Long‐term rice cultivation improved coastal saline soil properties and multifunctionality of subsoil layers

Abstract Rice cultivation has been found to be an effective and feasible approach for improving saline soils and increasing food production. Most studies on the improvement of rice cultivation on saline soil have focused on the several individual soil properties in the topsoil, and we know little about the importance of rice cultivation for improving multifunctionality in coastal saline soils. We investigated basic soil properties (soil physical sand content, soil physical clay content, pH, EC, soil organic carbon, total nitrogen, alkaline hydrolysis nitrogen, available potassium, available phosphorus), enzyme activities (urease, catalase, protease) and soil multifunctionality (SMF) in 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm and 80–100 cm soil layers with rice cultivated for 0 (tidal flat; CK), 20 (R20), 44 (R44) and 70 years (R70). We found that soil EC was alleviated markedly in the first 20 years after rice cultivation. Soil physical sand content, pH, EC and available potassium (AK) decreased while total nitrogen (TN), alkaline hydrolysis nitrogen (AN), urease (URE), catalase (CAT) activities and SMF increased with the increase in rice cultivation years. The highest soil total organic carbon (SOC) was shown in R44. Soil pH, EC, AK and physical sand content increased while SOC, TN, AN, enzyme activities decreased with the increase in soil depth. Redundancy (RDA) analysis showed soil physicochemical properties explained 97.53% of the variation in soil enzyme activities. Soil CAT, URE and protease (PRO) had a positive correlation with soil physical clay content, SOC, TN, AN and AP while negatively correlated with pH and AK. The increased SOC and clay content by rice cultivation might be the main reasons stimulating soil enzyme activities. In summary, long‐term rice cultivation could alleviate soil salinity, increased SMF down to 1 m, implying that rice cultivation effectively improved coastal saline soil, and the improvement could last for 70 years.