Effects of different amendments for the reclamation of coastal saline soil on soil nutrient dynamics and electrical conductivity responses

High salinity and macronutrient deficiencies are two important limitations of coastal saline soils. The present study focused on the changes in electrical conductivity (EC), and the redistribution of water soluble carbon (C), total nitrogen (N), and absorbable phosphorus (P) during the reclamation of coastal saline soil using different amendments. Eight soil treatments were tested: cotton straw powder (J), domestic sewage sludge (W), sewage sludge + cotton residue (J + W), beach sand (S), cotton straw powder + beach sand (J + S), domestic sewage sludge + beach sand (W + S), domestic sewage sludge + cotton residue + beach sand (J + W + S), and a control treatment (CK). Triplicate soil samples for each treatment were initially treated once with underground saltwater (with or without bacterial manure). After the first month of incubation, irrigation was conducted weekly. EC measurements in different soil layers showed that sewage sludge was the best amendment for reducing soil EC, while cotton straw powder had no significant effect. Concentrations of N and C increased with soil depth, while the highest P concentration was observed in the uppermost soil. Soil amended with organic matter showed the highest P concentrations, and P availability increased with the application of all amendments except sand, which had no significant effect. The compound treatments had more positive impacts on N availability than did single amendments; however, their effects on P concentration were minimal. The results indicated that sewage sludge was the most effective amendment for reclaiming coastal saline soil and improving the availability of macronutrients.