Tillage and amendment management in organic farm on salt-affected soils in Mediterranean polder-type agricultural land in Croatia

Salt-affected soils in the Mediterranean are difficult to reclaim under organic farming, where amendment options are limited, and hydrology strongly controls salt redistribution. In an oat–triticale–barley–oat rotation, we evaluated different amendments (control, gypsum – G3, gypsum plus sulphur – G3S1, G6S2, gypsum plus farmyard manure (FYM) – G6 + OM, and gypsum plus sulphur plus FYM – G3S1 + OM) and tillage (discing and discing plus ripping) interventions on a saline–sodic Anthrosol in the Raša valley, Croatia. Crop yields were recorded annually, and soil physical and chemical properties were determined at the beginning and end of the trial. Gypsum significantly increased exchangeable Calcium (Ca) and reduced exchangeable sodium percentage (ESP). At the end of the experiment, electrical conductivity (EC) decreased significantly. Water-stable aggregates (WSA) increased significantly in all plots with added amendments, while the control plots showed the poorest structure. Ripping generally lowered bulk density and penetration resistance compared with discing, but effects were treatment- and depth-specific. Yield benefits became most evident in the last two years: barley yield was significantly lower in the control than in all amended treatments, and oat yield was 26–50% higher in G6S2, G3S1 + OM, and G6 + OM than in the control. Overall, the results indicate that gypsum-based amendments, particularly when combined with FYM, can progressively improve soil condition and crop performance under organic management, while the benefits of deep loosening remain more variable and dependent on seasonal soil conditions.