Salt-affected soils are characteristics of arid and semi-arid zones of the world. This study was undertaken at Açu valley region of Rio Grande do Norte State, Brazil, by means of a field experiment conducted from April/90 to January/91. The objective of this study was to evaluate the effects of subsoiling and amendment additions (gypsum, farmyard manure and Copernica cerifera straw), on chemical properties of saline sodic soil. Subsoiling treatment provided beneficial effects decreasing soil exchangeable sodium percentage (ESP) and pH levels. Gypsum treatments increased soil exchangeable-Ca and salinity levels and decreased ESP to levels lower than 15% in soil layer depth to 0-0.15 m. Farmyard manure treatment decreased ESP levels, especially when associated with subsoiling and gypsum treatment. There is a natural imbalance in K:Ca:Mg ratios that increases with gypsum treatments requiring soil potassium correction in order to reach the equilibrium. The ratios between exchangeable and soluble cations ranged from 13 to 16:1 for calcium and magnesium and from 0.3 and 3.9:1 for sodium. Among the soluble cations, sodium was the only one decreased by subsoiling.
salinity; sodicity; gypsum; farmyard manure; Copernica cerifera straw; cation ratio