Abstract
Biochar is gaining significant attention due to its potential for carbon (C) sequestration, improvement of soil health, fertility enhancement, and crop productivity and quality. In this review, we discuss the most common available techniques for biochar production, the main physiochemical properties of biochar, and its effects on soil health, including physical, chemical, and biological parameters of soil quality and fertility, nutrient leaching, salt stress, and crop productivity and quality. In addition, the impacts of biochar addition on salt-affected and heavy metal contaminated soils were also reviewed. An ample body of literature supports the idea that soil amended with biochar has a high potential to increase crop productivity due to the concomitant improvement in soil structure, high nutrient use efficiency (NUE), aeration, porosity, and water-holding capacity (WHC), among other soil amendments. However, the increases in crop productivity in biochar-amended soils are most frequently reported in the coarse-textured and sandy soils compared with the fine-textured and fertile soils. Biochar has a significant effect on soil microbial community composition and abundance. The negative impacts that salt-affected and heavy metal polluted soils have on plant growth and yield and on components of soil quality such as soil aggregation and stability can be ameliorated by the application of biochar. Moreover, most of the positive impacts of biochar application have been observed when biochar was applied with other organic and inorganic amendments and fertilizers. Biochar addition to the soil can decrease the nitrogen (N) leaching and volatilization as well as increase NUE. However, some potential negative effects of biochar on microbial biomass and activity have been reported. There is also evidence that biochar addition can sorb and retain pesticides for long periods of time, which may result in a high weed infestation and control cost.
Highlights
Biochar, known as charred biomass or black carbon, is an organic material derived from different forms of organic biomass, such as wood, crop residues, animal manure, chicken manure, and municipal sludge, through pyrolysis under a broad temperature range (300–1000 ◦ C) and partial or anaerobic conditions [1,2]
The performance of biochar as a soil amendment depends on the specific physiochemical properties such as surface area, bulk density, pore structure and distribution, particle size, water-holding capacity (WHC), cation exchange capacity (CEC), pH, presence and richness of different functional groups, which can vary widely among biochars produced from different feedstock sources [6,10,17]
Biochar application can have a profound impact on soil pH, bulk density, aeration, porosity, CEC, WHC, nutrient balances, and other parameters of soil quality due to its intrinsic structure and physicochemical properties
Summary
Known as charred biomass or black carbon, is an organic material derived from different forms of organic biomass, such as wood, crop residues, animal manure, chicken manure, and municipal sludge, through pyrolysis under a broad temperature range (300–1000 ◦ C) and partial or anaerobic conditions [1,2]. When biochar is incorporated in the soil, it changes the physiochemical soil properties such as C, pH, cation exchange capacity (CEC), porosity, surface area, bulk density, water-holding capacity (WHC), nutrient use efficiency (NUE), available P and total N, among the other soil amendments [2,6,12]. It reduces the soil hardening and increases the porosity, which positively impacts the soil microbial community and nutrient cycling [11,13]. This review covers the physiochemical properties of biochar, feedstock source, production technology of biochar, effect of biochar on physiochemical properties of soil, nutrient cycling, soil microbial activity, NUE, water use eficiency (WUE), plant growth, production and quality of crops, and potential risks as well as limitations of biochar application on agricultural lands
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