Humus Acid Plus Organic Ameliorant Increase SOC and Sic by Inhibiting Salinity and Alleviating the Microbial Resource Limitation in Saline Soils

Abstract

Fertilization strategies have been widely studied as an effective strategy to improve the structure and fertility of saline soils. However, the effect of different fertilization strategies on soil carbon (C) pool is still not clear. We conducted two-year field experiment to investigate the effects of fertilization strategy on soil organic C (SOC) and soil inorganic C (SIC) contents and stocks at 0-20 cm and 20-40 cm layers in the semi-arid saline region of Western China. Our results showed that the application of organic ameliorant (OM), humus acid plus OM (HA+OM), and biofertilizer plus OM (B+OM) increased the content and stock of total C and SOC at 0-40 cm soil layer than the chemical fertilizer (CK) soils by 9%-40%, and HA+OM increased the content and stock of SIC at 0-40 cm soil layer by 18% after two years. In addition, soil microorganisms were generally limited by P, and HA+OM reduced microbial P and N limitations after two years application. The structural equation modeling (SEM) showed that reduced microbial N and P limitation under HA+OM was mainly directly driven by the reduction in EC content. The redundancy analysis (RDA) and correlation further confirmed that soil EC and microbial resource limitation were the main factors affecting soil C content. In addition, HA+OM promoted the positive regulation of SOC on SIC, which facilitated the formation of SIC. The higher accumulation of SOC and SIC under HA+OM were both beneficial to the enhancement on total C stock in saline soil. Overall, our results provided an effective regime to improve the soil saline and microbial environments, and increase the potential for rapid enhancement of soil C stock of saline soil in Northwest China.

Keywords: SOC, SIC, enzyme activities, microbial resource limitation, fertilization strategies, Saline Soil