Site-specific cotton management: Soil measurements

Authors: Sudduth, Kenneth - Ken

Submitted to: Missouri Agricultural Station Special Report
Publication Type: Other
Publication Acceptance Date: 8/10/2017
Publication Date: 8/31/2017
Citation: Sudduth, K.A. 2017. Site-specific cotton management: Soil measurements. Missouri Agricultural Station Special Report. University of Missouri Fisher Delta Research Center Field Day, September 31, 2017, Portageville, Missouri.

Interpretive Summary:

Technical Abstract: oil variability within fields has a large effect on crop growth and yield, often due to variations in soil texture and water holding capacity. This is particularly true in the alluvial soils of the Mississippi Delta, where profile sand contents can range from 20% to 90% within a field. Variable-rate irrigation, or VRI, is being investigated at the Fisher Delta Research Center as a way to address this variability in soil water holding capacity. Soil sensor measurements may be an efficient data source for VRI, but most soil sensors used in irrigation management are installed at just a few places within a field. These sensors can give readings that describe what happens over time, but don’t do a good job of characterizing spatial variability in soil properties or soil water status, especially in highly variable soils. Because of this, we are investigating several mobile sensor technologies that can be used to make maps of within-field soil variability. The overall goal is to combine this mapped data with data from point-based soil sensors to better characterize water holding capacity variations as an input for VRI management. In 2016 and 2017 we collected data with multiple soil sensors on several fields near Portageville. With mobile sensors, we measured soil electrical conductivity (EC) to different soil depths, soil reflectance as an indication of organic matter, and gamma radiation. We also collected data at several points in each field with a vertical probe that provided EC, force, and soil spectral reflectance data. By combining mobile and probe data we can accurately map soil texture variations across fields and by depth. We’re also collecting EC data within-crop this year to investigate how changes in soil water content affect sensor readings. Preliminary analysis of the EC data in comparison to data from Watermark and TDR moisture sensors installed in the same field looks promising. The information from this soil sensing project will help provide sustainable, state-of-the-art water management guidelines for Mid-South production systems.