By Roy A. Ulrich, technical agronomist for DEKALB/Asgrow in Southern Ohio
This is the time of year when growers can learn a lot about the crop, the growing season, weather, and the impact of some of the management decisions made earlier in the year. Unfortunately, it also coincides with the time of year that most people despise scouting fields. It is August. It is hot in the Eastern Corn Belt, pollen maybe still shedding in corn fields, early morning dew drenches your clothes 12 rows into the first field, etc. — I’ve heard all the excuses from growers, dealers and interns. However, the knowledge and insights gained this time of year can be invaluable as we head into harvest and for future growing seasons and management decisions.
In this age of technology, do we really need to scout fields? There are satellites constantly circling the globe sending images of fields. Drones can capture information from fields with incredible resolution. While these technologies are great and can be very useful in helping to direct and be more efficient in your scouting trips it does not replace scouting. These technologies can direct your scouting trips to not only the best parts of the field but also the toughest parts of a field to get a true picture of variability and overall field performance.
Some of the management topics that can be evaluated this time of year are nutrient management, disease pressure, insect pressure, and estimated yield potential.
The most important nutrient in corn is nitrogen. Plants showing nitrogen deficiency with the classic yellowing of the leaf making a V towards the stalk is the most common nutrient deficiency to appear during the growing season. Nitrogen deficiency showing up at this time of year can be a signal of applied nitrogen rate being too low to meet plant demands, loss of applied nitrogen either from leaching, denitrification, or volatilization, or the plants’ inability to extract nitrogen from the soil due to extremely dry conditions, limited root development, or damaged root systems from corn rootworm feeding.
Potassium deficiency has also been a common occurrence with the classic yellowing of the margins of the leaf making the V point away from the stalk in corn or yellowing of the margins of soybean leaves. Potassium deficiency can also be caused by a variety of situations with the first being a lack of sufficient amount of potassium applied to the crop to satisfy crop demands. Potassium uptake can also be negatively influenced by the lack of soil moisture and any root development or root damage issues limiting the plant’s ability to pull potassium from the soil.
Disease pressure can vary from year to year, field to field and product to product but the major foliar diseases to watch are gray leaf spot and northern corn leaf blight in corn and frogeye leaf spot in soybeans. When evaluating disease pressure from these three diseases, the two pieces that will have the biggest impact are environmental conditions that favor infection and the level of susceptibility of the product. At the point of writing this, the levels of all three of these diseases are very low due to the lack of available moisture to create a conducive environment for development, although conditions can change quickly.
Insect pressure can also vary significantly from year to year and from field to field. However, with the drier start to the season much of Ohio experienced, some insect populations may be on the rise from past years. At this point of the year much of the direct yield impact can be made in soybeans by some of those pods feeding insects such as bean leaf beetles and stink bug.
The most compelling reason for most to scout fields now is to try and estimate yield potential. There are differing techniques on estimating corn yield in terms of how to sample and the number of ears to pull. I would suggest utilizing the information from satellite or drone images to direct sampling across the variability that exists in all fields. Another word of caution is with the seed size factor used to calculate kernels/bushel with the extremely dry grain fill period we have experienced in parts of the state. For dry areas, that number may need to be much larger than normal.
While scouting at this point in the growing season is almost always hot, itchy, sweaty, wet, and uncomfortable, the insights gained with field observations when paired with knowledge of the growing season can help tweak management decisions going forward that will ultimately lead to more productive future growing seasons.