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Conservation of biodiversity and mitigation of global warming are two major environmental challenges today. In this context, the relationship between biodiversity (especially plant diversity) and soil carbon (C) sequestration (as a means of mitigating global warming) has become a subject of considerable scientific interest. This relationship was tested for homegardens (HG), a popular and sustainable agroforestry system in the tropics, in Thrissur district, Kerala, India. The major objectives were to examine how tree density and plant-stand characteristics of homegardens affect soil C sequestration. Soil samples were collected at four depths (0-20, 20-50, 50-80, 80-100 cm) from HG of varying sizes and age classes, and their total C content determined. Tree density and plant-stand characteristics such as species richness (Margalef Index) and diversity (Shannon Index) of the HG were also determined. Results indicated that the soil C stock was directly related to plant diversity of HG. Homegardens with higher, compared to those with lower, number of plant species, as well as higher species richness and tree density had higher soil carbon, especially in the top 50 cm of soil. Overall, within 1 m profile, soil C content ranged from 101.5 to 127.4 Mg ha -1 . Smaller-sized HG (\0.4 ha) that had higher tree density and plant-species density had more soil C per unit area (119.3 Mg ha -1 ) of land than larger-sized ones ([0.4 ha) (108.2 Mg ha -1 ). Soil C content, especially below 50 cm, was higher in older gardens. The enhanced soil-C storage in species-rich homegardens could have relevance and applications in broader ecological contexts.

The extent of carbon (C) sequestration in soils under agroforestry systems in relation to soil types (fraction sizes) and vegetation structure remains largely unexplored. This study examined soil C storage, an indicator of C sequestration potential, in homegardens (HGs), natural forest, and single-species stands of coconut (Cocos nucifera), rice (Oryza sativa)-paddy, and rubber (Hevea brasiliensis), in Thrissur district, Kerala, India. Soil samples collected from four depth zones up to 1 m were fractionated to three size classes (250 -2000 µm, 53 -250 µm, <53 µm) and their total C content determined. Total C stock (Mg ha −1 ) was highest in forests (176.6), followed by managed treebased systems, and lowest in rice-paddy field (55.6). The results show storage of higher amounts of C in the <53 µm fraction, the most stable form of C in soil, up to one-meter depth, in land-use systems with high stand density of trees such as forests and small-sized HG. Although the results do not allow comparison of changes in soil C stock in different land-use systems, they show higher C storage in soils under tree-based land-use systems compared with the treeless (ricepaddy) system, especially in lower soil depths, suggesting the higher soil C sequestration potential of tree-based systems, and thereby their role in reducing atmospheric concentration of carbon dioxide.

Composts with five different ratios of agricultural wastes, viz. rice straw (RS), wheat straw (WS), potato plant (PP), and mustard stover (MS) were prepared with or without fish pond bottom sediment to investigate the compost maturity and their suitability for field application. The composting process was monitored through the changes in physico‐chemical parameters and germination index (GI) at every 7 days interval of the composting process. All the composts were dark brown and smelled like forest soil within 56 days of composting, which reflected its matured status. On the basis of the physico‐chemical parameters (bulk density: 0.84 g/cm3; pH 7.05; electrical conductivity: 3.52 mS/cm; cation exchange capacity:82.4 cmol/kg; total carbon:321.4 g/kg; total nitrogen: 16.9 g/kg; As: 6.8 mg/kg; Cd: 2.96 mg/kg; Cr: 29.6 mg/kg, Cu: 243.6 mg/kg; Hg: 0.019 mg/kg; Ni: 24.3 mg/kg; Pb: 62.1 mg/kg and Zn: 812 mg/kg) and GI (89–96%), it could be concluded that RS/WS/PP/MS, 1:1:2:1 v/v/v/v with fish pond sediment produced better compost in accordance with the Indian compost standard. Application of a combined randomized block design analysis revealed that there is a significant difference in the responses of the five composts, in relation to the time of composting. Hierarchical clustering algorithm was applied with a view to form homogeneous groups of five different composts on the basis of different physico‐chemical parameters. Therefore, the ratio of waste incorporation is an important decision for composting and addition of pond sediment can improve the quality of compost.

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As a result of the coexistence of turfgrass and ornamentals in traditional landscapes, it is often impractical to separate fertilization and irrigation management among species. Furthermore, limited information is available on effects of turfgrass fertilizer on ornamental plants and vice versa. This research studied effects of two quick-release fertilizers (QRF) and one slow-release fertilizer (SRF) on quality and growth of turfgrass and ornamental plants and nutrient leaching. ‘Floratam’ St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze) was compared with a mix of common Florida ornamentals, including canna (Canna generalis L.H. Bailey), nandina (Nandina domestica Thunb.), ligustrum (Ligustrum japonicum Thunb.), and allamanda (Allamanda cathartica L.). All plants were grown in 300-L plastic pots in Arredondo fine sand. Less nitrate (NO3 −) was leached from turfgrass than from ornamentals and more NO3 − leached from QRF 16N–1.7P–6.6K than from SRF 8N–1.7P–9.9K. Quick-release fertilizers produced higher plant quality. This controlled environment research provides preliminary data on which in situ research may be modeled. Further research is required to verify how nutrient release rate affects turfgrass and ornamental quality and nitrate leaching in an urban landscape.

Consequent to the interest in converting degraded lands for cultivation of biofuel crops, concerns have been expressed about greenhouse gas (GHG) emissions resulting from changes in soil-carbon (C) stock following land conversions. A literature-based study was undertaken for estimating the magnitude of emission of GHGs, particularly carbon dioxide (CO 2 ), following an assessment of the extent and causes of land degradation and the nature of CO 2 emission from soils. The study estimated the potential for CO 2 emission resulting from changes in soilcarbon stock following land conversions, using oil palm (Elaeis guineensis Jacq.) as a case study. The analysis indicated that, overall, the magnitude of CO 2 emission resulting from changes in soil C stock per se following opening up of degraded land would be low compared with other potential sources of CO 2 emission. However, lack of data on critical aspects such as baseline soil C status was a limitation of the study. Soil respiration is the single best measure of GHG emission from soils. Fixation of C in additional biomass will compensate, over time, for C loss through soil respiration following a change in land use or land management, unless such changes involve conversion of existing large C stocks. Therefore, any net CO 2 emission from soils resulting from changes in soil C stock following opening up of degraded land is likely to be a short-term phenomenon. The estimations used in the study are based on various assumptions, which need to be validated by experimental field data.

Agro-ecological practices, including integration within farming systems, have increasingly been acknowledged as key development alternative to safeguard rural people's basic needs. It also enhances farmers' socio-ecological capacities to sustain livelihoods. This paper explores the multidimensional nature of agro-ecological practices and takes stock of its multiple outcomes in smallholder systems of developing countries. Literatures suggest that farm ers' foremost concern is to meet their socioeconomic , cultural and ecological needs in addition to combating multiple adversities caused by biotic and abiotic stresses. This asks for planned integration among the components in small farms leading to reduced stress and multiple benefits to the farm households. Integration among the components of farming system are often employed as a livelihood strategy in small farms and it plays a pivotal role in meeting the multidimensional needs of the farm family such as food security, risk reduction, income and employment, biodiversity, carbon storage and energy efficiency in farm. Public extension must appreciate IFS as a socio-ecological intervention, instead of a technology, to achieve varied desirable socioeconomic ecological outcomes.