Spatial structure analysis of field measurement soil water status along a line transect in a sandy soil

The spatial structures of soil water status, in terms of soil water content and tension, were examined on bare and cultivated soil in Ponticelli, Naples (Italy). Measurements were made in situ at 0.30 m depth on two transects consisting of 50 positions 1 m apart. Autocorrelation and spectral density functions were used to describe the spatial structure. Autocorrelation functions showed strong spatial dependence of variables also under cultivated plot. Spectral density functions for both moisture content and tension showed a concentration of variance at low frequencies. The variance in water tension increased as the soil dried; this trend agrees with predictions from stochastic theory. These results are valuable for sampling strategies and provide guidelines for the proper use of soil water status sensors for irrigation scheduling.