Enhancing potassium availability and dynamics in some Egyptian soils through biochar application.

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Potassium (K) deficiency is a critical limiting factor for crop productivity in Egyptian soils, especially those with coarse textures.
• Agricultural residues are abundant and can be converted into biochar, a soil amendment with potential to improve soil fertility and nutrient availability.

Purpose of the Study:

• To evaluate the impact of four different agricultural residue biochars on potassium (K) availability, K dynamics, soil physicochemical properties, and wheat growth in four Egyptian soil types.
• To determine the optimal biochar type and soil combination for enhancing K availability and crop productivity under arid conditions.

Main Methods:

• Pot experiments were conducted using four Egyptian soil types (sandy, loamy, clayey, calcareous) amended with 3% biochar (w/w) derived from sugarcane bagasse residues (SBR), olive stone pomace (OSP), orange fruit pomace (OFP), and maize stover residues (MSR).
• Soil physicochemical properties, K thermodynamic parameters (K_L, activity ratio, PBC^K, ΔG, K_G), and wheat biomass and nutrient uptake (N, P, K) were analyzed.
• Biochar properties, including surface area and nutrient content, were characterized.

Main Results:

• Biochar application significantly increased soil water-holding capacity (WHC) by 17-35.5% and cation exchange capacity (CEC) by 18-163%.
• K availability and thermodynamic parameters were substantially improved, with notable increases in labile-K (K_L) and potential buffering capacity (PBC^K) across different soil types and biochars.
• Wheat biomass (fresh and dry) increased by 25.9-84.6% and 16.9-63.8%, respectively, with enhanced N, P, and K uptake in wheat tissues (27.3-142.2%). Maize stover residues biochar (MSR) and olive stone pomace biochar (OSP) generally performed best.

Conclusions:

• Biochar application is a viable strategy to improve K availability, enhance soil physicochemical properties, and boost wheat productivity in deficient Egyptian soils.
• Matching specific biochar types (e.g., MSR, OSP) with soil characteristics is crucial for optimizing K availability and nutrient use efficiency.
• These findings support the use of biochar for sustainable soil fertility management, reducing reliance on mineral fertilizers in arid and semi-arid regions.