Management of the Parthenium hysterophorus through biochar formation and its application to rice-wheat cultivation in Pakistan

Abstract This study presents a suitable solution for management of the noxious weed Parthenium hysterophorus by using its biomass for biochar formation. The impact of application of Parthenium biochar on soil and the rice wheat cultivation system was observed over a period of one year in field experiments. The treatments applied to the field were biochar (BC) only, recommended commercial fertilizer (CF) only, BC along with 50% of CF (BC + CF), and Control, without any treatment. The growth parameters of the plants were measured in the rice and wheat crops. Commercial fertilizer showed the best agronomic performance in rice and wheat, while similar results were obtained in the BC + CF application. However, the results were not so significant with BC only. It was observed that biochar application can cut down the cost of fertilizer to half although the yield obtained is just as good as with full application of CF. Biochar acted as a conditioner in field soil and improved the C/N ratio. Structure of soil as well as the water and nutrient holding capacity of soil was improved owing to macroporous nature of biochar revealed by SEM. However, applied biochar was not found very stable as the C content applied to the soil in the form of biochar decreased in the soil over a one-year period from 47.39% to 36.54%. This could be due to some original plant residues left in the biochar on account of incomplete pyrolysis in the partial absence of oxygen indicating a high H/C ratio of 0.64. This research suggests application of Parthenium biochar at lower rates annually not only providing fresh C content and charged surfaces to the soil but also a substrate and C source to the microbes inhabiting the macropores and mesopores present in biochar as indicated by SEM. The char formed from Parthenium biomass was environmentally sustainable by utilizing renewable supply of biogas in a fabricated hybrid cooking stove.