To what extent can zero tillage lead to a reduction in greenhouse gas emissions from temperate soils?

Soil tillage practices have a profound influence on the physical properties of soil and the greenhouse gas (GHG) balance. However there have been very few integrated studies on the emission of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and soil biophysical and chemical characteristics under different soil management systems. We recorded a significantly higher net global warming potential under conventional tillage systems (26–31% higher than zero tillage systems). Crucially the 3-D soil pore network, imaged using X-ray Computed Tomography, modified by tillage played a significant role in the flux of CO2 and CH4. In contrast, N2O flux was determined mainly by microbial biomass carbon and soil moisture content. Our work indicates that zero tillage could play a significant role in minimising emissions of GHGs from soils and contribute to efforts to mitigate against climate change

Effect of tillage and soil amendments on soil quality and yield of clusterbean (Cyamopsis tetragonoloba) in shallow hardpan soils of arid Gujarat

A field experiment was conducted at CAZRI, Regional Research Station, Kukma-Bhuj during kharif 2009 to find out the management options for improving soil productivity and quality in shallow hard pan soils in arid Gujarat. There were four tillage treatments, viz no-tillage, minimum tillage, shallow tillage and deep tillage in main plots and four amendments (gypsum at 5 Mg/ha, farmyard manure (FYM) at 5 Mg/ha and both gypsum and FYM at 5 Mg/ha each and control) in sub plots. The results of the experiment showed that deep tillage along with the application of gypsum and FYM at 5 Mg/ha produced maximum yield and maximum net returns. The study found a decreased yield and negative net returns under no-tillage in these shallow hard pan soils. However soil biological and physical properties were better under no-tillage. Long term studies may be necessary to find out the applicability of no-tillage in these soils from a yield perspective

Examining the potential for climate change mitigation from zero tillage

The benefits of reduced and zero-tillage systems have been presented as reducing runoff, enhancing water retention and preventing soil erosion. There is also general agreement that the practice can conserve and enhance soil organic carbon (C) levels to some extent. However, their applicability in mitigating climate change has been debated extensively, especially when the whole profile of C in the soil is considered, along with a reported risk of enhanced nitrous oxide (N2O) emissions. The current paper presents a meta-analysis of existing literature to ascertain the climate change mitigation opportunities offered by minimizing tillage operations. Research suggests zero tillage is effective in sequestering C in both soil surface and sub-soil layers in tropical and temperate conditions. The C sequestration rate in tropical soils can be about five times higher than in temperate soils. In tropical soils, C accumulation is generally correlated with the duration of tillage. Reduced N2O emissions under long-term zero tillage have been reported in the literature but significant variability exists in the N2O flux information. Long-term, location-specific studies are needed urgently to determine the precise role of zero tillage in driving N2O fluxes. Considering the wide variety of crops utilized in zero-tillage studies, for example maize, barley, soybean and winter wheat, only soybean has been reported to show an increase in yield with zero tillage (7·7% over 10 years). In several cases yield reductions have been recorded e.g. c. 1–8% over 10 years under winter wheat and barley, respectively, suggesting zero tillage does not bring appreciable changes in yield but that the difference between the two approaches may be small. A key question that remains to be answered is: are any potential reductions in yield acceptable in the quest to mitigate climate change, given the importance of global food security

Impacts of zero tillage on soil enzyme activities, microbial characteristics and organic matter functional chemistry in temperate soils

Zero tillage management of agricultural soils has potential for enhancing soil carbon (C) storage and reducing greenhouse gas emissions. However, the mechanisms which control carbon (C) sequestration in soil in response to zero tillage are not well understood. The aim of this study was to investigate the links between zero tillage practices and the functioning of the soil microbial community with regards to C cycling, testing the hypothesis that zero tillage enhances biological functioning in soil with positive implications for C sequestration. Specifically, we determined microbial respiration rates, enzyme activities, carbon source utilization and the functional chemistry of the soil organic matter in temperate well drained soils that had been zero tilled for seven years against annually tilled soils. Zero tilled soils contained 9% more soil C, 30% higher microbial biomass C than tilled soil and an increased presence of aromatic functional groups indicating greater preservation of recalcitrant C. Greater CO2 emission and higher respirational quotients were observed from tilled soils compared to zero tilled soils while microbial biomass was 30% greater in zero tilled soils indicating a more efficient functioning of the microbial community under zero tillage practice. Furthermore, microbial enzyme activities of dehydrogenase, cellulase, xylanase, β-glucosidase, phenol oxidase and peroxidase were higher in zero tilled soils. Considering zero tillage enhanced both microbial functioning and C storage in soil, we suggest that it offers significant promise to improve soil health and support mitigation measures against climate change

Root exudate analogues accelerate CO 2 and CH 4 production in tropical peat

Root exudates represent a large and labile carbon input in tropical peatlands, but their contribution to carbon dioxide (CO2) and methane (CH4) production remains poorly understood. Changes in species composition and productivity of peatland plant communities in response to global change could alter both inputs of exudates and associated greenhouse gas emissions. We used manipulative laboratory incubations to assess the extent to which root exudate quantity and chemical composition drives greenhouse gas emissions from tropical peatlands. Peat was sampled from beneath canopy palms (Raphia taedigera) and broadleaved evergreen trees (Campnosperma panamensis) in an ombrotrophic wetland in Panama. Root exudate analogues comprising a mixture of sugars and organic acids were added in solution to peats derived from both species, with CO2 and CH4 measured over time. CO2 and CH4 production increased under most treatments, but the magnitude and duration of the response depended on the composition of the added labile carbon mixture rather than the quantity of carbon added or the botanical origin of the peat. Treatments containing organic acids increased soil pH and altered other soil properties including redox potential but did not affect the activities of extracellular hydrolytic enzymes. CO2 but not CH4 production was found to be linearly related to microbial activity and redox potential. Our findings demonstrate the importance of root exudate composition in regulating greenhouse gas fluxes and propose that in situ plant species changes, particularly those associated with land use change, may account for small scale spatial variation in CO2 and CH4 fluxes due to species specific root exudate compositions

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Not AvailableHighly weathered laterite soils are a characteristic feature of humid tropics with undulating topography and high rainfall. The crop of cashew (Anacardium occidentale L.) has been cultivated in such landscapes, mainly to prevent further degradation due to the drought hardiness of cashew and requirement of very limited soil disturbances for its cultivation. Providing proper nutrient management is important for balancing the nutrient removal by tree crops especially in poor fertile soils. A study was initiated, after 5 years of application of inorganic fertilisers and organic amendments to cashew in a weathered tropical soil, to evaluate the effects of organic and inorganic sources of nutrients on soil aggregation and biochemical characteristics. The experiment consisted of 11 treatments as Farm Yard Manure (FYM) alone; FYM+biofertiliser consortia; FYM, rock phosphate and wood ash; poultry manure; In situ composting using recyclable cashew biomass and weeds; In situ composting using recyclable cashew biomass and weeds+green manuring; vermicomposting of recyclable cashew biomass; FYM+organic cakes+recyclable cashew biomass+biofertiliser consortia; recommended dose of nitrogen, phosphorus and potassium fertiliser (NPK fertiliser); recommended NPK fertiliser+FYM; and control without nutrient application. Soil samples were collected from surface 0–30 cm layer. The soil samples were fractionated into three aggregate sizes, i.e.,>2mm (large macroaggregates), 0.25–2mm (small macroaggregates), 0.053 to 0.25mm (microaggregates) and<0.053mm (silt+clay size fraction) using wet sieving. The results indicated that the organic sources of nutrient application increased the proportion of large and small macroaggregates. The treatments receiving only inorganic nutrients and no nutrients contained significantly higher silt+clay fractions (47.7 and 45.5% respectively). A higher percentage of water stable aggregates (47.4–70.7%) and increased aggregate stability (mean weight diameter) (0.78–1.26 mm) was recorded with the application of organic sources of nutrients. Aggregates in the silt+clay size faction and microaggregates recorded significantly higher carbon compared to small and large macroaggregates. Compared to control, the application of different organic amendments increased the soil organic matter (SOM) by 2.2–12.7% in silt+clay size fraction; 14.6–37.0% in microaggregates; 18.4–51.7% in small macroaggregates and 17.7–50.9% in large macroaggregates. Our findings reinforce that the annual application of manures and amendments to weathered tropical soil is important to improve biological properties of soil in terms of soil enzyme activities, microbial carbon and nitrogen, and to prevent further degradation of soil under such fragile environment.Not Availabl

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Not AvailableHighly weathered laterite soils are a characteristic feature of humid tropics with undulating topography and high rainfall. The crop of cashew (Anacardium occidentale L.) has been cultivated in such landscapes, mainly to prevent further degradation due to the drought hardiness of cashew and requirement of very limited soil disturbances for its cultivation. Providing proper nutrient management is important for balancing the nutrient removal by tree crops especially in poor fertile soils. A study was initiated, after 5 years of application of inorganic fertilisers and organic amendments to cashew in a weathered tropical soil, to evaluate the effects of organic and inorganic sources of nutrients on soil aggregation and biochemical characteristics. The experiment consisted of 11 treatments as Farm Yard Manure (FYM) alone; FYM + biofertiliser consortia; FYM, rock phosphate and wood ash; poultry manure; In situ composting using recyclable cashew biomass and weeds; In situ composting using recyclable cashew biomass and weeds + green manuring; vermicomposting of recyclable cashew biomass; FYM + organic cakes + recyclable cashew biomass + biofertiliser consortia; recommended dose of nitrogen, phosphorus and potassium fertiliser (NPK fertiliser); recommended NPK fertiliser + FYM; and control without nutrient application. Soil samples were collected from surface 0–30 cm layer. The soil samples were fractionated into three aggregate sizes, i.e., >2 mm (large macroaggregates), 0.25–2 mm (small macroaggregates), 0.053 to 0.25 mm (microaggregates) and <0.053 mm (silt + clay size fraction) using wet sieving. The results indicated that the organic sources of nutrient application increased the proportion of large and small macroaggregates. The treatments receiving only inorganic nutrients and no nutrients contained significantly higher silt + clay fractions (47.7 and 45.5% respectively). A higher percentage of water stable aggregates (47.4–70.7%) and increased aggregate stability (mean weight diameter) (0.78–1.26 mm) was recorded with the application of organic sources of nutrients. Aggregates in the silt + clay size faction and microaggregates recorded significantly higher carbon compared to small and large macroaggregates. Compared to control, the application of different organic amendments increased the soil organic matter (SOM) by 2.2–12.7% in silt + clay size fraction; 14.6–37.0% in microaggregates; 18.4–51.7% in small macroaggregates and 17.7–50.9% in large macroaggregates. Our findings reinforce that the annual application of manures and amendments to weathered tropical soil is important to improve biological properties of soil in terms of soil enzyme activities, microbial carbon and nitrogen, and to prevent further degradation of soil under such fragile environment.Not Availabl

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Not AvailableSaline soil limits plant growth by affecting osmotic balance in soil-plant systems. Vast areas of saline deserts exist in arid areas of India where crop production is not feasible. One of the ways to effectively utilise such landscape is to use plant species adapted to such hostile environments. Field survey was carried out in two major saline desert ecosystem of western India, namely Great Rann of Kachchh (GRK) and Little Rann of Kachchh (LRK), during 2013 and 2014. The study indicated that these unique ecosystems were deficient in soil organic carbon with content less than 0.77%. Extremes of salinity are common in the study area recording salinity as high as 102.3 dS m-1 in GRK and 85.38 dS m-1 in LRK. The major halophytic plants were Aeluropus lagopoides, Sporobolus marginatus, Suaeda nudiflora and Cressa cretica. Aeluropus was able to grow in soils having salinity upto 27.7 dS m-1, whereas Sporobolus could grow in ecological niches with salinity as high as 83.1 dS m-1. The halophytic non grasses like Suaeda and Cressa were widely distributed in both the saline desert ecosystems. The presence of salts increased the plant population of Suaeda and Cressa up to certain salinity levels. Beyond salinity value of 9.9 dS m-1, the plant density of Suaeda decreased, whereas in Cressa, the salinity value beyond which reduction in population decreased was 27.2 dS m-1. These plants which are able to survive at extremely salinity environments, could be explored for greening saline deserts and could be used as local fodder resource to support livestock population.Not Availabl

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Not AvailableHighly weathered laterite soils are a characteristic feature of humid tropics with undulating topography and high rainfall. The crop of cashew (Anacardium occidentale L.) has been cultivated in such landscapes, mainly to prevent further degradation due to the drought hardiness of cashew and requirement of very limited soil disturbances for its cultivation. Providing proper nutrient management is important for balancing the nutrient removal by tree crops especially in poor fertile soils. A study was initiated, after 5 years of application of inorganic fertilisers and organic amendments to cashew in a weathered tropical soil, to evaluate the effects of organic and inorganic sources of nutrients on soil aggregation and biochemical characteristics. The experiment consisted of 11 treatments as Farm Yard Manure (FYM) alone; FYM + biofertiliser consortia; FYM, rock phosphate and wood ash; poultry manure; In situ composting using recyclable cashew biomass and weeds; In situ composting using recyclable cashew biomass and weeds + green manuring; vermicomposting of recyclable cashew biomass; FYM + organic cakes + recyclable cashew biomass + biofertiliser consortia; recommended dose of nitrogen, phosphorus and potassium fertiliser (NPK fertiliser); recommended NPK fertiliser + FYM; and control without nutrient application. Soil samples were collected from surface 0–30 cm layer. The soil samples were fractionated into three aggregate sizes, i.e., >2 mm (large macroaggregates), 0.25–2 mm (small macroaggregates), 0.053 to 0.25 mm (microaggregates) and <0.053 mm (silt + clay size fraction) using wet sieving. The results indicated that the organic sources of nutrient application increased the proportion of large and small macroaggregates. The treatments receiving only inorganic nutrients and no nutrients contained significantly higher silt + clay fractions (47.7 and 45.5% respectively). A higher percentage of water stable aggregates (47.4–70.7%) and increased aggregate stability (mean weight diameter) (0.78–1.26 mm) was recorded with the application of organic sources of nutrients. Aggregates in the silt + clay size faction and microaggregates recorded significantly higher carbon compared to small and large macroaggregates. Compared to control, the application of different organic amendments increased the soil organic matter (SOM) by 2.2–12.7% in silt + clay size fraction; 14.6–37.0% in microaggregates; 18.4–51.7% in small macroaggregates and 17.7–50.9% in large macroaggregates. Our findings reinforce that the annual application of manures and amendments to weathered tropical soil is important to improve biological properties of soil in terms of soil enzyme activities, microbial carbon and nitrogen, and to prevent further degradation of soil under such fragile environment.Not Availabl