Sougata Bardhan

Agroforestry for biomass production and carbon sequestration: an overview

Ever since the Kyoto Protocol, agroforestry has gained increased attention as a strategy to sequester carbon (C) and mitigate global climate change. Agroforestry has been recognized as having the greatest potential for C sequestration of all the land uses analyzed in the Land-Use, Land-Use Change and Forestry report of the IPCC; however, our understanding of C sequestration in specific agroforestry practices from around the world is rudimentary at best. Similarly, while agroforestry is well recognized as a land use practice capable of producing biomass for biopower and biofuels, very little information is available on this topic. This thematic issue is an attempt to bring together a collection of articles on C sequestration and biomass for energy, two topics that are inextricably interlinked and of great importance to the agroforestry community the world over. These papers not only address the aboveground C sequestration, but also the belowground C and the role of decomposition and nutrient cycling in determining the size of soil C pool using specific case studies. In addition to providing allometric methods for quantifying biomass production, the biological and economic realities of producing biomass in agroforestry practices are also discussed.

Homegarden agroforestry systems: an intermediary for biodiversity conservation in Bangladesh

Biodiversity conservation is one of the important ecosystem services that has been negatively impacted by anthropogenic activities. Natural forests (NF) harbor some of the highest species diversity around the world. However, deforestation and degradation have resulted in reduced forest land cover and loss of diversity. Homegarden agroforestry (AF) systems have been proven to be an intermediary for biodiversity conservation. In this study, we evaluate the effectiveness of home garden AF practices to conserve tree species diversity in Bangladesh and compare them with tree species diversity in NF. A total of nine locations were selected for this synthesis from published literature which comprised of five AF sites and four NFs. Shannon–Weiner Diversity Index (H) was similar for home-garden AF (3.50) and NF (2.99), with no statistical difference between them. Based on non-metric multi-dimensional scaling (NMDS) ordination analysis, the AF and NF plots showed distinct separation. However, Bray–Curtis dissimilarity index ranged from 0.95 to 0.70 indicating nearly no overlap in species composition to significant overlap between AF and NF. Based on our results, we conclude that AF can serve as an important ecological tool in conserving tree species diversity, particularly on landscapes where NF fragments represent only a small fraction of the total land area. Creating and maintaining AF habitats in such human dominated landscapes should be part of the biodiversity conservation strategy.

Soil Quality of a Mature Alley Cropping Agroforestry System in Temperate North America

Long-term effects of alley cropping on soils in the temperate zone are not widely known. Management, landscape, and soil depth effects on soil physical and biological properties were examined in a silver maple (Acer saccharinum L.) no-till corn (Zea mays L.)- soybean (Glycine max L.) rotation established in 1990 in northeast Missouri. Soils from crop alleys and tree rows were collected along transects traversing upper to lower landscape positions at three depths. Fluorescein diacetate hydrolase (FDA), β-glucosidase, β-glucosaminidase, and dehydrogenase activities were measured. Soil bulk density, aggregate stability, carbon (C), nitrogen N), and enzyme activities decreased with soil depth in alley and tree rows except for glucosaminidase. Soil physical and biological parameters did not differ significantly between alley and tree row. Landscape position effects were not significant for management or depth. Tree establishment improves soil quality in the crop alley as the system matures with improvements extended throughout the soil profile.

The potential for floodplains to sustain biomass feedstock production systems

Production of biofuels from corn or other food crops is considered unsustainable in the long term since it creates artificial shortages in food supply, increases in food price, and subsequent socioeconomic and environmental concerns. Second-generation biofuels, however, have shown promise, with improvement in technologies for converting cellulosic feedstocks into liquid transportation fuels. The development of biomass feedstock production systems and advanced biofuel refineries in floodplains and marginal lands can generate up to 45 t of biomass and 14,000 l of advanced biofuel per hectare per year, achieving considerable offset in dependence on fossil fuel. Promising biomass species for floodplains include short-rotation trees such as poplar and willow, perennial grasses such as Miscanthus and switchgrass, and annuals such as high-biomass sorghum. However, river floodplains are often susceptible to flooding and drought events, partly due to the impact of climate change on hydrological cycles and human interventions such as the construction of dams and levees. In the USA, floodplain biofuel production systems could generate up to 30% of renewable biofuels by 2022 and provide additional benefits such as carbon sequestration, GHG reduction and ecosystem sustainability. However, successful implementation will depend on the social adaptability and economic viability of such systems.

Nitrogen Mineralization Potential as Influenced by Microbial Biomass, Cotton Residues and Temperature

Integrating information on nitrogen (N) mineralization potentials into a fertilization plan could lead to improved N use efficiency. A controlled incubation mineralization study examined microbial biomass dynamics and N mineralization rates for two soils receiving 56 and 168 kg N ha−1 in a Panoche clay loam (Typic Haplocambid) and a Wasco sandy loam (Typic Torriorthent), incubated with and without cotton (Gossypium hirsutum L.) residues at 10 and 25°C for 203 days. Microbial biomass activity determined from mineralized carbon dioxide (CO2) was higher in the sandy loam than in clay loam independent of incubation temperature, cotton residue addition and N treatment. In the absence of added cotton residue, N mineralization rates were higher in the sandy loam. Residue additions increased N immobilization in both soils, but were greater in clay loam. Microbial biomass and mineralization were significantly affected by soil type, residue addition and temperature but not by N level.

Global achievements in sustainable land management

Identification and development of sustainable land management is urgently required because of widespread resource degradation from poor land use practices. In addition, the world will need to increase food production to meet the nutritional needs of a growing global population without major environmental degradation. Ongoing climate change and its impacts on the environment is an additional factor to consider in identifying and developing sustainable land use practices. The objectives of this paper are to: (1) provide a background to the need for sustainable land management, (2) identify some of its major components, and (3) discuss some examples of sustainable land management systems that are being practiced around the world. Some common components of this type of management are: (1) understanding the ecology of land management, (2) maintenance or enhancement of land productivity, (3) maintenance of soil quality, (4) increased diversity for higher stability and resilience, (5) provision of economic and ecosystem service benefits for communities, and (6) social acceptability. Several examples of sustainable land management systems are discussed to illustrate the wide range of systems that have been developed around the world including agroforestry, conservation agriculture, and precision agricultural systems. Improved technology, allowing for geater environmental measurement and for improved access and sharing of information, provides opportunities to identify and develop more sustainable land management practices and systems for the future.

Apparent soil electrical conductivity used to determine soil phosphorus variability in poultry litter-amended pastures.

The objectives of this research were to determine the relationship between soil apparent electrical conductivity (ECa) and soil P distribution, and to compare the effectiveness of noncontact mobile electromagnetic induction (EM) and direct contact methods for relating ECa to soil P. Studies were conducted at two locations in Southwest Missouri on a longterm forage fertility plot site and three 1 to 1.5 ha sites within beef cattle pasture fields, all having received long-term poultry litter applications. For the long-term plot site, both the direct contact ECa sensor deep reading and the EM-38 (Geonics) sensor in the shallow mode had significant positive correlations with soil test Bray-1 P at both the 0 to 5 and 5 to 15 cm sampling depths. Significant spatial variation in soluble, soil test Bray-1 and total P were observed by landscape position within pasture fields. In general, soil ECa was not significantly correlated with soluble, soil test Bray-1 and total P at each individual pasture site, but when data was combined over all three sites, significant relationships were observed between ECa measured by the EM-38 sensor and soil soluble P, soil test Bray-1 P and total P, especially when the vertical (deep) mode was used. The difference in performance of the two sensors between the two studies was attributed to the proportion of Research Article American Journal of Experimental Agriculture, 3(1): 124-141, 2013 125 coarse fragments contained in the soils and soil water content. These results suggest that soil ECa measurements may provide some useful information for evaluating spatial variation in soil P due to manure applications. However, further research is needed to assess the processes and factors affecting this relationship before it can be recommended for use for improved soil P management in individual farm fields with varying environmental conditions and management practices.

Development of a Variable-Source N Fertilizer Management Strategy Using Enhanced-Efficiency N Fertilizers

Abstract Variability in soil properties across agricultural landscapes in interaction with annual climatic variations affects crop response to N fertilizer applications and is a major challenge for development of effective N fertilizer practices that increase crop yield and reduce environmental N losses. The objectives of this research were to assess spatial differences in soil N availability in fields with poorly drained claypan soils containing low-lying or depressional areas and to determine the spatial variability in relative crop response and economic returns with application of enhanced-efficiency N fertilizers (EEF) compared with those of urea. A field trial (planted with corn (Zea mays L.)) was conducted in 2007 and 2008 in a claypan soil in northeastern Missouri that contained both side slope and low-lying landscape positions. Preplant N fertilizer treatments consisted of a nontreated control and 168 kg N ha−1 of urea, polymer-coated urea (PCU), urea + urease inhibitor (UI), and urea + nitrification inhibitor (NI). Grain yield response across landscape positions was ranked PCU > NI ≥ UI ≥ urea for 2007 and PCU > UI ≥ NI ≥ urea in 2008. Further mapping of yield differences from EEF compared with those of urea indicated areas of the field with yield benefits of up to approximately 5,100 kg ha−1 in 2007 and 7,100 kg ha−1 in 2008 with application of PCU, but some areas of negative yield differences were also observed. A variable-source N fertilizer strategy with use of EEF targeted to specific landscape positions and conventional N fertilizers used in the other parts of the field may be a possible management option in claypan soils or other poorly drained soils that include depressional or low-lying areas.