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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

A Multi-Factor Analysis of Sustainable Agricultural Residue Removal Potential

Agricultural residues have significant potential as a near term source of cellulosic biomass for bioenergy production, but sustainable removal of agricultural residues requires consideration of the critical roles that residues play in the agronomic system. Previous work has developed an integrated model to evaluate sustainable agricultural residue removal potential considering soil erosion, soil organic carbon, greenhouse gas emission, and long-term yield impacts of residue removal practices. The integrated model couples the environmental process models WEPS, RUSLE2, SCI, and DAYCENT. This study uses the integrated model to investigate the impact of interval removal practices in Boone County, Iowa, US. Residue removal of 4.5 Mg/ha was performed annually, bi-annually, and tri-annually and were compared to no residue removal. The study is performed at the soil type scale using a national soil survey database assuming a continuous corn rotation with reduced tillage. Results are aggregated across soil types to provide county level estimates of soil organic carbon changes and individual soil type soil organic matter content if interval residue removal were implemented. Results show interval residue removal is possible while improving soil organic matter. Implementation of interval removal practices provide greater increases in soil organic matter while still providing substantial residue for bioenergy production.

09 BIOMASS FUELS↗
DOE OSTI2015

Evaluations of CMIP5 simulations over cropland

Cropland is one of major sources of carbon lost to the atmosphere and directly contributes to the emissions of greenhouse gases. There is, however, large potential for cropland to reduce its carbon flux to the atmosphere and sequester soil carbon through conservative agriculture management including no-tillage, perennial and/or deep root crops, irrigation, and organic fertilization etc. But these estimations on carbon emissions and sequestrations over cropland under future climate changes and variability remain largest uncertain among all other terrestrial biomes. Global climate and earth system models are an effective tool to study the cropland responses and feedbacks to present and future climate, yet most models in the latest couple model intercomparsion project phase 5 (CMIP5), generally treat cropland similarly as grassland with tuned parameters and do not account for realistic crop phenology, physiology, and management. In this study, we will evaluate the limitations and deficiencies of the CMIP5 models without process-based crop growth models over cropland by comparing their simulations against FLUXNET observations at eight cropland sites. The results show that: (1) the observed and simulated annual cycles generally are not consistent in either phase or amplitude; (2) the MPI and IPSL model families have better skills in the annual cycles of gross primary product (GPP), net ecosystem production (NEP), and terrestrial ecosystem respiration (TER) than other models at the corn/soybean and cereal sites respectively; (3) none of the CMIP5 models successfully simulate the observed two-peak pattern in the annual cycles of sensible heat fluxes at the corn/soybean sites; (4) the simulated GPPs and NEPs of the CESM1, BCC model families and NorESM1-M are much smaller than the observations for entire year; (5) model members from same model family normally simulate similar annual cycles both in phase and magnitude, but the model members from the CESM1 model family with different atmospheric models have different annual cycles; (6) the biases both in phases and magnitudes of annual cycles for the biogeochemical variables (GPP, NEP and TER) are generally larger than those biogeophysical variables (sensible and latent heat fluxes). Because of the above limitations and deficiencies of CMIP5 simulations over cropland, it is essential to incorporate process-based crop growth models into ESMs to improve the model physics and performance over cropland.

AGRICULTURE↗