1. Precision Soil Mapping for Landscape Hydrology and Crop Management in an Agricultural Landscape
Qing Zhu1, Henry Lin1, Xiaobo Zhou1, J.A. Doolittle2 and Jun Zhang1
1Dept. Crop and Soil Sciences, The Pennsylvania State University. 2USDA-NRCS.
Introduction and Objective
Second order soil map
To advance hydropedology and hydrologic modeling, we need enhanced ways of mapping soils in greater detail and with higher precision.
Our objective is to develop a more precise soil map for investigating site-specific water movement and crop management using the combined information of soil properties, topography, geophysical surveys, crop
yields, and soil moisture monitoring.
Precision soil map
Materials and Methods
Materials
Study site: The Kepler Farm at Penn State.
The second order soil survey (Fig.1).
Soil core descriptions: 145 cores; 70 of them for intensive description and testing (Fig.1).
Electromagnetic induction (EMI) surveys: First time,
EM38 and EM31; second time, Dualem-2 meter.
Depth to bedrock: 77 observations; map was
generated by regression-kriging.
Soil moisture and crop yield data: Surface soil moisture (0~0.2-m) collected at May 27th, June 15th, July 12th, and July 18th 2005 (Fig.1); dry mass yield
data in 2002, 2004 and 2005.
Fig 1. DEM, second order soil survey, and soil cores distribution in the study farm located in central Pennsylvania.
Results and Discussions
Second order soil map
EM31-vertical
EM-HCP
Depth to bedrock
Depth to clay layer
Precision soil map
Refined soil map
Methods
Refining the second order soil map:
Depth to bedrock is used to refine the delineations of Opequon and Hagerstown soil series and their transition zones. 99% confidence intervals of apparent electrical conductivity of different soil series were used to delineate map units of other soil series (Table.1).
Generating precision soil map:
Maps of A horizon texture and depth to clay layer were selected to modify the refined soil map because they have close relationship with both soil moisture (collected at May 27th, June 15th, and July 18th 2005) and crop
yield (2002 and 2005).
Surface texture
Fig. 2. Averages and 95% confidence intervals of crop yields (2002) and mean surface soil moisture of different mapping units in the second order soil map vs. the precision soil map generated in this study. Since soil moisture in May 27th, June 15th, and July 18th 2005 and crop yield in 2002 and 2005 to find factors (A horizon texture and depth to clay layer) were used to modify the refined map, we used soil moisture and crop yield collected in other times in this figure to validate out results.
Summaries and Conclusions
A refined soil map was generated from the information of EMI
surveys, DEM and depth to bedrock (Fig. 2).
Precision soil map for investigating site-specific water movement and crop management were generated by modifying the refined soil map with depth to clay layer and A
horizon texture (Fig. 2).
Precision soil map provides enhanced information than the current second order soil map for crop yield and soil moisture management (Fig. 3).
Table 1. The 99% confidence intervals of the ECa values for the five soil series mapped at the Kepler Farm
Soil series
No. soil cores
EM 31-V
mS/m
EM-HCP
Oqequon 48
(6.70, 7.80)
(7.47, 9.03)
Hagerstown 63
(7.81, 10.11)
(9.16, 10.29)
Murrill 17
(7.44, 9.88)
(11.25, 12.30)
Nolin 10
(10.65, 13.80)
(10.50, 13.08)
Melvin 7
(15.00, 16.54)
(16.43, 20.99)
Fig. 2. Procedure used for generating a precision soil map for soil moisture and crop management at the Kepler Farm.