The potential of cropping systems and soil amendments for carbon sequestration in soils under long‐term experiments in subtropical India

Abstract

An understanding of the dynamics of carbon (C) stock in soils, as impacted by management strategies, is necessary to identify the pathways of C sequestration in soils and for maintaining soil organic C (SOC) at a level critical for upkeeping soil health and also for restraining global warming. This is more important in tropical and subtropical region where soils are inherently low in organic C content and the production system is fragile. We evaluated the long-term role of crop residue C inputs to soil in SOC sequestration and also the critical value of C inputs for maintenance of SOC across five different ricebased cropping systems and four soil management practices including a fallow (no cultivation since initiation of the experiments) using five long-term (7-36 years) fertility experiments in subtropical India. Cropping per se always caused a net depletion of SOC. Such depletion was inversely proportional to the amount of crop residue C incorporated into the soils (r 5À0.92, P 5 0.001). Balanced fertilization with NPK, however, caused an enrichment (9.3-51.8% over the control) of SOC, its extent being influenced by the cropping systems. Long-term application of organic amendments (5-10 Mg ha À1 yr À1 ) through farmyard manure (FYM) or compost could increase SOC hardly by 10.7% constituting only 18% of the applied C, the rest getting lost through oxidation. The total quantity of soil C sequestered varied from À11.5 to 14.5 Mg C ha À1 and was linearly related (r 2 5 0.40, P 5 0.005) with cumulative crop residue C inputs to the soils. On an average, the rate of its conversion to SOC came out to be 6.4%. This was more in presence of added organics (6.9%) than in its absence (4.2%). For sustenance of SOC level (zero change due to cropping) we found that a minimum quantity of 2.9 Mg C is required to be added per hectare per annum as inputs. The cropping systems and the management practices that could provide C input higher than the above critical level are likely to sustain the SOC level and maintain good soil health in the subtropical regions of the Indian subcontinent.

Effect of Long-Term Double Rice Cultivation with Different Management Practices on C Sequestration and Economics under Hot Semi-Arid Climate in India

“…Double rice cultivation needs intensive tillage, puddling thereby destroying soil structure, and subsequently affecting distribution and stability of the aggregates (Six et al, 2002) which resulted in declining carbon content of soils. Our results are in line with Mandal et al, (2007) and Majumder et al, ( , 2008 who reported similar magnitude of SOC depletion (2-15% of fallow). .…”

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“…This observation is in line with results of other studies showing the addition of exogenous organic matter like compost resulting in an enhancement of soil organic carbon storage in addition to improvement of many functions related to the presence of organic matter (Lashermes et al, 2009, Okae-Anti et al, 2013. In tropical soils, the impact of organic amendment on long-term carbon storage might be rather small (Mandal et al, 2007). However, many studies noted their beneficial effects on nutrient cycling (Ngo et al, 2012;Kaur et al, 2005).…”

Atmospheric CO<sub>2</sub> source and sink patterns over the Indian region

“…Several model simulation studies have analysed the influence of increased CO 2 future scenarios on monsoon dynamics and precipitation (Cherchi et al, 2011;May 2011;Meehl and Washington, 1993;Meehl et al, 2000). Furthermore, other studies have shown that tropospheric CO 2 concentrations can be influenced by the strength of the monsoon and El Niño circulations (Mandal et al, 2006;Jiang et al, 2010;Schuck et al, 2010;Wang et al, 2011). Tiwari et al (2011) andBhattcharya et al (2009) have shown effects of the Indian summer monsoon on the distribution of atmospheric CO 2 .…”