Effect of Woody Organic Matter Amendments on Soil Water-Salt Dynamics in Saline-Alkali Soil Restoration.

Intensive agricultural practices have resulted in severely degraded soils, especially where evaporation of irrigation water in semi-arid regions has produced highly saline soils. Our team has been investigating the use of woody organic matter amendments to jumpstart the restoration of degraded, salinized soils in Ningxia, China. Two experiments were conducted to study soil water and salinity distribution in saline-alkali soil during the process of restoration. Treatments consisted of two amendment types (straw and wood chips) and four different amounts (control, 1%, 3%, and 5%). Water content at field capacity increased with increasing organic matter content. Straw-amended soils had higher field capacity and lower bulk density than comparable woody amended soil. When flushed with water, a greater amount of salt was leached from the wood-amended than the straw-amended treatments (17.8g salt from 3% wood treatment vs 11.6g and 9.9g salt removed from straw treatment and control). The wood chip treatment displayed a significant long-term effect of suppressing and controlling soil salt in the surface soil layer. Soil salt content was 42.99% and 14.13% lower in wood chip treatment than in the control and straw treatments, respectively. A micro-plot field experiment was conducted both with and without irrigation and with three treatments:  CM+CI (wood chips mulching and incorporation), CK_P (plastic film mulching), and CK_T (tillage). Under irrigation, CM+CI not only significantly enhanced water storage capacity of the 10～30 cm soil layer, but also continuously preserved soil moisture. Soil water content was 3.52% and 1.22% higher in CM+CI than in treatments CK_T and CK_P respectively, across the entire period. Moreover, treatment CM+CI established a favorable soil solution system to lower salt and salt removal rate to 51.92% and 7.91%, as compared with CK_T and CK_P. No such differences were exhibited without irrigation. Wood chip amendments show great potential to help improve salinized soils.