Reducing sampling intensity in order to investigate

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revealed different spatial structures among studied soil properties and .... distribution of pH, available phosphorus (AP), HA and OM in Croatia on regional scale.
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Reducing sampling intensity in order to investigate spatial variability

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of soil pH, organic matter and available phosphorus using co-kriging

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techniques. A case study of acid soils in Eastern Croatia

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Abstract

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Soil pH, hydrolytic acidity (HA), organic matter (OM) and plant available

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phosphorus (AP) are factors controlling the environmental-friendly soil

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management in agroecosystems. These parameters are highly variable in space.

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The objective of this work is to study spatial variability of pH, HA, OM and AP

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using several interpolation methods in Eastern Croatia. A total of 1004 (0 - 30

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cm) soil samples were collected, and several univariate and multivariate

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interpolation performances were tested. The results showed that soils of the study

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area had high HA and AP, while pH and OM was low. The variogram analysis

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revealed different spatial structures among studied soil properties and

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demonstrate a need for variable-rate management. Soil pH and OM had lower

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spatial variability compared to AP and HA. Ordinary kriging was the most

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accurate method to estimates the studied variables. The incorporation of auxiliary

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variables increased the precision of the estimations for HA. Soil AP and OM

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showed different results for spatial prediction obtained by co-kriging. Overall the

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incorporation of pH as auxiliary variable increased the prediction of the models.

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However, more co-variates should be incorporated in further models, in order to

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identify with more precision areas that need to be restored.

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Keywords: agroecosystem, soil fertility, site-specific fertilisation, GIS,

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multivariate geostatistic

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Introduction

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Soil degradation is a human-induced phenomena and it represents a global problem that

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occurs at all soils and climatic conditions (Kisic et al. 2016; Ebeling et al. 2016;

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Bogunovic & Kisic 2017). It represents the greatest problem for soils in their provision

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and regulating ecosystem services. Due to soil acidity degraded soils represent one of

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the most important limitations for optimal crop production worldwide. Approximately

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one third of the world’s soils are acidic (pH

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