Location: Northwest Irrigation and Soils Research
Project Number: 2054-12000-013-014-I
Project Type: Interagency Reimbursable Agreement
Start Date: Mar 20, 2024
End Date: Aug 31, 2031
Objective:
1. Quantify cumulative nitrous oxide (N2O) emissions in irrigated semiarid cropping systems in southern Idaho.
2. Determine temporal patterns of N2O fluxes as affected by dairy manure, dairy wastewater, crop residue management, tillage, nitrogen fertilization, and deficit irrigation.
3. Quantify medium-term effects (3-10 years) of crop residues and long-term effects (greater than 10 years) of dairy manure/wastewater on soil health, carbon balances, and crop yields.
Approach:
We will continue monitoring nitrous oxide (N2O) emissions at a long-term dairy manure application site in Kimberly using an automated chamber system. This study will provide emissions data for up to 10 years since the last manure application. Measurements will occur in years 2025, 2027, and 2029, in a dairy forage rotation with 3 replications per treatment. The treatments include synthetic fertilizer only and manure (plus fertilizer as needed) that was applied annually (2012-2019) in the fall at 17, 35, and 52 Mg/ha (dry wt.). Unlike manure solids, dairy wastewater is commonly applied via sprinkler irrigation to croplands, with some fields having received wastewater for decades. This results in a large buildup of soil nitrogen and no accounting of GHG losses from these fields has occurred to date. We propose to measure N2O emissions from at least 3 producer fields that have been under dairy wastewater irrigation for various periods of time (> 10 years). Following a set transect across the fields, we will measure emissions on a weekly basis, throughout the year, using a manually placed static chamber with gas analyzer. The transect will include the center pivot corners that have not received dairy wastewater, so that background emissions can be determined from the same field. To better understand GHG emissions under regional crop residue management strategies, we propose to measure emissions from a barley-barley-dry bean and wheat-barley-dry bean rotation that was initiated in 2021. The study was arranged in a split-plot design where the main plot factor was tillage (no-tillage and conventional tillage) and the sub-plot factors were rotation and residue management (removed and retained). There will be 4 replications per treatment combination and N2O emissions will be measured weekly using a manually placed static chambers in project years 3 to 7 (2024-2027). In addition, we propose to determine the effect of deficit irrigation on seasonal GHG emissions in a dry bean production system with and without nitrogen fertilization. Deficit irrigation is a strategy where water is applied at rates below those needed to meet the demand from evapotranspiration (ET). We will measure N2O emissions from plot-scale field experiments during 2025-2027, where irrigation is managed at 100, 75, 50, and 25% of estimated crop ET using sprinkler irrigation. Emissions will be measured weekly during the growing season from 4 replicates per treatment.
