Timing Is Everything: A Test Case to Reduce Nitrous Oxide Emissions from Sorghum by Shifting Biogeochemical Control Points with Alternative Irrigation and Nitrogen Application
Abstract
The heterogeneity of nitrous oxide (N2O) emissions is due to biogeochemical control points that vary in both space and time. Irrigated, fertilized systems are excellent cases to apply the control point concept in N2O abatement since N2O flux in these systems is predicted by user-defined water and nitrogen inputs. Water use for agriculture can be reduced with proper timing and appropriate cropping, and lower water inputs can reduce the duration of denitrifying conditions. Matching N addition to plant demand reduces excess soil N for microbial conversion to N2O. Sorghum (Sorghum bicolor) is an arid-adapted, N-efficient crop and a model to test alterations in water and N with plants in the field. We asked if irrigation quantity (typical vs. "conservation irrigation" = 40% reduction) and N fertilizer application (all at planting, or "split" = 50% at planting, 50% 30 days post-planting) affect sorghum production, field-measured N2O emissions, soil respiration and soil C inputs from roots. Harvested biomass was highest from sorghum under full irrigation receiving split N fertilizer application. Soils under conservation irrigation and split N produced the lowest N2O emissions, and on some dates we observed net N2O consumption. Fully irrigated sorghum soils receiving all N at planting produced the most N2O early in the growing season but produced negligible emissions in the last month of the growing season. Conservation irrigation resulted in a 2-month lag between when N and water were applied, and the highest N2O emissions were measured. Root C inputs inferred from 13C, soil NO3- and soil NH4+ data will be presented with trace gas results. Reducing N2O emissions by managing biogeochemical control points is promising, especially given our observations of limited yield loss due to fewer inputs. Since these data were collected over the course of a growing season, they also allow for identifying spatial and temporal changes in soil physio-chemical control points that can be used to create a progressive in-season management framework to reduce N2O emissions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B21K2491D
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0469 Nitrogen cycling;
- BIOGEOSCIENCESDE: 0490 Trace gases;
- BIOGEOSCIENCES