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Vol. 10, Special Issue 12 (2021)

Conservation tillage and integrated nutrient management impact on soil organic carbon fractions, labile soil organic matter pools and microbial community under rice-wheat cropping system: A review

Author(s):
Rajaram Choudhary, RK Naresh, M Sharath Chandra, Nimay Chandra Giri, K Lokeshwar and Himanshu Tiwari
Abstract:
Soil tillage can affect the stability and formation of soil aggregates by disrupting soil structure. Frequent tillage deteriorates soil structure and weakens soil aggregates, causing them to be susceptible to decay. Physical, chemical, and biological fractions of SOC pools, such as coarse particulate organic matter C (CPOM-C), microbial biomass carbon (MBC), and mineralizable C (Cmin) respond to changes in management practices and provide sensitive indication of changes in the SOC dynamics than commonly reported total soil C alone. POC reduction was mainly driven by a decrease in fine POC in topsoil, while DOC was mainly reduced in subsoil. Fine POC, LFOC and microbial biomass can be useful early indicators of changes in topsoil organic C. In contrast, LFOC and DOC are useful indicators for subsoil. Reduced proportions of fine POC, LFOC, DOC and microbial biomass to soil organic C reflected the decline in soil organic C quality caused by tillage and straw Management practices. Average SOC concentration of the control treatment was 0.54%, which increased to 0.65% in the RDF treatment and 0.82% in the RDF + FYM treatment. Compared to F1 control treatment the RDF+FYM treatment sequestered 0.33 Mg C ha-1 yr-1 whereas the NPK treatment sequestered 0.16 Mg C ha-1 yr-1. The difference of total SOC stocks between NT and CT decreased with soil depth, confirming that the SOC benefits of NT are concentrated to the immediate topsoil still subject to direct seeding.
The plots under ZT had nearly 11% and12% higher total SOC and particulate organic matter-C (POM-C) concentrations, respectively, compared with CT (~12 and 4 g kg-1 soil, in that order) plots in the 0- to 5-cm soil layer. Plots under F4 and F5 had significantly higher total SOC and POM-C contents than F2 and F3 treated plots in both soil layers. Although the labile pools of SOC were positively affected by ZT and fertilization, the recalcitrant pool was not. Plots under ZT had higher macro-aggregates, mean weight diameter (MWD), and macro-aggregate-associated SOC compared with CT in the surface soil layer only. Similarly, F4 or F5 treated plots had higher macro-aggregates, MWD, and macro-aggregate-associated SOC compared with F1, F2, or F3 treated plots in that layer.
Labile organic carbon (LOC) fractions and related microbial community in soils are considered to be early and sensitive indicators of soil quality changes. The tillage treatments significantly influenced soil aggregate stability and OC distribution. Higher MWD and GMD were observed in plowing every 2 years (2TS), plowing every 4 years (4TS) and no plowing (NTS) as compared to plowing every year without residue (T). With increasing soil depth, the amount of macro-aggregates and MWD and GMD values were increased, while the proportions of micro-aggregates and the silt+ clay fraction were declined. The OC concentrations in different aggregate fractions at all soil depths followed the order of macro-aggregates>micro-aggregates>silt+ clay fraction. In the 0-5 cm soil layer, concentrations of macro-aggregate-associated OC in 2TS, 4TS and NTS were 14, 56 and 83% higher than for T, whereas T had the greatest concentration of OC associated with the silt+ clay fraction in the 10-20 cm layer. Total organic C increased significantly with the integrated use of fertilisers and organic sources (from 13 to 16.03 g kg–1) compared with unfertilized control (11.5 g kg–1) or sole fertiliser (NPKZn; 12.17 g kg–1) treatment at 0–7.5 cm soil depth. Averaged across soil depths, labile fractions like microbial biomass C (MBC) and permanganate-oxidisable C (PmOC) were generally higher in treatments that received farmyard manure (FYM), sulfitation pressmud (SPM) or green gram residue (GR) along with NPK fertiliser, ranging from 192 to 276 mg kg–1 and from 0.60 to 0.75 g kg–1 respectively compared with NPKZn and NPK + cereal residue (CR) treatments, in which MBC and PmOC ranged from 118 to 170 mg kg–1 and from 0.43 to 0.57 g kg–1 respectively. Oxidisable organic C fractions revealed that very labile C and labile C fractions were much larger in the NPK+FYM or NPK+GR+FYM treatments, whereas the less-labile C and non-labile C fractions were larger under control and NPK+ CR treatments.
Pages: 739-756  |  270 Views  50 Downloads
How to cite this article:
Rajaram Choudhary, RK Naresh, M Sharath Chandra, Nimay Chandra Giri, K Lokeshwar and Himanshu Tiwari. Conservation tillage and integrated nutrient management impact on soil organic carbon fractions, labile soil organic matter pools and microbial community under rice-wheat cropping system: A review. The Pharma Innovation Journal. 2021; 10(12S): 739-756.

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