Spatial variability of soil water content and salinity in a semi-arid agricultural field / Rumslig variabilitet av markvattenhalt och salinitet i ett semiaritt fält
One technique for collecting rainwater and prevent soil erosion applied on large areas in Tunisia involves the use of soil ridges (1-1.5 m high). These contour ridges are constructed parallel to topographical isolines. The effects of the contour ridges on the soil water content distribution, bulk soil salinity ECa, and soil water salinity (ECw) were investigated in the catchment of El-Gouazine in central Tunisia. In total 258 measuring points were obtained in an 80 m x 120 m area. Spatial maps of ECw, ECa, and water contentƒndisplayed essentially a random variation and no apparent pattern within the sampling area. A geostatistical analysis, however, displayed spatial correlation for all variables. A variational analysis displayed small measurement errors as compared to small-scale variation in the soil. A potential risk with soil ridges could be salt accumulation just upstream the ridges, however, no such effect could be observed in the studied area.