Delineation of site-specific management units for operational applications using the topographic position index in La Pampa, Argentina

MIEZA, MARÍA SOLEDAD; CRAVERO, WALTER RUBÉN; KOVAC, FEDERICO DARÍO; BARGIANO, PABLO GASTÓN

COMPUTERS AND ELETRONICS IN AGRICULTURE

ELSEVIER SCI LTD

Año: 2016 vol. 127 p. 158 - 167

0168-1699

In this work we propose the use of the topographic position index (TPI), which takes into account thelocal topography for a given neighborhood, to delineate management units (MU) for site-specific systems.This study was performed in the province of La Pampa, in central Argentina, an area with sandy soilswhere the main limiting condition for crops is soil moisture. Usually, multi-annual yield maps are usedfor the delineation of MU. However, those are strongly influenced by issues that could be related to uncalibrateddata and previous agronomical practices. Thus, there was a need for a methodology based onstable and unbiased parameters. The methodology was developed for a representative 100 ha field. Theaverage size and orientation of the topographic structures were characterized applying the autocorrelationfunction on the topographic data, which was then used to determine an optimum neighborhood sizefor the TPI. TPI performed better than the topographic map to characterize the variability of the field. Thecorrelation between yield and TPI was higher (r = 0.74) than that between yield and topography (r = 0.54).The resulting management units were delineated using an unsupervised classification approach on theTPI maps. From the confusion matrices, the overall accuracy was higher for the TPI derived maps thanfor the topography derived maps (62% against 47%) when compared to a yield map used as reference.We estimate that this methodology could be used for operational applications, the only requirementbeing topographic data for a given field, since it is simple, the algorithms used are unbiased and it couldbe performed using free software