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DOE OSTI2022

Using a Multi‐Institutional Ensemble of Watershed Models to Assess Agricultural Conservation Effectiveness in a Future Climate

This study investigates the combined impacts of climate change and agricultural conservation on the magnitude and uncertainty of nutrient loadings in the Maumee River Watershed, the second-largest watershed of the Laurentian Great Lakes. Two scenarios — baseline agricultural management and increased agricultural conservation — were assessed using an ensemble of five Soil and Water Assessment Tools driven by six climate models. The increased conservation scenario included raising conservation adoption rates from a baseline of existing conservation practices to feasible rates in the near future based on farmer surveys. This increased adoption of winter cover crops on 6%–10% to 60% of cultivated cropland; subsurface placement of phosphorus fertilizers on 35%–60% to 68% of cultivated cropland; and buffer strips intercepting runoff from 29%–34% to 50% of cultivated cropland. Increased conservation resulted in statistically significant (p ≤ 0.05) reductions in annual loads of total phosphorus (41%), dissolved reactive phosphorus (18%), and total nitrogen (14%) under the highest emission climate scenario (RCP 8.5). While nutrient loads decreased with increased conservation relative to baseline management for all watershed models, different conclusions on the true effectiveness of conservation under climate change may be drawn if only one watershed model was used.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2016

Nuclear Data Sheets for A = 41

Available information pertaining to the nuclear structure of all nuclei with mass numbers A=41 ranging from Al (Z=13) to Ti (Z=22) are presented. The experimental reaction and decay data are evaluated and any inconsistencies or discrepancies are noted. The adopted values for various level properties (such as the spin, parity and and halflife) and gamma properties (energy, intensity and multipole character) are given. Since the prior evaluation several new measurements have expanded our knowledge of A=41 nuclides. The half-life of the ground state of {sup 41}Si has been determined and a single excited state identified. Excited levels in {sup 41}P have been observed for the first time. In {sup 41}Cl, seven new excited states have been identified in deep inelastic and heavy ion transfer reactions. Half-lifes for four states in {sup 41}Ar have been updated and additional levels with gammas have been included from a new measurement using the multiple ion transfer reaction. In {sup 41}Ca via charge-exchange reaction measurements, several new excited states were observed. A number of new resonances in {sup 41}K have been identified via the (p,γ) reaction. There remains a significant discrepancy in the half-life of the first excited state (980 keV) in {sup 41}K, with measurements differing by more than an order of magnitude. Transfer reactions suggest that this M1 transition should be l-forbidden, however, several measurements yield a lifetime which suggests a sizable M1 strength. Further measurements to resolve the current conflicts would be beneficial.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Phosphorus in agricultural soils: drivers of its distribution at the global scale

Phosphorus (P) availability in soils limits crop yields in many regions of the world, while excess of soil P triggers aquatic eutrophication in other regions. Numerous processes drive the global spatial distribution of P in agricultural soils, but their relative roles remain unclear. Here, we combined several global datasets describing these drivers with a soil P dynamics model to simulate the distribution of P in agricultural soils and to assess the contributions of the different drivers at the global scale. We analyzed both the labile inorganic P (P ILAB ), a proxy of the pool involved in plant nutrition and the total soil P (P TOT ). We found that the soil biogeochemical background (BIOG) and farming practices (FARM) were the main drivers of the spatial variability in cropland soil P content but that their contribution varied between P TOT vs P ILAB . Indeed, 97% of the P TOT spatial variability could be explained by BIOG, while BIOG and FARM explained 41% and 58% of P ILAB spatial variability, respectively. Other drivers such as climate, soil erosion, atmospheric P deposition and soil buffering capacity made only very small contribution. Lastly, our study is a promising approach to investigate the potential effect of P as a limiting factor for agricultural ecosystems and for global food production. Additionally, we quantified the anthropogenic perturbation of P cycle and demonstrated how the different drivers are combined to explain the global distribution of agricultural soil P.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2026

Transgenic Mixed‐Linkage‐Glucan Enhancement Affects Root Characteristics and Decomposition in Soils of Contrasting Vegetation History

ABSTRACT Development of transgenic bioenergy sorghum [ Sorghum bicolor (L.) Moench] with increased contents of mixed‐linkage (1,3;1,4)‐β‐glucan (MLG) is an important step towards enhancing quality of bioenergy feedstocks. Since MLG‐enhancement leads to greater biomass digestibility, our overarching hypothesis is that root residues of MLG‐enhanced plants may be more readily decomposed in the soil, potentially creating new opportunities for optimizing soil carbon (C) sequestration, nutrient cycling, and overall agricultural sustainability. The study examined morphological, chemical, and enzymatic characteristics of fine and coarse roots of four bioenergy sorghum genotypes. Then, we incubated the roots within soils with contrasting vegetation histories while measuring C mineralization, microbial biomass C (MBC), and activity of hydrolytic enzymes and calculating vector length and vector angle enzymatic stoichiometry parameters. The results indicated that MLG‐enhancing transformations increased root total nitrogen (N) contents, decreased C/N ratios, and were associated with higher MLG concentrations in fine than in coarse roots. Incubations with transgenic roots led to 16%–38% higher MBC and 19%–41% lower microbial metabolic quotient (qCO 2 ). While enzyme activity differed markedly among the studied genotypes, it did not directly respond to MLG levels in root tissues. The increase in MBC without concurrent increases in C mineralization or hydrolytic enzyme activities in transgenic genotypes suggests that MLG enhancement promoted microbial anabolic retention of root‐derived C rather than stimulating catabolic decomposition. Enzymatic vector results indicated that these parameters reflect a variety of drivers behind microbial enzyme production, including availability of specific substrates, such as MLG here, and/or deficiency in specific nutrients, such as phosphorus (P). The study confirms the positive impacts from the roots of engineered MLG‐enhanced bioenergy plants on soil microbial activity and highlights the interactive influences on the MLG‐enhancement effects from root size and inherent soil properties.

Mahmoodabadi, Majid [Department of Plant, Soil, an↗

DOE OSTI2017

Effect of iron sulphate on the phosphorus speciation from agro-industrial sludge based and sewage sludge based compost

Highlights: • Composting of agro-industrial and waste water sewage sludge promoted organic P mineralization. • Mineralized P is mainly adsorbed/precipitated on calcium. • FeSO{sub 4} reduced organic P mineralization and its further adsorption/precipitation on calcium. - Abstract: Composting is considered a suitable process for organic waste management, providing stable products that can be safely utilized as fertilizers, but little is still known about the variation of phosphorous (P) extractability during the stabilization process. In this work, sequential chemical extraction (SCE) with increasing strength extractants (H{sub 2}O; 0.5 M NaHCO{sub 3} pH 8.5; 0.1 M NaOH, 1 M HCl) was applied for P speciation over 56 days of composting of either agro-industrial or urban wastewater sludge with green waste treated (AIC{sub Fe+}; SSC{sub Fe+}) or not (AIC{sub Fe−}; SSC{sub Fe−}) with FeSO{sub 4} (2% v/v). Composting strongly reduced the H{sub 2}O-P, promoting the organic-P (P{sub o}) mineralization from the labile fraction (H{sub 2}O + NaHCO{sub 3} 40%), in addition to the increases of NaHCO{sub 3}- and HCl-extractable inorganic-P (P{sub i}) in both AIC{sub Fe−} and SSC{sub Fe−} (+20% on average). The FeSO{sub 4} treatment did not negatively affect the process, reducing the P{sub o} mineralization during composting by increasing the NaOH-P, also protecting this fraction from fixation in the sparingly soluble fraction. The final P fractionation (%) was in AIC{sub Fe−}: NaOH (41) = NaHCO{sub 3} (38) > HCl (18) > H{sub 2}O (3); in AIC{sub Fe+}: NaOH (53) > NaHCO{sub 3} (24) = HCl (22) > H{sub 2}O (2); in SSC{sub Fe−}: NaOH (46) > NaHCO{sub 3} (29) > HCl (21) > H{sub 2}O (4) and in SSC{sub Fe+}: NaOH (66) > NaHCO{sub 3} (13) > HCl (20) > H{sub 2}O (1). Composting reduced the more easily leachable fraction (labile-P{sub o}), reducing the risk of P loss by increasing the long-term available P fraction (NaOH-P). This was enhanced by the FeSO{sub 4} addition. Further investigation into soil behaviour and plant availability of P from this source is needed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Marine phytoplankton stoichiometry mediates nonlinear interactions between nutrient supply, temperature, and atmospheric CO 2

Marine phytoplankton stoichiometry links nutrient supply to marine carbon export. Deviations of phytoplankton stoichiometry from Redfield proportions (106C :1P) could therefore have a significant impact on carbon cycling, and understanding which environmental factors drive these deviations may reveal new mechanisms regulating the carbon cycle. To explore the links between environmental conditions, stoichiometry, and carbon cycling, we compared four different models of phytoplankton C :P: a fixed Redfield model, a model with C : P given as a function of surface phosphorus concentration (P), a model with C P given as a function of temperature, and a new multi-environmental model that predicts C : P as a function of light, temperature, and P. These stoichiometric models were embedded into a five-box ocean circulation model, which resolves the three major ocean biomes (high-latitude, subtropical gyres, and tropical upwelling regions). Contrary to the expectation of a monotonic relationship between surface nutrient drawdown and carbon export, we found that lateral nutrient transport from lower C: P tropical waters to high C: P subtropical waters could cause carbon export to decrease with increased tropical nutrient utilization. It has been hypothesized that a positive feedback between temperature and p CO 2 atm will play an important role in anthropogenic climate change, with changes in the biological pump playing at most a secondary role. Here we show that environmentally driven shifts in stoichiometry make the biological pump more influential, and may reverse the expected positive relationship between temperature and p CO 2,atm . In the temperature-only model, changes in tropical temperature have more impact on the Δ p CO 2,atm (~41 ppm) compared to subtropical temperature changes (~4.5 ppm). Our multi-environmental model predicted a decline in p CO 2,atm of ~ 46 ppm when temperature spanned a change of 10 °C. Thus, we find that variation in marine phytoplankton stoichiometry and its environmental controlling factors can lead to nonlinear controls on p CO 2,atm , implying the need for further studies of ocean C : P and the impact on ocean carbon cycling.

58 GEOSCIENCES↗