Advanced Agrilytics

Assessing Crop Health & Making Decisions: Protecting Profitability in a Challenging Growing Season

In most of the Corn Belt, the growing season has been contentious to say the least. Some areas were able to plant early (prior to April 20), where cooler ambient and soil temperatures slowed emergence and early growth. Following that, and for many who planted after April 20, dry soil conditions and some days of increased temperature led to many early-season issues.

Early-planted corn in many cases has remained stunted and shorter, even following some much-needed rainfall. Later-planted corn, while slower growth through V6, is in a somewhat rapid growth phase (V6 or V7 to V14) and has overtaken some of the earlier-planted corn. It seems as though corn planted just prior to the dry period, that reached canopy before water limitations persisted, mitigated the stress better than what was planted earlier or later.

While we cannot predict in any season when the absolute correct time to plant will be, it is best to try and limit the risks (within reason) that any plant will endure as stand is established and rapid growth occurs.

In some cases of the early-planted corn, short and “stacked” internodes have been commonly observed. In some extreme cases, V7 to V8 corn with shortened internodes only 12 to 18 inches in height are present in fields. In all planting scenarios, there are many causes, some compounding, that have led to decreased growth:

  1. Many of the extremely shortened corn plants have browned, disease-infected (most likely pythium) hypocotyls that are hypothesized in slowing plant growth – not actually killing the plant, but taking resources away to fight off the infection.

  2. Potassium (K) deficiency and water limitations have been widespread across our geography. While early visual symptoms occurred on the water-limited acre initially, symptomology extended across multiple in-field environments. Limited access to nutrients due to low soil moisture content impeded the availability of K regardless of soil K concentration, but in some cases lower (<90 ppm K) exacerbated moisture limitations and created extreme “stacked” internodes in corn plants.

  3. In traveling and speaking with our agronomy team, sidewall compaction has also been a persistent occurrence – specifically in the lower-lying field environments, but not limited to these acres. While sidewall compaction or “hatched roots” are not the worst observed compared to previous years, the impact has been large in stunting early growth, and more specifically, root growth. Hindered or delayed root growth in many fields is common, but limited soil moisture (even with some recent rains) is reducing our ability to access sidedress nitrogen (N). While the percentage of N is largely accessed through mass flow (soil water movement) and not root interception, increased root exploration aids in access because of distance traveled of any element and increased surface area to uptake nutrients when present. The dry conditions have limited the plant’s ability to grow through the sidewall compaction and reduced access to many of the heavily required nutrients during rapid growth.

Fungicides to Support Plant Health

Recent conversations have revolved around fungicide application and/or timing, with specific emphasis on the plant health component. We know through past research that the plant health benefit is real, and application in the V10 to V12 stages will promote increased plant health or decrease the impact of moisture limitations and/or increased ambient temperature through lowering of the respiration rate. This increases the stored carbohydrate reserves in the lower internodes of corn plants.

At this stage of growth, we will commonly be checking the “building” of carbohydrates in the lower stalk. Today internode 6 and 7 should be full (smooth, glassy/watery, and no “Styrofoam” present).

It is uncommon to completely fill internode 8 and this year is no exception, with very little carbohydrate (1/3 to 1/2) of internode 8 filled and the remainder having the vascular bundle surrounded by white foam in the internode. With the early months of this growing season, the plant did not have a good opportunity to build carbohydrate reserves (dry conditions, limited nutrient uptake, increased respiration) and will ultimately need some help with carbohydrate retention during the later vegetative stages for use during grain fill. This stored reserve will, on average, represent 33% of what is required for grain fill, with the remaining 66% coming from photosynthesis during these stages. In many of our geographies the crop will need help from us and the weather.

While assessing today what has happened is extremely informative, we also need to make decisions on how to help the crop we do have. We have always followed the mantra to “never give up on a crop”, but that said, protecting profitability is also a priority.

Depending on the amount of rainfall the crop has received, we would recommend proceeding differently in each scenario.

If you have had sufficient rainfall to satisfy long term crop requirements (>2.5 inches) 

With the weather that has been received, there is much more time to make a decision on future management. Increased soil moisture, and if you have canopy established, will create an environment under the canopy promoting disease (Gray Leaf Spot, Tar Spot). Checking on progression of GLS and other diseases would be a factor in driving the decision, especially if you have limited carbohydrate reserves. In that scenario, disease will have greater impact on final yield than if the plant had an abundance of stored carbohydrate.

If canopy has not been achieved, then we would suggest waiting and examining how the crop reacts in the following 7 days. Rapid growth is just that, and it will not take long to understand if the required resources and plant status is adequate to support increased/rapid growth. During the next 7 to 10 days the assessment of change in crop will aid in making the next management decision.  

If you have had approximately 1.5 inches of rain over the last 10 days

With the recent rainfall received, there is a sense of relief. The crop growing will remove approximately 2.5 tenths of soil moisture through evapotranspiration daily, so be prepared: We will experience soil moisture limitations again. During these periods, examining the crop (root size and soil exploration, stalk size, overall plant structure) and knowing the field status (soil K and phosphorus (P) concentrations, soil structure, past history specifically in years of limited soil moisture) will inform a decision.  

At these moments in the growing season with the current crop status and weather received, generally it is a time to prepare the crop for upcoming stressors. Making the decision to spray today is stressful, particularly when a later (R2) application will also be warranted. Even if crop progression is not what typically is experienced with planting date and time of year, if the crop stand is even, stalk size is acceptable and consistent (approximately 1 inch in diameter at this time), and P and K concentrations (>120 ppm) are acceptable to support the plant during drier periods of time, our recommendation would be to apply fungicide in the vegetative stages (even if you plan on an R2 application) for the plant health benefit.   

If you have not had sufficient rainfall (<1 inch)

As those in this situation know, decisions will be extremely difficult. As mentioned previously, crop and soil status should influence the fungicide decision at this time. With a stand that is well established, no rooting issues (good exploration), canopy established, and soil conditions being favorable, preparing the crop for upcoming periods of soil moisture limitations is warranted. From our internal research in 2022 (where there were dry periods in June around V6 to V9 and very little disease present), a single V10 fungicide application had similar response as R2 application, compared to the control receiving no fungicide. Unlike the last growing season, if rainfall and disease progression is limited, then a V10 to V12 application will fortify the crop and a later fungicide application may not be required.

If the crop condition is not consistent, has short stature and limited canopy (perhaps leaves are still rolling in the late afternoon), the root system is limited and/or the soil P/K status is not sufficient, waiting on the growing to unfold would be the suggestion. In these situations, we are depending on favorable weather conditions (similar to the 2022 growing season) to create opportunities for crop advancement and efficacy of future management.  

In conclusion, it’s critical that we assess the current crop regularly. We utilize these observations heavily for the next growing season and beyond. Many of our management decisions are used to “de-risk” the weather impact by sub-field environment. For example, we understand many need to be planting earlier when conditions may not be perfect and sidewall compaction will be present on a percentage of acres.

With that known, what strategies can we deploy to aid when soil moisture is limited, to ensure a viable crop?

Let us contact you to get started on your personalized, unbiased recommendations