Influence of Irrigation and Crop Rotation Sequence on Soybean Cyst Nematode (SCN) Populations

Impact on Soybean Production and Value

Soybean growers can be better informed of the SCN population levels in their land based on soil texture characteristics, for example, sandy soil fields have higher risk of having higher SCN population densities. Also, growers can be informed on the SCN population density decline they would expect to see after annual corn rotation provided they have data on SCN population levels before rotation and soil pH. This can help growers to be more informed on how there SCN management program is working.

Loren Giesler (2013)

Key Terminology

Pi is the designation of the initial population of soybean cyst nematode (SCN) in a field before planting a crop.

Pf is the designation of the final population of SCN after a crop has been harvested from the field.

Quantitative data is data that can be measured and deals with numbers (i.e. length, weight, percentage, etc.).

Qualitative data is data that cannot be measured and deals with descriptions (i.e. textures, appearance, color, etc.).

SCN population density refers to the number of SCN eggs detected per volume of soil tested.

Study Objectives

The objectives of this project are to: 1.) Determine the effects of crop rotation patterns on soybean cyst nematode populations in Nebraska; and 2.) Determine the effect that irrigation has on SCN population dynamics within the studied rotations of objective 1.


The research findings have established significant information on the relationship of soil factors on SCN field population densities and formal estimates of the % population decline observed after annual corn rotation in Nebraska. One finding has provided quantitative basis of the relationship of specific soil textural proportions with SCN population densities. The findings indicated that compared with silt and clay sand had a stronger association with SCN population densities. This supports the hypothesis that higher SCN population densities occur in sandy soils than in silt and clay soils, a hypothesis which, until before this study, had been limited to qualitative descriptions based mainly on textural classes. Using a modeling approach, the research showed that soil pH and SCN population levels before corn rotation are two major determinants of the expected SCN mortality after annual corn rotation.

Additional Information

Quantitative relationship of soil texture with the observed population density reduction of Heterodera glycines after annual corn rotation in Nebraska