| Biochar amendments to soils had aroused much interest for having potential for greenhouse gas mitigation,soil improvement and increased crop productivity.However,little attention has been focused on the influence of biochar amendments on herbivorous insect pests.To investigate potential effects of biochar addition on biology of the brown planthopper(BPH),Nilaparvata lugens,following questions were addressed in this thesis study.(1)How do biochar amendments to soils influence feeding behaviors and life history of N.Lugens?(2)Whether biochar addition have effects on feeding behaviors of N.lugens?(3)How do biochar amendments to nitrogen-doped soils affect life history of N.Lugens?The study found negative effecs of biochar application on N.Lugens biology.The main results and conclusions of this study are as follow.1.Effects of biochar amendments to infertile soils on developmental and reproductive performances of N.lugensThe present study investigated whether a biochar amendment affected developmental and reproductive performances of the rice brown planthopper feeding on rice plants.The biochar from the pyrolysis of wheat straw was used for treatments of soils(from a fallow rice field)and the treated soils were applied to grow rice seedlings in small vials,in which N.lugens life history was observed.The nymphal development time was delayed and nymph-to-adult survival decreased with a high level of 200 g/kg biochar application.Herbivore life time fecundity decreased with increasing amounts of biochar,from 256 eggs under the control down to 69 eggs under the high level(200 g/kg)of biochar application.Egg-hatching rate significantly decreased at the highest biochar level(200 g/kg),compared to the other lower biochar levels.Our results suggest that biochar amendment to rice fields may have negative impacts on the rice brown planthoppers when applied at level of 200g/kg of soil.2.Effects of biochar amendments to infertile soils on feeding behaviors of N.lugensThe BPH feeding behaviors are effected by chemical stimulus.Probing stimulants induce active probing,and sucking behavior was controlled by sucking stimulants and sucking inhibitors.These stimulants or inhibitors are mainly amino acid,silicate and flavonoids in plants.Biochar amendments will alter plants on the absorption of nitrogen and silicon,and affect the carbon nitrogen ratio of plants.These changes will affect the content of these stimulants and inhibitors in plants and influence of BPH feeding behavior.Feeding behaviors of BPH were compared by using electronic penetration graph technique(EPG).The results shown:1)Biochar amendments can significant increase frequency of probing and decrease frequency of phloem sap.2)Compared to control treatment,biochar amendments decreased intracellular activity and phloem sap ingestion duration,and extended activity in the xylem region.Among the total monitoring time,29.45%± 6.83%(about 0.5 times of which was used in the control treatment)and 35.91%±6.20%(significantly higher than the time used in the control treatment)was for the BPH eating the phloem liber and the xylem of the rice respectively when the amount of biochar adjunction reached 200 g.kg-1.The results of the experiment indicates that the biochar amendments against the feeding behavior of the BPH.3.Effects of biochar amendments to nitrogen-rich soils on life history of N.lugensNitrogen,one of the limiting factors for plant growth,will affect the plant absorption of nitrogen and the effect of biochar.We made laboratory experiments to investigate effects of wheat-biochar amendment to rice field soils with rich nitrogen on the major rice pest Nilaparvata lugens in developmental and reproductive performances.Biochar amendments did not affect nymphal development time.Compared with the control,the biochar amendment of 50 g/kg reduced nymph-to-adult survival and proportion of emerging brachypterous adults.Biochar amendment of 50 g/kg markedly reduced life time fecundity and egg hatching rate,compared with the control.These results suggest that biochar amendments in nitrogen rich soil may have a negative effect on life history traits of N.lugens. |
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