Studies that involve soil attributes variability help the analysis of the behavior of hydrophysical attributes in space, to support the decision-making process within the conception of precision agriculture. The aim of the present paper was to characterize the spatial variability of the surface infiltration and its relation to some soil physical attributes. The sampling was done with a rectangular mesh of 64 points with perpendicular distances of 52 m × 45 m between sampling points. The attributes studied were bulk density, contents of sand, silt and clay, soil moisture, cumulative infiltration, basic infiltration, sorptivity, and saturated hydraulic conductivity (Ks). Data were analyzed using descriptive statistics and geostatistics, identifying the relationship between attributes, using the Pearson correlation and cluster analysis. Results suggest a behavior of parameters close to normal, attributes related to soil water movement had greater variability, with low basic infiltration (1.46 cm h -1 ) and Ks (0.80 cm h ) show limitations by compaction. Cumulative infiltration and Ks attributes did not fit to models of spatial distribution, finding ranges of 150 m for the other attributes, distance to optimize future sampling for the study of spatial variability. Pearson correlation and cluster analysis allowed establishing relationships between soil attributes; spatial relationships were corroborated in contour maps, where we observed the influence of clay and sand content in the behavior of bulk density, and the influence of these attributes in processes of water infiltration into the soil.

The Andean paramo is an important global carbon sink and has a fundamental ecological function of capture, regulation and supply of water resources. The soil CO2 efflux is a natural process through which the carbon is released into the atmo sphere by molecular diffusion. The aim of this study was to establish the effect of different land use and soil managements practices over CO2 efflux in the Paramo de Guerrero, using the soil respiration chamber technique. We evaluated five differ ent land covers present in the Paramo de Guerrero (paramo vegetation, pasture, two tillage cover and potato crop). Our results show that soil respiration was lower in the paramo (0.42 g CO2 m-2 h-1) than in the others land uses, probably due to the higher moisture content (57.1% on average). The tillage practices showed a primary physical effect, continued by the increase of the velocity of biological and chemical processes drived by soil microorganisms, such as microbial respiration and organic matter mineralization. This study demostrates that moisture and soil temperature were not the main drivers of CO2 flux in the conditions of the Paramo de Guerrero, but the agricultural management and the land use affect differentially the accumulation and release dynamics of soil organic carbon to the atmosphere.

In Colombia, the zone of the greatest agricultural expansion includes soils within the native savanna system. These soils are Oxisols, which have a stable structure but are susceptible to physical degradation. The objective of this paper was to study the spatial variability of the soil physical properties with the aim of determining management units. This study was carried out in the municipality of Puerto Gaitán, Meta, Colombia, in an area of 5100 ha where nodes were placed every 320 m in a grid. The samples were taken from the surface (A H ) and subsurface (B H ) horizons in which the texture, pore distribution, saturated hydraulic conductivity (K S ), bulk density (B D ) and soil particle density (P D ) were determined. The data analysis was conducted using descriptive statistics, geostatistics and multivariate analysis. The predominant textures of the soil were loam and sandy loam. High values of B D , high values of microporosity, low presence of mesopores and slow K S were found, which result in physical limitations for adequate development of crops. The B D and the total porosity were the properties that best characterized the soil and showed the greatest number of significant correlations with the other physical properties. The K S was the only property that did not show spatial dependence. Geostatistics allowed the identification of spatial variability patterns, estimation of the properties at non-sampled sites, and identification of management units of the properties that fit the semivariogram models. Multivariate analysis identified the most representative properties of the soil and permitted the establishment of management units. 767 In Colombia, Oxisols appear in the so-called Llanos Orientales (Eastern Plains), which cover more than 20 million hectares (Phiri et al., 2001) of which more than Camacho-Tamayo et al.

En sistemas productivos del Piedemonte de los Llanos Orientales de Colombia se evaluaron va-rios indicadores para determinar la calidad de los suelos de la región.  Para el efecto, en un muestreo aleatorio se incluyeron once sistemas y en cada uno de ellos se tomaron cinco mues-tras de suelo para evaluar las propiedades principales y seleccionar aquellas con posibilidades para ser incluidas como indicadores de calidad.  Los resultados de la caracterización completa fueron analizados mediante componentes principales (ACP).  Por su importancia fueron prioriza-das como indicadores de calidad las propiedades siguientes: carbono orgánico, pH, acidez inter-cambiable, calcio y magnesio intercambiable y hierro.  Con estos indicadores se propone una clasificación de la calidad química de los suelos de la región, que puede ser de gran utilidad en la implementación de sistemas de monitoreo que permitan la evaluación de la degradación de los suelos a través del tiempo debidos a cambios en los sistemas de uso.

The study of water infiltration processes into the soil helps to understand hydrological processes, soil degradation and solutes transport, with significant support to minimize runoff processes. The aim of this study was to evaluate the infiltration behaviour through Kostiakov, Kostiakov-Lewis and Philip models. This research was carried out at the Puerto López municipality (Meta-Colombia). The methodology included the implementation of 64 infiltration tests, using double ring infiltrometer, located in a rectangular grid sampling of 52m by 45m. At each grid point soil samples were taken at 10cm depth, to determine texture, bulk density and volumetric moisture. With the experimental infiltration curves adjustments were made to the empirical models for each point. For data analysis descriptive statistics were implemented in order to understand the behaviour and dispersion of soil properties. Correlations between soil properties and parameters of the estimated models were also established. The experimental data were better fit the Kostiakov-Lewis model, following the model of Kostiakov, with an R 2 of 0.99 and 0.98, respectively. The property of higher incidence over the infiltration was the bulk density, showing an inverse correlation with most of the parameters. The infiltration variability indicates the desirability of identifying management zones, to avoid a deficit or excess water, which can carry the crop to water stress or contribute to runoff processes.