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Saltwater intrusion is a potential risk damaging crop diversity and productivity due to degraded soil physicochemical properties. However, little is known about how salinity affects the structure and function of soil nematodes community in intensive rice cultivated area. This study aimed (1) to assess the impacts of saltwater intrusion on the nematode community in alluvial and acid sulfate soils; and (2) to evaluate its relation with soil conditions. Saltwater intrusion reduced the abundance of both free-living nematodes (FLN) and plant-parasitic nematodes (dominated by Hirschmanniella) in soils. FLN community was different among sites with different physicochemical properties. The omnivorous genera Aporcelaimellus and Thornenema were only found in non-salt-affected alluvial soil, whilst Mesodorylaimus was dominant in salt-affected acid sulfate soil, suggesting that this genus might be tolerant to higher EC and soluble Na+, K+, Ca2+. The bacterivorous nematodes (dominant taxa Chronogaster, Rhabdolaimus) were dominant in both non-salt affected and salt-affected alluvial soils, which accounted for 48% and 40%, respectively, whilst it accounted for 21% in salt-affected acid sulfate soil. The abundance of fungivorous nematodes (Aphelenchoides, Ditylenchus, Filenchus) were greater in salt-affected alluvial soil in contrast to the other treatments, suggesting that these might be tolerant to salinity and low pH. Saltwater intrusion reduced biological diversity (Margalef, Shannon-Wiener, and Hill’s indices), maturity index (∑MI, MI25), and clearly affected functional guilds of nematode community, especially c-p 5 group was reduced in both salt-affected soils. This study suggests that saltwater intrusion showed a potential risk in the degradation of soil properties, as indicated by the altered nematode community, trophic structure, functional guilds and their ecological indices in paddy fields.

An integration of a shrimp production cycle into the traditional system of rice farming is an adopted practice by farmers due to saline intrusion and changes of environmental condition in Vietnam. Aquacultural pond sludge or biological waste has the potential to cause environmental pollution if it is not managed well. However, the sludge from shrimp ponds in rice-shrimp farming systems can provide nutrition and maintain soil fertility for the integrated rice crop production. A randomized block field experiment was conducted on a rice-shrimp farm to test the fertilizer value of sludge for rice over two consecutive seasons in Vietnam. Five treatments of sludge and fertilizer rates were applied in field experiments including control, sludge application alone, recommended fertilizer rate, reduced fertilizer rate, and combination of sludge and reduced fertilizer rate. The results consistently proved that the pond sludge can provide large quantities of plant available nutrients such as ammonium nitrogen, total nitrogen and organic matter. The use of sludge either alone or in combination with the reduced fertilizer rate produced optimal rice yields while fertilizer cost of rice production was reduced. This finding indicates that the use of sludge is able to save cost of production to rice-shrimp farmers and reduce adverse impacts of pond sludge released on the surrounding environment.

This paper presents a summary of our results on studies of synthesis and biomedical application of optical nanoparticles. Gold, dye-doped silica based and core–shell multifunctional multilayer (SiO2/Au, Fe3O4/SiO2 ,F e3O4/SiO2/Au) water-monodispersed nanoparticles were synthesized by chemical route and surface modified with proteins and biocompatible chemical reagents. The particles were conjugated with antibody or aptamer for specific detecting and imaging bacteria and cancer cells. The photothermal effects of gold nanoshells (SiO2/Au and Fe3O4/SiO2/Au) on cells and tissues were investigated. The nano silver substrates were developed for surface enhanced Raman scattering (SERS) spectroscopy to detect melamine.