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Vol. 11, Issue 2 (2022)

Influence of tillage practices, fertilization and straw alters on soil aggregates, organic carbon composition and microbial community in rice-wheat cropping system: A review

K Lokeshwar, RK Naresh, SP Singh, Manisha, Rajaram Choudhary, Mohd Shah Alam and Himanshu T
In India, the average soil organic carbon (SOC) content of cultivated land is 30% less than the world average. Therefore, cultivation management-induced changes in SOC dynamics are necessary, especially in Typic Ustochrept soils, where the SOC stocks are limited. 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. SOC pools, such as coarse particulate organic matter C (CPOM-C), microbial biomass carbon (MBC), and mineralizable C (C min) 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 Cha-1yr-1whereas the NPK treatment sequestered 0.16 Mg Cha-1yr-1.
Relative to the control (no nutrient input CK), long-term fertilization appreciably increased SOC storage by 134, 89 and 129 kg ha–1 yr–1 under CF, and 418, 153 and 384 kg ha–1 yr–1 under organic manure plus chemical fertilizers (MCF) in plough layer soils (0–20 cm). The mineral-associated OC (MOC) pools accounted for 72, 67 and 64% of the total SOC with sequestration rates of 76, 57 and 83 kg ha–1yr–1 under chemical fertilizers (CF) and 238, 118 and 156 kg ha–1 yr–1 under MCF, respectively. Moreover, the MOC pool displayed a saturation behavior under MCF conditions. The particulate OC (POC) accordingly constituted 27, 33 and 36% of SOC, of which Light-POC accounted for 11, 17 and 22% and Heavy-POC for 17, 16 and 15% of SOC, respectively. The sequestration rates of POC were 58, 32 and 46 kg ha–1yr–1 under CF, and 181, 90 and 228 kg ha–1 yr–1 under MCF in which Light-POC explained 59, 81 and 72% of POC under CF, and 60, 40 and 69% of POC under MCF, with Heavy-POC accounting for the balance. Compared with CK, the application of CF alone did not affect the proportions of MOC or total POC to SOC, whereas MCF application markedly reduced the proportion of MOC and increased the POC ratio, mainly in the Light-POC pool. The distribution of SOC among different pools was closely related to the distribution and stability of aggregates.
Compared to conventional tillage, conservation tillage (no-tillage coupled with straw return) increased water-stable large macro-aggregates (>2 mm) by 35.18%, small macro-aggregates (2–0.25 mm) by 33.52% and micro-aggregates by 25.10% in the topsoil (0–20 cm). The subsoil (20–40 cm) also showed the same trend. Compared to conventional tillage without straw return, large and, small macro-aggregates and micro-aggregates in conservation tillage were increased by 24.52%, 28.48% and 18.12%, respectively. Straw return also caused a significant increase in aggregate-associated carbon (aggregate-associated C). No-tillage coupled with straw return had more total aggregate-associated C within all the aggregate fractions in the topsoil. But the different is that conventional tillage with straw return resulted in more aggregate-associated C than conservation tillage in the subsoil. No-tillage combined with straw return produced the highest carbon preservation capacity (CPC) of macro-aggregates and micro-aggregates in the topsoil. A considerable proportion of the SOC was found to be stocked in the small macro-aggregates under both topsoil (74.56%) and subsoil (67.09%).
The review study confirmed that conservation tillage with organic manure amendment not only sequestered more SOC but also significantly altered the composition of SOC, thus improving SOC quality, which is possibly related to the SOC saturation level. Thus, straw return integrated with mineral fertilization in rice- wheat croplands leads to increased SOC stocks. However, those effects of straw return are highly dependent on fertilizer management, cropping system, soil type, duration period, and the initial SOC content.
Pages: 539-555  |  288 Views  64 Downloads

The Pharma Innovation Journal
How to cite this article:
K Lokeshwar, RK Naresh, SP Singh, Manisha, Rajaram Choudhary, Mohd Shah Alam, Himanshu T. Influence of tillage practices, fertilization and straw alters on soil aggregates, organic carbon composition and microbial community in rice-wheat cropping system: A review. Pharma Innovation 2022;11(2):539-555.

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