Abstract:
There is a global concern about progressive increases in greenhouse gases
especially CO 2 in the atmosphere by human-induced activities. An increasing
awareness about environmental pollution by CO 2 emissions has led to recognition
of the need to enhance soil C sequestration for minimizing greenhouse effects, by
sequestering
C
through
sustainable
agricultural
management
practices.
Conventional tillage has many benefits including reducing soil compaction,
preparing favorable seedbed, and controlling weeds, contrarily; it accelerates
erosion, off-site movement of nutrients, and enhances loss of soil organic matter.
Conservation management systems like no-till (NT) and crop rotation have been
reported to increase soil organic C content by creating less disturbed environment.
Variations in the soil C substances due to tillage operations or crop rotations have
been recognized, however, the information on C sequestration is limited. The
present study was planned to improve our understanding that how no-till and crop
rotation can enhance C sequestration and soil quality. The study was conducted on
Vanmeter farm of the Ohio State University South Centers at Piketon Ohio, USA from
2002 to 2007. Tillage treatments included conventional (CT) and no-till (NT) were
factored into continuous corn (CC), corn-soybean (CS) and corn–soybean-wheat-
cowpea (CSW) rotations by following randomized complete block design with 6
replications.
The findings of present long-term study revealed that no-till had
significantly improved biological, chemical, physical and humified carbon
fractions compared to conventional tillage. In case of biological parameters total
microbial biomass (C mic ), basal (BR), and specific respiration rates (qCO 2 ),
potentially mineralizable carbon (C min ), increased because of no-till compared to
conventional tillage. Microbial biomass and associated biological properties
decreased significantly with increase in soil depth irrespective of tillage; however,
the decrease was higher in case of no-till than conventional till. Among crop
rotations corn soybean wheat showed significantly improved impact on microbial
biomass and associated biological properties. However, crop rotation had variable
effect on biological properties along the soil depth.Soil physical parameters like aggregate stability, macroaggregate,
particulate organic matter and particulate organic carbon and nitrogen were
significantly improved with no–till as compared with conventional tillage. When
measured along the soil depth they decreased significantly with increase in soil
depth. Corn soybean wheat rotation had significantly improved the various
physical parameters as compared with continuous corn and corn soybean.
Likewise, No-till showed significant increase in total, active, passive salt
extractable and microwave extractable carbon and nitrogen fractions compared to
conventional tillage. Among crop rotation corn-soybean-wheat had higher values
of physical parameters as compared with other crop rotation treatments. Tillage
and crop rotation had non-significant interaction influence on biological, chemical
and physical parameters; however, with time as factor the interaction significantly
influenced the biological, chemical and physical properties.
Total humified carbon, sugar free humified carbon concentration and stocks
did not vary significantly, however, the humic, fulvic acid, humic and fulvic acid
glucose and humin contents were significantly increased under no-till and
decreased under conventional tillage over time. Similar effects on humified carbon
fractions by crop rotation were observed. Tillage and crop rotation had a non-
significant interaction on humified carbon fraction, the inclusion of time as a factor
with tillage and crop rotation interaction significantly influenced the carbon
fraction.
No-till with all crop rotation acted as net biological, chemical, physical and
humified carbon sink while conventional till with different crop rotation acted as a
carbon source. The estimated soil quality index was significantly higher in soil
under no-till than conventional tillage. Similarly the corn soya bean wheat had
shown significant difference in soil quality index as compared with other crop
rotations. Sensitivity index revealed that soil microbial biomass can be utilized as
sensitive indicator of soil quality.