European Journal of Agronomy 13 2000 295 – 308
Application of factorial kriging for mapping soil variation at field scale
S. Bocchi
a,
, A. Castrignano`
b
, F. Fornaro
b
, T. Maggiore
a
a
Dipartimento di Produzione Vegetale sezione Agronomia, 6ia Celoria
2
,
20133
Milan, Italy
b
Istituto Sperimentale Agronomico, 6ia C. Ulpiani
5
,
70125
Bari, Italy Received 3 November 1999; received in revised form 23 March 2000; accepted 4 May 2000
Abstract
Use of precision farming technologies requires better understanding of soil variability in physical, hydraulic and chemical properties. Some of that variation is natural, some is the result of the management history of the field. So,
to match agricultural inputs and practices to site-specific conditions, the factorial kriging algorithm FKA was used to analyze spatial variability 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, measured at two depths within a single field in north Italy. A linear model of coregionalization,
including, 1 a nugget effect; 2 an exponential structure 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 cross-variograms of the properties
of top layer. Cokriged regionalized factors, related to short and long-range variation, were then mapped to characterize soil variation across the field. Short-range soil variation was produced essentially by differences in soil
texture, whereas long-range variation in organic carbon concentration resulted in dishomogeneity of soil water retention. Quite probably, the variation in organic carbon concentration was caused by the patchy discharge of liquid
manure made on the field. FKA, combining pedological expert knowledge with geostatistical techniques, could be very useful to farmers so that each area within a field is managed appropriately. © 2000 Elsevier Science B.V. All
rights reserved.
Keywords
:
Spatial variability; Geostatistics; Factor kriging; Mapping www.elsevier.comlocateeja
1. Introduction
Soil specific management Stafford et al., 1996 is a recent concept of field management referring
to practices varying within a field according to soil or site conditions. Conventional farmers man-
age fields as if they were homogeneous, i.e. one set of practices is applied to the entire field. Such
management may be inefficient due to over-treat- ing and under-treating some portions of a field.
This may increase costs, decrease net economic return, contribute to surface and ground water
Corresponding author. Tel.: + 39-02-70600164; fax: + 39- 02-70633243.
E-mail address
:
stefano.bocchiunimi.it S. Bocchi. 1161-030100 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S1161-03010000061-7
pollution and waste energy. As an example, in those farms where high levels of intensification in
breeding and cropping sectors have been reached, soil contamination may arise. High quantities of
slurries are generally accumulated in specific tanks built near the cattleshed, allowing farmer to store
them for several months or use as fertilizers at the right time. Nevertheless, the distribution is not
always homogeneous since farmers tend to dis- charge the slurries mainly in those fields located
near the tanks and often from the road without entering the field, which could result in uneven
distribution on the entire soil surface. All that may cause the presence of sites or strips of accu-
mulation within the same field. To recover soil homogeneity, using site-specific technologies re-
quires more precise knowledge of physical, chemi- cal and hydrological variation in soils. Natural
variation results from complex geological and pedological processes, which may sometimes ex-
plain most of soil variation, but management can also induce variation. Producers are well aware of
soil variation within fields and increasingly want to map soil properties and to know the possible
sources of their variation — if man is causing soil contamination or general degradation, soil man-
agement must be appropriately suited to site-spe- cific properties.
The first step in soil characterization is to record the main properties and then seek plausible
explanations for their distributions in the light of the statistical analysis. Geostatistical methods are
useful for describing and understanding the spa- tial distribution of measured variables. Variogra-
phy and kriging have been used to study the distribution of physical, chemical and hydrologi-
cal properties of soils under grain crops and pas- ture Davidoff and Selim, 1988; West et al., 1989;
Cahn et al., 1994; Borges and Mallarino, 1997, analyzed variable by variable. At present, there
are few papers on the application of multivariate geostatistics to spatial data. Nevertheless, soil
variables generally appear to be correlated to some degree and so an analysis of coregionaliza-
tion could be more revealing Goovaerts and Webster, 1994; Webster et al., 1994; Dobermann
et al., 1995, 1997; Castrignano` et al., 1998, 2308. The objective of this paper is to show how
multivariate geostatistical techniques, such as fac- torial kriging, can characterize spatial variation of
an agronomic field in north Italy, which had received high quantities of slurry, and then prove
useful for a more efficient management of the cattle slurries produced in the farm.
2. Materials and methods
