Abstract
Biochar is a material produced by the pyrolysis of agro-industrial waste, which has become one of the most promising management tools to improve soil quality. The aim was to determine the effects of incorporating biochar from different coffee wastes in sandy soil, cropped with maize, on soil chemical and microbial attributes. The experiment followed a factorial design 2 × 3 + 1 with two types of biochar, including coffee ground (CG) or coffee husk (CH) in 3 doses (4, 8, and 16 t·ha-1) and a control fertilized solely with bovine manure (3 t·ha-1). The variables analyzed were soil organic carbon, chemical attributes, microbial biomass (C, N and P), soil basal respiration and microbial gene abundance (16S rRNA, 18S rRNA and nifH gene). Most chemical attributes were strongly increased by CH application, while CG at 8 t·ha-1 increased the soil C:N ratio (3.5 times), P (2.1 times) and K+ (7.9 times) and at 4 t·ha-1 increased the C content, microbial biomass C and N (3, 2.1 and 1.6 times, respectively). The application of CG biochar at 16 t·ha-1 showed trend to increase the abundance of bacteria, fungi and diazotrophic genes (11, 10 and 2%, respectively). Contribution of both coffee biochar types, but mainly CH, was more effective than the soil that received organic manure alone. Biochar from coffee wastes is a promising tool to improve sandy soil quality.
Highlights
Excessive application of chemical fertilizers for improved plant growth and yield has become a serious problem around the world due to excessive losses to the environment leading to both eutrophication of water bodies and greenhouse gas emissions
Biochar soil mixtures properties were significantly affected by type of coffee waste and dose used (Table 2)
This study demonstrated that soil nutrients and microbial biomass increased in response to the type and doses of biochar
Summary
Excessive application of chemical fertilizers for improved plant growth and yield has become a serious problem around the world due to excessive losses to the environment leading to both eutrophication of water bodies and greenhouse gas emissions. There has been an increasing search for alternatives that reuse more waste, are accessible to producers and are environmentally friendly, such as biochar (Liu et al 2018). More than 200 million tons of biomass from agro-industry wastes are not exploited in Brazil and its usage would be advantageous (Martinez et al 2019). Biochar may serve as an economic alternative to producers by reducing dependence on chemical fertilizers, as well as reusing agro-industrial waste with potential applicability on several crops (Lima et al 2018). Biochar is a carbonaceous-rich material produced from biomass waste by pyrolysis with a wide temperature range between 100 and 700 °C (Rangabhashiyam and Balasubramanian 2019)
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