Regional Variation of Net Anthropogenic Nutrient Inputs and Cropland Nutrient Use Efficiency across the Continental United States, 1987-2012
Abstract
Agricultural production and associated environmental impacts can vary significantly because of regional differences in crops, resource use and production practices, in addition to climatic factors. Here, we review patterns of regional agricultural production, nitrogen and phosphorus use efficiency (NUE, PUE), and regional inputs of nitrogen (N) and phosphorus (P) over the period 1987-2012, based on the Farm Resource Region categories developed by the Economic Research Service (USDA-ERS). Across the US, NUE often decreased regionally on decadal time scales, mainly due to increased use in mineral N fertilizer above crop N requirements. However, PUE increased in some of the same regions due to steady or increasing rates of crop production with more slowly increasing or decreasing rates of P fertilizer usage per area of total cropland. The Heartland region dominates production of major crops and thus tends to drive national patterns. NUE and PUE are positively associated with fertilizer as a percentage of total nutrient inputs to major crops in a majority of individual regions (and in all regions considered together), however the Northern Crescent region departs from this pattern, showing negative relationships. Conversely, the potential nutrient inputs from livestock excretion (i.e. manure), expressed as a percentage of total N or P inputs, show negative relationships with corresponding NUE or PUE, except in the Northern Crescent. NUE is positively associated with crop N fixation in all regions except Northern Great Plains. In regions dominated by livestock production such as the Southern Seaboard and Eastern Uplands, feed demand can exceed local crop production, and thus manure N and P levels appear related to net inputs of food and feed to the region, though the relationships are different for N than for P. The significant regional variations in patterns of agricultural production and nutrient use efficiency vs nutrient inputs, as well as differences between regional trends of N and P, have implications for environmental quality and food security.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC23H1299S
- Keywords:
-
- 0402 Agricultural systems;
- BIOGEOSCIENCESDE: 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCESDE: 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGE