Search

We studied the effects of tillage, crop residues, and green manure on soil carbon pools and hydrolytic enzyme activity in a sandy loam after five cycles of the rice-wheat system (RWS). Four main plot treatments in rice were combinations of wheat straw and Sesbania green manure (GM) management: (1) puddled transplanted rice (PTR) with no wheat straw, (2) PTR with 25% wheat stubbles (12–15 cm long) retained, (3) PTR with no wheat straw plus GM, and (4) PTR with 25% wheat stubbles plus GM. Three subplots treatments in subsequent wheat were (1) conventional tillage with rice straw removed, (2) zero tillage (ZT) with rice straw removed, and (3) ZT with 100% rice straw retained as a surface mulch. The results showed that PTR with wheat stubbles retained plus GM and ZT wheat with rice straw retained (ZTWRS100) significantly (p< 0.05) increased all the carbon pools and hydrolytic enzymes except phenol oxidase and peroxidase activities. The carbon management index under ZTWRS100 retained was significantly higher than zero-till or conventional till wheat without residue. The principal component analysis identified active carbon, less labile carbon pools; xylanase and dehydrogenase hydrolytic enzymes as the most reliable sensitive indicators for assessing soil quality for conservation agriculture (CA) – based practices in RWS. The study showed that adoption of PTR with 25%-anchored wheat stubbles retained plus GM in rice followed by ZTWRS100 in wheat was the best crop production strategy for enhanced carbon pools, hydrolytic enzymatic activities and gives an idea of its overall fitness for carrying out ecosystem functions. [ABSTRACT FROM AUTHOR]

Agricultural residues in excess of livestock fodder are garnering global attention and stern concerns owing to their accountable share in environmental hazards due to the lack of effective disposal mechanisms and indiscriminate burning. Recycling these residues for biochar production using pyrolysis is a cost-effective and locally feasible technique which offers a twin-prong solution addressing both climate and soil health issues. This research work compares a portable kiln prototype that is affordable and easy to use, with a muffle furnace at three distinct pyrolytic temperatures (400 °C, 500 °C, and 600 °C) to produce biochar from the stalks of maize and pigeonpea. The biochar properties were characterized using Electron Microscopy-Electron Dispersive X-ray (SEM-EDX), X-ray Diffraction (XRD), Fourier Transmission Infrared Spectroscopy (FTIR), and Thermogravimetric Analysis (TGA). The findings indicate significant variations in biochar properties based on raw material source, pyrolytic method, and varied temperatures. Higher pyrolysis temperatures were found to reduce the amorphous organic phase and alter the ultrastructure of biochar, as evidenced by XRD analysis. SEM imaging showed macropores in oval and round shapes with crystalline deposits. The carbon content, as per EDX, decreased with increasing temperature, aligning with changes in functional groups. Edinburgh's stability test revealed that kiln biochar has more stable carbon content compared to biochar produced using muffle furnace and the stable carbon increased with the rise in temperature. A comparative analysis demonstrated that biochar quality at 400–500 °C in a muffle furnace was on par with that produced in the portable kiln at 400 °C. Therefore, considering the kiln's portability, efficiency, cost-effectiveness, and scalability, it is a promising decentralized method for biochar production, offering a cutting-edge solution for agricultural waste management and soil carbon enhancement. [Display omitted] • The study involves redesigning and development of low-cost portable kiln for economical and decentralized biochar production using pigeonpea and maize stalks. • Physiochemical characterization of kiln biochar produced at 400 °C is comparable to muffle furnace biochar produced at 400 °C and 500 °C. • The stable carbon content is more in biochar produced using kiln compared to muffle furnace. • The heavy metal content in the biochar produced is less than critical limits (International biochar initiative). • The low capital and operational cost of kiln proves the technology economical and scalable. [ABSTRACT FROM AUTHOR]

• CA-based PB/ZT with SSNM significantly improved and stabilised SOC. • No-tillage in PB, LI < 1 in surface soil signify the loss of lability. • Lower depth SOC in CT and unfertilized plot is more sensitive to higher temperature. • Adoption of CA with SSNM can counteract the ill effects of climate change on SOC. • Q 10 of SOC mineralization is an important indicator to forecast soil C-dynamics. Assessment of temperature sensitivity of soil organic carbon (SOC) mineralization from soils of long-term precision conservation agriculture (CA) plots is essential to forecast soil C dynamics. Under CA, varying quantity of inorganic nutrient application had differential impact on SOC. At the same time study of SOC mineralization at different simulated temperatures is important as global climate change affects C-cycle of an agro-ecosystem. To assess the impact of tillage and nutrient management on SOC build-up, a long-term study (five year old) with 3-tillage practices [ZT-zero tillage; PB-permanent beds, & CT-conventional tillage] in main plot and 4-nutrient management strategies [unfertilized, farmer fertilizer practice-FFP, recommended fertilizers- Ad-hoc and a site specific nutrient management-SSNM] in sub-plot in a maize-wheat-mungbean system was chosen. To measure the build-up and thermal sensitivity of SOC, soil samples from 3- depths (0–7.5, 7.5–15 and 15–30 cm) were collected. The kinetics of C-mineralisation was studied through laboratory incubation at 3-temperatures (27, 32 and 37 °C) for 90 days. The PB/ZT and SSNM had significantly higher SOC compared with CT and unfertilized plots, respectively. Although the cumulative C mineralization after 90-days of incubation followed the trend of SOC content among the treatments, while decay rates of SOC mineralization showed somewhat different trend. In all the tillage treatments the percentage of SOC mineralised ranged between 3.3–5.8% at 27 °C, 5.2–8.1% at 32 °C and 7.3–10.9% at 37 °C. At higher temperature, higher SOC decay rates were observed under CT and unfertilized plots compared with PB/ZT and SSNM plots, respectively. The SOC from lower soil depth in CT and unfertilized plots was more temperature sensitive (Q 10 = 4.03 and 4.89, respectively) compared to those under CA-based PB/ZT (Q 10 = 2.63–2.82) and SSNM (Q 10 = 2.15) based balanced nutrition, respectively. The SOC in lower soil depth (7.5–15 and 15–30 cm) is 1.3 and 2.1 times more temperature sensitive respectively than surface soil depth of 0–7.5 cm soil depth. Higher proportion of less labile SOC under CT and unfertilized plots might be the reason for higher temperature sensitivity. In the inevitable and impending global climate change scenario, we might lose a sizeable amount of sequestered C, which is otherwise stable at present ambient temperature. [ABSTRACT FROM AUTHOR]

• Enrichment in soil organic carbon was observed under ZT diversified cropping system. • Conservation agriculture improved aggregate indices. • ZT and crop diversification improved particulate and aggregate associated carbon. • Conservation agriculture showed higher system productivity. Intensive tillage based management practices are threatening soil quality and systems sustainability in the rice-wheat belt of Northwest India. Furthermore, it is accentuated with puddling of soil, which disrupts soil aggregates. Conservation agriculture (CA) practices involving zero tillage, crop residue management and suitable crop rotation can serve as better alternative to conventional agriculture for maintaining soil quality. Soil organic carbon is an important determinant of soil quality, playing critical role in food production, mitigation and adaptation to climate change as well as performs many ecosystem functions. To understand the turnover of soil carbon in different forms (Total organic carbon-TOC; aggregate associated carbon-AAC; particulate organic carbon- POC), soil aggregation and crop productivity with different management practices, one conventional agriculture based scenario and three CA based crop management scenarios namely conventional rice-wheat system (Sc1), partial CA based rice-wheat-mungbean system (Sc2), full CA-based rice-wheat-mungbean system (Sc3) and maize-wheat-mungbean system (Sc4) were evaluated. TOC was increased by 71%, 68% and 25% after 4 years of the experiment and 75%, 80% and 38% after 6 years of the experiment in Sc4, Sc3 and Sc2, respectively, over Sc1 at 0–15 cm soil depth. After 4 years of the experiment, 38.5% and 5.0% and after 6 years 50.8% and 24.4% improvement in total water stable aggregates at 0–15 and 15–30 cm soil depth, respectively was observed in CA-based scenarios over Sc1. Higher aggregate indices were associated with Sc3 at 0–15 cm soil depth than others. Among the size classes of aggregates, highest aggregate associated C (8.94 g kg−1) was retained in the 1-0.5 mm size class under CA-based scenarios. After 6 years, higher POC was associated with Sc4 (116%). CA-based rice/maize system (Sc3 and Sc4) showed higher productivity than Sc1. Therefore, CA could be a potential management practice in rice-wheat cropping system of Northwest India to improve the soil carbon pools through maintaining soil aggregation and productivity. [ABSTRACT FROM AUTHOR]

Given the increasing scarcity of production resources such as water, energy and labour coupled with growing climatic risks, maize-based production systems could be potential alternatives to intensive rice-wheat (RW) rotation in western Indo-Gangetic Plains (IGP). Conservation agriculture (CA) in maize systems has been widely promoted for minimizing soil degradation and ensuring sustainability under emerging climate change scenario. Such practices are also believed to provide mitigation co–benefits through reduced GHG emission and increased soil carbon sequestration. However, the combined effects of diversified crop rotations and CA-based management on GHG mitigation potential and other co-benefits are generally over looked and hence warrant greater attention. A field trial was conducted for 5–years to assess the changes in soil organic carbon fractions, mineral–N, N 2 O emission and global warming potential (GWP) of maize-based production systems under different tillage & crop establishment methods. Four diversified cropping systems i.e. maize–wheat–mungbean (MWMb), maize–chickpea– Sesbania (MCS), maize–mustard–mungbean (MMuMb) and maize–maize– Sesbania (MMS) were factorially combined with three tillage & crop establishment methods i.e. zero tilled permanent beds (PB), zero–tillage flat (ZT) and conventional tillage (CT) in a split–plot design. After 5–years of continued experimentation, we recorded that across the soil depths, SOC content, its pools and mineral-N fractions were greatly affected by tillage & crop establishment methods and cropping systems. ZT and PB increased SOC stock (0–30 cm depth) by 7.22–7.23 Mg C ha −1 whereas CT system increased it only by 0.88 Mg C ha −1 as compared to initial value. Several researchers reported that SOC & mineral–N fraction contents in the top 30 cm soil depth are correlated with N 2 O–N emission. In our study, global warming potential (GWP) under CT system was higher by 18.1 and 17.4%, compared to CA-based ZT and PB, respectively. Among various maize systems, GWP of MMS were higher by 11.2, 6.7 and 6.6%, compared that of MWMb (1212 kg CO 2 –eq. ha −1 ), MCS (1274 kg CO 2 –eq. ha −1 ) and MMuMb (1275 kg CO 2 –eq. ha −1 ), respectively. The results of our study suggest that CA and diversified crop rotations should be promoted in north-western IGP and other similar agro-ecologies across the globe for ensuring food security, restoration of soil health and climate change mitigation, the key sustainable development goals (SDGs). [ABSTRACT FROM AUTHOR]

Maize-based crop rotations are advocated as alternate to rice-based systems in South Asia due to better suitability for diverse ecologies, higher yields with less water use and more palatable maize fodder compared to rice, and increased demand of maize from piggery and poultry industries. Alternate tillage and crop establishment practices are important management strategies for tackling the issues of soil health deterioration and over exploitation of underground water resources, particularly in rice based intensive crop rotations. The conservation agriculture (CA) based tillage and crop establishment practices such as zero tillage (ZT) and permanent raised beds (PB) hold potential to enhance soil organic carbon (SOC), physical and biological properties for sustainability of soil health. Therefore, a long term study was conducted to evaluate the twelve combinations of tillage practices (03) and irrigated intensive maize based crop rotations (04) on organic carbon, physical properties and microbial biomass and enzymatic activities of a sandy loam (Typic Haplustept) soil in north-western India. The tillage practices consisted of ZT, PB and conventional tillage (CT) in main plots and four diversified intensive maize based crop rotations (MWMb: Maize-Wheat-Mungbean, MCS: Maize-Chickpea- Sesbaina , MMuMb: Maize-Mustard-Mungbean, MMS: Maize-Maize- Sesbania ) in sub plots. In this study we analysed the SOC, physical and biological properties of soil at various depths after 7 years of continuous ZT, PB and CT in diversified maize rotations. Compared to CT plots, the soil physical properties like water stable aggregates (WSA) > 250 μm were 16.1-32.5% higher, and bulk density (BD) and penetration resistance (PR) showed significant (P < 0.05) decline (11.0–14.3 and 11.2–12.0%) in ZT and PB plots at 0–15 and 15–30 cm soil layers. The soil organic carbon (SOC) increased by 34.6-35.3% at 0–15 cm, and 23.6-26.5% at 15–30 cm soil depths with conservation agriculture (ZT and PB) based crop establishment techniques over CT. Similarly, the soil microbial biomass carbon (MBC) under CA based systems increased by 45–48.9% in 0–30 cm profile depth of a sandy loam (Typic Haplustept) soil. Significant (P < 0.05) improvement in soil enzymatic activities i.e., Fluorescein diacetate, dehydrogenase, β Glucosidase and Alkaline phosphatase was also recorded in the CA based treatments. Significant (P < 0.05) synergistic effects of summer legumes (mungbean and Sesbania ) with winter legume/cereal in crop rotations were observed on SOC,WSA, BD, PR and K sat at 0–15 and 15–30 cm depths. Interaction between tillage and crop rotations were significant (P < 0.05) for soil organic carbon, physical properties and enzymatic activities. Thus our long-term study suggests that CA based crop management with selected diversified maize based rotations (MCS and MWMb) can be advocated as sustainable intensification strategy in light textured soils of north-western India and other similar agro-ecologies of South Asia. [ABSTRACT FROM AUTHOR]

Conservation agriculture (CA), comprising minimum soil disturbance, retention of crop residues and crop diversification, is widely promoted for reducing soil degradation and improving agricultural sustainability. It is also claimed to mitigate climate change through soil carbon sequestration: we conducted a meta-analysis of soil organic carbon (SOC) stock changes under CA practices in two tropical regions, the Indo-Gangetic Plains (IGP) and Sub-Saharan Africa (SSA), to quantify this. In IGP annual increases in SOC stock compared to conventional practice were between 0.16 and 0.49 Mg C ha −1 yr −1 . In SSA increases were between 0.28 and 0.96 Mg C ha −1 yr −1 , but with much greater variation and a significant number of cases with no measurable increase. Most reported SOC stock increases under CA are overestimates because of errors introduced by inappropriate soil sampling methodology. SOC increases require careful interpretation to assess whether or not they represent genuine climate change mitigation as opposed to redistribution of organic C within the landscape or soil profile. In smallholder farming in tropical regions social and economic barriers can greatly limit adoption of CA, further decreasing realistic mitigation potential. Comparison with the decreases in greenhouse gas emissions possible through improved management of nitrogen (N) fertilizer in regions such as IGP where N use is already high, suggests that this is a more effective and sustainable means of mitigating climate change. However the mitigation potential, and other benefits, from crop diversification are frequently overlooked when considering CA and warrant greater attention. Increases in SOC concentration (as opposed to stock) in near-surface soil from CA cause improvements in soil physical conditions; these are expected to contribute to increased sustainability and climate change adaptation, though not necessarily leading to consistently increased crop yields. CA should be promoted on the basis of these factors and any climate change mitigation regarded as an additional benefit, not a major policy driver for its adoption. [ABSTRACT FROM AUTHOR]

Recently conservation agriculture (CA) using the principles of zero tillage, crop residue management and suitable crop rotation has gained the momentum and quite popular among the farmers. Researchers throughout the globe have shown the potential of CA in enriching soil organic carbon storage in various soil types and cropping systems. But there is very limited study on the effect of CA on soil humic acid content and their stability and abundance of functional groups. An experiment was conducted in an Alfisols with four scenarios (designated as Sc) namely conventional farmers practice (Sc1) of transplanted rice (TPR) followed by conventional tilled broadcasted wheat (CT- wheat) with residue removal, transplanted rice (TPR) followed by zero tillage (ZT) wheat and mung bean with partial residue retention (Sc2), direct seeded rice (DSR) followed by ZT- wheat and mung bean with full residue retention (Sc3), ZT-maize followed by ZT-wheat and mung bean (Sc4) at the research farm of ICAR-Central Soil Salinity Research Institute, Karnal, Haryana, India. The objectives of this study were to assess the humic acid (HA) content and stability of soil carbon through desorption study and to characterize the functional groups of HA by Fourier Transform Infrared (FTIR) spectroscopy under different scenarios. HA was extracted from soil samples collected from 0 to 15 and 15–30 cm depth after rice harvesting in 2018 after nine years of the experiment. Results showed that Sc4 recorded significantly highest HA content at 0–15 depth (4.23 g/kg) and 15–30 cm soil depth (2.08 g/kg). Lower E4/E6 ratio revealed higher stability and humification of humic acid carbon under CA based scenarios. Lowest desorption rate constant (0.20/day) was observed under Sc4 indicating higher organic carbon stability in soil. Higher labile carbon and nitrogen was observed in soils under Sc3 as revealed through desorption study. FTIR spectroscopy results confirmed the prevalence of higher number of functional groups (O C O, C O or CHO) in HA under CA based scenarios with an order of Sc4 >Sc3 >Sc2 >Sc1. Therefore, CA is not only efficient in enriching the organic carbon in soil but also in more stable complex of HA with soil particles having long term implications in soil carbon sequestration for future posterity. • Conservation agriculture (CA) effects on humic acid (HA) content and behaviour was studied. • CA based maize-wheat-mungbean showed highest HA content. • Desorption study reflected higher stable carbon under CA based maize system. • FTIR spectroscopy reveals complex functional groups in HA under CA based systems. • CA has potential to store more carbon in stable forms compared to conventional agriculture. [ABSTRACT FROM AUTHOR]

• Medium term conservation agriculture (CA) and balanced nutrition (BN) improved the soil quality index (SQI). • Mean weight diameter, TOC and available K are important parameters for soil quality index. • CA + BN is the bound between soil quality and crop productivity. • Sequestered C utilize for better soil physical environment and climate resilience. • Higher microbial activities increased FDA,DHA,ßGA, APAand boost nutrient availability. Conventional tillage practices and imbalanced use of inorganic fertilizers is well known to result in poor soil health. Alternative tillage and precision nutrient management are important strategies for tackling the issues of soil health deterioration, particularly in cereal-based intensive cropping systems. Therefore, we conducted a 4-year study with the objective of (a) monitoring the changes in soil physical, biological and chemical properties and crop productivity, (b) development of soil quality index-SQI, and monitor its' changes against system productivity as management goal, and (c) studying the changes in soil organic carbon-SOC in relation to annual C input. The experiment was laid out in a split-plot design with 3-tillage practices [zero tillage-ZT; permanent beds-PB; and conventional tillage-CT] and 4-nutrient management strategies [Control (unfertilized), farmers' fertilizer practice-FFP, recommended fertilizers doses- Ad-hoc and site specific nutrient management-SSNM] under a continuous maize (Zea mays L.) - wheat (Triticum aestivum L.)- mungbean (Vigna radiata L. Wilczek) rotation in a sandy loam soil (Typic Haplustept) of north-western Indo-Gangetic plains (NW-IGP) of India. The ZT/PB with SSNM/ Ad-hoc nutrient management resulted in higher values of a) physical parameters viz., water stable aggregates >250 μm, saturated hydraulic conductivity (K sat) and mean weight diameter-MWD, b) chemical parameters viz., SOC, available N, P, and K, and c) biological parameters viz., microbial biomass carbon and enzyme activities (fluorescein diacetate hydrolase, dehydrogenase, ß-glucosidase and alkaline phosphatase) compared with CT and unfertilized treatments. The CA practices recorded an increase in WSA (12–21%), MWD (14–29%), and K sat (11–14%) compared with CT at the 0-0.15 m and 0.15–0.30 m soil depths, respectively. The PB-SSNM registered (44.1%) higher SOC content as compared to CT-unfertilized plots. Values for MBC, FDA and βGA declined in the order SSNM= Ad-hoc >FFP > Control. While, the DHA declined in the order SSNM> Ad-hoc =FFP > Control. Principal component analysis included MWD, SOC and available K in the minimum data set (MDS) as the soil quality indicators. Adoption of PB/ZT resulted ∼22.5% higher SQI compared with CT. The SSNM plots improved SQI by ∼19.3% and ∼5.3% over unfertilized and FFP. The SSNM based CA practices attained a significantly higher annual C sequestration rate than other treatments. Therefore, adoption of CA with SSNM and Ad-hoc nutrient management in intensive cereal based systems of NW-IGP is essential for improving nutrient cycling, soil quality, crop productivity and C-sequestration potential. [ABSTRACT FROM AUTHOR]

Intensive tillage coupled with crop residue burning in rice-wheat (RW) system is a serious issue that causes soil degradation and environmental pollution. Soil organic carbon (SOC) is one of the main indicators of soil health and system's sustainability. Zero-tillage has been widely recommended as an alternative for improving carbon sequestration in soil under different ecologies. But the SOC sequestration is very inconsistent and varied as it depends on the crop management practices. This study was performed in the western Indo-Gangetic plains (IGP) of India where RW system contributes 40% to the total country's food grain basket; however there exists issue of its sustainability because of declining SOC coupled with open field crop residue burning. Therefore, we evaluated the effects of different management scenarios (Sc) namely Sc1 (conventional till rice-wheat cropping system; business as usual), Sc2 (partial climate smart agriculture (CSA)-based rice-wheat-mungbean system), Sc3 (CSA-based rice-wheat-mungbean system), and Sc4 (CSA-based maize-wheat-mungbean system) on SOC pools and biological properties after 4 crop cycles (year 2009–2013). Soil samples were collected from surface and sub surface layers (0–15 and 15–30 cm soil depth) after rice harvesting in 2013. Results showed that the SOC stock at surface layer was higher by 70% with Sc4 than Sc1 (16.2 Mg C ha−1) (P < 0.05). All the forms of carbon in different pools were higher (P < 0.05) with Sc4 and Sc2 over Sc1 at 0–15 and 15–30 cm soil depths, respectively. At surface soil SOC pools were found in order of Sc4 > Sc3 > Sc2 > Sc1 (P < 0.05). Higher lability index (LI) (2.1) and stratification ratio (SR) (2.5) of organic carbon were observed in CSA-based systems (Sc2 and Sc4). At surface layer (0–15 cm) the CSA- based scenarios (mean of Sc2, Sc3 and Sc4) showed higher (P < 0.05) enzyme activities viz. dehydrogenase (641 μgTPF g−1 24 h−1) and alkaline phosphatase (158 μg p-nitrophenol g−1), and microbial biomass carbon (MBC) (787 μg g−1) and microbial biomass nitrogen (MBN)(98 μg g−1) compared with Sc1. Higher value of the basal soil respiration (34%) was also observed with CSA-based scenarios (Sc2, Sc3, Sc4). Surface soil layer showed maximum counts of fungi, bacteria and actinomycetes in Sc4. MBC, fungal population and SOC were the most sensitive biological soil parameters identified through principal component analysis (PCA) which can be used for soil quality assessment. Therefore, medium term adoption of climate smart agricultural practices involving zero-tillage, crop establishment, residue management and crop diversification in rice-wheat system can significantly improve the systems productivity by improving SOC and soil biological quality. • Organic carbon stock was improved under climate smart agriculture (CSA) based cereal systems. • MBC, MBN, microbial population and soil enzymes were improved in CSA. • CSA practices enhanced the systems productivity. • MBC, fungal population and SOC were the most sensitive indicators identified. [ABSTRACT FROM AUTHOR]