Effect of the Amendment Modality in Oases System on Soil Fertility

The agriculture practices differ from one oasis to another in south Tunisia, we proceeded to analyze the effects of three methods of implementation of the sandy amendment on the main physical and chemical properties of degraded oasis soil by compaction and salinization. The first modality is to introduce gypsum sand amendment after the removal of the topsoil layer (RT), the second is the application of the gypsum sand amendment directly in the original soil after it has been tilled in advance (T) and the third modality is the application of gypsum sand amendment without any tillage (T0). The results obtained showed that the three modalities modified the physical and chemical properties of the amended soil in comparison to the untreated soil the original soil of the oasis (U). The (RT) and (T) modalities are significantly more advantageous than the T0 modality in improving the physical characteristics of the soil: soil porosity achieves a maximum of 48.06 ± 0.08% in RT agriculture practices, the same case for the hydraulic conductivity of the soil. The soil chemical property pH and CE, the RT and T0 modalities are significantly more advantageous than the T modality they achieve respectively for the soil pH 7.31, 7.31, and 7.34 compared to 7.25 for untreated soil. For the soil salinity, the RT modality reduces more soil salinity than the other agriculture practices to achieve 4.73 mS/cm compared to 8.38 mS/cm for untreated soil (U). In terms of economic profitability, considering the expenses on the one hand and the revenues (gain in production) on the other hand, the terms T0 and T are more advantageous than the RT modality with, respectively, 1840 TD/ha, 1640 TD/ha, and – 260 TD/ha. .