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DOE OSTI2015

Over 150 years of long-term fertilization alters spatial scaling of microbial biodiversity

Spatial scaling is a critical issue in ecology, but how anthropogenic activities like fertilization affect spatial scaling is poorly understood, especially for microbial communities. Here, we determined the effects of long-term fertilization on the spatial scaling of microbial functional diversity and its relationships to plant diversity in the 150-year-old Park Grass Experiment, the oldest continuous grassland experiment in the world. Nested samples were taken from plots with contrasting inorganic fertilization regimes, and community DNAs were analyzed using the GeoChip-based functional gene array. The slopes of microbial gene-area relationships (GARs) and plant species-area relationships (SARs) were estimated in a plot receiving nitrogen (N), phosphorus (P), and potassium (K) and a control plot without fertilization. Our results indicated that long-term inorganic fertilization significantly increased both microbial GARs and plant SARs. Microbial spatial turnover rates (i.e., z values) were less than 0.1 and were significantly higher in the fertilized plot (0.0583) than in the control plot (0.0449) (P < 0.0001). The z values also varied significantly with different functional genes involved in carbon (C), N, P, and sulfur (S) cycling and with various phylogenetic groups (archaea, bacteria, and fungi). Similarly, the plant SARs increased significantly (P < 0.0001), from 0.225 in the control plot to 0.419 in the fertilized plot. Soil fertilization, plant diversity, and spatial distance had roughly equal contributions in shaping the microbial functional community structure, while soil geochemical variables contributed less. Results indicated that long-term agricultural practice could alter the spatial scaling of microbial biodiversity. Determining the spatial scaling of microbial biodiversity and its response to human activities is important but challenging in microbial ecology. Most studies to date are based on different sites that may not be truly comparable or on short-term perturbations, and hence, the results observed could represent transient responses. This study examined the spatial patterns of microbial communities in response to different fertilization regimes at the Rothamsted Research Experimental Station, which has become an invaluable resource for ecologists, environmentalists, and soil scientists. The current study is the first showing that long-term fertilization has dramatic impacts on the spatial scaling of microbial communities. In addition, by identifying the spatial patterns in response to long-term fertilization and their underlying mechanisms, the study makes fundamental contributions to predictive understanding of microbial biogeography.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

Nitrogen Fertilization Restructured Spatial Patterns of Soil Organic Carbon and Total Nitrogen in Switchgrass and Gamagrass Croplands in Tennessee USA

Nitrogen (N) fertilizers can potentially alter spatial distribution of soil organic carbon (SOC) and total nitrogen (TN) concentrations in croplands such as switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.), but it remains unclear whether these effects are the same between crops and under different rates of fertilization. 13 C and 15 N are two important proxy measures of soil biogeochemistry, but they were rarely examined as to their spatial distributions in soil. Based on a three-year long fertilization experiment in Middle Tennessee, USA, the top mineral horizon soils (0–15 cm) were collected using a spatially explicit design within two 15-m 2 plots under three fertilization treatments in SG and GG croplands. A total of 288 samples were collected based on 12 plots and 24 samples in each plot. The fertilization treatments were no N input (NN), low N input (LN: 84 kg N ha -1 in urea) and high N input (HN: 168 kg N ha -1 in urea). The SOC, TN, SOC/TN (C: N), δ 13 C and δ 15 N were quantified and their within-plot variations and spatial distributions were achieved via descriptive and geostatistical methods. Results showed that SG generally displayed 10~120% higher plot-level variations in all variables than GG, and the plot-level variations were 20~77% higher in NN plots than LN and HN plots in SG but they were comparable in unfertilized and fertilized plots in GG. Relative to NN, LN and HN showed more significant surface trends and spatial structures in SOC and TN in both croplands, and the fertilization effect appeared more pronounced in SG. Spatial patterns in C: N, δ 13 C and δ 15 N were comparable among different fertilization treatments in both croplands. The descending within-plot variations were also identified among variables (SOC > TN > δ 15 N > C: N > δ 13 C). This study demonstrated that N fertilizations generally reduced the plot-level variance and simultaneously re-established spatial structures of SOC and TN in bioenergy croplands, which little varied with fertilization rate but was more responsive in switchgrass cropland.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2024

Vadose zone flushing of fertilizer tracked by isotopes of water and nitrate

Abstract A substantial fraction of nitrogen (N) fertilizer applied in agricultural systems is not incorporated into crops and moves below the rooting zone as nitrate (NO 3 − ). Understanding mechanisms for soil N retention below the rooting zone and leaching to groundwater is essential for our ability to track the fate of added N. We used dual stable isotopes of nitrate (δ 15 N–NO 3 − and δ 18 O–NO 3 − ) and water (δ 18 O–H 2 O and δ 2 H–H 2 O) to understand the mechanisms driving nitrate leaching at three depths (0.8, 1.5, and 3.0 m) of an irrigated corn field sampled every 2 weeks from 2016 to 2020 in the southern Willamette Valley, Oregon, USA. Distinct periods of high nitrate concentrations with lower δ 15 N–NO 3 − values indicated that a portion of that nitrate was from recent fertilizer applications. We used a mixing model to quantify nitrate fluxes associated with recently added fertilizer N versus older, legacy soil N during these “fertilizer signal periods.” Nitrate leached below 3.0 m in these periods made up a larger proportion of the total N leached at that depth (∼52%) versus the two shallower depths (∼13%–16%), indicating preferential movement of recently applied fertilizer N through the deep soil into groundwater. Further, N associated with recent fertilizer additions leached more easily when compared to remobilized legacy N. A high volume of fall and winter precipitation may push residual fertilizer N to depth, potentially posing a larger threat to groundwater than legacy N. Optimizing fertilizer N additions could minimize fertilizer losses and reduce nitrate leaching to groundwater.

Agriculture↗

DOE OSTI2014

PTK2b function during fertilization of the mouse oocyte

Highlights: • PTK2b is expressed in oocytes and is activated following fertilization. • PTK2b suppression in oocytes prevents fertilization, but not parthenogenetic activation. • PTK2b suppression prevents the oocyte from fusing with or incorporating bound sperm. • PTK2b suppressed oocytes that fail to fertilize do not exhibit calcium oscillations. - Abstract: Fertilization triggers rapid changes in intracellular free calcium that serve to activate multiple signaling events critical to the initiation of successful development. Among the pathways downstream of the fertilization-induced calcium transient is the calcium-calmodulin dependent protein tyrosine kinase PTK2b or PYK2 kinase. PTK2b plays an important role in fertilization of the zebrafish oocyte and the objective of the present study was to establish whether PTK2b also functions in mammalian fertilization. PTK2b was activated during the first few hours after fertilization of the mouse oocyte during the period when anaphase resumption was underway and prior to the pronuclear stage. Suppression of PTK2b kinase activity in oocytes blocked sperm incorporation and egg activation although sperm-oocyte binding was not affected. Oocytes that failed to incorporate sperm after inhibitor treatment showed no evidence of a calcium transient and no evidence of anaphase resumption suggesting that egg activation did not occur. The results indicate that PTK2b functions during the sperm-egg fusion process or during the physical incorporation of sperm into the egg cytoplasm and is therefore critical for successful development.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

The long-term effects of acute exposure to ionising radiation on survival and fertility in Daphnia magna

The results of recent studies have provided strong evidence for the transgenerational effects of parental exposure to ionising radiation and chemical mutagens. However, the transgenerational effects of parental exposure on survival and fertility remain poorly understood. To establish whether parental irradiation can affect the survival and fertility of directly exposed organisms and their offspring, crustacean Daphnia magna were given 10, 100, 1000 and 10,000 mGy of acute γ-rays. Exposure to 1000 and 10,000 mGy significantly compromised the viability of irradiated Daphnia and their first-generation progeny, but did not affect the second-generation progeny. The fertility of F{sub 0} and F{sub 1}Daphnia gradually declined with the dose of parental exposure and significantly decreased at dose of 100 mGy and at higher doses. The effects of parental irradiation on the number of broods were only observed among the F{sub 0}Daphnia exposed to 1000 and 10,000 mGy, whereas the brood size was equally affected in the two consecutive generations. In contrast, the F{sub 2} total fertility was compromised only among progeny of parents that received the highest dose of 10,000 mGy. We propose that the decreased fertility observed among the F{sub 2} progeny of parents exposed to 10,000 mGy is attributed to transgenerational effects of parental irradiation. Our results also indicate a substantial recovery of the F{sub 2} progeny of irradiated F{sub 0}Daphnia exposed to the lower doses of acute γ-rays. - Highlights: • Viability of irradiated daphnids and their F{sub 1} progeny is compromised. • Viability of the F{sub 2} progeny of irradiated parents is not affected. • Total fertility of irradiated daphnids and their F{sub 1} progeny declines with the dose. • Total fertility of the F{sub 2} progeny of parents exposed to 10,000 mGy is compromised. • The decreased fertility among the F{sub 2} progeny is transgenerational phenomenon.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2015

Exposure to bisphenol A in young adult mice does not alter ovulation but does alter the fertilization ability of oocytes

Follicle growth culminates in ovulation, which allows for the expulsion of fertilizable oocytes and the formation of corpora lutea. Bisphenol A (BPA) is present in many consumer products, and it has been suggested that BPA impairs ovulation; however, the underlying mechanisms are unknown. Therefore, this study first evaluated whether BPA alters ovulation by affecting folliculogenesis, the number of corpora lutea or eggs shed to the oviduct, ovarian gonadotropin responsiveness, hormone levels, and estrous cyclicity. Because it has been suggested (but not directly confirmed) that BPA exerts toxic effects on the fertilization ability of oocytes, a second aim was to evaluate whether BPA impacts the oocyte fertilization rate using an in vitro fertilization assay and mating. The possible effects on early zygote development were also examined. Young adult female C57BL/6J mice (39 days old) were orally dosed with corn oil (vehicle) or 50 μg/kg bw/day BPA for a period encompassing the first three reproductive cycles (12–15 days). BPA exposure did not alter any parameters related to ovulation. Moreover, BPA exposure reduced the percentage of fertilized oocytes after either in vitro fertilization or mating, but it did not alter the zygotic stages. The data indicate that exposure to the reference dose of BPA does not impact ovulation but that it does influence the oocyte quality in terms of its fertilization ability. - Highlights: • Bisphenol A targets the fertilization ability of oocytes. • Bisphenol A does not alter ovulation. • Young adult females may be susceptible to the effects of bisphenol A on fertilization.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2012

Fate of phosphorus in Everglades agricultural soils after fertilizer application

Land use changes, agricultural drainage and conventional cultivation of winter vegetables and sugarcane cropping in the Everglades Agricultural Area (EAA) may alter soil conditions and organic matter decomposition and ultimately influence the fate of phosphorus (P). Theses agricultural practices promote soil subsidence, reduce the soil depth to bedrock limestone and increase the potential for incorporation of limestone into the root zone of crops. The incorporation of limestone into surface soil has significantly increased soil pH which in turns causes greater fixation of P fertilizer into unavailable forms for plant growth. Additional P fertilization is thus required to satisfy crop nutrient requirements in plant-available P form. It is important to determine how the mixing of bedrock limestone into soils influences the behavior of P fertilizers after their application. To accomplish this task, P fertilizers were applied to (1) typical cultivated soils and to (2) soils that have never been fertilized or extensively tilled. The changes in P concentrations over time were then compared between the two land uses, with differences being attributable to the impacts of cultivation practices. The P distribution in soil varied between land uses, with sugarcane having more P in inorganic pools while the uncultivated soil had more in organic pools. Water-soluble P concentrations in soil increased with increasing fertilizer application rates for all sampling times and both land uses. However, concentrations in uncultivated soil increased proportionally to P-fertilized soil due to organic P mineralization. At all sampling times, plant-available P concentrations remained higher for uncultivated than sugarcane soil. Lower P concentrations for sugarcane were related to adsorption by mineral components (e.g. limestone). Cultivated soils have higher calcium concentrations resulting from incorporation of bedrock limestone into soil by tillage, which increased pH and fostered sequestration of plant-available P into stable calcium-bound P pools. This greater P retention for sugarcane was reflected in the greater proportion of P in inorganic pools compared to uncultivated soils. Some lands within the EAA, including wetlands and seasonally-flooded prairies, are being reclaimed for water quality purposes. However, long-term effects of fertilization and cropping practices described in this document indicate that direct conversion from active farming, such as from sugarcane production directly to wetlands, may be problematic due to the changes in nutrient dynamics that may occur. The shift directly to wetlands may, in fact, release considerable amounts of P into the Everglades, thwarting the intent of the land use change. The inorganic P component in sugarcane soils may lead to the regeneration of soluble P in frequently flooded land uses such as wetlands. While most of the inorganic P pools are unavailable to sugarcane, the direct conversion of sugarcane soils to wetlands may facilitate P release. Here, reclamation of sugarcane fields for environment uses would benefit by an intermediate step to allow for a short duration of seasonal flooding allowing for P conversion from inorganic to organic forms. Prolonged flooding of organic soils previously used for intensive agriculture is not recommended.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Maturation and fertilization of echinoderm eggs: Role of actin cytoskeleton dynamics

Highlights: • Meiotic maturation of starfish oocytes involves the rearrangement of actin filaments and intracellular Ca{sup 2+} increases. • The actin cytoskeleton plays a role in optimizing the Ca{sup 2+} release mechanisms during oocyte maturation. • F-actin dynamics regulates Ca{sup 2+} signaling and cortical granules exocytosis at fertilization in starfish and sea urchin eggs. • Monospermic fertilization is heavily dependent upon the integrity of the actin cytoskeleton of the egg cortex. Starfish and sea urchin are excellent models to study the mechanisms that regulate oocyte maturation and egg activation. Hormonal stimulation of starfish oocytes and their following interaction with spermatozoa induce rapid changes of F-actin and Ca{sup 2+} increases which are prerequisites for normal fertilization and development. Fully grown oocytes isolated from the gonads of starfish contain a large nucleus (∼60–70 μm) (termed germinal vesicle, GV), which is arrested at the first prophase of meiosis. If inseminated, these immature oocytes are penetrated by additional spermatozoa. However, starfish oocytes naturally shed into the sea have already initiated the (meiotic) maturation and are normally fertilized between GV breakdown and the extrusion of the first polar body. This is considered the optimum period to ensure monospermic instead of polyspermic fertilization. By contrast, sea urchin eggs are fertilized only after being fully matured, i.e., at the end of the two meiotic divisions. Here, we provide a comparative review of the role of the actin cytoskeleton in oocyte maturation and fertilization in starfish and sea urchin. It has become increasingly evident that the exquisite regulation of the cortical F-actin is involved in nearly all aspects of the molecular events taking place during the progression of meiotic maturation and fertilization.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2020

Herbicide, fertilization, and planting density effects on intensively managed loblolly pine early stand development

Production forestry in the southeast US has been partially transitioned to intensively managed short rotations (~10 years), in which multiple silvicultural interventions are performed during forest development. Understanding the responses to silvicultural practices and continued refinement of site-specific recommendations is critical to sustainably maximize forest production. We evaluated the effects of silvicultural practices (herbicide, fertilization, and planting density) on growth, stand homogeneity, and above- and belowground biomass accumulation and partitioning of loblolly pine (Pinus taeda) throughout early stand development (age 5 years) in the southeastern US. Five treatments with eight replications each were tested: no herbicide and no fertilization (C); herbicide only (H); herbicide and half-reduced fertilization rate (R); herbicide and full fertilization (F); and increased stand density (60+ %; 1346 vs. 2152 trees per hectare) with herbicide and full fertilization rate (D). Allometric equations generated from destructive harvests were applied to annual diameter measurements to estimate plot-level biomass and allocation. Herbicide was crucial to promote stand uniformity and increase yield (~600+ % stem biomass compared with C at age 5). Aboveground biomass was similar in R and F treatments, which was ~25% higher than in H at age 5. Increasing planting density along with multiple herbicide and fertilizer applications yielded higher biomass without compromising individual tree size (diameter and height). There was little effect of silviculture practices on allocation patterns. Our results parallel what was found for fertilization with herbicide from a number of loblolly stands under similar conditions and indicate a ~28% volume gain with fertilization during early stand development. Similarly, our results were consistent with other studies implementing similar differences in planting density and suggest a ~26% volume gain through early stand development with an initial 60% increase in planting density. Furthermore, our study helps to understand complex relationships between production and silvicultural practices during early stand development and demonstrates that silvicultural prescriptions can be optimized to increase sustainability of production forestry

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

The Impact of Stand Age and Fertilization on the Soil Microbiome of Miscanthus × giganteus

Yield of the perennial grass Miscanthus × giganteus has shown an inconsistent and unpredictable response to nitrogen (N) fertilizer, yet fertilization underpins the crop’s environmental and economic sustainability. The interactions among soil microbial communities, N availability, and Miscanthus × giganteus and management may explain changes in plant productivity. In this study, soil samples from different stand ages of Miscanthus × giganteus in a replicated chronosequence field trial were used to investigate the effects of stand age and N fertilizer rates on microbial community structure. We hypothesized that there is a definable Miscanthus × giganteus soil microbiome and that this community varies significantly with stand age and fertilization. Our results showed that the main phyla in soil microbial communities, regardless of plant age, are similar but microbial community structures are significantly different. The variation in observed microbial communities generally decreases with older stand ages. The amount of N fertilizer applied also affected the microbial community structure associated with different aged Miscanthus × giganteus. Specifically, the relative abundance of Proteobacteria (Alphaproteobacteria and Gammaproteobacteria) and Acidobacteria (subgroup Gp1) increased shortly after fertilization and was more associated with younger Miscanthus × giganteus. Furthermore, our results show a significant relationship between bacterial α diversity and fertilization rates and that this response is also affected by stand age. Overall, our results emphasize linkages between microbial community structure, plant age, and fertilization in Miscanthus × giganteus.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

Impacts of corn intercropping with soybean, peanut and millet through different planting patterns on population dynamics and community diversity of insects under fertilizer reduction

Corn is one of the key grain crops in China and the excessive use of chemical fertilizers and pesticides seriously damages the ecological environment in fields. To explore a more scientific and reasonable way to plant corn and simultaneously reduce the overuse of chemical fertilizers and pesticides, the impact of corn intercropping with soybean, peanut, and millet, respectively, through five planting patterns, including three intercropping patterns (2 corn rows to 2, 3 and 4 rows of soybean/peanut or 2, 4 and 6 millet rows, respectively) and two monoculture patterns of corn and soybean, peanut or millet under normal (600 kg/ha) and reduced (375 kg/ha) levels of NPK (N:P 2 O 5 :K 2 O = 15:15:15) fertilization on the population abundance and community diversity of insects, leaf nutrients, and induced plant hormones jasmonic acid (JA) and salicylic acid (SA) was studied in 2018 and 2019. The results showed that the insect community indexes of the species number ( S ), the diversity index ( H ), and the uniformity index ( E ) generally increased under intercropping and were significantly higher than those under corn monoculture. The prevalence of Asian corn borer ( Ostrinia furnacalis ) on the intercropping corn plants decreased by based on the average of seven surveys per year for each treatment 2.9 to 17 heads per 30 plants compared with that on the monoculture corn plants. The number of natural enemy insect species on corn plants under intercropping was significantly higher than that under corn monoculture. That is, intercropping may decrease the population of Asian corn borers by increasing S , H , E , and natural enemy insect species (NEI). Moreover, intercropping type and fertilizer level significantly affected corn leaf nutrient contents. Compared with the normal fertilizer level, fertilizer reduction significantly reduced the foliar contents of amino acids, soluble protein, and soluble sugar in corn plants. In addition, corn–soybean and corn–peanut intercropping significantly increased the three nutrient contents in corn leaves compared with corn monoculture. In terms of corn nutrients, intercropping could compensate for the effects of fertilizer reduction. The foliar content of JA in corn–soybean intercropping was significantly higher than in corn monoculture. Under corn–soybean and corn–peanut intercropping, SA was significantly lower than under corn monoculture. Overall, intercropping, not fertilizer reduction, can significantly increase insect community diversity while reducing the population abundances of the key insect pest species on corn plants. Intercropping reduced the SA content, increased amino acids and thus reduced the susceptibility of corn to the pest insects.

Li, Likun↗

DOE OSTI2025

Risk of Mortality in Family Members of Men Seeking Fertility Assessment

Objective: To assess mortality in family members of men seeking fertility assessment. Subfertility serves as a biomarker for overall somatic health, and poor semen quality is associated with increased risk of hospitalization and mortality from chronic conditions. However, it is unclear if these risks extend to family members of men with low sperm count. Design: Retrospective cohort study. Subjects: Family members, up to third-degree relatives, of men in the Subfertility, Health and Assisted Reproduction and the Environment cohort who underwent a semen analysis as part of a fertility assessment 1996–2017. Relatives of men with a recorded total sperm count who lived in Utah for ≥1 year 1904–2017 were included in the analysis (N = 22,280 families). Exposure: Individuals were classified by family membership. Families were classified as relatives of azoospermic (0M), oligozoospermic (<39M), or normozoospermic (≥39M) men. The average total sperm count of the proband (male relative) with fertility assessment was also included as a continuous exposure measure. Main Outcome Measures: The main outcomes were all-cause and cause-specific mortality risk by sex, age, and degree of relation: first-, second-, and third-degree. Cox proportional hazard models were used to test the association between fertility classification and mortality, controlling for sex, race/ethnicity, and birth year. Results: A total of 666,437 relatives of men with fertility assessment (N deaths = 183,974) were included in the analysis. Relative to normozoospermia families, all-cause mortality risk increased in oligozoospermia families (hazard ratio [HR] oligozoospermia , 1.03; 95% confidence interval [CI], 1.01–1.05). Close relatives, first- (HR oligozoospermia , 1.17; 95% CI, 1.07–1.28) and second-degree relatives (HR azoospermia , 1.11; 95% CI, 1.04–1.20; HR oligozoospermia , 1.05; 95% CI,1.01–1.09), of azoospermic and oligozoospermic men had the highest all-cause and cause-specific mortality risk, including death attributed to cardiovascular disease or congenital birth conditions. Conclusion: Our results suggest that familial all-cause and cause-specific mortality risk differ by fertility phenotype. Families of azoospermic and oligozoospermic men showed significantly increased risk, particularly for close relatives. This study provides further evidence that shared genetic and/or environmental factors could influence both fertility and somatic health.

Male fertility↗

DOE OSTI2016

Nitrogen fertilization challenges the climate benefit of cellulosic biofuels

Cellulosic biofuels are intended to improve future energy and climate security. Nitrogen (N) fertilizer is commonly recommended to stimulate yields but can increase losses of the greenhouse gas nitrous oxide (N 2 O) and other forms of reactive N, including nitrate. We measured soil N2O emissions and nitrate leaching along a switchgrass ( Panicum virgatum ) high resolution N-fertilizer gradient for three years post-establishment. Results revealed an exponential increase in annual N2O emissions that each year became stronger (R 2 > 0.9, P < 0.001) and deviated further from the fixed percentage assumed for IPCC Tier 1 emission factors. Concomitantly, switchgrass yields became less responsive each year to N fertilizer. Nitrate leaching (and calculated indirect N2O emissions) also increased exponentially in response to N inputs, but neither methane (CH4) uptake nor soil organic carbon changed detectably. Overall, N fertilizer inputs at rates greater than crop need curtailed the climate benefit of ethanol production almost two-fold, from a maximum mitigation capacity of–5.71 ± 0.22 Mg CO 2 e ha –1 yr –1 in switchgrass fertilized at 56 kgNha –1 to only –2.97 ± 0.18 MgCO 2 e ha –1 yr –1 in switchgrass fertilized at 196 kgNha –1 . In conclusion, minimizing N fertilizer use will be an important strategy for fully realizing the climate benefits of cellulosic biofuel production.

09 BIOMASS FUELS↗

DOE OSTI2022

Improved Moisture Management Technology for Eco-N-Control Fertilizer

Three fertilizer technologies to manage nitrogen (N) release rates in soil dominate the market today: 1) bulk controlled-release technologies, which use the intrinsic solubility properties of a N-organic co-polymer to control N release; 2) barrier-based controlled-release technologies, which use porous polymer or sulfur coatings as a physical barrier to control N release from encapsulated N nutrients; and 3) slow-release technologies, which use enzyme inhibitors to chemically slow down the transformation of N nutrients into ammonia (NH 3 ) or to temporarily reduce populations of bacteria in the soil that are responsible for converting ammonium (NH 4 + ) to highly soluble nitrates. These technologies are expensive and provide only limited control of N-release rates. Also, from another environmental perspective, synthetic polymer coatings do not decompose easily and will accumulate over time with continuous application of fertilizer. For most of the past two decades we have been developing the Eco-N-Control solid-nitride fertilizer technology, a type of bulk controlled-release technology. With Eco-N-Control, solid-nitride compounds weather like a mineral, slowly releasing N at a rate determined by their composition. Testing by an industrial collaborator, however, showed that earlier versions of Eco-N-Control released at 25% of the desired rate when deployed in unsaturated soils. The overall goal of the current project, therefore, was to strengthen our IP position and the potential for licensing of Eco-N-Control solid-nitride fertilizer technology by developing new ways to manage the level of moisture in contact with the fertilizer when applied to soil thereby ensuring the desired N-release rate. We achieved this goal by developing a biodegradable polymer cross-linking approach that substantially improved performance of our patented solid-nitride fertilizer. We found that cross-linking an environmentally friendly and biodegradable polymer with a mixture of solid nitrides, other N-nutrient compounds and other additives offers several advantages: 1) mechanical robustness of fertilizer beads, 2) chemical stability during storage, 3) maintenance of sufficient water content in the vicinity of the nitride, and 4) control of N-release rates. We also updated our N-release testing protocol to more realistically simulate the conditions found in soil. Finally, we filed an invention disclosure record to protect these new aspects of Eco-N-Control technology, which offers a potential way to lower both agricultural and industrial pollution by providing an efficient N-delivery mechanism to plants.

42 ENGINEERING↗

DOE OSTI2019

Data from: Nitrogen fertilization challenges the climate benefit of cellulosic biofuels

Cellulosic biofuels are intended to improve future energy and climate security. Nitrogen (N) fertilizer is commonly recommended to stimulate yields but can increase losses of the greenhouse gas nitrous oxide (N2O) and other forms of reactive N, including nitrate. We measured soil N2O emissions and nitrate leaching along a switchgrass (Panicum virgatum) high resolution N-fertilizer gradient for three years post-establishment. Results revealed an exponential increase in annual N2O emissions that each year became stronger (R 2 > 0.9, P < 0.001) and deviated further from the fixed percentage assumed for IPCC Tier 1 emission factors. Concomitantly, switchgrass yields became less responsive each year to N fertilizer. Nitrate leaching (and calculated indirect N2O emissions) also increased exponentially in response to N inputs, but neither methane (CH4) uptake nor soil organic carbon changed detectably. Overall, N fertilizer inputs at rates greater than crop need curtailed the climate benefit of ethanol production almost two-fold, from a maximum mitigation capacity of −5.71 ± 0.22 Mg CO2e ha−1 yr−1 in switchgrass fertilized at 56 kg N ha−1 to only −2.97 ± 0.18 Mg CO2e ha−1 yr−1 in switchgrass fertilized at 196 kg N ha−1. Minimizing N fertilizer use will be an important strategy for fully realizing the climate benefits of cellulosic biofuel production.

09 BIOMASS FUELS↗

DOE OSTI2024

Tropical dry forest response to nutrient fertilization: a model validation and sensitivity analysis

Abstract. Soil nutrients, especially nitrogen (N) and phosphorus (P), regulate plant growth and hence influence carbon fluxes between the land surface and atmosphere. However, how forests adjust biomass partitioning to leaves, wood, and fine roots in response to N and/or P fertilization remains puzzling. Recent work in tropical forests suggests that trees increase fine root production under P fertilization, but it is unclear whether mechanistic models can reproduce this dynamic. In order to better understand mechanisms governing nutrient effects on plant allocation and improve models, we used the nutrient-enabled ED2 model to simulate a fertilization experiment being conducted in a secondary tropical dry forest in Costa Rica. We evaluated how different allocation parameterizations affected model performance. These parameterizations prescribed a linear relationship between relative allocation to fine roots and soil P concentrations. The slope of the linear relationship was allowed to be positive, negative, or zero. Some parameterizations realistically simulated leaf, wood, and fine root production, and these parameterizations all assumed a positive relationship between relative allocation to fine roots and soil P concentration. Model simulations of a 30-year timeframe indicated strong sensitivity to parameterization and fertilization treatment. Without P fertilization, the simulated aboveground biomass (AGB) accumulation was insensitive to the parameterization. With P fertilization, the model was highly sensitive to the parameterization and the greatest AGB accumulation occurred when relative allocation to fine roots was independent of soil P. Our study demonstrates the need for simultaneous measurements of leaf, wood, and fine root production in nutrient fertilization experiments and for longer-term experiments. Models that do not accurately represent allocation to fine roots may be highly biased in their simulations of AGB, especially on multi-decadal timescales.

Environmental Sciences & Ecology↗

DOE OSTI2019

Fertilizer timing affects nitrous oxide, carbon dioxide, and ammonia emissions from soil

The impact of interactions between management and climate on nitrous oxide (N 2 O), carbon dioxide (CO 2 ), and ammonia (NH 3 ) emissions are not well understood. This study quantified the effect of urea fertilizer application timing on inorganic N movement, immobilization, and the gaseous emissions of N 2 O-N, CO 2 -C, and NH 3 -N. Urea was applied once, at two rates (0 and 224 kg ha -1 ) on six dates (early fall, 20 Sept. 2017; mid-fall, 11 Oct. 2017; early winter, 1 Nov. 2017; early spring, 1 May 2018; mid-spring, 22 May 2018; and early summer, 12 June 2018). Gaseous emissions, soil temperature, and soil moisture were measured every 4 h for 21 consecutive days following urea application. Changes in soil inorganic N contents were used to determine the amount of inorganic N remaining in the soil, nitrification, immobilization/fixation, and leaching. For all fertilizer application dates, the cumulative fertilizer derived N 2 O-N emissions for the 21 days following application were <0.05% of the applied N. Fertilizer-derived N 2 O-N emission rates were higher than N 2 O-N emission rates in the unfertilized soil in early fall and early summer. Even though the highest net N 2 O-N emissions occurred in early spring, the application of fertilizer did not increase emissions. The highest net N 2 O-N + NH 3 -N emissions occurred in cool soils (early spring) in soils with water filled pore space (>60%). These findings indicate that intergovernmental panel on climate change (IPCC) default value of 1% of applied N for N 2 O emissions improved by considering the fertilizer application date.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2019

Integrated Use of Maize Bran Residue for One-Step Phosphate Bio-Fertilizer Production

The development of bio-fertilizer inoculants is important and desirable. Two phosphate-solubilizing Bacillus subtilis strains were inoculated onto maize bran residue (MBR), which was used as bio-fertilizer carrier and a primary source of nutrients in a medium used for semi-solid fermentation. Water holding capacity, swelling capacity, scanning electron microscopy, and shelf-life assays demonstrated that ground MBR had satisfactory properties for a bio-fertilizer carrier. The maximal soluble phosphorus (P) reached 642.7 ± 0.43 mg l{sup −1} in an orthogonal test under the following optimal conditions: a pH of 7.0, a cultivation temperature of 31 °C, a medium water content of 160%, and a filling capacity of 500 g l{sup −1}. The bio-fertilizer produced by MBR improved the growth of wheat (Triticum aestivum L.) and Chinese cabbage (Brassica rapa pekinensis) with respect to plant height (by up to 18.36%) and the lengths of roots (by up to 34.03%, 27.22%, separately) in a pot experiment. This study integrated the production and storage of a bio-fertilizer to realize the one-step production of a solid bio-fertilizer using MBR.

60 APPLIED LIFE SCIENCES↗