C.O.R.N. Newsletter: 2023-27

Episode 23 of Battle for the Belt is now available: https://www.youtube.com/watch?v=CI5c3MeX4WE&t=1s

In Episode 23, we talk with Dr. Jim Ippolito about soil fertility and problems we have seen this summer. Dr. Ippolito is new to Ohio State University and came to us from Colorado State University as a Professor of Soil Health and Fertility. He has worked in soil science for 30 years.

Soil Fertility
During this growing season, we had a long dry period in June with parts of the state not receiving rain for three weeks or more. Both corn and soybeans began to show symptoms of potassium deficiency. The dry weather can be a direct cause of potassium deficiency in the plant. This is because potassium is taken up by the plant by way of diffusion (i.e., from an area of high potassium concentration in the soil to an area of low potassium concentration at the root). Diffusion will only occur when soil moisture is present. Therefore, the soil may contain potassium but does not have the means to move it to the root and into the plant. As we began to receive more rainfall, the potassium deficiencies caused by the dry weather faded away.

Soybeans around the state are between R3 and R5 and there are many questions discussing micronutrient foliar fertilizers. Leaves absorb these foliar applied nutrients through stomata, which are the opening and closing mechanisms of the leaf allowing transpiration and respiration. When the plant is stressed, the goal of the plant is to conserve water and therefore close the stomata for water conservation. To absorb these nutrients, the stomata need to be open. According to recent research on foliar fertilizers, in the state of Ohio, most foliar fertilizers do not have a yield response. On the occasion that a yield response is seen, there is visual symptomology of a nutrient deficiency. In Ohio, the most common micronutrient deficiency that will lead to a yield response with foliar fertilizer is manganese (Figure 1). [For the full article on foliar fertilizers, click here.]

If you are seeing nutrient deficiencies in your field, to diagnose the issue it is important to take both plant tissue samples and soil samples for plant available nutrients from the ‘good areas’ and ‘bad areas’ of the field, keeping in mind that the soil types should be either identical or very similar to begin with. This will reveal whether the soil has a deficiency, or the problem was caused by the environment. One key to discovering the cause of a nutrient deficiency is to look at the pH on your soil reports. The pH of the soil is one of the controlling factors of plant available nutrients. Micronutrient deficiencies tend to occur as the pH moves above 7 while some of our macronutrients begin to have problems with a low soil pH, around 6 or below (Figure 2).

For more information on soil fertility management you can access a free PDF of the Tri-State Fertilizer Recommendations Guide for corn, soybeans, wheat, and alfalfa here.

Battle For the Belt Location Updates
Corn at the Wooster location has the greatest plant height variability across planting dates. The third planting date is most uniform. We will be measuring plant height, ear height, and number of leaves towards the end of the season to verify if planting date or hybrid caused more differences. Disease has been more prevalent in planting date one and two than in planting date three in corn. Frogeye leaf spot was found in soybeans at the Wooster location last week, occurring in planting date two, but only in 1/10 plants.

The early-planted corn at the Western Research Station is at R4. This is the kernel dough stage and occurs around 24 days after silking, when the kernels begin to have a thicker (starch) consistency. Moisture is typically around 70% and kernels are unlikely to abort at this stage. Gray leaf spot is the most prevalent here but seems to have less incidence in later planting dates. Planting date five is close to the stage for disease rating as well. Soybeans have frogeye leaf spot in every planting date; however, there is minimal occurrence in planting date five.

Corn at the Northwest location has had tar spot begin to show up. In our disease rating we observe the ear leaf of ten plants per plot. The average occurrence was 3/10 plants with only a couple of stromata on the leaf. When this disease came in planting date one, two, and three were all in grain fill stages but planting date four and five were either at silking or close to tasseling. The soybeans had frogeye occur in each planting date, however in planting date five which is at R3 (beginning pod) only had a 2/10 plant occurrence.