نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشجوی دکتری گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه زنجان
2 گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه زنجان
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Objectives: Most of the research carried out on biochar- iron oxide/hydroxide composites (BC-FeOX) have focused on the removal of phosphorus from polluted environments. However, by examining the release kinetics of loaded phosphorus on biochar-iron oxide/hydroxide composites, it can be studied as a slow released fertilizer in calcareous soils. Therefore, the present study was conducted with the aim of investigating the kinetics of phosphorus release from phosphorus-containing composites based on biochar-iron oxide/hydroxide and also investigating different models of phosphorus release in the aquatic environment.
Materials and methods: An experiment was conducted to investigate the phosphorus release kinetics over time from phosphorus-containing composites based on biochar-iron oxide\hydroxide as a factorial-split plot design. The experimental treatments were two levels of biochar (residuals of wheat straw and walnut shell), four levels of iron oxide\hydroxide (goethite, hematite, ferrihydrate and magnetite), four levels of phosphorus (0, 5, 10 and 20% by weight) as triple superphosphate (TSP) and two methods of making composite (coated form and granulated form). In the granulation method, the powdered mixture of TSP and BC-FeOX was used as the granulation core until the formation of granule cores with a diameter of 4-3.5 mm. In the coating method, until the formation of granules with a diameter of about 2.8 to 3.3 mm, only TSP powder was used and then BC-FeOX powder was used for coating. Phosphorus release kinetics at 0.25, 0.5, 1, 6, 12, 24, 48, 72, 120 and 240 hours were obtained by plotting the changes of phosphorus concentration against time.
Results: The results showed that the phosphorus release rate over time from composites containing phosphorus based on biochar-iron oxide\hydroxide was higher at the beginning of the experiment compared to the duration of the experiment. In the treatments containing wheat straw biochar, the phosphorus release percentage was 3.8% lower than the treatments containing walnut shell biochar. By increasing the level of phosphorus in composites, more phosphorus percentage was released, so that the average percentage of phosphorus released from fertilizer composites containing phosphorus levels of 0, 5, 10, and 20% at 1 hour after the start of the experiment was 2.1%, 9.2%, 15.3%, and 18.4% respectively. The order of phosphorus release during the experiment in treatments containing iron oxide\hydroxides was magnetite > hematite > ferrihydrate > goethite, so that after 24 hours from the start of the experiment, the phosphorus release percentage for magnetite, hematite, ferrihydrate and goethite in granulated form was 75.8, 73.8, 67.6 and 65.9% respectively and it was the coated form 45.9, 38.8, 36.3 and 36.7, respectively. Actually the percentage of phosphorus release in coated form composites was significantly higher than granular form composites from the start of the experiment until 24 hours, but after this time there was no significant difference. The fitting of different kinetics models showed that the best model for phosphorus release from phosphorous composites based on biochar-iron oxide\hydroxide was the nonlinear pseudo-first-order equation (r2=0.99). However, two models of parabolic diffusion (r2=0.94) and Elovich equation (r2=0.97) also showed a very good fitting for phosphorus release from composites. So, the order of the best fitted models for the phosphorus release from composites was nonlinear pseudo-first-order equation > Elovich equation > parabolic diffusion model > linear equation.
Conclusion: In conclusion, the unique role of engineered biochar by iron hydroxides can provide a place to carry phosphorus as an essential nutrient for plants in order to improve the efficiency use of fertilizer, and for practical application in agricultural lands, it is necessary to do more field and supplementary work as well as long-term evaluation of the use of such fertilizers in the environment of plant growth.
کلیدواژهها [English]
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