Greater knowledge of the short- and long-term effects of biomass production practices on soil biological and chemical properties is needed to determine influences on sustainable land management. Soil samples under switchgrass (Panicum virgatum L.), other forage grasses, cultivated crops, and forest were collected seasonally at six locations. Soil organic C (SOC), total N, soil microbial biomass C (SMBC) and N (SMBN), soil mineralizable C and N, and basal soil respiration (BSR) were in general greatest under long-term coastal bermudagrass [Cynodon dactylon (L.) Pers.] pasture (>40 years), second highest under Alamo switchgrass and kleingrass (Panicum coloratum L.) planted in 1992 and forest, followed by Alamo switchgrass planted in 1997, and was lowest under the cultivated soils. Soil organic C at 0-5 cm was 42-220% greater in soils under Alamo switchgrass planted in 1992 than cultivated soils, except at College Station where SOC values under Alamo planted in 1992 and the cultivated rotation were not significantly different. Although the rotation treatment is cultivated at this location, two high residue crops are used, wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench.]. Similar trends were noted for total N, SMBC, SMBN, mineralizable C and N, BSR, and the ratio of SMBC/SOC. Insufficient information was collected in this study to determine whether the parameters evaluated for forest and switchgrass were different. In addition to its high yield potential, adaptation to marginal sites and tolerance to water and nutrient limitations, switchgrass appeared to be a competitive crop in terms of land sustainability, resulting in enhanced soil quality characteristics compared to long-term cultivated soils.

Greater knowledge of the short- and long-term effects of biomass production practices on soil biological and chemical properties is needed to determine influences on sustainable land management. Soil samples under switchgrass (Panicum virgatum L.), other forage grasses, cultivated crops, and forest were collected seasonally at six locations. Soil organic C (SOC), total N, soil microbial biomass C (SMBC) and N (SMBN), soil mineralizable C and N, and basal soil respiration (BSR) were in general greatest under long-term coastal bermudagrass [Cynodon dactylon (L.) Pers.] pasture (>40 years), second highest under Alamo switchgrass and kleingrass (Panicum coloratum L.) planted in 1992 and forest, followed by Alamo switchgrass planted in 1997, and was lowest under the cultivated soils. Soil organic C at 0-5 cm was 42-220% greater in soils under Alamo switchgrass planted in 1992 than cultivated soils, except at College Station where SOC values under Alamo planted in 1992 and the cultivated rotation were not significantly different. Although the rotation treatment is cultivated at this location, two high residue crops are used, wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench.]. Similar trends were noted for total N, SMBC, SMBN, mineralizable C and N, BSR, and the ratio of SMBC/SOC. Insufficient information was collected in this study to determine whether the parameters evaluated for forest and switchgrass were different. In addition to its high yield potential, adaptation to marginal sites and tolerance to water and nutrient limitations, switchgrass appeared to be a competitive crop in terms of land sustainability, resulting in enhanced soil quality characteristics compared to long-term cultivated soils.

Due to rapid urbanization agricultural lands in metropolitan areas are shrinking.  As a result our cities are getting more dependent on distant places for food, which is making the food system vulnerable. In the context of rapid urbanization and climate change a resilient agricultural system of Dhaka could be one of the key to ensure a sustainable future. To investigatethe impact of urbanization and climate change on the resilience of the agricultural system of Dhaka a resilience assessment of agricultural system of Dhaka has been done. The study followed the resilience assessment wordbook for practitioner as method of assessment. As methods to collect and analyze data field studies, interview, GIS analysis, policy analysis were conducted. This study shows that, urbanization is directly responsible for changes in both quality and quantity of the agricultural land of Dhaka whereas climate change does not affect directly. Even with this rapid urbanization there is still scope to take measures to make agricultural system resilient by preserving land within Dhaka metropolitan area. Therefore two Strategies have been proposed. First one is; increasing local food production without administrative reformation and the second; reducing the future demand by administrative and economic decentralization of Dhaka. Both of the strategies will require strong political will along with recognition of importance of agricultural land within the city boundary.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Changes in land use can take into soil chemical and physical quality degradation. In the hillside areas of the Rio Grande do Sul State (RS) land degradation vulnerability is elevated, due to the combination of a strong undulated to mountainous relief and shallow soils. The general purpose of this study was to evaluate the chemical and physical attributes of soils located in the Sul-riograndense Plateau Border under different land uses. Two representative sites of the Plateau Border, characterized by steep slope areas with prevalence of family farms, were selected (Silveira Martins county (SM) and São João do Polêsine county (SJ)), and also a transition area situated between the Plateau Border and the Medium Plateau (Júlio de Castilhos county (JC)). In SM soil samples were collected in areas of no-tillage (PD), tillage (PC), reforestation (RF) and native forest (MN). In SJ soil samples were collected under native forest (MN), secondary forest (MS), old cropping (LV), new cropping (LN) and abandoned cropping (LA) areas. In JC the samples were collected under native forest (MN), native prairie (CN) and no-tillage (PD) areas. Samples were collected from 0 to 10cm and from 10 to 20cm. Modifications were observed in soil chemical and physical attributes due to the different land uses when compared to the native forest. In systems that do not receive constant external additions, a decrease in soil chemical fertility was observed. Soil organic matter content decreased as the land use intensity increased. C-O-alquyl was the carbon group that presented the largest contribution in the spectra of 13C NMR, independent of the land use system. The main physical alterations observed were the decreases of soil macroporosity, total porosity and saturated hydraulic conductivity and the increase in soil density when compared to soil natural conditions. Soil aggregation parameters did not show to be good indexes to identify changes due to the land use in this study. / As mudanças na utilização das terras podem levar à degradação da qualidade química e física do solo. Nas áreas de encosta do estado do Rio Grande do Sul (RS) a vulnerabilidade à degradação das terras é elevada, devido a combinação de relevo forte ondulado a montanhoso e solos com pequena profundidade efetiva. O objetivo geral deste trabalho foi avaliar as características químicas e físicas do solo de áreas situadas no Rebordo do Planalto na região central do RS, sob diferentes usos da terra. Para isso foram selecionadas duas áreas representativas da região denominada Rebordo do Planalto, caracterizada por áreas de encosta com predomínio da agricultura familiar em pequena escala (Silveira Martins (SM) e São João do Polêsine (SJ)) e uma área de transição entre o Rebordo do Planalto e o Planalto Médio (Júlio de Castilhos (JC)). Em SM foram coletadas amostras de solo no sistema de plantio direto (PD), plantio convencional (PC), reflorestamento (RF) e mata nativa (MN). Em SJ foram coletadas amostras de solo sob os usos na mata nativa (MN), mata secundária (MS), lavoura velha (LV), lavoura nova (LN) e lavoura abandonada (LA). Em JC as amostras foram coletadas em áreas de mata nativa (MN), campo nativo (CN) e plantio direto (PD). As amostras foram coletadas na profundidade de 0-10 e 10-20 cm. Através dos resultados obtidos, observaram-se modificações nas características químicas e físicas do solo em função dos diferentes usos da terra, ao comparar com a mata nativa. Em sistemas que não recebem adições constantes de fontes externas, ocorreu uma depressão da fertilidade química. A matéria orgânica do solo teve diminuição nos teores, conforme aumentou a intensidade de uso da terra. O grupo C-O-alquil foi o grupo de carbono que apresentou a maior contribuição nos espectros de RMN 13C, independente do sistema de uso da terra. As principais alterações físicas ocorridas em comparação com as condições naturais do solo, foram diminuições da macroporosidade, porosidade total e condutividade hidráulica saturada e aumento na densidade do solo. Os parâmetros de agregação do solo, neste trabalho, não se mostraram como bons índices de avaliação para identificar mudanças em função dos diferentes usos da terra.