Grazing Management

Grazing Management Effect on Micro- and Macro- Scale Fate of C and N in Rangelands
 

Rationale

Grazing strategies are developed to target the spatial and temporal utilization of rangelands for a variety of ecosystem services. However, grazing induces pulses of energy and nutrients by defoliation, trampling of vegetation and litter, and deposition of dung and urine. The outcomes of these pulses on nutrient availability for rangeland production and other ecosystem services like soil carbon sequestration and greenhouse gas (GHG) emissions are less understood. As such, advancing the knowledge of how the spatial and temporal pattern of nutrient return in rangeland ecosystems can influence nutrient cycling at the landscape scale will benefit not only the livestock industry but also society through contribution to the long-term mitigation of GHGs and groundwater pollution.

Goals

The goal of the proposed project is to contribute to the understanding of how contrasting nutrient return patterns influence the nature and fate of the nutrient pulse at both the micro (i.e., at or near a urine/dung patch) and macro (pasture) scales in rangelands. The project objectives include a) quantifying the size of nutrient pulses (litter, trampled biomass, urine, and dung across years and grazing strategies; b) determining the patterns of nutrient return in pastures in relation to grazing strategies and the influence on soil N mineralization, C sequestration, and phosphorous availability; c) assessing the decomposition rate and nutrient fate from dung through the transport and transformations of N and C into soil and atmosphere with and without dung beetle colonization and across water availability scenarios, d) developing relationships of stocking density, spatial/temporal nutrient return, dung beetle abundance, and micro-scale nutrient fate to improve pasture level estimations of existing process-based biogeochemical models on nutrient cycling in rangelands.

This project is supported by Agriculture and Food Research Initiative
Competitive Grant Program no. 2013-67019-21394 from the USDA
National Institute of Food and Agriculture.

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