Production, characterisation and quality assessment of biochar

Abstract

Crop residues in fields can cause considerable crop management problems if they accumulate. Composting is a viable option for crop residue management. However composting of plant twigs and woody plant residues is difficult as they take longer time for decomposition. Conversion of crop residue biomass into biochar and using it as a soil amendment is a nascent approach and then suggested as an alternative to composting and crop residue burning. Biochar is produced by controlled burning of biomass with little or no oxygen, known as pyrolysis. Research information on biochar in agricultural use in India is scanty. Very few reports are available on production, characterization and use of biochar as soil amendment. The present study was proposed against this backdrop to produce biochar from crop residues and to study the effect of biochar on the performance of crops. The investigation entitled ‘Production characterisation and quality assessment of biochar’ was conducted to assess the effect of production methods and materials used on the character of biochar and to study its suitability as soil amendment for amaranth. Woody wild growth, coconut petiole and herbal waste residues left after composting were the three materials used for biochar production. Biochar was produced using heap and drum methods. Biochar was characterised by percentage mass recovery and by physical and chemical distinctiveness. Methods of production and materials used had significant influence on the characteristics of biochar. Drum method gave higher biochar recovery compared to heap method. Porosity, water holding capacity and carbon content were higher in biochar produced from woody wild growth. All biochars showed alkaline pH with the highest pH in coconut petiole biochar. An increase in NPK content was noticed in biochar compared to the materials used. A pot culture experiment was conducted to study the soil amendment effect of biochar on crop performance. The treatments consisted of six biochars produced from three materials using two methods of production, along with three levels of fertilizers ie, 100 per cent recommended NPK, 75 per cent NPK and absolute control( without any fertilizers). Biochar materials were mixed at a 1:1 ratio on volume basis with soil and assessed their effect on the growth and yield of amaranth. They were also compared with treatment of ordinary potting mixture receiving FYM and 100 per cent NPK. A residual crop was raised in the same pot after the experiment and the yield of the crop was noted. For the first crop, the highest yield was obtained in the ordinary potting mixture which received 100 per cent NPK when compared with the biochar treatments. For the second crop, the highest yield was observed in the woody wild growth biochar receiving 100 per cent NPK. This indicated the nutrient retention property of biochar and its long term benefit. Biochar from woody wild growth recorded the highest carbon content, porosity and water holding capacity and produced better yields, among the different biochar materials. Biochar along with 100 per cent NPK recorded the highest yield compared to biochar treatments without fertilizers. Because of the high water holding capacity of biochar, irrigation could be given to the crops once in three days for the biochar applied treatments instead of twice daily as was done in ordinary potting mixture. Increase in pH of the soil was noticed after the experiment indicating its efficiency as a soil amendment in acidic soil. Beneficial properties of biochar like high carbon content, alkaline pH and high water and nutrient holding capacity revealed the suitability of biochar as a soil amendment.