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Vol. 11, Special Issue 4 (2022)

Macro-aggregate dynamics over time and changes in soil organic carbon concentration and stability variation in top and deep soils under conservation agriculture based practices in rice-wheat system: A review

Author(s):
Rajaram Choudhary, RK Naresh, Yogesh Kumar, Manisha, Shivam Kaushik, K Lokeshwar, Rameshwar Choudhary and Mohd Shah Alam
Abstract:
Deteriorating soil health, diminishing soil organic carbon (SOC), development of subsurface hard compact layer and declining system productivity are barriers to achieving sustainable production in the traditional rice–wheat cropping system (TA) in the North Western Indo-Gangetic Plain of India. Conservation agriculture (CA), which favors minimum soil disturbance and crop residue retention, could be a viable alternative to the TA to address most of those major problems. Zero tillage combined with crop rotation and crop residues retention resulted in a higher proportion of macro-aggregates. In the 0–5 cm layer, plots with a crop rotation and monoculture of maize and wheat in ZT + R had the greatest proportion of large stable macro-aggregates (40%) and highest mean weighted diameter (MWD) (1.7 mm). Compared with CT, RT significantly increased the proportion of small macro-aggregates by 23%–81% in the 10–80 cm layer and the OC content in small macro-aggregates by 1%–58% in the 0–80 cm layer.
RT significantly increased (by 24%–90%) the OC content in mineral-SOC within small macro-aggregates in the 0–60 cm layer, while there was a 23%–80% increase in the 0–40 cm layer with NT. The plots with CT had the largest proportion of micro-aggregates (27%). In the 5–10 cm layer, plots with residue retention in both CT and ZT or with monoculture of wheat in plots under ZT without residues (1.4 mm) had the greatest MWD. The 0–10 cm soil layer had a greater proportion of small macro-aggregates compared to large macro-aggregates and micro-aggregates. The contribution of macro-aggregates to SOC stock was larger (36–66%) under CA in the 0–7.5-cm soil layer. Adoption of CA improved the macro-aggregate content, MWD and GMD of aggregates, and aggregation ratio. The reports show that deep rooted, crop-based systems, have higher total soil C stocks and more C in the smallest (< 53 μm) soil fractions indicating the recalcitrant (longer-term storage) nature of C and implying consequent ecosystem benefit of reduced chances for soil C release back to the atmosphere. Moreover, the mean stratification ratio (SR) (i.e. a ratio of the concentrations of SOC in the soil surface to those in a deeper layer) of SOC for 0–5:5–10, 10–15, 15–20, 20–25 and 25–30 cm were found higher (> 2) under CA practices compared to intensive tillage-based conventional agricultural practice.
Furthermore, because conventional cultivation destroyed aggregates, the dominant aggregate size fractions were < 0.5 mm for farmland and > 0.5 mm for other land uses. Compared to the corresponding values in farmland, the mean weight diameter (MWD) in forestland and grassland increased by 808%–417%, and the stability ratio of water-stable aggregate (WSAR) increased by 920%–553%. Aggregate formation and its dominant size fraction were associated closely with its carbon fractions.
Pages: 1423-1436  |  199 Views  48 Downloads
How to cite this article:
Rajaram Choudhary, RK Naresh, Yogesh Kumar, Manisha, Shivam Kaushik, K Lokeshwar, Rameshwar Choudhary and Mohd Shah Alam. Macro-aggregate dynamics over time and changes in soil organic carbon concentration and stability variation in top and deep soils under conservation agriculture based practices in rice-wheat system: A review. The Pharma Innovation Journal. 2022; 11(4S): 1423-1436.

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