Relationships Between Soil Phosphorus Fractions and Greenhouse Gas Emissions in Degraded Red and Black Soils Amended With Magnesium Treated Biochar

ABSTRACT This study investigated the effects of pristine biochar (BC) and magnesium‐treated biochar (Mg‐BC), applied at 0%, 1%, and 2.5% (w/w), on the relationship between P fractions and GHG emissions in two degraded soils. Soil physiochemical properties were improved in response to BC and Mg‐BC treatments. Enzyme activities increased with BC and Mg‐BC treatments, where Mg‐BC showed better effects. Similarly, increasing biochar did increase the labile‐P pool while decreasing the moderately labile P (MP) and residual P pools in both soils, and the effects observed under Mg‐BC treatment were more pronounced than those in the BC treatment. Compared to CK, BC and Mg‐BC increased CO 2 emissions by 76%–138% and 44%–127% in red soil, and by 14%–33% and 8%–23% in black soil, respectively. In contrast, N 2 O emissions decreased by 11%–29% and 17%–44% in red soil, and by 12%–23% and 16%–31% in black soil, respectively. Multivariate redundancy analysis revealed that biochar‐induced improvement in labile P, enzyme activities, and soil properties were positively correlated with CO 2 , whereas negatively associated with N 2 O emission. The structural equation modeling (SEM) revealed that biochar type and dose had a minor influence on CO 2 emissions, but on the other hand, considerably decreased N 2 O emissions ( R 2 = 0.82–0.89) by increasing soil nutrients (SOC, NH 4 , AP, and LP) in black soil, and pH, enzymes, and soil nutrients in red soil. Our results demonstrated that biochar application reduces N 2 O emissions by improving soil pH, nutrients, and enzyme activities in degraded soils, with a greater impact under Mg‐BC treatment.