Landscape Nutrient Budgets Dataset (TREND)
What is TREND?
The Trajectories Nutrient Datasets (TREND) are multi-year nutrient input (Fertilizer, Livestock Manure, Biological N fixation, Atmospheric Deposition, Domestic Waste), output (Crop Removal) and surplus (difference between inputs and outputs) datasets.
These data products are being developed across North America, based on information available in various disparate datasets such as the census of agriculture, population census, as well as coefficients in the literature. This dataset is designed to facilitate research into the spatial and temporal changes in anthropogenic nutrient dynamics.
What Do You Get from the Portal?
Currently, our portal displays data for Nitrogen Budgets in the US (1930 - 2017), and Phosphorus Budgets across Canada (1961 - 2016), but the next version of the website will have both Nitrogen and Phosphorus budgets across North America.
The data products are developed at the county-scale - an administrative unit at which census data is easily available. We also plan to provide information at the 250-m grid scale, and aggregated to the watershed scale in later versions of the product.
What are the Methods to Develop the County-Scale Data Product?
Information on synthetic fertilizer use is based on fertilizer sales data that is available at the county scale in the US and the provincial scale in Canada. The county-scale US fertilizer use dataset was created by stitching together three different datasets: [1930-1944: Cao et al. (2018), 1945–1985: Alexander and Smith (1990), 1987–2012: Brakebill and Gronberg (2017)]. For Canada the county-scale fertilizer use dataset was created by using provincial fertilizer sales data that was distributed to the counties within the province, based on the harvested crop area in each province.
Livestock manure was estimated using county-scale livestock inventory data available through the US and Canadian agricultural census, and animal specific N and P coefficients, that took into consideration changing livestock weights over multiple decades. Manure was estimated for the major livestock categories and aggregated to estimate total manure.
Domestic waste includes nitrogen and phosphorus in human excreta, as well as P from laundry and dish detergents. This is estimated as a function of the population census, N and P content in human excreta, and literature estimate of P content in detergent over time. Of course, much of this waste is treated in wastewater treatment plants and only a small fraction of it is released back to the environment. However, given the efficiency of wastewater treatment varies depending on location and has changed a lot over the past 50 years, our estimates are prior to treatment.
Biological N fixation (BNF) is the process by which microorganisms living in the root nodules of leguminous plants convert atmospheric nitrogen gas (N₂) into plant-available forms like ammonia (NH₃). For the USA, BNF was estimated using crop area and yield based methods for all major nitrogen fixing crop types (Soybean, Peanuts, Lentils, Dry beans, Hay (alfalfa and non-alfalfa), Cropland pasture.
Throughout the growing season, crops uptake nitrogen and phosphorus from the soil and store it in their biomass. During harvest, the nutrients stored in the crops are removed from the system. Crop nutrient removal is estimated using county-scale harvested area and crop yield data from Census (Canadian and US census), as well as crop-specific nutrient content estimates from literature.
Nutrient surplus is defined as the difference between all of the nutrient input and outputs. Each component was calculated at a county-scale in units of kg N ha-1 yr-1 and kg-P ha-1 yr-1.
Nutrient Surplus = Inorganic fertilizer + Livestock manure + Atmospheric Deposition + Biological Fixation + Domestic Waste - Crop Removal - Pasture Removal
Further details on these methodologies are provided in Byrnes et al 2020 and Malik (2021).