Figure. Time series of P fertilizer consumption and average application rates for all crops (a) and P fertilizer application rates (b) for 11 crop types in the contiguous US. All cropland is the total planting area, while the fertilized area is the proportion of the cropland that receives P fertilizer. In (b), light-colored bars denote the application rate over fertilized area, and dark-colored bars show the modified application rate with the assumption that the county-level P fertilizer consumption was distributed over all the croplands. Both start from zero on the y axis.
Since the mid-19th century, the production of synthetic phosphorus (P) fertilizers from phosphate rock grew rapidly, continuing until the mid-20th century. P application was reported to exceed the crop needs by up to 50 % in many regions across the contiguous US (CONUS), raising the risk of surplus P loss through runoff and erosion. It is essential to understand the spatial distribution and temporal dynamics of P fertilizer use to improve P use efficiency in agriculture and to mitigate the environmental impacts of excessive P. Our study reconstructed a long-term spatially explicit P fertilizer management (application timing and methods) dataset at a 4 km × 4 km resolution from 1850 to 2022 in the CONUS by reconciling the top-down sales/expenditure data and bottom-up crop-specific survey data, as well as fertilizer management practices (i.e., application timing and method).
Across the CONUS, the P fertilizer application rate over fertilized areas in the contiguous US increased from 0.9 g P m⁻² yr⁻¹ in 1940 to 2.1 g P m⁻² yr⁻¹ in 1980, then stabilized around 1.7 g P m⁻² yr⁻¹ to the present. Approximately 60 % of cropland in the CONUS received synthetic P fertilizer inputs. Since 1850, the hotspots of P fertilizer use have shifted from the southeastern and eastern US to the Midwest and the Great Plains, driven by changes in cropland distribution and P fertilizer application rate across different crop types. Corn, soybean, and cotton in the Midwest and the Southeast receive over 60 % of their annual P fertilizer pre-planting and through broadcasting — a management practice that might increase the risk of P loss. Promoting efficient P fertilizer management, encompassing the proper application rate, timing, and method, is essential for enhancing P use efficiency and thus contributes to economic, social, and environmental sustainability and profitability.
Citation: Cao, P., Yi, B., Bilotto, F., Gonzalez Fischer, C., Herrero, M., and Lu, C.: Crop-specific management history of phosphorus fertilizer input (CMH-P) in the croplands of the United States: reconciliation of top-down and bottom-up data sources, Earth Syst. Sci. Data, 16, 4557–4572, https://doi.org/10.5194/essd-16-4557-2024, 2024.
Spatial distribution of P fertilizer application rates in 1990, 1940, 1960, 1980, 2000, and 2020 in the contiguous US at a resolution of 4 km × 4 km.
Comments