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Soil organic carbon and labile and recalcitrant carbon fractions attributed by contrasting tillage and cropping systems in old and recent alluvial soils of subtropical eastern India.

ABSTRACT: Conservation agriculture-based sustainable intensification (CASI) technologies comprising zero-tillage with crop residue retention (>30%) on the soil surface, diversified cropping systems, and balanced nutrient management are recognized as operative and efficacious strategies to ensure food security in the parts of South Asia. The present investigation was a component of CASI technologies undertaken in the farmers' field of Malda (old alluvial Inceptisol) Coochbehar (recent alluvial Entisol) district, West Bengal (subtropical eastern India). This study was conducted to evaluate the short-term impact of contrasting tillage (zero and conventional) and cropping systems (rice-wheat and rice-maize) on total organic carbon (TOC) and its fractions, viz., labile pool-1 (LP1), labile pool-2 (LP2) and recalcitrant carbon (RC) fractions after 4-year trial of conservation agriculture (CA) in the old and recent alluvial soils. Soil samples were collected from three depths (0-5, 5-10, and 10-20 cm), and thus, our study was focused on two factors, viz., cropping system and tillage. Results pointed that TOC along with LP1, LP2, and RC fractions under rice-maize (RM) cropping system were significantly (p<0.05) greater (15-35%) over rice-wheat (RW) system as a result of higher residue biomass addition. Zero-tillage (ZT) improved the C fractions by 10-20% over conventional tillage (CT) in all aspects. TOC and its fractions were observed to be greater under the ZT system in the topmost soil depths (0-5 and 5-10 cm), but the same system failed to improve these at 10-20 cm. Interestingly, the CT increased all the fractions at 10-20 cm depth due to the incorporation of crop residues. The concentration of TOC along with its fractions decreased with increasing soil depth was evident. Comparatively, all the C fractions, including TOC were maximum in soils from Malda sites as compared to Coochbehar sites because of a higher amount of residue biomass application, higher clay content, and greater background content of C in these soils. All the studied C fractions showed a significant correlation (r = >0.635; p<0.01) with TOC among all the soil depths in both the districts but the relationship with soil texture showed some interesting results. TOC fractions were significantly correlated (p<0.01) with clay particles indicating that its higher stabilization with clay in old alluvial Inceptisol (Malda); while in recent alluvial Entisol (Coochbehar), sand particle showed its strong relation with TOC fractions. Higher stratification ratio (SR) in the ZT system suggested that the concentration of TOC and its fractions are confined to the upper soil layers whereas in the case of CT, by and large, the distribution of these was comparatively high in subsequent soil depths due to residue incorporation effect. The concentration of C fractions in soils followed the order: TOC > RC > LP2 > LP1. The present investigation concluded that ZT under the RM system increases the turnover rates of C in both soil types but the amount of clay influences the stabilization/storage of C.

SUBMITTER: S R

PROVIDER: S-EPMC8675705 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Tillage intensive cropping practices have deteriorated soil physical quality and decreased soil organic carbon (SOC) levels in rice-growing areas of South Asia. Consequently, crop productivity has declined over the years demonstrating the need for sustainable alternatives. Given that, a field experiment was conducted for six years to assess the impact of four tillage based crop establishment treatments [puddled transplant rice followed by conventional tillage in wheat/maize (CTTPR-CT), non-puddled transplant rice followed by zero-tillage in wheat/maize (NPTPR-ZT), zero-till transplant rice followed by zero-tillage in wheat/maize (ZTTPR-ZT), zero-tillage direct seeded rice followed by zero-tillage in wheat/maize (ZTDSR-ZT)], two residue management treatments [residue removal, residue retention (~33%)], and two cropping systems [rice-wheat, rice-maize] on soil aggregation, carbon pools, nutrient availability, and crop productivity. After six years of rotation, in top 0.2?m soil depth, zero-till crop establishment treatments (ZTTPR-ZT and ZTDSR-ZT) had higher (p?<?0.05) total organic carbon (TOC) over conventional tillage treatment (CTTPR-CT). Zero-till crop establishment treatments increased very-labile C faction (Cfrac 1) by 21% followed by labile fraction (Cfrac 2) (16%), non-labile fraction (Cfrac 4) (13%) and less-labile fraction (Cfrac 3) (7%). Notably, higher passive C-pool in conservation tillage practices over CTTPR-CT suggests that conservation tillage could stabilize the recalcitrant form of carbon that persists longer in the soil. Meantime, zero-till crop establishment treatments had higher (p?<?0.05) water stable macro-aggregates, macro-aggregates: micro-aggregates ratio and aggregate carbon content over CTTPR-CT. The treatment NPTPR-ZT significantly increased soil quality parameters over CTTPR-CT. However, the effect was not as prominent as that of ZTTPR-ZT and ZTDSR-ZT. Retention of crop residue increased (p?<?0.05) TOC (12%) and soil available nutrients mainly available-P (16%), followed by available-K (12%), DTPA-extractable Zn (11%), and available-S (6%) over residue removal treatment. The constructive changes in soil properties following conservation tillage and crop residue retention led to increased crop productivity over conventional CTTPR-CT. Therefore, conservation tillage (particularly ZTTPR-ZT and ZTDSR-ZT) and crop residue retention could be recommended in tropical rice-based cropping systems for improving soil quality and production sustainability.

Project description:Soil rotational tillage is an effective measure to overcome the problems caused by long-term of a single tillage, but the effect of the interval time of rotational tillage practices is not very well understood. Therefore, we conducted a 3-year field study in a wheat-maize cropping system to evaluate the effects of rotary tillage (RT) in rotation with plowing tillage (PT) on soil properties in northern China. Four practices were designed as follows: 3 years of RT to a depth of 10-15 cm (3RT), 3 years of PT to a depth of 30-35 cm (3PT), 1 year of PT followed by 2 years of RT (PT+2RT), and 2 years of PT followed by 1 year of RT (2PT+RT). Within 20 cm of the surface soil, the 3RT treatment significantly increased the soil quality index (SQI) by 6.0%, 8.8% and 13.1%, respectively, relative to the PT+2RT, 2PT+RT and 3PT treatments. The improvement was closely related to the significant increase in the soil organic carbon (SOC) and available nutrients concentrations in the 0-20 cm depths and the improvement of soil invertase, urease, alkaline phosphatase and catalase activities in the topsoil (0-10 cm). However, the opposite effects were observed in the subsoil (20-40 cm). Compared with the 3RT treatment, the 3PT, 2PT+RT and PT+2RT treatments decreased soil bulk density, and significantly enhanced enzyme activities, resulting in an increase in SQI of 32.6%, 24.4% and 0.7%, respectively, especially in the 3PT and 2PT+RT treatments, the difference was significant. When averaged across to all soil depths, the SQI under the 3RT and 2PT+RT treatments was much higher than that under the other treatments. The yields of wheat and maize under the 2PT+RT treatment were 15.0% and 14.3% higher than those under the 3RT treatment, respectively. The 2PT+RT treatment was the most effective tillage practice. These results suggest that RT in rotation with PT could improve soil quality in the soil profile whilst enhancing crop yield after continuous RT, and the benefits were enhanced with an interval time of one year. Therefore, the 2PT+RT treatment could act as an effective method for both soil quality and crop yield improvement in a wheat-maize cropping system under straw incorporation conditions.

Project description:Organic reduced tillage aims to combine the environmental benefits of organic farming and conservation tillage to increase sustainability and soil quality. In temperate climates, there is currently no knowledge about its impact on greenhouse gas emissions and only little information about soil organic carbon (SOC) stocks in these management systems. We therefore monitored nitrous oxide (N2O) and methane (CH4) fluxes besides SOC stocks for two years in a grass-clover ley - winter wheat - cover crop sequence. The monitoring was undertaken in an organically managed long-term tillage trial on a clay rich soil in Switzerland. Reduced tillage (RT) was compared with ploughing (conventional tillage, CT) in interaction with two fertilisation systems, cattle slurry alone (SL) versus cattle manure compost and slurry (MC). Median N2O and CH4 flux rates were 13 μg N2O-N m-2 h-1 and -2 μg CH4C m-2 h-1, respectively, with no treatment effects. N2O fluxes correlated positively with nitrate contents, soil temperature, water filled pore space and dissolved organic carbon and negatively with ammonium contents in soil. Pulse emissions after tillage operations and slurry application dominated cumulative gas emissions. N2O emissions after tillage operations correlated with SOC contents and collinearly to microbial biomass. There was no tillage system impact on cumulative N2O emissions in the grass-clover (0.8-0.9 kg N2O-N ha-1, 369 days) and winter wheat (2.1-3.0 kg N2O-N ha-1, 296 days) cropping seasons, with a tendency towards higher emissions in MC than SL in winter wheat. Including a tillage induced peak after wheat harvest, a full two year data set showed increased cumulative N2O emissions in RT than CT and in MC than SL. There was no clear treatment influence on cumulative CH4 uptake. Topsoil SOC accumulation (0-0.1 m) was still ongoing. SOC stocks were more stratified in RT than CT and in MC than SL. Total SOC stocks (0-0.5 m) were higher in RT than CT in SL and similar in MC. Maximum relative SOC stock difference accounted for +8.1 Mg C ha-1 in RT-MC compared to CT-SL after 13 years which dominated over the relative increase in greenhouse gas emissions. Under these site conditions, organic reduced tillage and manure compost application seems to be a viable greenhouse gas mitigation strategy as long as SOC is sequestered.

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Soil organic carbon and labile and recalcitrant carbon fractions attributed by contrasting tillage and cropping systems in old and recent alluvial soils of subtropical eastern India.

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