Effect of Biochar Application Rate on Physiochemical and Biological Properties of a Sandy Soil

  • Nahid M. Khalifa

Student thesis: Master's Thesis

Abstract

Desertification is a global problem that is the result of poor soil quality, and is primarily caused by soil erosion that is associated with losses of Soil Organic Carbon (SOC). Therefore increasing SOC can also improve soil quality and enhance food production. One way to do this is soil application with ‘biochar’ - a term used to describe charcoal generated from pyrolysis of green waste. Numerous reports have shown that soil quality is improved after application of biochar, but very little is known about the impact of application rate on soil properties and soil water drainage. The aim of this study is to assess the effect of biochar application rate (1, 5 and 10% per soil dry weight) on sandy soil properties and soil drainage quality (nitrate and phosphate concentrations). The biochar for this study was produced from palm tree waste via slow pyrolysis at 400 oC. Our results show that higher application rates of biochar have a positive impact on soil physiochemical properties. Specifically, soil bulk density decreased from 1.54 g/cm3 to 1.07 g/cm3 , water holding capacity increased by 20%, soil CEC increased by more than 3 meq/100g soil, and soil sodicity decreased. One caveat for higher biochar loads is the potential for ground water pollution because higher concentrations of NO3-N (6.74 mg/l ) and PO43--P ( 1.99 mg/l) were present in soil water drainage of the 10% (w/w ) biochar amended soils when compared with control NO3-N (2.33 mg/l) and PO4-P ( 0.15 mg/l). A long-term study will be required to investigate whether this is a real problem or if it is a residual effect of initial biochar application. Finally, biochar application rate appears to have an influence on soil microbiology. Specifically, hierarchical clustering of data from Denaturing Gradient Gel Electrophoresis show a shift in microbial community structure that is dependent on biochar application rate. Soil respiration was also the highest on day 7 for 10% biochar amended soils, which then decreased to control levels on day 14 of a soil incubation study. This suggests that biochar application may have a priming effect on soils.
Date of AwardJul 2014
Original languageAmerican English
SupervisorLina Yousef (Supervisor)

Keywords

  • Soil Organic Carbon (SOC)
  • "Biochar Application
  • Pyrolysis
  • Water Drainage.

Cite this

'