Biochar can play a key role in nutrient cycling, potentially affecting nitrogen retention when applied to soils. In this project, laboratory experiments were conducted to investigate the adsorption properties of bamboo charcoal (BC) and the influence of BC on nitrogen retention at different soil depths using multilayered soil columns. Results showed that BC could adsorb ammonium ion predominantly by cation exchange. Ammonium nitrogen (NH 4 + -N) concentrations in the leachate of the soil columns showed significant differences at different depths after ammonium chloride application to the columns depending on whether BC had been added. Addition of 0.5% BC to the surface soil layer retarded the downward transport of NH 4 + -N in the 70-day experiment, as indicated by measurements made during the first 7 days at 10 cm, and later, in the experimental period at 20 cm. In addition, application of BC reduced overall cumulative losses of NH 4 + -N via leaching at 20 cm by 15.2%. Data appeared to suggest that BC could be used as a potential nutrient-retaining additive in order to increase the utilization efficiency of chemical fertilizers. Nonetheless, the effect of BC addition on controlling soil nitrogen losses through leaching needs to be further assessed before large-scale applications to agricultural fields are implemented.
The objective of this study was to evaluate the effects on chemical and microbiological properties of paddy soil of shortterm biochar, straw, and chemical fertilizers compared with chemical fertilization alone. Five soil fertilization treatments were evaluated: regular chemical fertilizers (RF), straw+regular chemical fertilizers (SRF), straw biochar+regular chemical fertilizers (SCRF), bamboo biochar (BC)+regular chemical fertilizers (BCRF), and straw biochar+70% of regular chemical fertilizers (SC+70%RF). Their effects were investigated after approximately 1.5 years. The soil pH and cation exchange capacity (CEC) were significantly higher in biochar-treated soils. The soil phosphorous (P) and potassium (K) content increased with biochar application. The soil Colwell P content was significantly increased with the addition of straw biochar (SCRF). The oxygen (O):carbon (C) ratio doubled in BC picked from the soil. This indicated that BC underwent a significant oxidation process in the soil. The denaturing gradient gel electrophoresis (DGGE) fingerprints of microbial communities differed among the treatments. Soils with added biochar had higher Shannon diversity and species richness indices than soils without biochars. The results suggest that biochar can improve soil fertility.
In order to observe the tree species effect on soil N status, soil microbial biomass C and N (C mic , N mic ), potential N mineralization and potential nitrification (under laboratory incubation conditions, 22°C) in different subhorizons (LOf 1 , Of 2 , Oh and mineral soil at 0-10 cm depth) were determined at three forest sites in central Germany. At each site, two contrasting stands (Beech, Norway spruce or Scots pine) were selected, where the initial soil conditions were similar. Three sampling dates that represented different stages of tree growth were selected: growing season -August, dormant season -November, after budbreak -April. In organic layers, C mic -to-total C (C t ) ratios under beech and under conifer were 0.72-4.74% and 0.34-2.11%, respectively. N mic -to-total N (N t ) ratios were 2.47-11.61% and 0.71-5.77%, respectively. Both concentrations of C mic and N mic were significantly affected by the stand type and sampling time. Potential N mineralization rates, ranging from 3.7 to 19.7 mg N kg )1 d )1 , showed no clear pattern in relation to stand type. However, potential nitrification rates were mostly significantly higher under beech than under contrasting conifer. In mineral soils, concentrations of C mic and N mic showed a clear temporal pattern in the order: August>November>April. The average N mic and N mic -to-N t were higher in soils from beech than conifer, while C mic and C mic -to-C t ratios were similar between the two forest types. In organic layers, the highest values of C mic -to-N mic ratio and C mic were found in November samples, especially under beech. By contrast, in mineral soils the highest value of C mic -to-N mic ratios were found in April samples, and at that time the C mic concentrations were the lowest, especially under conifer. These results revealed the differences in microbial growth form and survival strategy associated with different tree species and soil layers.
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