Changes in soil properties for 6 years of using the freshwater snail (Ampullaria tischbeini Dohrn) in a reclaimed sodic soil

Purpose A field experiment was carried out to assess the effects of using the freshwater snail ( Ampullaria tischbeini Dohrn) in a reclaimed sodic soil that contains low salt concentrations for 6 years. Materials and methods A field experiment was conducted during 2010–2015 at the experimental station located in Yomju County, North Phyongan Province, DPR Korea. Initial soil sampling was performed at random from the plots after rice harvest just before the start of the experiment in the early November 2009; these were analyzed for basic soil properties such as pH, macronutrients, exchangeable cations, bulk density, and water infiltration. Soil sampling for the present study was performed after the rice harvest each year for 6 years, to determine the effect of using A. tischbeini on soil properties. Results and discussion The bulk density and infiltration rate in the experimental plots with snails were significantly improved as compared to the control plot without snails at 0–10, 10–20, and 20–30 cm soil depths. Compared to controls, the experimental plots had significantly higher pH (average 5.6 vs. 4.6, P < 0.01) and organic matter content (average 3.5 vs. 1.9%, P < 0.01). Calculations for 0–10 cm soil depth showed that the experimental plots with snails contained 38.3 and 33.1 mg kg −1 more N and P contents than control plots without snails, respectively. Like N and P, the soil in the experimental plots had significantly higher available K contents compared with control plots. The soil also showed a dissimilar pattern of change in the concentration of exchangeable ions (Na + , Ca 2+ , and Mg 2+ ) with a decrease in the Mg 2+ to Ca 2+ ratios. Conclusions A. tischbeini plays an important role in the improvement of soil physical-chemical properties, although our field experiment with the snail has not been carried out under different conditions of soil, climate, distribution of crops, fertilizer application, and agricultural management. Further work now needs to assess the direct effects of the use A. tischbeini on soil microbes and micronutrients under different field conditions.