Battle for the Belt: Season 3, Episode 8: Wet Weather and Nitrogen Loss

Season 3, Episode 8 of Battle for the Belt is now available: https://www.youtube.com/watch?v=3H-eyJkPUNI

In Episode 8, we are with Dr. Manbir Rakkar, Ohio State Extension Fertility and Nutrient Management Specialist, discussing management of nitrogen under saturated soil conditions.

What are the implications of excess or surplus water in planting and nitrogen losses?

Water is essential for crop growth and high yields; however, too much has the potential to cause several problems. With wet conditions, fieldwork can be delayed, and planting in saturated soil greatly increases the risk of soil compaction. If already planted, standing water can disrupt the germination processes and even suffocate the roots of the crop. Important to note is the effect that excess water has on nitrogen losses. Management of nitrogen is especially difficult in flooded or waterlogged conditions. Nitrogen is a highly important macronutrient, but in these environments, nitrogen losses from the soil are accelerated, causing developmental issues or yellowing in corn (Figure 1).

Figure 1. Yellowed corn at the Northwest location on May 13th. Photo credit: Taylor Dill

What are the main nitrogen forms in the soil?

here are two main forms of nitrogen in the soil: organic nitrogen and inorganic nitrogen. Organic nitrogen is found in soil organic matter. In general, 1% of organic matter holds about 2,000 lbs. of nitrogen per acre, but only about 20 lbs./acre are available for plants to utilize during the growing season. Inorganic nitrogen is in the form of ammonium (NH₄⁺) and nitrate (NO₃^-), and these are more readily available to plants. We get these forms either through mineralization of organic matter or from fertilizers like urea or UAN.

What are the main nitrogen loss pathways?

There are several pathways for the loss of nitrogen, dependent on field conditions. Volatilization occurs in hot and dry conditions. This is especially the case with broadcasted urea. A common occurrence with heavy rainfall is runoff and erosion. Nitrogen applied to the surface can be washed away. In well-drained, coarse-textured soils, leaching may occur, causing the nitrogen to flow out of the root zone of the plant. Denitrification takes place in fine-textured soils and is the conversion of nitrate into gases. These escape into the atmosphere. The process worsens with higher soil temperatures and longer periods of saturation.

What options are out there to mitigate nitrogen losses?

The key to managing nitrogen losses is by following the four R’s of nutrient stewardship:

• Right Time: Synchronization of the nitrogen supply and the crop demand. Split applications may reduce losses and better align with crop uptake. This can include the addition of a fraction of nitrogen pre-planting, or at planting, followed by an application of the remaining nitrogen at V4-V6, when the plant requires it the most.
• Right Placement: Nitrogen should be placed where the crop can access it and where less losses are expected. One of the best methods for placement is sidedressing in a 2-by-2, or two inches to the side of the row, and two inches below the soil surface. Broadcast nitrogen applications are an option as well, but often more susceptible to losses.
• Right Source: Fertilizer types should be selected based on what is suitable for your field’s conditions. Nitrogen inhibitors may be a necessary addition if your field is susceptible to nitrogen losses. Some forms of N are at higher risk of losses than others.
• Right Rate: Applications should be neither too much nor too little. The rate is often based on crop needs, soil tests, and decision tools such as the Corn Nitrogen Rate Calculator are available.

What are some tools and resources for aiding in nitrogen management?

• Tri-State Fertilizer Recommendations: A regional guide to nutrient management practices. https://agcrops.osu.edu/FertilityResources/tri-state_info
• Corn Nitrogen Rate Calculator (CNRC): Helps to determine economic optimum nitrogen rates. https://www.cornnratecalc.org/
• Ohio State C.O.R.N Newsletter: Timely updates on general crop management, including nutrients and weather. https://agcrops.osu.edu/newsletter/corn-newsletter
• Extension educators and specialists: Reach out for localized advice and support.

Field & Crop Progress Updates

All three locations successfully added another planting date this past week! A stretch of consecutive dry days allowed soils to dry down enough, providing suitable conditions for planting before some additional rain moved in. Wooster and Northwest locations planted the third planting date on Monday, May 12^th. Western was also able to plant on May 12^th, getting the second planting date in the ground. Table 1 summarizes field conditions in those three sites at the most recent date of planting.

Table 1. Planting date soil and air temperature conditions for the first day of planting at the Northwest Agricultural Research Station in Wood County, the Wooster Campus in Wayne County, and the Western Agricultural Research Station in Clark County. The soil and air temperature data were retrieved from https://weather.cfaes.osu.edu/; reported as average temperatures.

Soybeans from earlier planting dates range from VC to V1 across locations, with Western being slightly ahead despite being planted three weeks behind the others (Table 2). Corn stages range from V2 in planting date two to V3 in planting date one, with western again being slightly ahead of the other locations, as represented in figures 2 and 3.

Figure 2. Corn planting date one progress comparison between locations. Photo credits: Maria Kessler and Taylor Dill

Figure 3. Soybean planting date one progress comparison between locations. Photo credits: Maria Kessler

Table 2. Precipitation, soil temperature, average air temperature, cumulative GDDs, and stage at the Western Agricultural Research Station, the Northwest Agricultural Research Station, and Wooster Campus. Weather data retrieved from: https://weather.cfaes.osu.edu/. 

If you would like to learn more, check out our research updates through C.O.R.N. article updates and YouTube Videos this growing season! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.