Influences of phosphate addition on fungal weathering of carbonate in the red soil from karst region.

Affiliation

Tian D(1), Su M(2), Zou X(2), Zhang L(3), Tang L(2), Geng Y(2), Qiu J(2), Wang S(4), Gao H(5), Li Z(6).
Author information:
(1)Anhui Province Key Lab of Farmland Ecological Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China; Research Centre of Phosphorus Efficient Utilization and Water Environment Protection along the Yangtze River Economic Belt, Anhui Agricultural University, Hefei 230036, China; College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
(2)College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
(3)Anhui Province Key Lab of Farmland Ecological Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China; Research Centre of Phosphorus Efficient Utilization and Water Environment Protection along the Yangtze River Economic Belt, Anhui Agricultural University, Hefei 230036, China.
(4)College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China; Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Nanjing Agricultural University, Nanjing 210095, China.
(5)Anhui Province Key Lab of Farmland Ecological Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China; Research Centre of Phosphorus Efficient Utilization and Water Environment Protection along the Yangtze River Economic Belt, Anhui Agricultural University, Hefei 230036, China. Electronic address: [Email]
(6)College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China; Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: [Email]

Abstract

Carbonate in soil from karst region is a substantial carbon sink on Earth. Many karst regions are covered by P-deficient soil. This study evaluated the influences of phosphate addition on fungal weathering (by typical phosphate-solubilizing fungus Aspergillus niger) of carbonate in the soil with red color from karst region. Two weathering pathways were recognized, i.e., biochemical and biomechanical deterioration. The biochemical pathway was performed by dissolving carbonate via secreting organic acids. Meanwhile, the dominant organic acid, i.e., oxalic acid, induced the formation of calcium oxalate, which prevented the loss of Ca2+ cations. It was estimated that the ideal carbonate solubilization driven by geological fluorapatite and fungal weathering is up to 3.3% per year, based on the equation of 12 × (RBase + RPSF) × m × (Areal/APSF). Moreover, fungal weathering of carbonate is very sensitive to the solubility of phosphates. Phosphates supply essential P source for the fungal growth and subsequently raise water-soluble P content in the soil. The addition of bioapatite (a variety of natural apatite with relatively high solubility) elevated the value to 4.6% (a ~ 40% enhancement compared with FAp). This research hence elucidated the tight correlation between carbonate weathering and P supply. Inorganic C release driven by P availability and microbial weathering should be addressed in karst region.