Analysis of soil fertility and its anomalies using an objective model

Abstract

In this work, the use of an objective method, the formulation of the Rasch measurement model, which synthesizes data with different units into a uniform analytical framework, is considered to get representative measures of soil fertility potential in an experimental field. Thus, two types of information about the soil were obtained from soil samples taken at 70 locations: first, the textural components were determined, and, secondly, deep (ECa-90) and shallow (ECa-30) soil apparent electrical conductivity, approximately 0-90 and 0-30 cm depths, respectively, were measured. A latent variable, denominated soil fertility potential, was defined. It is supposed, and later it is verified, that all soil properties previously indicated have a marked influence on the latent variable. The adequate assignment of categorical values across properties measures and the good fit of the data are checked as a previous phase to properly compute the Rasch measures. After applying the Rasch methodology, it was obtained that both electrical conductivities are the most influential properties on soil fertility potential, getting moreover a ranking of all soil samples according to their fertility potential and the unexpected behaviors, called misfits, of some soil samples, which constitute a very useful information to better match soil and crop requirements as they vary in the field, being a rational basis for a site-specific crop management.

Characterization of soil fertility using the Rasch model

“…Probably, this fact is due to the important relationship existing between both soil properties (Moral et al, 2010). This result is consistent with the high values of Infit and Outfit, MNSQ and ZSTD, shown in Table 1 (Moral et al, 2012).…”

“…Soil properties measures were categorically coded according to a plan where each sample was rated on a scale (1-5) for each soil property. Details of this process can be found in Moral et al (2012).…”

“…The useful information this statistical tool can generate can give new insight from an agricultural point of view. Moral et al (2012) applied the Rasch model to obtain rational measures of soil fertility potential in a field, from ECa and textural components obtained at some soil samples. It was obtained that ECa was the most influential property on soil fertility potential.…”

Modeling of Atmospheric Pollution in Urban and Rural Sites Using a Probabilistic and Objective Approach

“…There is no general rule to initially define the correct number of categories. Following the experience in previous works [12,13], five categories were chosen. After analyzing some parameters, it was clear that this number was appropriate for the three locations.…”

“…The Rasch model have been successfully used in many studies, proven their practical utility in different cases related to the environment [8,9,[11][12][13]. As far as we know, there is no previous application of this useful methodology in this field.…”