Effect Of Excessive Applications Of Calcium Sulphate and Ammonium Sulphate In Soil pH, Electrical Conductivity, Sodium and Micronutrient Availability.

Several agricultural areas in northeast Florida suffer from saltwater intrusion in the Floridian aquifer due to their proximity to the Atlantic coastline and local geology. Calcium sulphate (CS) has been used in large quantities as a source of Ca to potato plants and there are indications CS could be used to suppress the salinity problems.  The objective of this study was to investigate the effects of high rates of CS and ammonium sulphate (AS) on the dynamics of soil pH, electrical conductivity (EC), Na and micronutrient availability. Soil samples were collected from a NE potato field with high salinity and high level of nutrients in the soil. Application rates were equivalent to 0 to 4 ton/ha of CS and 0 to 0.6 ton/ha of AS. The soil was incubated for 60 days at 25٥C while maintaining the soil moisture at 60% of field capacity. After incubation, the soil was extracted with KCl 2M and analyzed for pH, EC, Na, Mn and Zn. Increased rates of CS rates resulted in a small decrease in soil pH, from 5.9 to 5.7,and in linear increase of EC (EC=1.307-4.78*10^-4CS, R²=0.9). At the application rate of 200 kg/ha of AS, common N-rate for potatoes, resulted in a decrease of pH from 5.9 to 5.2, while the EC increased from 1.3 to 3.0 dS/m. Extractable Na increased exponentially with the application of CS  and AS . The soil availability of Na increased with the decrease of soil pH and was described by a quadratic function (Na = -658.32 +379.47pH-40.77pH², R² =0.66). The soil availability of the micronutrients Mn and Zn was not affected by application of CS. Applications of AS resulted in a linear (R²=0.95) and exponential (R²=0.56) increase of availability for Mn and Zn, respectively.