Neoformation of pedogenic carbonate and conservation of lithogenic carbonate by farming practices and their contribution to carbon sequestration in soil

Abstract

Land use change, tillage practices and straw incorporation are known to affect soil organic carbon (SOC) as well as soil inorganic carbon (SIC) turnover in agricultural soils. SOC and SIC, particularly pedogenic carbonates (PC), were assessed in a semi-humid region of China to a depth of 160 cm. δ 13 C values were used to calculate the percentage of PC and lithogenic carbonates (LC) in the total SIC. Over the 39-y period of intensive agriculture including 14 y of tillage straw experiment, three treatments, i.e., tillage with wheat and maize straw return (TWM), tillage with wheat straw return (TW), and wheat and maize straw return with no-tillage (WM) showed an increase of PC compared to a native plantation plot (NP). The significantly higher SOC stock via no-tillage was limited to top 1 m soil and there was no significant difference between tillage and no-tillage treatments at 0-160 cm depth. The changes of SOC caused by the tillage and maize straw addition were negligible compared to the gain in PC. Tillage, crop residues incorporation and irrigation played an important role in the turnover of PC and LC. SIC accumulation resulted from combination of neoformation of PC and conservation of LC. Neoformation of silicatic PC sequestered at least 0.49, 0.47, and 0.29 Mg C ha -1 y -1 in TWM, TW, and WM treatments, respectively, with reference to NP plot. We concluded that to evaluate the long term impacts of land use and farming practices on soil C storage, change of pedogenic and lithogenic carbonates and soil organic carbon in deeper soil profiles should be integrated on regional and global scales.

Effects of nitrogen fertilization on pot‐grown wheat photosynthate partitioning within intensively farmed soil determined by 13C pulse‐labeling

“…The partitioning of soil CO 2 in carbonate soils presents particular challenges ( Tamir et al., ; Plestenjak et al., ; Meng et al., ). In carbonate‐containing soils with pH > 7, the following four sources may be the main contributors to CO 2 respiration: (1) root‐derived CO 2 ( i.e ., unlabeled wheat root in this study, δ 13 C = –23‰) ( Kuzyakov and Larionova , ; Kuzyakov , ), (2) SOM‐derived CO 2 ( Kuzyakov and Larionova , ; Kuzyakov , ), (3) CO 2 from either root‐derived or SOM‐derived that has been retained in the soil solution in the form of ( Amundson et al., ; Zamanian et al., ) or (4) exchanged with soil carbonate (SIC‐δ 13 C = –2.7‰ in this study) ( Tamir et al., ; Plestenjak et al., ; Zamanian et al., ; Bughio et al., ).…”

“…The δ 13 C values of the acidified soil and plant samples were determined using an isotope‐ratio mass spectrometry (DELTAplus XP, ThermoFinnigan, Bremen, Germany) in the Stable Isotope Facility at the University of California, Davis, USA. The CO 2 for δ 13 C measurements of soil solid carbonate was collected from a vacuum system in which soil samples reacted with 100% H 3 PO 4 at 70°C for 3 h ( Bughio et al., ). The collected CO 2 was then analyzed for δ 13 C values using a mass spectrometer DELTA V Advantage (Thermo Fisher Scientific, USA) located at the Third Institute of Oceanography in Xiamen, China.…”

“…Hence, in carbonate‐containing soils, quantifying soil respiration from biological sources can be particularly challenging as soil inorganic carbon (SIC) dissolution may contribute to CO 2 efflux ( Tamir et al., ; Plestenjak et al., ; Meng et al., ). There is also speculation that, due to exchange between CO 2 , , and CaCO 3 in carbonate soils, CO 2 respired by roots and microorganisms might be trapped in SIC (leading to carbonate precipitation), as long as remains in the soil solution ( Chen and Wang , ; Bughio et al., ; Zamanian et al., ). Consequently, following 14 C labeling in carbonate‐containing soils, although 14 C released by roots will be not imprinted directly by any 14 C from CaCO 3 ( Swinnen et al., ), a part of 14 CO 2 released can occur in soil solution as , which can give small underestimation of the produced CO 2 if the solubility of soil CO 2 is neglected ( Blagodatskaya and Kuzyakov , ; Zamanian et al., ).…”

“…However, in carbonate‐containing soils, carbonates are involved the dissolution [Eq. is shifted to the right] and recrystallization (in the reverse direction) reactions of CaCO 3 ( Gocke et al., ; Bughio et al., , ; Zamanian et al., ): …”

Rhizosphere Effects of Maize and Wheat Increase Soil Organic and Inorganic Carbon Release in Carbonate-Rich Soils: A Three-Source 13C Partitioning Study

“…The δ 13 C values of acidified soil and plant samples were determined using isotope-ratio mass spectrometry (DELTAplus XP, ThermoFinnigan, Bremen, Germany) in the Stable Isotope Facility at the University of California, Davis, United States. The CO 2 for δ 13 C measurements of soil solid carbonate was collected from a vacuum system in which soil samples reacted with 100% H 3 PO 4 at 70°C for 3 h (Bughio et al, 2017). The collected CO 2 was then analyzed for δ 13 C values using a DELTA V Advantage mass spectrometer (Thermo Fisher Scientific, United States) located at the Third Institute of Oceanography in Xiamen, China.…”