Geoscience Reference
In-Depth Information
16
Delineating Site-Specific
Management Units Using
Geospatial EC
a
Measurements
Dennis L. Corwin, Scott M. Lesch, Peter J. Shouse,
Richard Soppe, and James E. Ayars
ContentS
16.1 Introduction ......................................................................................................................... 247
16.2 Materials and Methods........................................................................................................ 248
16.2.1 Study Site............................................................................................................... 248
16.2.2 Yield Monitoring and EC
a
Survey......................................................................... 248
16.2.3 Sample Site Selection, Soil Sampling, and Soil Analyses..................................... 248
16.2.4 Statistical and Spatial Analyses............................................................................. 249
16.3 Results and Discussion........................................................................................................ 249
16.3.1 Correlation between Crop Yield and EC
a
.............................................................. 249
16.3.2 Exploratory Statistical Analysis ............................................................................ 250
16.3.3 Crop Yield Response Model Development............................................................ 251
16.4 Delineated Site-Specific Management Units ...................................................................... 252
References ...................................................................................................................................... 254
16.1 IntRodUCtIon
Site-specific crop management (or site-specific management, SSM) is a means of managing the
spatial variability of edaphic (i.e., soil related), anthropogenic, topographic, biological, and meteo-
rological factors influencing crop yield. The aim of SSM is to increase crop productivity, sustain
the soil-plant environment, optimize inputs, increase profitability, and minimize detrimental envi-
ronmental impacts. The spatial variability of edaphic factors is a consequence of pedogenic and
anthropogenic activities, which produce variation in soil physical and chemical properties within
agricultural fields. In the arid southwestern United States, the primary soil properties influencing
crop yield are salinity, soil texture and structure, plant-available water, trace elements (particularly
B), and ion toxicity from Na
+
and Cl
−
(Tanji, 1996).
Bullock and Bullock (2000) indicated that efficient, reliable methods for measuring within-field
variations in soil properties are important for precision agriculture. Because apparent soil electrical
conductivity (EC
a
) is influenced by a variety of soil properties (i.e., salinity, water content, texture,
bulk density, organic matter, and temperature) and is a reliable measurement that is easy to take,
geospatial measurements of EC
a
have become one of the most frequently used measurements to
characterize within-field variability for agricultural applications (Corwin and Lesch, 2003). Geo-
spatial measurements of EC
a
have been used to characterize spatial variation in soil salinity and
nutrients such as NO
3
−
, water content, texture-related properties, bulk density-related properties
such as compaction, leaching, and organic matter-related properties (Corwin and Lesch, 2005a).
247
