Agronomy Talk

AGRONOMY TALK: MANAGING THREATS TO EARLY PLANTED SOYBEANS

Published on Friday, April 10, 2020

Twenty years of Beck’s Practical Farm Research (PFR)® data indicates that one key to optimizing soybean yield over time is early planting. Early planting of soybeans increases the number of nodes, which creates additional pods and higher yield.

Early planting does not come without risks. With earlier planting dates, the seed and seedling can be exposed to more disease pressure from pathogens such as pythium that are generally associated with colder, wetter conditions commonly found early in the spring. In recent weather trends, it is raining more frequently with higher total precipitation from each event, leading to extended periods of soil saturation. These heavy rainfall events can create more disease pressure even when planting in warmer soils. Wet and warm soils often favor Phytophthora and rhizoctonia, so the pattern of heavier rainfall events also means that later planted soybeans can face increased disease pressure.

OBSERVED CHANGES IN VERY HEAVY PRECIPITATION 

One of the clearest trends in the observational weather record of the U.S. is an increasing frequency and intensity of heavy precipitation events. Over the last century there was a 50% increase in the frequency of days with precipitation over 101.6 mm (four in.) in the upper Midwestern U.S.; this trend is statistically significant.


Source: Global Change Information System. https://toolkit.climate.gov/image/762

Seed treatments are a vital tool that every farmer should employ to maximize additional potential profit and to capture the benefits of early planting while reducing risk from exposure to additional disease pressure. As with herbicides and foliar fungicides, it’s important to choose a seed treatment that provides multiple modes of action against diseases.

Although seedling diseases are some of the biggest yield robbers in soybeans, probably the two biggest issues that reduce soybean yields in the U.S. annually are soybean cyst nematode (SCN) and Sudden Death Syndrome (SDS). The first step farmers can and should take in their battle to protect yield is to test for the soybean cyst nematode. Refer to our agronomy brief on soybean cyst nematode for directions on how to pull soil tests for cyst nematodes.

Choosing varieties that are resistant to SCN is always the first step in cyst nematode management; however, recent university research indicates that an over-reliance on one source of resistance (PI88788) is likely leading to a breakdown of the resistance mechanism found in these varieties. Until new sources of resistance are discovered, another strategy to fight the impact of SCN is seed treatments.

Sudden death syndrome is often associated with both early planting and SCN infestations. As with SCN, selecting varieties with high levels of tolerance to the disease is the first line of defense; however, pairing varietal tolerance with seed treatment protection is a multi-layered approach that provides the best protection.

Farmers who are managing for high-yielding soybeans are planting earlier, which puts more pressure on the system to manage for diseases and some insects. Seed treatments combined with varietal selection and proper agronomic practices can and will mitigate some of the risks and help growers continue to achieve higher yields.

 

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Author: Jim Schwartz

Categories: Agronomy, Agronomy Talk

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