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Potential role of biochar in water management in rainfed agriculture

Author: Flavia, Namagembe

Awarding University: University of Edinburgh, Scotland

Level : MSc

Year: 2012

Holding Libraries: Institute of Commonwealth Studies Library ;

Subject Terms: Biochar ; Sugarcane ; Saccharum officinarum ; Bamboo ; Arundinaria alpina ; Soils ;

Abstract:

The economies of the three East African region (Uganda, Kenya and Tanzania), which is the region of interest in this study still rely largely on rainfed agriculture accounting to approximately 80% of the total agricultural production. With the increasing threats from climate variability, the region is prone to extreme conditions of drought and floods. Inadequate soil moisture and low soil fertility have been the challenges facing rainfed agriculture in the region and several approaches have been employed to help manage agricultural water sustainably. Previous studies indicate that incorporation of biochar into sandy soil improves its water retention capacity. This study demonstrates how addition of biochar produced from different feedstock biomass of sugarcane (Saccharum officinarum Linn) trash and bamboo (Arundinaria alpina) leaves and branches, all obtained from the region using both the laboratory controlled equipment at 350 oC, 450 oC and 550 oC and a traditional stove, to sandy soil has the potential improve the soil?s water holding capacity. This way, biochar can thus play a significant role in water management in agriculture in the East African region with the aim of reducing agricultural input and maximizing crop yields. For the traditional stove, it was difficult to control the temperature while producing the biochar but the highest steady temperature reached during production was recorded. The hydrologic properties including water holding capacity and hydrophobicity of sandy soil, biochars and soil-biochar mixtures were measured using the gravimetric method and the molarity of ethanol drop test respectively. Additionally, porosity was determined using the mercury porosimetry method in order to compare the pore size distribution of the biochars with their hydrologic properties. Biochars produced from different feedstock biomass under different production conditions varied in their hydrologic behavior and influenced soil?s hydrologic properties differently when added to it. The study demonstrates water retention increases in a sandy soil after addition of 2, 5 and 7 weight % biochar (20, 50, and 70 t ha-1 respectively).

The potential of biochar produced from Eichhornia crassipes and Prosopis juliflora to enhance soil water holding capacity of drylands soils

Author: Aller, Deborah

Awarding University: University of Edinburgh, Scotland

Level : MSc

Year: 2012

Holding Libraries: Institute of Commonwealth Studies Library ;

Subject Terms: Biochar ; Evironmental degradation ; Soils ; Eichhornia crassipes ; Prosopis juliflora ; Northern Kenya ;

Abstract:

Environmental degradation, agricultural productivity, food security, fresh water scarcity, and the adaptation to and mitigation of climate change are all significant concerns of the 21st century. Biochar is a highly porous, carbon rich material which is a natural soil amendment being investigated to address these current issues. Expanding agricultural production into dryland environments where sandy soils dominate is highly likely to be of great importance for ensuring future global food security, as population and food demands continue to increase. Sandy soils have little ability to store water, making food production difficult and crop yields an unreliable source of food and income for inhabitants living in these environments. This study looked at the water holding capacity (WHC) and hydrophobicity of Eichhornia crassipes and Prosopis juliflora for use as biochar, to potentially enhance soil moisture storage and thus agricultural productivity, with a particular focus on arid and semi-arid lands (ASALs) and northern Kenya. Both are invasive species found in Kenya which was the reason for their selection for use in this study. Biochar was produced at 350?C, 450?C, and 550?C in a Carbolite furnace and also in a Sampada gasification stove, to mimic traditional kiln char production. Biochar WHC was examined at mixtures of 2%, 5%, and 7%, corresponding to a field application rate of roughly 20 t ha-1, 50 t ha-1, and 70 t ha-1, respectively. Results demonstrated that both biochars increase soil WHC the greatest at a 7% application rate. The greatest hydrophobicity values were apparent at 350?C, with E. crassipes the more hydrophobic of the two. Mercury porosimetry analysis, which compares various characteristics of the pore space in relation to physical properties of the biochar, is consistent with the WHC data, revealing that as the total intruded volume increases the water holding capacity increases. Overall E. crassipes and P. juliflora show potential for use as biochar, but P. juliflora with its greater lignin content, is likely the better choice.