Influence of salinity in irrigation water on forage sorghum and soil chemical properties

Soluble salts found in wastewater can be toxic when used for irrigation of forages. Thus, two greenhouse experiments were conducted to investigate effects of saline [CaCl2:NaCl (3:1, w:w)] treatments on soil chemical properties and 'Dekalb FS-5' forage sorghum [Sorghum bicolor (L.) Moench], Treatments for the first experiment consisted of a nonsaline control or 500 mt pfa solution with an electrical conductivity (EC) of 10 dS m(-1) applied once. In the second experiment, treatments were salinity levels of 1.7, 3.5, 5.2, 8.5,and 12.2 dS m(-1) applied in non-nitrogenous Hoagland's solution as the sole source of irrigation. Both experiments were replicated four times. For both experiments forage sorghum was seeded in pots containing 7 kg of air-dried Amarillo fine sandy loam soil. Sorghum survivability and plant height were measured. In the second experiment, water use by sorghum was also measured. Plants were harvested 7 wk after seeding, weighed, dried at 55 degrees C, weighed and ground for subsequent mineral analysis. After harvest, soil salinity, pH, and in the second experiment, extractable soil elements were determined. Soil salinity increased, while soil pH decreased, with the salinity treatments. Extracted soil calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), manganese (Mn), and cadmium(Cd) increased while sulfur (S), iron (Fe), and copper (Cu) decreased, and aluminum (Al) and zinc (Zn) exhibited no change with increasing salinity. Sorghum aerial plant and root production decreased with increasing salinity. Plant Ca, strontium (Sr), Mn, and Cd levels increased with increasing salinity. In contrast, sorghum K, P, and S levels declined with increasing salinity.