Field and laboratory studies indicate that utilisation of biological geotextiles constructed from palm-leaves and other selected organic materials are an effective, sustainable and economically viable soil conservation technique. The three-year plus

Forest plantations have expanded rapidly in response to financial support from the state and local governments and have had significant positive impacts on rural livelihoods and development in Vietnam, since the late 1980s. This study used net present value (NPV) and internal rate of return (IRR) to examine the economic performance of plantations for three species, Acacia mangium Willd, Eucalyptus (Eucalyptus urophylla S.T. Blake × Eucalyptus camaldulensis Dehn), and Manglietia conifera Dandy, in Bac Kan province. On the basis of an annual discount rate of 6%, the results showed that rural households earned positive financial returns from forest plantations with seven-year rotations. Eucalyptus generated the highest NPV but A. mangium generated the greatest IRR. The plantations were facilitated by financial support from the state, land tenure reforms, and wood exports. The results provide valuable business information and policy implications for both local farmers and policy makers. Since the farmers consider more of the short term and economic return of the plantations, the results provide valuable information for policy makers to apply subsidies and other support to promote plantations with significant ecological and environmental benefits for sustainable development of rural economies.

Integrated Agriculture Aquaculture (IAA) is characteristic with diversity of small-scale production systems in the Red River Delta, Vietnam where most integrated aquaculture systems are closely associated to the VAC model, an ecosystem production that three components: garden (V), pond (A) and livestock pen (C) are integrated. These VAC systems effectively use all the available land, air, water and solar energy resources, and also effectively recycle by-products and waste for providing diversified agricultural products to meet the complex nutritional demands of rural communities. The IAA systems are dynamic, diverse and subject to economic and environmental changes. By investigating 167 aquaculture households, the traditional VAC, New VAC, Animal Fish (AF) and Commercial Fish (FS) systems are identified as four existing IAA systems. This paper presents the main characteristics and economic efficiency of these IAA systems. The study's results indicate clear evidence that the traditional VAC system and New VAC system are the most efficient and effective models. The findings of this study have shed light on the important role of integrated aquaculture systems to food security and economic development of households and local communities. The VAC systems are likely to propose for improving household food security and developing the local economy.

Available studies do not allow comparison and quantification of the effects of biological geotextiles on runoff and water erosion rates under different agro-environmental conditions. Hence, this paper addresses this issue by comparing runoff and soil loss data obtained from field experiments (using different types of biological geotextiles) conducted in the United Kingdom, Hungary, South Africa, China, Thailand and Vietnam. Palm leaf mats (Borassus and Buriti mats) were used in the European countries. In the UK, Borassus mats were used as whole plot cover (area coverage $76 per cent; termed Borassus completely covered to differentiate from the Borassus buffer strip plots) and as buffer zones (area coverage $10 per cent), whereas Buriti mats were used only as buffer zones (area coverage $10 per cent). Only Lala mats were used in South Africa. Elsewhere (China, Thailand and Vietnam) biological geotextiles were constructed using other indigenous local materials, such as bamboo, rice straw and maize stalks. Biological geotextiles were used on bare plots in South Africa and the European countries. In the UK, plots were maintained bare by need based herbicide spraying. However, in South Asia, different crops were grown on the geotextile-covered plots. Results suggest that biological geotextiles were very effective for soil erosion control in all locations and the effectiveness for decreasing soil erosion rates by water was in the range of $67-99 per cent. The effectiveness of biological geotextiles in reducing runoff volume was in the range of $26-81 per cent. In the UK, total runoff and soil loss (during 8 January 2007-6 May 2008; total precipitation ¼ 1145.8 mm) from the Borassus (one metre wide) buffer zone plots (cover percentage $7.6 per cent) were, respectively, $81 and $93 per cent less than bare plots. In Hungary and China, plots with $38 and 22 per cent geotextile-cover, respectively, had $88 and 96 per cent less soil loss, than bare plots. In most months with low precipitation (depth) in Hungary and the UK, runoff volume was greater from plots with geotextile-cover than from bare soils. However, complete data sets indicate that in the UK and Hungary, runoff reduction by different treatments over bare plots ranged between $26 and 81 per cent. Results from the UK showed that plots with buffer strips of Borassus and Buriti mats had similar effects in reducing soil losses as completely covered plots of the Borassus mats. Thus, foreseeing biological geotextilecover on vulnerable segments of the landscape is highly effective for soil erosion control.