Corn and Rice Cultivation Affect Soil Organic and Inorganic Carbon Storage through Altering Soil Properties in Alkali Sodic Soils, Northeast of China

Abstract

Soil organic carbon (SOC) and soil inorganic carbon (SIC) play essential roles in carbon cycling in terrestrial ecosystems; however, the effects of crop cultivation on them are still poorly understood, especially in alkali sodic soils widely distributed in semiarid regions. Alkali sodic soils from cornfields and paddies with cultivation years of 5, 15, and 25 were analyzed here to assess the response of soil properties and soil carbon pools to crop cultivation. Soil pH and exchangeable sodium percentages decrease in accordance with cultivation years, while enzyme activity (amylase, invertase, and catalase) shows a contrary trend. Soil pH and exchangeable sodium percentages are negatively correlated with SOC, but positively correlated with SIC. Redundancy analysis reveals an obvious relationship between SOC and invertase activity. The percentage of δ 13 C SOC found here is approximately -24.78% to -22.97% for cornfields and approximately -26.54% to -23.81% for paddies, suggesting that crop cultivation contributes to SOC sequestration and stocking, increasing with cultivation years. The percentage of δ 13 C SIC found here is approximately 1.90% to 3.73% , proving that lithogenic inorganic carbon is the major SIC, where the stock decreases with increasing cultivation years. Significant total carbon stock loss is observed in cornfields, while it is preserved at 120 Mg ha −1 in paddies. We conclude here from the results that corn and rice cultivation reduce alkali sodic conditions in soil, thereby improving soil enzymes and favoring SOC stocking, but reducing SIC stocks.

The Development and Utilization of Saline–Alkali Land in Western Jilin Province Promoted the Sequestration of Organic Carbon Fractions in Soil Aggregates

“…Soda saline-alkali soil is the dominant type of soil in the region, and the major anions present are CO 3 2− and HCO 3 − [16]. The area was covered with native degraded grass vegetation (Leymus chinensis) before cultivation, without any prior cultivation or fertilization [17].…”

Soil Enzyme Activities Affect SOC and TN in Aggregate Fractions in Sodic-Alkali Soils, Northeast of China

“…On the other hand, this might be attributed to the developed maize root system in the surface soil, for it releases large amounts of enzymes via metabolism [3]. In our previous studies, we have observed decreasing enzyme activities followed by increasing soil alkaline status and long-term maize cultivation [39]. However, no obvious relationships or significant increases or decreases in enzyme activity in aggregates following oil sodic-alkali status were detected among fields.…”

“…Our previous studies have found that maize cultivation in sodic-alkali soils has significantly improved soil physical-chemical properties, enriching SOC content and increasing enzyme activities [39]. Soil enzymes showed positive relationships with SOC storage, where INV and CAT were closely related to SOC in the studied areas [39].…”

“…Our previous studies have found that maize cultivation in sodic-alkali soils has significantly improved soil physical-chemical properties, enriching SOC content and increasing enzyme activities [39]. Soil enzymes showed positive relationships with SOC storage, where INV and CAT were closely related to SOC in the studied areas [39]. Aggregates are a major residence of micro-organisms and store large amounts of SOC and TN in soil, which means most biochemical reactions, including reactions between SOC, TN, and enzymes, take place inside of aggregates.…”