| Biogas slurry which is rich in nitrogen, phosphorus, potassium and other macronutrients and calcium, copper, iron, manganese, zinc and other micronutrients, provide adequate nutrients for crop growth. Therefore, biogas slurry as a liquid fertilizer return to farmland becomes an effective way to digestion of a large number of biogas. In order to provide theoretical basis and technical support for the utilization of biogas slurry, a field experiment was conducted to investigate the effects of different ratios (0%,25%,50%and75%) of biogas slurry nitrogen, which substituted chemical nitrogen fertilizer, on the yield and quality of aquatic vegetables (Oenanthe javanica); meanwhile, pay close attention to the environmental risk under biogas slurry application and try to elaborated the reasons that biogas slurry promotes crop growth under pot experiment. The main findings are as follows:The results indicated that the yields of Oenanthe javanica amended with25%,50%and75%ratio of biogas slurry were6.05%,66.67%and44.44%, respectively, which were all higher than that amended with chemical fertilizer treatment. The highest yield of Oenanthe javanica appeared in the treatment amended with50%ratios of slurry, which was82541.3kg·hm-2.There were no significant differences in chlorophyll, carotenoid, vitamin C, cellulose and protein contents in the stem and leaf of Oenanthe javanica between different ratios biogas slurry treatments and chemical fertilizer treatment.The soluble sugar contents in stem and leaf of Oenanthe javanica of other four treaments were lower than that of chemical fertilizer treatment. Compared with chemical fertilizer treatment, nitrate contents intreatments with biogas slurry application ratio of25%,50%and75%were decreased by6.31%,31.92%and18.63%, respectively, and the nitrate contents in N50treatment was lowest, which was675.72mg·g-1. In conclusion, the application of biogas slurry for substitution of chemical nitrogen fertilizer on Oenanthe javanica could promote the growth of Oenanthe javanica and improve its quality, also could reduce the nitrate contents of Oenanthe javanica. In this paper, the best slurry application ratio was50%or so.In the field experiment, the concentration change trend of NH4+-N in the soil surface water under different fertilization treatments was the same to and TN concentration. Because of rainfall, the concentration of NH4+-N and TN in soil surface water changes slightly before planting30days. After planting30days, the concentration of NH4+-N and TN in soil surface water reached the peak rapidly, and the ammonia volatilization also reached the peak when planting30days, and then decreased gradually. Except CK, the concentration of NH4+-N and TN in soil surface water had little difference between other treatments in summer, whose trend was reached the peak in initial stage of fertilization and then decreased gradually.After topdressing, the accumulative ammonia volatilization in spring and summer was1.56kg·hm-2and2.14kg·hm-2, respectively; the results in summer were slightly higher than that of spring. Accumulative ammonia volatilization decreased with the slurry ratio increasing. Ammonia volatilization from soils almost happened in the beginning of topdressing, and all treatments was positively and significantly correlated with the concentration of NH4+-N in soil surface water (P<0.01).A pot experiment which planting Oenanthe javanica by different dosage of slurry was conducted to explain the phenomenon that slurry promoted growth of plant. The results showed that the fresh weight of shoots in treatment SU was40.08g and the plant height was37.59cm, which all lower significantly than S (P<0.05). The content of vitamin C and Nitrate in the leaves and stems of Oenanthe javanica between two treatments (S and SU) had no significant difference. The biomass between SU and CK treatment had no significant difference, but the fresh weight of shoots and plant height in treatment SU lower18.8%and16.5%than CK, respectively. The the fresh weight of shoots and plant height in treatment SF were the highest, which were64.23g and49.53cm, respectively, higher significantly than CK, N50and SU treatment (P<0.05). The content of chlorophyll, carotenoid and vitamin C in stem of Oenanthe javanica in treatment SF were higher than treatment N50(P<0.05), which were no obvious difference with N50in leaf (P<0.05). The content of nitrate in leaf of Oenanthe javanica in treatment SF was significantly higher than N50(P<0.05), which had no no obvious difference with N50in stem (P<0.05).The concentration of TN in soil surface water in chemical fertilizer treatment No was higher than other treatments during whole growth period, which had no difference between each treaments. The concentration of TN in soil surface water in each treatment after the second topdressing was slightly lower than the first topdressing. The concentration of NH4+-N in soil surface water among each treatment has the same law with TN. Except CK, the concentration of NH4+-N in soil surface water reached the peak in earlier days after fertilizing, and then decreased gradually. The concentration of NH4+-N in soil surface water among each treatment during first topdressing reached peak when planting15days, which was later4days than the peak of TN. The concentration of NH4+-N in SF treatment was always higher than N50, and what in SU was higher than treatment S. The concentration of NH4+-N in soil surface water in each treatment after the second topdressing was slightly higher than the first topdressing.The results in the pot experiment shows that the organic particles, phosphorus and potassium in slurry have great effect to the growth of Oenanthe javanica. There may still exist inhibiting substance in slurry which inhibit the bolting of Oenanthe javanica. |
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