronutrient availability;
• physically deliver nutrients to plants;
• provide additional sites on roots’ nitrogen-fixing nodules;
• reduce plant stress;
• compete with and produce antibiotics that suppress plant pathogens;
• and stimulate the plant’s own immune system.
PGPRs make phosphorus and micronutrients more available for plant use by directly producing acids or stimulating plants to produce acids to dissolve phosphorus. PGPRs also produce siderophores, a kind of chelate that wraps around nutrients and protects them from both soil tie-up and use by pathogens.
Another benefit of PGPRs is the production of hormones that influence plant growth. Many produce IAA, a kind of auxin that encourages lateral root development. The result is a better-branched root system with more root hairs. In legume crops inoculated with nitrogen-fixing bacteria rhizobia, these additional root hairs provide more sites for nodule development. Even more nodules can be produced if the seed is inoculated with both rhizobia and a secondary bacteria that increases root hair development.
Plants inoculated with beneficial soil bacteria have shown reduced responses to heat stress. In this way, beneficial bacteria may reduce plant stress similar to strobulurin fungicides such as Headline and Stratego.
PGPRs also can reduce disease in at least four ways:
1. Crowding – Crowding root zones and leaf surfaces with good bacteria, they reduce sites where pathogens establish.
2. Competition – Beneficial bacteria steal nutrients from pathogens.
3. Antibiotics – Many beneficial bacteria produce their own antibiotics to fight off pathogens.
4. Immune Stimulation – Beneficial bacteria stimulate the plant’s own immune system to defend against disease.
At PCT | Sunrise, we have included beneficial microorganisms in our starter and foliar fertilizers for years. We comb through dozens of peer-reviewed university studies from around the world to identify which species are best to include in our products. Organisms are selected for biological benefits, compatibility with other ingredients and shelf-life in our products. While our exact species are trade secrets, we select spore-forming bacteria that are able to quickly enter dormancy under adverse conditions and germinate as conditions improve.
Beneficial bacteria/PGPR technology is here to stay. In the face of increasing regulations and pest resistance, they represent a win-win technology for growers who seek to improve yield and conserve the environment. Emerging technologies to identify and engineer these organisms will continue their advance in agriculture.
The 4Rs – Doing Right in a Changing Fertilizer EnvironmentWe all seek to minimize nutrient losses to surface waters. No farmer wants to lose purchased nutrients. Whether you are farming in the highly regulated Lake Erie watershed or not all in agriculture play a role in nutrient management. Regulation is intensifying in Ohio and other states as well. What do we do?
What farmers always do in the face of adversity? Learn. Adapt. Improve production so more nutrients find their way into our grain tank and not our streams. In industry lingo, we will embrace the 4Rs of nutrient stewardship.
1. The Right Rate. Start with timely and accurate soil samples. Match soil nutrient levels to historical yield levels and future yield goals. We will better match nutrient application rates to crop needs, using the Sunrise Precision Solutions team and other services for variable rate applications. Sunrise Cooperative customer-owners interested in variable-rating their nitrogen can work with our Precision Solutions Specialists to precisely map areas where nitrogen should and should not be reduced.
2. The Right Source. We will deliver balanced plant nutrition to our crops, in forms that are most efficiently recovered by plants. Recent research conducted at Purdue University shows that modern corn and soy genetics use mineral nutrition different that older genetics. Modern genetics are primarily selected based on yield, as trend line yield for both corn and soy increases plant nutrition needs change as well. Additionally, these nutrients must be properly formulated; soil elements and spray tank ingredients will tie up several micronutrients unless they are properly formulated with stable chelates such as EDTA.
3. The Right Time. We will time fertilizer availability for quick uptake and maximum crop benefit. In cases where we cannot apply nutrients exactly when crops require them, we will use nitrogen stabilizers and chelates to ensure nutrients remain in the root zone in forms available to the plant. We will also time nutrition to weather conditions that can challenge plant nutrition, whether that is cold soils at planting that limit phosphorus or hot, dry temperatures later that limit potassium, manganese or boron.
4. The Right Place. Where appropriate, we will physically place nutrients where they are most available to the plant. In soil, this includes bands in, below or beside the furrow. Because nutrients are vulnerable near the soil surface, we will concentrate them in areas where they are more resistant to loss and closer to plant roots. In the case of some nutrients, like manganese and boron, the best way to feed the plant may be through the leaves, using foliar fertilizers.
For some farms a cover crop system can be managed successfully. Research shows that grass cover crops can help to reduce nitrate release into tiles from our fields. However, recent research shows that cover crops have the opposite impact on phosphorous leaching from our fields. Root channels created by aggressive root systems help create channels through soil where Dissolved Reactive Phosphorous can more easily move. In addition, all crops recycle plant material – thus minerals – to the soil surface where they decompose over time. This results in higher concentrations of minerals at the surface. Cover crops can also reduce erosion and build soil organic matter. In some cases, they may reduce survival of seeds from hard-to-control weeds.
Sunrise Cooperative is committed to supporting and recognizing the stewardship of our customers and will continue to deliver new technologies compatible with nutrient regulations and eligible for conservation awards.
“Where danger is, grows the saving power also,” wrote Martin Heidegger, a German philosopher. We have challenges ahead, but also incentives to produce more food, with better quality and fewer nutrients than ever before. We will continue to improve, and help the public understand just how far we have come.
Maintain Soil Fertility Now to Avoid Intensive Intervention LaterKey Points:
According to Michigan State, 200 bushels of corn removes 70 pounds P2O5and 54 pounds K2O. 60 bushels of soybean removes 53 pounds P2O5and 84 pounds K2O. How will this reduce soil test levels?
200 bushels of corn reduces the soil P2O5test level by about 8 pounds and the K2O test level by over 13 pounds. 60 bushels of soybeans reduces soil P2O5almost 6 pounds and soil K2O over 9 pounds. These numbers are based on the old rule that adding/removing 9 pounds of P2O5will increase/decrease the soil P2O5test level by 1 lb, and adding/removing 4 pounds of K2O will increase/decrease the soil K2O test level by 1 lb.
To replace P and K removed by corn, we need 134 pounds MAP (11-52-0) and 90 pounds potash (0-0-60). Over 100 pounds MAP and 140 pounds potash is needed to replace P and K removed by soybeans.
Actually, these ratios change with soil test levels. According to the University of Kentucky, the 9:1 ratio of fertilizer P2O5to soil P2O5test level is accurate around soil test levels of 30 lb/ac. It takes over 14 pounds P2O5to build the soil P2O5by 1 pound when the soil test level recedes below 15.
In other words, it takes 50 percent more P2O5to build a soil test level by 1 pound P2O5in infertile soil than in fertile soil. This greater ratio also applies to nutrient removal: soil test levels will decrease 50 percent faster with P2O5removal in infertile soils.
Similarly, the 4:1 ratio of fertilizer K2O to soil test K2O is most appropriate to soil tests levels around 275 pounds/ac K2O. Soils testing around 175 lb/ac K2O require 5 pounds/ac K2O fertilizer — 20 percent more — to raise the soil test level 1 pound. Test levels in infertile soils also decrease 20 percent faster with K2O removal.
Also note that potassium gets fixed, or trapped, in clay soils, so as potassium levels decrease, more sites become vacant to trap new potassium. Therefore, K2O requirements increase even faster in these soils as test levels decline.
These results have important implications for soil fertility management: as soil test levels of P and K decrease, it will take more fertilizer per pound soil test value to repair them.
Managing Nitrogen Through Nitrate TestingEnd-of-season stalk nitrate testing can help you measure whether your crop received adequate nitrogen. The test measures the amount of nitrogen returned to the stalk after grain fill. Therefore, if your corn stalk ends the season with adequate nitrate, then you know nitrogen sufficiently flowed from the seed, to grain and back to stalk.
Key Points
When to Sample
How to Sample
Interpretation
| PPM NO3 | TEST LEVEL |
|---|---|
| 0-250 | Low |
| 250-700 | Marginal |
| 700-2,000 | Optimal |
| 2,000+ | Excessive |
*Universities have published different NO3 levels as as low, adequate and excessive levels.
Soybeans and PotassiumPotassium’s primary plant function is to regulate the direction of water flow between cells and different plant tissues. The xylem and the phloem, which is the plants “plumbing,” relies on potassium to direct its direction of flow. The xylem moves water and nutrients upward and outward while the phloem moves sugars and water downward toward roots. Just as in your home plumbing, higher pressure in one plant region (like your water main) will push sap towards areas of lower pressure (like an open faucet)
Leaves act as solar panels that are switched on during the day. Just as a lightning rod absorbs static electricity and harmlessly channels it to ground, leaves depend on converting potent solar energy to sugars that can be safely transferred and stored. Plants absorb sunlight which is converted to energy via photosynthesis. The plant uses water – H2O + C – carbon from carbon dioxide in the air to make plant sugar or sucrose – C12H22O11. Plant sugars are then respired at night through chemical reactions in the plant to fuel plant and seed growth. The ultimate goal of a plant is to simply produce as many potential offspring as possible. Our goal is to manipulate the plant into producing large numbers of offspring and have the offspring be as large as possible.
Potash soil test levels have widely declined during the past several years, and need to be more closely monitored. Growing conditions that limit uptake of nutrients include reduced root mass from excessive soil moisture early for some and periods of very dry soil where potassium and other nutrients are held tightly to the soil and thus are not available for plant uptake. Potash is a mobile nutrient in the plant so deficiencies typically show as yellow tips at the lower leaves of the plant. One interesting aspect is that aphids love beans that are low in potassium levels. It is very common to the largest aphid populations on soy plants with low K levels.
If you are witnessing these conditions in your crop, what can you do? Consider a foliar fertilizer that directs potassium directly to plant leaves. Often, it is tempting to reduce foliar fertilizer cost by focusing on one or two nutrients. Effective fertilization, however, depends on having adequate potassium to distribute sugars (and foliar nutrients) to other plant parts.
Don’t stand by while your soybeans go into shock. Give them a shot of potassium with their next foliar feeding.
