Kentucky Small Grain Growers Association

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Research Report: Irrigating the Soil to Maximize the Crop

Irrigating the soil.JPG

By Ole Wendroth, Javier Reyes, and Chad Lee, University of Kentucky

Full Report (PDF)

Despite sufficient total annual rainfall in Kentucky, irrigation for efficient crop production and for securing high yields becomes increasingly relevant because draught periods often occur at times and crop growth stages when the water is needed.

Due to geomorphology of our Kentuckian landscapes, farmers’ field soils exhibit substantial spatial variability of properties. Within the same field, the soil type can vary between silt loam and silty clay loam, or clay loam due to erosion processes that have caused former B-horizons that were rich in clay to now become the top horizon. These geomorphological processes have triggered a pattern of soil heterogeneity with different soil hydraulic properties. Due to this heterogeneity, we can find zones with locally differing water infiltration behavior.

We hypothesize that these zones and their different soil functions need to be considered for irrigation management. Zones with high clay contents cannot take up water at the same rate as zones with silt loam soil can. Irrigation rate needs to be adapted for the spatial variability of infiltration capacity in order to avoid unintended water losses.

In the full report—found on the KySGGA web site,, we show how the locations of different functional zones within a farmer’s field can be derived from other information sources. According to the purpose of this project, with the results presented in the research report, we demonstrate “a strategy for deriving a map of functional soil water characteristics based on easily obtainable land surface observations.”

Our research Project is conducted at Hillview Farms (Trevor Gilkey) in Princeton, Caldwell County. The Hargis field is equipped with a center pivot irrigation system which covers a total area of approximately 70 acres. Over the past three years, we have been taking numerous soil and crop data sets, many of which typically can be taken under farm conditions without extreme experimental efforts and laboratory analyses. In the following, we briefly describe the source of information for different maps and how helpful these different measurements or surveys are in delineating mapping zones for site-specific or variable-rate irrigation management.

This is an ongoing research project, and we encourage growers to contact the researchers to more fully utilize the information being gained from this project.