Igor Bogunović

Spatial distribution of soil chemical properties in an organic farm in Croatia

Soil pH, electrical conductivity (EC), organic matter (OM), available phosphorus (AP), and potassium (AK) are some of the most important indicators of soil fertility. These soil parameters are highly variable in space and time, especially in agricultural areas, with implications for crop production. The aim of this work was to study the spatial variability of pH, EC, OM, AP and AK using kriging and co-kriging methods in the Rasa River Valley (Croatia). As co-variates for each variable we considered the distance from the sea (DFS), distance from the river channels (DFC), pH, EC, OM, AP and AK. Only the variables with a significant correlation with the predictor were used as predictor variables. The results showed that soils of the study area had high pH, EC, OM and AK values and a low concentration of AP. The spatial variability was high for EC and low for pH levels. pH, EC, OM and AK had significant positive correlations. All these variables had significant negative correlations with AP. The exponential model was the best to model OM, AK and AP. Spherical and Gaussian models were the most accurate to model pH and EC. Spatial dependence was high for soil AK, EC and pH, and moderate for soil OM and AP. The incorporation of auxiliary variables increased the precision of the estimations. CoK_DFS was the best method to predict soil EC and AP, while Cok_EC, was better to estimate soil pH and Cok_pH and Cok_OM predicted soil OM and AK with the best accuracy. The maps produced with the best predictors showed that pH, EC, OM and AK had high levels in the northern and eastern parts of the study area. The opposite trend was identified in relation to the AP spatial pattern.

The role of tillage and crops on a soil loss of an arable Stagnic Luvisol

ABSTRACT The poor physical, chemical and biological properties make Stagnic Luvisol highly susceptible to water erosion on sloping terrains. The objective of this paper is to estimate the effect of different tillage treatments and crops (maize, soybean, winter wheat, spring barley, oilseed rape) on water erosion. The highest erosion in investigation period (1995–2014) was recorded in the control treatment with fallow, followed by the treatment that involved ploughing and sowing up and down the slope. Significantly, lower soil losses were recorded in no-tillage and treatments with ploughing and sowing across the slope. Regarding the crops significantly higher soil losses were recorded in spring row crops (maize and soybean) compared to high-density winter crops (wheat and oilseed rape) and double crop (spring barley with soybean). In the studied period, an average loss of 46 mm of the plough layer was recorded in the control treatment, while in treatment with ploughing and sowing up and down the slope average annual soil loss was 10 mm. According to the results of this study no-tillage and tillage across the slope are recommended as tillage which preserves soil for the next generations in agro-ecological conditions of continental Croatia.

Reducing sampling intensity in order to investigate spatial variability of soil pH, organic matter and available phosphorus using co-kriging techniques. A case study of acid soils in Eastern Croatia

ABSTRACT Soil pH, hydrolytic acidity (HA), organic matter (OM) and plant available phosphorus (AP) are factors controlling the environmental-friendly soil management in agroecosystems. These parameters are highly variable in space. The objective of this work is to study spatial variability of pH, HA, OM and AP using several interpolation methods in Eastern Croatia. A total of 1004 (0–30 cm) soil samples were collected, and several univariate and multivariate interpolation performances were tested. The results showed that soils of the study area had high HA and AP, while pH and OM were low. The variogram analysis revealed different spatial structures among studied soil properties and demonstrate a need for variable-rate management. Soil pH and OM had lower spatial variability compared to AP and HA. Ordinary kriging was the most accurate method to estimate the studied variables. The incorporation of auxiliary variables increased the precision of the estimations for HA. Soil AP and OM showed different results for spatial prediction obtained by co-kriging. Overall, the incorporation of pH as auxiliary variable increased the prediction of the models. However, more co-variates should be incorporated in further models, in order to identify with more precision areas that need to be restored.

Soil compaction in vineyards of different ages in Pannonian Croatia. Part I. Influence of machinery traffic and soil management on compaction of individual horizons.

Soil compaction is one of the most important problems in agricultural production. Tillage system with frequent machinery traffic due protection, agrotechnic operation and harvesting has effect on different soil compaction levels in the vineyards. The aim of this study was to determine and compare the soil resistance, soil bulk density and soil moisture within and between rows in the seven-year and thirty-year vineyard due to tillage and compacting by machinery traffic. Results show statistically lower soil resistance to a depth of 40 cm in tilled interrow position in all vineyards as a direct effect of tillage. The values of bulk density in both vineyards are lowest in row position which is convenient for root growth. Increased values of bulk density that can restrict root development are recorded in interrows position in all vineyards. The moisture content of all vineyards increases with depth. Greater deviation in compaction between seven-year and thirty-year vineyard is not recorded. The research results indicate that the soil management is more important factor than the number of machinery passes. Soil resistance values does not give a complete information about compaction because of all the factors it is most depend on current soil moisture.

Mapping soil organic matter in the Baranja region (Croatia): Geological and anthropic forcing parameters

Spatial mapping of soil organic matter (SOM) and evaluation of the related natural and anthropic influencing factors are crucial to monitor the extent of degraded land and the evolution of soil functions. The objective of this work is to study the spatial distribution of SOM in a highly exploited agricultural area in the Baranja Region (Croatia). The spatially dense dataset available (4825 top-soil samples from 0 to 30 cm) allowed to produce reliable SOM maps using geostatistical interpolation kriging algorithms and to study the relationships with possible influencing factors. The interpolation has been conducted by means of two approaches. In one approach, the overall data set is considered for computing a global variogram and performing a direct interpolation of SOM values. In the second approach, the data are stratified according to two different geological and morphogenetic domains, Holocene Domain (HD) and Pleistocene Domain (PD), and a distinct geostatistical analysis is performed in each domain. The results showed that average SOM in the studied region was 2.29%, indicating a future need for adopting sustainable soil management practices in this region. SOM was significantly higher in HD (2.64%) than PD (1.97%) domain. SOM in PD generally had a much lower global variability. Global dataset analysis reveals that regional intrinsic factors prevail over local intrinsic and extrinsic factors in determining SOM spatial patterns. In contrast, the stratified approach can filter the effect of regional variability related to the main geological and geomorphological setting. The structural spatial correlation in PD is weaker than in HD, as manifested by spatial patches of low and high SOM content with smaller extension in PD with respect to HD. The strong relationships between SOM spatial patterns and geological/geomorphological factors suggest the possibility of adopting finer subdivision criteria in future research.

Soil Compaction in different ages vineyards in Pannonian Croatia. Part II. Modeling spatial variability of soil compaction parameters in vineyard

Geostatistical modeling with different interpolation methods represents progress in describing and monitoring the spatial variability of soil properties. By choosing the proper interpolation method it is possible to produce distribution maps of investigated soil properties which are characterized by significant accuracy, and thus reduced required number of samples for the soil description and determination. On the example of determined soil penetration resistance and collected undisturbed soil samples from thirty years and seven years vineyards, and with geostatistical data analysis followed by comparison of interpolation models, spatial maps of soil resistance, bulk density and soil moisture are produced. This paper presents the applicability of GIS for characterization the spatial variation of soil resistance, bulk density and soil moisture based on 72 undisturbed samples collected at three depths (0-10 cm, 11-20 cm and 21-30 cm) and 177 measured soil penetration resistance in each of the studied vineyards located in central Croatia. The study points to the usefulness of geostatistical techniques analysis of spatial distribution of some physical soil properties. The results provided in graphical form and their associated variance, indicating the possibility of using geostatistical analysis for the sustainable management of soils in the vineyards and plans for soil conservation in the study area.