Location: Delta Water Management Research
Project Number: 6024-13000-004-081-I
Project Type: Interagency Reimbursable Agreement
Start Date: Apr 3, 2024
End Date: Aug 31, 2031
Objective:
Contribute to the Inflation Reduction Act Measurement Monitoring Reporting and Verification Action Area 2-Cropland through measurement of cropland methane and nitrous oxide emissions.
Approach:
Field-scale: This study includes seven EC systems, all located on commercial-sized fields in Arkansas. Five of the systems are in a rice-soybean rotation. Two are in a rice-ricesoybean rotation. First study in the rice-soybean rotation will use three fields; a MIRI control, furrow irrigated, and furrow with a recirculating pump. The second study in the rice-soybean rotation will have a conventional cascade flood or MIRI field compared to a MIRI-AWD. Given the annual rotation, the study sites will have rice and soybean in opposite years. The third study will be during the two rice years of a rice-rice-soybean rotation. All fields in each of the three studies will be planted in the same variety for each study. It is unlikely that all fields will be planted in the same variety. Water applied will be measured with an in-line flowmeter. Yield will be obtained using a combine harvester and/or hand sampling. Grain samples will be analyzed for grain quality.
Plot-scale: One research project will be conducted on rice-soybean rotation field trials established in 2021 and located in Harrisburg, AR. On a 16-ha field, two cropping systems replicated three times will be compared namely: Conventional flooded hybrid rice (low CH4 emitting parental genotypes) with urea fertilizer (CF) and smart rice practice consisting of furrow irrigation, low emitting hybrid rice (low CH4 emitting parental genotypes) fertilized with S-enriched urea (RR). N rates and pest management will be the same to both
systems following the state recommendation except irrigation and type of N fertilizer. The vented flux chamber method coupled with gas chromatography will be used to quantify emissions of CO2, N2O, and CH4 and gas samples will be collected at weekly interval throughout rice crop cycle and more frequently around irrigation events, following N fertilizer applications, and dry periods. Complete description of the chamber method and experimental design are discussed in Adviento-Borbe et al. (2013) and Karki et al. (2021). Within each rice system, grain yield will be measured in three locations (top, middle, and
bottom of field) using a 1 m2 harvest area and irrigation water use will be measured using flowmeters. To compare GHG mitigating potentials and scaling factors of two rice systems, global warming potential (GWP) of N2O and CH4 will be calculated in CO2 equivalents (kg CO2 eq ha-1) for 100-year time horizon using the radiative forcing potentials relative to CO¬2 of 273 and 28 for N2O and CH4, respectively (IPCC, 2021). Yield-scaled GWP (GWPY) will be expressed as GWP per unit mass of rice grain (kg CO2 eq Mg grain-1). GHG emissions, grain
yields, and water use will be compared in fields under CF and RR systems using advanced statistical data analyses.
