Study on Leaching Loss of Nitrogen in Ricefields by Using Large Undisturbed Monolith Lysimeters

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Interdependence between Natural Habitats and Ricefields for Rice Pest Management in the Agusan Marsh Floodplain

This paper describes how aquatic insect diversity in major natural habitats of Agusan marsh relates with nearby ricefields to determine the interdependence between them for sustainable rice production through natural pest control and for conservation of aquatic fauna in the marsh. Sampling for one year including two cropping seasons of rice production was conducted in various natural habitats of the marsh and in the adjoining rice fields. Both the natural habitats and rice fields were characterized in relation to determining habitat suitability for aquatic insects. The sedge-dominated swamp had the highest diversity among the natural habitats, while the fern-dominated swamp had the lowest. In the adjacent ricefields, diversity was similarly highest in the site near the sedge-dominated swamp, while the lowest was in the ricefields adjoining the Sago forest. Species composition of aquatic insects among the habitats differed between the wet and dry seasons. However, similarity patterns exist between natural habitats and rice fields. The closer similarity in species composition between natural habitats and ricefields indicates habitat connectivity which is an important consideration in planning and effective pest management and ecologically sound rice farming in the marsh.

Immatures of Lutzia fuscana(Wiedemann,1820)(Diptera:Culicidae) in ricefields:implications for biological control of vector mosquitoes

Objective:Rice fields are dynamic mosquito larval habitats with assemblage of different predator taxa,including the larva of the mosquitoes Lutzia.Entomological surveillance in the ricefields is essential to evaluate the potential of these predators as biological resource to regulate vector mosquito population.In view of this,a survey of ricefields for immatures of different mosquito species including Lutzia was conducted.Methods:Survey of selected ricefields was carried out to evaluate the species composition of mosquitoes.Laboratory evaluation of the immatures of Lutzia mosquitoes was carried out to assess its predation potential using mosquitoes and chironomid as preys.Results:The survey revealed the presence of five mosquito species belonging to the genera Anopheles and Culex and the predatory immatures of the mosquito Lutzia Juscana(Wiedemann,1820).The ratio of prey and predatory larva ranged between 1.46 and 4.78 during the study period,with a significant correlation on the relative abundance of the larval stages of Lt.Juscana and Anopheles and Culex larvae.Under laboratory conditions,a single IV instar larvae of Lt.fuscana was found to consume on an average 5 to 15 equivalent instars of Anopheles sp.and Culex sp.larvae per day depending on its age.The prey consumption reduced with the larval stage approaching pupation.When provided with equal numbers of chironomid and Anopheles or Culex larvae,larva of Lt.fuscana consumed mosquito larvae significantly more compared to chironomids.Conclusion: The survey results and the preliminary study on predation are suggestive of the role of Lt.Juscana in the regulation of vector mosquito populations naturally in the ricefields.Since Lt.Juscana is common in many Asian countries,further studies on bioecology will be helpful to justify their use in mosquito control programme.

Effects of Biomineral Liquid from Spartina alterniflora on Growth,Body Color and Nutritional Components of Ricefield Eels,Monopterus albus

[Objective]The paper was to develop new fodder additives and to strengthen comprehensive utilization of Spartina alterniflora resources.[Method]The effects of biomineral liquid from S.alterniflora on growth,nutritional components of ricefield eels were studied.[Result]（1）0.5%of biomineral liquid had significant effect on weight gain rate,which was 8.37%higher than that in control group（P〈0.01）.Further supply of biomineral liquid could not increase the weight gain rate.Furthermore,biomineral liquid had no effect on the survival rate of ricefield eels.（2）Ricefield eels had certain changes in body color in the0.5%biomineral liquid group,and some ricefield eels were yellowing.（3）The contents of Cr,Fe,Zn in body of ricefield eels in treatment group were significantly higher than that in control group,but was lower than that in wild eel group,and the content of Se in treatment group was lower than that in control group and wild group（P〈0.01）.（4）The contents of K,Mg in muscle of ricefield eels in treatment group were higher than those in control group and wild eel group.The contents of ash and Ca in treatment group were close to that in control group but were higher than that in wild eel group.The content of crude fat in treatment group was close to that in wild eel group but was lower than that in control group.The contents of Zn,Se,Ni in treatment group were higher than that in control group and wild eel group,and the contents of Cr,Fe,Cu were close to that in control group and were higher than that in wild eel group（P〈0.01）.No significant differences were observed in the contents of moisture,crude fat and P among the three groups（P〉0.05）.[Conclusion]Addition of biomineral liquid from S.alterniflora could speed up the growth of ricefield eels and significantly improve their flesh quality,but had no significant effect on survival rate of ricefield eels.

Lysimetry study on the leaching loss of nitrogen from double-rice-cropped ricefield

The effect of N fertilizer application in ricefield on the environmental quality of ground-water was evaluated using large undisturbedmonolith lysimeters.Soil in lysimeters wassilty-clay-loamy paddy soil(Haplaquept)with apH of 6.5,15.4g/kg organic C,1.55g/kg to-tal N,88 mg/kg available N,399 mg/kg A1-abbas-P,67.5 mg/kg exchangeable K,and14.1 cmol/kg CEC.The lysimetry experiment was laid out atHangzhou during the early-rice season(ER,May-Jul)and late-rice season(LR,Jul-Oct)in 1991-1994.Three plot treatments were es-tablished,i.e.,urea plot(UN,applied urea150 kgN/ha per cropping season),ammoniumbicarbonate plot(CN,applied ammonium bi-carbonate 150 kgN/ha per cropping season),and control plot(CK,no N application).Allof the plots also received single superphosphateat 45 kg P/ha and KC1 at 75 kg K/ha.The

日本古倭人稻作文化滥觞于中国古吴越

日本古倭人的稻作文化,与中国古代存在于从东南沿海到云贵高原的越文化,有深刻的同源关系。而其中之古吴越区,则为日本古倭人稻作文化源头。 一、古倭人稻作之源在中国吴越 日本九州2300年前绳纹文化之末的夜臼·板付1式时期遗存中,有多处发现稻痕,被认为是日本稻作之肇始。在熊本县、长崎县的一些文化遗址及佐贺县宇木汲田、福冈县板付遗址里,有炭化稻米,一些陶器上也有稻壳压痕,甚至有稻田及水沟等灌溉设施遗迹。其后在约当公元前后3个世纪的弥生时期,种植稻谷极为普遍。它迅速成为最兴旺的经济活动,是关系人们生存繁衍的最重要的物质生产。中国古代史籍自《后汉书·东夷列传》、《三国志·魏书·倭人传》起,多载日本列岛古倭人以种禾稻为业。 种植水稻,是古倭人最主要的文化特征。稻作在日本列岛的出现,实际比夜臼·板付1式时期稍早。而由于中国浙江余姚河姆渡、桐乡罗家角等古文化遗址的发掘。