Long-term fertilization restructured spatial patterns of soil phosphorus, organic matter, and bulk density in Florida soils

Decades of fertilization have led to the accumulation of phosphorus (P) in soils, complicating its management and contributing to degradation in Florida’s agricultural systems. Our objective was to quantify the impact of years of fertilization on P stocks and distribution within the soils of this agriculturally significant region. The study employed traditional methods and geostatistics to analyze data gathered from an intensive grid sampling approach across a network of paired sites in Lake City, St. Augustine, and Grandin, FL. The soil samples were analyzed for total P using X-ray fluorescence, bulk density (Db), and soil organic matter (SOM). Our findings revealed an average 44% increase in P due to long-term fertilizer application, with variability in accumulation across different sites. Agricultural practices also led to lower organic matter levels (21–68% decrease) and higher Db (7–24% increase) in cultivated soils. Fertilized fields showed a stronger spatial dependence for Db and SOM compared to unfertilized fields, measured by the nugget: sill (NS) ratio. Additionally, soil P exhibited stronger spatial correlations in fertilized fields, varying with crop type, soil type, and fertilizer application methods. The greater within-plot variances observed for most soil properties, especially in unfertilized fields, indicate the need for scientists to better match sample sizes to the variability of soil properties being studied. This research offers resource and land managers, policymakers, and scientists with quantitative insights into legacy P, guiding site-specific monitoring efforts (e.g., sample size requirements and field-scale variability) and regional forecasting and management strategies (e.g., regional variability).