Introduction: Phosphorus is one of the essential macronutrients required for plant growth, playing a critical role in processes such as photosynthesis, energy transfer, and cell division. However, inorganic phosphorus in soil is often present in insoluble and plant-unavailable forms, particularly in soils with high pH or elevated levels of phosphorus-fixing elements. Consequently, phosphorus use efficiency in agricultural systems tends to be low, leading to excessive application of chemical fertilizers, which in turn poses significant environmental concerns.
In recent years, the use of biological soil amendments such as biochar and carbon black has gained attention as a sustainable approach to improving the stability and availability of nutrients in soil. Biochar, produced through the pyrolysis of biomass under low oxygen conditions, is characterized by its porous structure, high cation exchange capacity, and considerable sorption ability, all of which contribute to nutrient retention and controlled release. Similarly, carbon black—a by-product of incomplete combustion of carbonaceous materials—can influence soil phosphorus dynamics due to its unique chemical properties.
Moreover, soil moisture acts as a crucial factor in nutrient dynamics. Variations in moisture levels can affect the physical, chemical, and biological processes in soil, thereby altering the distribution and chemical forms of inorganic phosphorus. Given the increasing occurrence of droughts and irregular irrigation due to climate change, it is essential to investigate the combined effects of moisture regimes and soil amendments on phosphorus behavior.
Therefore, this study aims to evaluate the simultaneous effects of carbon black and biochar on the chemical distribution of inorganic phosphorus in soil under different moisture conditions. The findings of this research are expected to provide valuable insights for optimizing phosphorus management and enhancing the sustainability of agricultural systems.In recent years, the use of biological soil amendments such as biochar and carbon black has gained attention as a sustainable approach to improving the stability and availability of nutrients in soil. Biochar, produced through the pyrolysis of biomass under low oxygen conditions, is characterized by its porous structure, high cation exchange capacity, and considerable sorption ability, all of which contribute to nutrient retention and controlled release. Similarly, carbon black—a by-product of incomplete combustion of carbonaceous materials—can influence soil phosphorus dynamics due to its unique chemical properties.
Moreover, soil moisture acts as a crucial factor in nutrient dynamics. Variations in moisture levels can affect the physical, chemical, and biological processes in soil, thereby altering the distribution and chemical forms of inorganic phosphorus. Given the increasing occurrence of droughts and irregular irrigation due to climate change, it is essential to investigate the combined effects of moisture regimes and soil amendments on phosphorus behavior.
Therefore, this study aims to evaluate the simultaneous effects of carbon black and biochar on the chemical distribution of inorganic phosphorus in soil under different moisture conditions. The findings of this research are expected to provide valuable insights for optimizing phosphorus management and enhancing the sustainability of agricultural systems.


Materials and Methods: In this study, a factorial experiment with four replications was conducted in 2023 using a completely randomized design to investigate the chemical distribution of inorganic phosphorus in soil affected by carbon black and biochar under different moisture conditions. The experimental factors included: 5% carbon black, 5% biochar, a combination of 2.5% carbon black and 2.5% biochar, and a control; two moisture levels (field capacity and saturation); and two incubation periods (30 and 60 days). The chemical forms of phosphorus were determined using the sequential fractionation method proposed by Jiang and Gu (1989).

Results and Discussion: The results showed that the application of biochar and carbon black under different moisture conditions led to significant changes in the availability of various chemical forms of phosphorus. Specifically, the use of carbon black as a soil amendment resulted in increases of 76.5% in octacalcium phosphate, 99% in occluded phosphate, and 46% in total phosphorus. Application of biochar led to an 88% increase in dicalcium phosphate, an 81% increase in available phosphorus, and a 10.9% increase in soil pH. The combined application of both amendments caused a 37% increase in aluminum phosphate and a 53% increase in apatite. However, this treatment also led to a 1% reduction in soil iron phosphate.

Conclusion: Overall, the use of biochar and carbon black presents a promising solution for enhancing phosphorus availability in soil and improving plant health.