- Title
- Biochar and nutrient interactions in soil
- Creator
- Hossain, Md Zahangir
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Excessive amounts of animal manures and the production of a large volume of biosolids pose severe environmental problems concerning their safe disposal and management. Thermochemical treatment of biowaste materials via pyrolysis can convert them into value-added products such as biochar-based fertilisers. The nitrogen, phosphorus, potassium, and other nutrient contents are higher in manure- and biosolid-based biochars than in plant residue- and wood waste-based biochars. The nutrient contents and pH of biochar are affected by the nature of feedstock material and pyrolysis conditions. Biochar application increases nitrogen retention in soil by reducing leaching and gaseous losses and increases phosphorus availability by decreasing the leaching process in soil. However, biochar shows inconsistent (positive and negative) impacts in soil for potassium and other nutrients. Biochar also alters soil biological properties by increasing microbial populations, enzyme activity, soil respiration, and microbial biomass. Finally, nutrient use efficiency and nutrient uptake improve with the application of biochar to soil. Thus, biochar can serve as: firstly, a potential nutrient reservoir for plants; and secondly, an excellent amendment to improve soil properties. With these aspects in mind, this study aimed to enrich biochar with nutrients and examine their availability to plants. Due to the heterogeneous nature of various manures' composition and physicochemical characteristics and differences in preparation procedures, it is difficult to predict the corresponding biochar fertiliser values. Here, fourteen biochars were produced from one biosolid sample and thirteen animal manures samples by slow pyrolysis at 300 °C. The biochar yield of various feedstocks ranged from 39 to 81%, with the highest yield for grain-fed cow manure. The highest N and K content was found in chicken manure biochar (57.8 and 29.2 g kg–1, respectively), while the highest P was found in biosolid biochar (40.5 g kg–1). Three principal components (PC) explained 86.8% and 83.3% of the variances in the feedstocks and biochars, respectively. The results of this study suggested that biochars produced from different manures and biosolids may potentially be a source of soil nutrients and trace elements. Therefore, four feedstocks including biosolid, cow manure, chicken manure and chicken litter were used to synthesise nutrient-enriched biochar fertiliser products. Urea and KH2PO4 were used to enrich the biochar products with the three major nutrients - N, P and K - which were then added to feedstocks and biochars using pre- and post-pyrolysis nutrient enrichment methods. This modification method less influenced the P, K, and other nutrients when the feedstocks were not acidified during the nutrient impregnation process. However, the levels of P and K in NEBCs were significantly increased when feedstocks were acidified before pyrolysis. Nutrient enrichment via post-pyrolysis modification significantly increased the N, P, K and S levels. The findings of this study confirmed that the post-pyrolysis method was superior in producing novel nutrient-enriched fertiliser. For evaluating the nutrient-enriched biochars, a short-term (28 days) incubation study and a pot study were conducted under controlled environmental conditions. This study evaluated the nutrient release and mobility from NEBCs added at two different rates (1 and 5%) to two contrasting Australian soils. The NEBCs were derived from cow manure, chicken manure and biosolid biochar. This study showed that NEBCs changed soil pH in two soils and thus enhanced the availability of plant nutrients in both soils with the biochar rates and incubation time. Moreover, the added NEBCs also increased the N, P and K concentrations in soil pore water, while the nutrient release from the NEBCs was slower than chemical fertilisers. The pot study showed that available N, P and K increased by up to 15, 30 times and 25%, respectively, in NEBCs amended soils by altering the soil pH. Similarly, the DHA was also enhanced by the biochar application in soils. The shoot and root biomass was increased 2- to 4-fold and 66% over the control treatment. The canola shoot's N, P and K concentrations were increased by 3–4 times, 38% and 72%, respectively. The study revealed that the nutrient uptake by plants was significantly increased in NEBCs amended plants. In conclusion, biochar production at 300 °C confirmed that the manure and biosolid derived biochar contained high levels of N, P and K nutrients. Results strongly suggested that the nutrient-enriched biochar can be produced by modifying biochar with chemical fertilisers after pyrolysis. The nutrient-enriched biochar released nutrients slowly compared to the respective chemical fertilisers in the soils. The application of nutrient-enriched biochars improved plant growth and biomass yield. The plants can uptake more nutrients from the biochar amended soils than fertiliser treated soils. This work also encourages future research opportunities in effective resource recycling by converting animal wastes into novel fertilisers, thereby contributing to the circular economy.
- Subject
- biochar; manure; biosolid; fertiliser; crop
- Identifier
- http://hdl.handle.net/1959.13/1508824
- Identifier
- uon:56159
- Rights
- Copyright 2022 Md Zahangir Hossain
- Language
- eng
- Full Text
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