Xiaoyan Yang,Yuhua Kong,Erhui Guo,Xiangwei Chen,·Limei Li
Phosphorus (P) is used to enhance agricultural productivity. Organic acids increase the release of inorganic phosphorus (P i ) into soil solutions and thereby improve phosphorus utilization in soils; however, the effects of both organic acids and the soil organic matter contents on P i release are poorly understood. To assess the importance of these factors in determining phosphorus availability, the release of soil P i fractions (i.e. aluminium-bound phosphorus (Al-P), iron-bound phosphorus (Fe-P), occluded phosphorus (O-P) and calcium-bound phosphorus (Ca-P)) was evaluated on addition of organic acids (citric, oxalic and malic acids) to soils from Mollisols region that had different organic matter contents and received phosphorus fertilizer. Biochemically produced humic acid was used to modify soil organic matter contents. Among P i fractions, the Fe-P fraction had the highest concentration in all the soils with different organic matter contents. In the presence of organic acids, the release of P i fractions decreased as the soil organic matter increased. Among the fractions, Al-P had the highest release, followed by Fe-P. Comparison among various organic acids revealed that oxalic acid was the most effective for P i release. Path analysis showed that Al-P release had larger direct-path and indirect-path coefficients, which implied that Al-P release had the largest contribution to total P i (TP i ) release. We concluded that the effectiveness of organic acids in improving soil phosphorus availability was most pronounced in soils with low organic matter contents, but further field-scale research is needed to confirm this. Al-P was the most effective source of inorganic phosphorus in Mollisols.
Extensive import of mixed phthalate esters (PAEs) threatens
Mollisol
ecosystems. Nevertheless, mechanisms through which plant roots orchestrate
the cometabolic degradation of PAEs and couple this with soil humification
remain unclear. This study integrated plant physiology, untargeted
metabolomics, and genome-resolved metagenomics to decipher response
trajectories of the Pak Choi–Mollisol root–microbe system
across a mixed PAEs gradient. The findings indicated that under mild
stress (5 mg/kg), plants sustained a “growth-driven”
homeostasis alongside a stable rhizospheric microbiome. In contrast,
acute toxicity (20 mg/kg) initiated pronounced metabolic shifts, characterized
by a “survival-overgrowth” strategy. Specifically, carbon
fluxes shifted from primary assimilation to secondary defense hubs.
This physiological tradeoff reversed the root exudate profile, shifting
from basic carbohydrates to massive efflux of specific organic acids
and phenolics. Critically, these allelochemicals functioned as exogenous
elicitors, selectively recruiting specific metagenome-assembled genomes
(MAGs). Genomic evidence confirmed that single keystone MAGs (Pseudomonas
and Burkholderia) coharbored pcaG/H and extracellular laccase genes,
establishing a self-contained cometabolic module for concurrent PAEs
degradation and carbon stabilization. Consequently, based on correlative
multiomics evidence, extensive carbon efflux was associated with a
putative coupling between PAEs detoxification and stable humic carbon
accumulation, as indicated by a 48.7% increase in the humification
index (HIX). Ultimately, this multiomics framework elucidates the
plant-driven enhancement of carbon sinks within contaminated soils.
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