RESUMO
Currently, reasonable disposal of municipal sewage sludge is one of the important issues in the field of resources and environmental science. Sludge is rich in large amounts of organic matter and available nutrients, promoting soil fertility, soil physical structure and biological properties. However, sludge contains a variety of heavy metals, organic contaminants and other hazardous substance, especially heavy metals, which are the bottlenecks of agricultural application of sludge. To improve the sewage sludge utilization efficiency and decrease the effect on soil, this essay made a summary on domestic and foreign studies on plant-soil interaction ecosystem with sewage sludge to provide a theoretical basis and scientific guidance for advancing sewage sludge utilization efficiency.
Assuntos
Agricultura , Metais Pesados , Esgotos , Solo , Poluentes do SoloRESUMO
Organic nitrogen can play an important role in plant growth, and soil pH changed greatly due to the over-use of chemical fertilizers, but the effects of soil pH on the competitive uptake of amino acids by plants and rhizosphere microorganisms are lack of detailed research. To study the effects of soil pH on the uptake of amino acids by maize and soil microorganisms, two soils from Hangzhou and Tieling were selected, and the soil pH was changed by the electrokinesis, then the 15N-labeled glycine was injected to the centrifuge tube with a short-term uptake of 4 h. Soil pH had a significant effect on the shoot and root biomass, and the optimal pH for maize shoot growth was 6.48 for Hangzhou red soil, while it was 7.65 for Tieling brown soil. For Hangzhou soil, the 15N abundance of maize shoots under pH=6.48 was significantly higher than under other treatments, and the uptake amount of 15N-glycine was also much higher. However, the 15N abundance of maize shoots and roots under pH=7.65 Tieling soil was significantly lower than it under pH=5.78, but the uptake amount of 15N-glycine under pH=7.65 was much higher. The microbial biomass C was much higher in pH=6.48 Hangzhou soil, while it was much lower in pH=7.65 Tieling soil. According to the results of root uptake, root to shoot transportation, and the competition with microorganisms, we suggested that although facing the fierce competition with microorganisms, the maize grown in pH=6.48 Hangzhou soil increased the uptake of glycine by increasing its root uptake and root to shoot transportation. While in pH=7.65 Tieling soil, the activity of microorganisms was decreased, which decreased the competition with maize for glycine, and increased the uptake of glycine by maize.
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Aminoácidos , Solo , Zea mays , Fertilizantes , Nitrogênio , Raízes de PlantasRESUMO
On the basis of field soil sampling, this paper investigated the distribution characteristics of soil different nitrogen (N) forms and its influence factors in the different typical zonal soils. The results showed that the concentrations of soil extractable total N, extractable organic N and adsorbed amino acids extracted with 0.5 mol·L-1 K2SO4 significantly increased along the altitudinal gradient in the different vertical soils, and their mean concentrations were greater than that in the horizontal soils. The concentrations of soil different N forms widely varied with the soil type in the different horizontal soils. On average, the concentration of soil adsorbed amino acids was approximately 5-fold greater than that of the free amino acids, representing 21.1% of soil extractable organic N. It indicated that the soil adsorbed amino acids extracted with the strong salt solution could serve as an important form of soil organic N. Pearson correlation analysis showed that extractable total N, extractable organic N, ammonium and amino acids in vertical soils were positively correlated with soil organic matter and total N (r=0.57-0.93, P<0.05), but negatively correlated with soil pH and nitrate (r=-0.37--0.91, P<0.05). In the horizontal soils, soil extractable total N, nitrate, organic matter, total N, alkali-hydrolyzable N and cation ions (e.g. K+, Ca2+, Mg2+) were all positively correlated with soil pH (r=0.36-0.85, P<0.05), whereas negatively correlated with soil ammonium and amino acids (r=-0.39--0.81, P<0.05).
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Nitrogênio/análise , Solo/química , Adsorção , Aminoácidos/análise , Concentração de Íons de Hidrogênio , Nitratos/análiseRESUMO
Plant can directly take up the intact amino acids, thus bypass the microbial mineralization of organic nitrogen. As an excellent carbon and nitrogen source, there exists competition for amino acid absorption between plant roots.and soil microorganisms. And the total flux of amino acids in soil may be enormous due to the extensive sources and short half-life. Studies on amino acid nitrogen nutritional contribution for plant by the technique of nitrogen isotopic tracer, has become a research topic in recent years ,which will help us better understand the principle of soil fertility. This paper summarized the recent researches on amino acid morphological characteristics in soil and its metabolic mechanism and nitrogen nutritional contribution for plant in different ecosystems, and discussed the present status and development trend of the amino acid circulation mechanism in the plant-soil-microorganism ecosystem and its bioavailability for plant. Finally, the topics of environmental regulating mechanism of amino acid bioavailability, amino acid carbon-nitrogen metabolism, and how to improve the field organic nitrogen management were all the core issues to be resolved.
