Humic substances to reduce salt effect on plant germination and growth

Soluble humic substances and saline solutions (NaCl solution or compost water extract) were tested in laboratory experiments of fertigation. The saline solutions were used at two levels of electrical conductivity (EC) (0.5 and 4 mS cm− 1); humic substances (HS) were solubilized in distilled water at two concentrations as humic carbon (HC) (30 and 60 mg L− 1). A mixture of NaCl solution with an EC of 4 mS cm− 1 and humic substances at 60 mg L− 1 as HC was also used to evaluate if HS can reduce the effect of NaCl on Lepidium sativum germination and Maize growth. Germination tests carried out without soil, showed that the best treatment was with HS. Growth tests, using an English soil seeded with Maize, presented the best result when the mixture of saline solution–humic substances was used; while the worst plant performance was obtained with NaCl solution alone. In addition, the treatments with NaCl solution alone caused, in the treated soil, a high release of C and N in soluble forms which could cause environmental pollution problems. Finally, a stimulation of soil metabolic potential occurred using HS at low concentration as HC.