Introduction and motivation Nutrient input to agricultural watersheds is a very popular topic among researchers, engineers and stakeholders. Researchers in United State Geographic Services (USGS) spent a considerable amount of time and efforts to generate fertilizr estimation dataset from synthetic fertilizer and manure. Based on the dataset published by USGS, the author developed an R package, ggfertilizer, to retrieve, summarize and visualize fertilizer data in contiguous U.S.A.
In this post, the author is going to briefly introduce the basics of ggfertilizer and provide a smooth and clear workflow to generate a reproducible fertilizer usage map.
What are storm hysteresis effects? Generally, in order to investigate the dynamics of stream discharge and solute concentrations (C-Q relationship) in a watershed, researchers and environmental engineers usually set up monitoring stations in the watershed outlet. As the temporal dynamics of discharge and solute concentration is an integration of complex hydrological and biochemical processes, the relationship between solute concentration and discharge, hereafter called C-Q relationship, is mostly non-linear. If we plot the concentration against discharge within one storm event in a plot, we are supposed to see a non-linear loop, instead of a linear regression curve.