Enhancement of Green Soybean Growth and Yield in Alluvial Soil by Potent N2-fixing Rhizospheric Bacteria.

<b>Background and Objective:</b> Nitrogen fertilizer causes adverse effects on the environment aspect, so biological nitrogen sources should be applied in agriculture. The objective of the study was to evaluate the efficacy of N₂-fixing rhizospheric bacteria in improving soil fertility, nitrogen (N) uptake, growth and yield of green soybean (<i>Glycine max</i> (L.) Merr). <b>Materials and Methods:</b> The pot experiment was conducted with 9 treatments (i) 100% N of recommendation of fertilizer formula (RFF), (ii) 85% N, (iii) 70% N, (iv) 55% N, (v) 85% N and a mixture of <i>Enterobacter cloacae</i> ASD-07 and ASD-28, (vi) 70% N and a mixture of ASD-07 and ASD-28, (vii) 55% N and a mixture of ASD-07 and ASD-28, (viii) 0% N and ASD-07 and ASD-28, and (ix) 0% N, without bacteria<i>,</i> with four replications in in-dyke alluvial soil collected from Chau Phu District, An Giang Province. <b>Results:</b> The use of a mixture of the two N₂-fixing rhizospheric strains<i> </i>as biofertilizers at 85% N level improved NH₄⁺ content and N uptake with an increase of 3.1 mg kg¹ and 95.8 mg pot¹, respectively. They also produced higher values in growth including plant height, number of leaves, stem diameter and yield components including pod number, pod diameter, seed length, seed diameter and seed thickness. <b>Conclusion:</b> The application of a mixture of the two N₂-fixing rhizospheric strains resulted in replacing 15% N of RFF, but it still improved the yield.

Effect of Olyset Net on Mosquito Larvae and Their Heteroptera Predators in Water Jars in Southern Vietnam.

Residents of Vietnam living in areas with water shortages collect and store tap water, when it is available, in containers, such as jars, which is then used for their daily activities. Although these water jars are important breeding sites for mosquitoes, Vietnam legislation prohibits the use of chemical larvicides in such containers. The effect of Olyset Net on the abundance of mosquito larvae and their Heteroptera predators (Micronecta spp. and Veliidae) in jars was evaluated via field experiments conducted in Tan Chanh, Long An, Vietnam. The number of Aedes larvae decreased when the jars were covered with the Olyset Net, while the numbers of non-Aedes mosquito larvae (Culex and Anopheles), and those of Micronecta and Veliidae, did not vary until the end of the experiment. However, Micronecta population increased after removing the Olyset Net from the jars, and consequently Aedes larvae decreased due to these changes in the Micronecta, 26 days after the Olyset Net was removed. Incomplete use of Olyset Net failed to control mosquitoes in water jars based on the invasion of adult mosquitoes, and in water transferred by residents among the jars, which might contain larvae. These results suggest that Micronecta, as well as Olyset Net, can be considered as control agents for mosquito larvae.

Heteropteran insects as mosquito predators in water jars in southern Vietnam.

Residents of Vietnam living in areas with water shortages and/or poor tap water maintain water storage containers, such as jars, in and around their domiciles in order to store water used in daily life. Although these water jars are known to be important breeding sources of the Aedes mosquito, use of chemical larvicides in such containers is legally prohibited in Vietnam. In this study, we identified the dominant mosquito insect predators in water jars in and around residences located in Tan Chanh, Long An, southern Vietnam. Of 3,646 Heteroptera collected from such jars, Corixidae (Micronecta spp.) and Veliidae (Microvelia spp.) were revealed to be the dominant predators. Polymerase chain reaction (PCR) analysis revealed that 40% of Micronecta and 12% of Veliidae had Aedes aegypti-positive reactions, indicating that these two dominant Heteroptera are important predators of Ae. aegypti. Our results suggest that aquatic Heteroptera may be an important mosquito control agent in addition to the currently used copepods.

Mosquitoes and their potential predators in rice agroecosystems of the Mekong Delta, southern Vietnam.

Culex tritaeniorhynchus, Cx. gelidus, and Cx. quinquefasciatus, known vectors of Japanese encephalitis (JE), are distributed in rice agroecosystems in Asian countries. Very few integrated studies on the breeding habitats of rice-field mosquitoes, including JE vectors, have been conducted in Vietnam. We investigated the mosquito fauna and potential predators in 8 rice growing areas in the Mekong Delta region of southern Vietnam, during the wet and dry seasons of 2009. Mosquitoes and their predators were collected from a variety of aquatic habitats (rice fields, ponds, wetlands, shrimp ponds, ditches, canals, and rivers). We collected 936 Culex spp. (354 Cx. tritaeniorhynchus, 240 Cx. vishnui s.l., 189 Cx. fuscocephala, and 42 Cx. gelidus), 33 Uranotaenia, 25 Anopheles, and 9 Mimomyia (4 Mi. chamberlaini) in the dry season. During the rainy season, we collected 1,232 Culex spp. (132 Cx. vishnui s.l., 66 Cx. tritaeniorhynchus, 9 Cx. gelidus, 4 Cx. fuscocephala, and 2 Cx. bitaeniorhynchus), 236 Anopheles spp. (40 An. vagus and 1 An. sinensis), and 7 Uranotaenia (3 Ur. lateralis). Heteroptera such as Micronecta, Veliidae, and Pleidae were abundant and widely distributed in both seasons. Based on a stepwise generalized linear model, the abundance of mosquitoes and their predators in rice fields was high when the rice plant length was short and water depth was shallow. Therefore, the use of insecticides during the earlier stages of rice growth should be avoided in order to preserve the predator populations.