The impact of biochar on soil functioning in two contrasting climates

Muhamad, Khasifah and Quinton, John and Semple, Kirk (2016) The impact of biochar on soil functioning in two contrasting climates. PhD thesis, Lancaster University.

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Previous research has demonstrated that biochar addition to soil improves the soil’s physical and chemical characteristics, reduces nutrients leaching, increases crop yield and enhances microbial activity in the soil. This has attracted significant research interest into the effects of biochar application on soil in recent years. However, the literature on tropical soils following biochar addition is scarce. Even though more biochar studies were conducted in temperate soil, the physical and chemical characteristics of temperate soils vary widely, and may respond differently upon biochar addition. Moreover, to date, tropical and temperate soils studies are conducted separately. Therefore, this thesis investigates the effect of biochar amendment on the soil’s physical, chemical and biological properties in two different climates at the same time. The aims of this study were to determine the effect of biochar ageing on tropical and temperate soil characteristics and also to assess the effect of different particle sizes and application rates on temperate soil properties. The present study comprised of two sets. The first set involved incubation of soils and biochar for up to 360 days (tropical soil), 300 days (temperate soil part 1) and 30 days (temperate soil part 2). The soils were kept and incubated in sealed jars. The soil’s biological, chemical and physical properties were tested as to whether they were enhanced by the addition of biochar. The second set was a nutrients leaching study. In this part of the study, the soils and biochars were packed into glass and PVC columns. Ammonium, nitrate and phosphate leaching were measured to assess whether biochar application reduces nutrients leaching from the soil columns. The results from the tropical and temperate soils revealed that at the 2% application rate, the addition of biochar increased the soil’s carbon and pH (P<0.05), had a limited effect on the mineralization of 14C glucose and water retention, a marginal effect on the cation exchange capacity, and no effect on the microbial biomass, total nitrogen, inorganic phosphorus and aggregate stability (P>0.05). Biochar also reduced the concentration of ammonium leaching (P<0.05) and showed an unclear pattern on the sorption of nitrate and phosphate of biochar in the soil’s leachates (P>0.05). At a higher application rate (5%), biochar increased the temperate soil’s carbon and pH (P<0.05), increased microbial activity, especially when using the finest particle size (0.1mm) (P<0.05), increased microbial growth (P<0.05) and reduced nitrate leaching in unfertilized temperate soil (P<0.05). These results were drawn from a small-scale study (laboratory study). The effects of biochar on a larger scale, for example in a long-term field study, must be investigated further to examine whether similar results can be obtained in a real condition. This is important to assist and provide farmers with information about the use of biochar before applying biochar in a vast agricultural area.

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Thesis (PhD)
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29 Mar 2016 08:56
Last Modified:
21 May 2024 01:58