Reactive Transport Modeling of Microbially Driven Nutrient Transformation for Sustainable Soil–Environment Systems

The sustainable soil–environment systems need a transition to process-based nutrient management approaches that are more efficient in nutrient use and reduce ecological degradation than current chemically intensive nutrient management systems. Traditional fertilizer methods are inefficient at nutrient utilization in soils due to uncontrolled transport, leaching and losses during reactions, leading to imbalances and environmental pollution. To overcome this difficulty, this study considers soil as a coupled reactive transport system where microbial processes control nutrient transformation, mobility and availability. Experimentally determined key parameters were biomass carbon of microbes, coefficient of nutrient effective diffusion, reaction kinetic constants and soil aggregation indices, which were used in a reaction–diffusion model to explain microbially mediated nutrient dynamics. Regression analysis, variance analysis and correlation modeling were used to assess the relationship between microbial activity and system-level performance measures including nutrient-use efficiency and crop yield. The findings indicate a statistically significant enhancement of nutrient utilization under microbially enhanced conditions, as reflected in improved system-level metrics. Nutrient retention ratio increased from 0.54 under conventional management to 0.78 with the proposed framework, while mean crop yield increased from 3,450 kg/ha to 4,210 kg/ha. Nutrient loss decreased from 38.5 to 21.2 and the soil aggregation index improved from 0.46 to 0.60 indicating better structural stability and reduced susceptibility to leaching. All reported improvements were statistically significant at P < 0.05. Regression analysis further showed that microbial activity indices were strongly and positively correlated with yield performance, with coefficients of determination (R2) exceeding 0.85. The study concludes that the concept of soil modeling as a microbially regulated reactive transport medium is a sound scientific foundation for the optimization of nutrient delivery in environmental systems.