Application of factorial kriging for mapping soil variation at field scale

Use of precision farming technologies requires better understanding of soil variability in physical, hydraulic and chemical properties. Some of that v ariation is natural, some is the result of the management history of the fi eld. So, to match agricultural inputs and practices to site-specific condit ions, the factorial kriging algorithm (FKA) was used to analyze spatial var iability in some soil physical, hydraulic and chemical properties (sand and silt concentrations, water contents corresponding to potentials of - 10, - 50, - 100, - 200, - 1000 and - 1500 kPa and organic C concentration), meas ured at two depths within a single field in north ItaIy. A linear model of coregionalization, including, (1) a nugget effect; (2) an exponential struc ture with an effective range of 120 m and (3) an exponential structure with an effective range of 350 m, was fitted to the experimental direct and cro ss-variograms of the properties of top layer. Cokriged regionalized factors , related to short and long-range variation, were then mapped to characteri ze soil variation across the field. Short-range soil variation was produced essentially by differences in soil texture, whereas long-range Variation i n organic carbon concentration resulted in dishomogeneity of soil water ret ention. Quite probably, the variation in organic carbon concentration was c aused by the patchy discharge of liquid manure made on the field. FKA, comb ining pedological expert knowledge with geostatistical techniques, could be very useful to farmers so that each area within a field is managed appropr iately. (C) 2000 Elsevier Science B.V. All rights reserved.