Dramatic changes in climatic conditions have precipitated increases in the severity and frequency with which saltwater intrusions occur in Vietnam's Mekong Delta. These intrusions threaten agricultural sustainability and rural livelihoods. Little research has explored how rural farmers perceive this threat, and what factors influence them to change farming practices to adapt to the altered environment. This study attempts to understand how rice farmers in Soc Trang province perceive and respond to saltwater intrusions. This geographical area is a main agricultural region in Vietnam's Mekong Delta. Data were obtained from interviews with 80 rice farmers and four key agricultural officers in two districts of Soc Trang province. Results found that farmers are becoming aware of the relationship between climate change and saltwater intrusions, and that this awareness is significantly influenced by educational levels and numerous sources of both informal and formal information. In addition, characteristics related to a farm's location, including its access to water sources, when combined with access to information, appeared likely to influence Soc Trang farmers' risk perceptions. Individual farmers have responded to the now-irregular and intensifying saltwater intrusions by implementing both intentional and unintentional adaptations. Further, significant differences were observed between local adaptation strategies in various geographical locations at the district level. The absence of a strong correlation between Soc Trang rice farmers' perceptions of risks and their decisions to implement adaptive responses was also observed. This suggests that having knowledge of a threat is not sufficient to motivate individuals to take steps to mitigate it.

   This study aims at testing the effects of a washing process on the germination of komatsuna (Brassica rapa var. perviridis) for three days. Cattle manure ash (CMA) was washed with deionized water to reduce electrical conductivity (EC). Not-washed ash (NWA) and washed ash (WA) were used in this experiment. Solutions extracted from NWA and WA (solid:water = 1:20) were diluted at different ratios and had EC values ranging from 0.6 to 28.4 deci-Siemens (dS) m^-1. Potassium (K) solutions (1, 2, 3, and 4 dS m^-1 as KCl) and phosphorus (P) solutions (5.2 and 2.5 mg P L^-1 as KH₂PO₄, adjusted to EC of 1 or 2 dS m^-1) were used for germination tests. Results showed that the washing process reduced EC and therefore enhanced shoot elongation. However, the washing process did not affect germination rates (p > 0.05). Stimulation of root and shoot elongation was seen at EC less than 3 dS m^-1 and K ranging from 3.5 to 16 mM. Potassium in NWA and WA was a stimulating factor for the elongation of roots and shoots for three days in the seedling stage, but K was reduced to 67% in the WA extract. Meanwhile, soluble P negligibly affected the growth of roots and shoots. In conclusion, K in both NWA and WA promoted the growth of roots and shoots. The washing process should be considered when EC is limited to less than 3 dS m^-1 by application rates.

   A laboratory experimental study was conducted to investigate the effects of different coffee waste biochar materials at three temperatures on nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions from agricultural soil in Central Vietnam. Soil amended with 2% normal biochar, 2% functional biochar (with a high NO₃-N adsorption capacity of 20 g N kg^-1) or no addition was adjusted at 60% water holding capacity, conditioned with 100 mg N-NO₃ kg^-1 dried-soil and aerobically incubated at 25℃, 30℃ or 35℃ for 21 days. N₂O and CO₂ emissions were measured on days 1, 3, 5, 7, 14 and 21. Results showed that the addition of normal biochar caused more CO₂ emission but less N₂O emission compared to the functional biochar application. At 25℃, biochar amendment had a neutral or positive effect on N₂O and CO₂ emissions. At 35℃, biochar amendment reduced N₂O and CO₂ emissions compared to the control. However, there was little difference in N₂O and CO₂ emissions among biochar treatments. In addition, with increasing temperature, a positive correlation between temperature and N₂O and CO₂ emissions with the non-biochar amendment and a negative correlation between temperature and N₂O with the biochar treatments were observed. This is because temperature probably affects the rate of microbial processes mediating respiration and denitrification and the soil-biochar mixture's mobilization of N availability.