Vol. 6, Issue 6 (2018)
Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and associated organic carbon fractions in conservation agriculture: A review
Author(s): RK Naresh, Sunil Kumar, SS Dhaliwal, Vivek, Onkar Singh and Vishal Chaudhary
Abstract: Decomposition of fresh crop residues quickly leads to the formation of water-stable (WS) soil macro-aggregates. How the initial soil organic carbon (SOC) concentration affects macro-aggregation is still unclear, and the consequences for short-term retention of crop-residue C and N are unknown. Water-stable macro-aggregate formation per unit of residue-C added was greater in the SOC-poor subsoil than in the SOC-rich topsoil. Large macro-aggregates (>1000 mm) in the SOC-poor subsoil were enriched in 13C and 15N in both particulate organic matter (POM, >50 mm) and fine particle size (<50 mm) fractions compared to the SOC-rich topsoil. We postulate that the retention of residue-C and -N in both POM and fine fractions within WS macro-aggregates is due to the large-scale occlusion of coarse material and small-scale adsorption of organic substances occurring concomitantly in soil. Although the labile pools of SOC were positively affected by conservation tillage practices (CT–NT, NT–NT, and NT–CT), the less labile pool was only influenced by the continuous NT and NT–CT in the 0- to 5-cm depth. Plots under NT–NT and NT–CT had about 27 and 19% higher labile SOC pool than CT–CT plots (5.65 g C kg–1 soil), and NT–NT and NT–CT plots had about 14 and 11% higher less labile SOC pool than CT–CT plots (2.61 g C kg–1 soil) in that soil layer. SOC storage decreased with soil depth, with a significant accumulation at 0-20cm depth. Across treatments, aggregate-associated C at a depth of0–10cm was higher in the conservation agriculture (CA) treatment than in the conventional tillage (CT) treatment. The advantage of the CA treatment weakened with soil depth, while the amount of aggregate-associated C remained higher for the CT treatment. There were more macro-aggregates in the CA treatment than in the CT treatment, while CT treatment had more micro-aggregates. The sum of macro-aggregate contributing rates for clay-humus stability of soil organic C (SOC) was significantly superior to that of the micro-aggregates. Water-stable aggregates increased by 34.5% in the CA with residue retention treatment, effectively improving the soil structure. Furthermore, 0.25–1.00 and 1–2mm aggregates had the highest SOC microbial biomass storage and responded rapidly to the various tillage treatments. Greater proportion of micro-aggregates within macro-aggregates in the plots under NT–NT compared with CT–CT was also observed in the surface layer only. Plots under NT–NT had about 10% higher coarse (250–2000 μm) intra-aggregate particulate organic matter-C (iPOM–C) within >2000 μm sand free aggregates in the 0- to 5-cm soil layer compared with CT–CT plots. The fine (53–250 μm) iPOM–C within the 250- to 2000-μm aggregates was also higher in the continuous NT plots compared with CT within both >2000 and 250 to 2000 μm sand free aggregate size classes in that soil layer. The application of conservation tillage practices to be crucial for maintaining soil quality and stability of organic carbon in soils of the North West IGP.
Pages: 749-758 | 387 Views 54 Downloads
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How to cite this article:
RK Naresh, Sunil Kumar, SS Dhaliwal, Vivek, Onkar Singh, Vishal Chaudhary. Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and associated organic carbon fractions in conservation agriculture: A review. Int J Chem Stud 2018;6(6):749-758.
