Biochar for Saline-Sodic Soil Reclamation, Phosphorus Retention, and Crop Growth Improvement

  • Author / Creator
    Dugdug, Abdelhafid AS
  • Biochar incorporation into soils influences many of the soil’s physical/chemical properties. The potential of using biochar for reclamation of saline-sodic soils is not well evaluated. Furthermore, how salinity would influence Phosphorus (P) sorption capacity of biochar is not clear. The main goals of this research were to determine the possibility of using biochar on amelioration of a saline-sodic soil and reduce the loss of P from soils, and to evaluate how growth and yield of wheat responses to a biochar amended saline-sodic soil. The biochars used in this research were produced from wheat straw, hardwood, and willow wood at pyrolysis temperature ranged between 500 and 550 °C. The used soils were sampled from the plow layer (0.1 m) of saline-sodic and non-saline soils of a local farm in Alberta, Canada. The influence of salinity and biochar type on P sorption by biochar was evaluated through a P sorption isotherm experiment. The hardwood biochar was selected as a soil amendment for followed experiments based on its high P sorption capacity. The effect of biochar application at different rates (0, 2, 5 and 8% [w/w]) on reducing salinity and leaching loss of P was evaluated using column leaching experiments. The 0 and 5% of biochar application rates were selected to evaluate the growth and yield of spring wheat in a pot experiment. The responses of the crop to biochar, manure and soil type treatments were evaluated by measuring plant nutrient contents and plant growth and productivity. Phosphorus sorption by wheat straw and hardwood biochars increased as the P concentration in solution increased, with willow wood biochar exhibiting an opposite trend for P sorption. However, the pattern for P sorption became similar as the other biochars after the willow wood biochar was de-ashed. Willow wood biochar had the highest P sorption followed by hardwood and wheat straw biochars. Salinity in the aqueous solution influenced P sorption by hardwood and willow wood but not by wheat straw biochar. The electrical conductivity (EC) in leachates from a hardwood biochar amended saline-sodic soil decreased with increasing biochar application rate; however, an opposite trend occurred during sequential events. Biochar addition significantly increased movement of water through the soil and prevented waterlogging of the saline-sodic soil; however, it reduced water retention time in the soil which likely resulted in variation of leachate’s EC of the biochar treatments. Generally, biochar addition significantly reduced EC of saturated paste extracts (ECe), exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and some of the soluble and exchangeable cations. The evaluation of the effectiveness of hardwood biochar for reducing leaching loss of P from a non-saline soil revealed that leaching loss of total P (TP), dissolved reactive P (DRP) and multivalent cations from manured soil was significantly decreased with the increasing biochar application rate. The reduction of leaching losses of multivalent cations in association with increasing soil pH due to biochar application is suggested to be responsible for the large reduction of TP and DRP. Separate application of biochar and manure increased nutrient availability. However, the nutrient availability was highest when the saline-sodic soil received a combined application of manure and biochar. Nutrient concentrations in the plant tissue were increased by biochar application, but not by manure application. The crop in the treatment with biochar + manure application to the saline-sodic soil had the highest survival rate, nutrient contents, dry matter, and yield. However, manure application without biochar significantly reduced the survival rate in the non-saline soil. The significant response of crops to biochar application, particularly in the saline-sodic soil, was attributed to the role of biochar in improving soil physical/chemical properties, and in facilitating the leaching of salts from the rooting zone. Hardwood biochar is an effective P sorbent relative to the other two biochars used. Application of hardwood biochar at 5% was the optimal rate for reducing salinity while minimizing P leaching losses from soils. Also, application of this biochar enhanced general soil quality including soil pH, water holding capacity and infiltration, and fertilization use efficiency by plant and resulted in improvement in plant productivity; therefore, this biochar should be beneficial for saline-sodic soil reclamation as well as for reducing the negative effect on water quality from excessive P input.

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  • Degree
    Doctor of Philosophy
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    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.