Effects of humic acids on the yield and mineral nutrition of cucumber (Cucumis sativus L.) grown with different salinity levels

Effect of humic acid (polymeric polyhydroxy acid) on the yield and nutrient uptake of cucumber grown under three different saline conditions was investigated. The experiment was conducted under natural greenhouse conditions. Salinity was achieved by adding 0, 28 and 56 mmol NaCl/kg soil levels. Humic acid was applied at the rates of 0, 1.0 and 2.0 g/kg soil. Salinity decreased the fruit yield, however humic acid partly depressed this negative effect of salinity. Nitrogen, Na and Cl content of leaf and stem tissues of the plant were increased as a result of salinity. Potassium content of the leaves increased, while it was decreased in stem by the salinity regardless of applied humic acid. Concentration of Ca in stem raised and decreased in leaves due to salinity. Iron and Zn content of the leaf and stem tissues were increased by salinity and humic acid treatments. Salinity has not a clear effect on the Zn content of the plants, while humic acid increased Zn content of the plants.