Spatial and Temporal Patterns of Soil Water Content in Organic Vegetable Production System.

Studies on spatial and temporal patterns of soil water content have been focused on understanding the soil water dynamics in agricultural soils, and on reducing the number of observations in space and time while still being able to monitor the important soil water processes in field. The spatial distribution of soil water content in relation to the patterns of texture, soil organic carbon, growth rate of vegetation and landscape morphology is not well understood. Therefore, the aim of the study was to evaluate the following aspects of soil water content: i) the spatial and temporal variability pattern within the study site, ii) the factors that affect spatial variations of soil water content and, iii) the distribution and stability of wettest and driest locations in the field. The experiment was carried out in Seropedica, Brazil, in an area of 2502 m². Soil water content was monitored across a 10 by 10 m grid. At each point of the grid, Time Domain Reflectometers  sensors were installed at the 0.05, 0.15 and 0.30 m soil depths. Soil moisture was monitored 27 times over two growing season. The soil water content at the three depths followed the same pattern over depth and was highest in the deepest layer. Soil water content exhibited temporal stability within but not across both seasons. Depending on the magnitude of soil water content and on the phase of redistribution, drying or wetting the intensity of temporal stability varied. Due to less pronounced stability, the number of observations to be taken during the wet season has to higher than for the dry season. Correlation between soil water and clay content varied with depth and time, indicating a different manifestation of underlying soil properties on water dynamics.