Can mineralization of soil organic nitrogen meet maize nitrogen demand?

Osterholz, William R.; Rinot, Oshri; Liebman, Matt; Castellano, Michael J.

doi:10.1007/s11104-016-3137-1

Cited by 63 publications

(43 citation statements)

References 63 publications

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“…Gross ammonification rate (i.e., the conversion of SOM-N to NH + 4 ) was used to determine the direction of effect of N fertilizer addition on SOM mineralization. Within 24 h of sampling, gross ammonification rate was measured on the field-fresh soils during a 24 h incubation using conventional 15 N isotope pool dilution method (Hart et al, 1994) with blank correction (Stark and Hart, 1996) that was adapted to intensively managed Iowa agricultural soils (Osterholz et al, 2017). As a result, these assays were made at the sampled moisture content (which differed across treatments) and room temperature (21 • C) which was very similar to field temperature.…”

Section: Soil Moisture Inorganic N Pools Size and Gross Ammonificatmentioning

confidence: 99%

Nitrogen Fertilizer Suppresses Mineralization of Soil Organic Matter in Maize Agroecosystems

et al. 2019

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The possibility that N fertilizer increases soil organic matter (SOM) mineralization and, as a result, reduces SOM stocks has led to a great debate about the long-term sustainability of maize-based agroecosystems as well as the best method to estimate fertilizer N use efficiency (FNUE). Much of this debate is because synthetic N fertilizer can positively or negatively affect SOM mineralization via several direct and indirect pathways. Here, we test a series of hypotheses to determine the direction, magnitude, and mechanism of N fertilizer effect on SOM mineralization and discuss the implications for methods to estimate FNUE. We measured the effect of synthetic N fertilizer on SOM mineralization via gross ammonification at two long-term experiments in central and southern Iowa, USA with replicated plots of continuous maize that received one of three "historical" N fertilizer rates (zero, moderate or high) from 1999 to 2014. In 2015, prior to our measurements, we split the historical N fertilizer rate plots into two subplots that received either the site-specific agronomic optimum N rate or zero N fertilizer. At the onset of rapid maize N uptake, N fertilizer reduced gross ammonification by 13-21% (2-5 kg NH 4-N ha −1 d −1). A companion laboratory experiment rejected the hypothesis that differences in net primary productivity between fertilized and unfertilized treatments explained the negative effect of N fertilizer on SOM mineralization. Moreover, the NH + 4 pool size was negatively correlated with the gross ammonification rate (r 2 = 0.85, p < 0.001). Thus, we conclude that NH + 4-N fertilizer had a direct suppressive effect on SOM mineralization. These results demonstrate that the direct effect of N fertilizer on microbial activity can exceed the indirect effects of N fertilizer via large changes in NPP that alter organic matter inputs, soil temperature and moisture content. The magnitude of this effect and specificity to NH + 4-N has significant implications for fertilizer management as well as the measurement and modeling of agroecosystem N dynamics including FNUE.

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Section: Soil Moisture Inorganic N Pools Size and Gross Ammonificatmentioning

confidence: 99%

Nitrogen Fertilizer Suppresses Mineralization of Soil Organic Matter in Maize Agroecosystems

et al. 2019

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“…According to soil 15 N measurements, between 18 and 40% of the fertilizer N applied at planting was recovered in the surface 15 cm of soil at the onset of the maximum rate of maize N uptake (five-leaf stage; ∼4 weeks after fertilizer application; Osterholz et al, 2017a). Approximately 5-10 kg N ha −1 would be expected to be present in a maize crop at this growth stage (Abendroth et al, 2011), and a portion may have moved to deeper soil layers following rain events after application.…”

Section: Fertilizer N Recovery In Topsoil (0-15 Cm)mentioning

confidence: 99%

Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize

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et al. 2018

Agriculture, Ecosystems & Environment

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Nitrogen fertilizer management can impact soil organic C (SOC) stocks in cereal-based cropping systems by regulating crop residue inputs and decomposition rates. However, the impact of long-term N fertilizer management, and associated changes in SOC quantity and quality, on the fate of N fertilizer inputs is uncertain. Using two 15-year N fertilizer rate experiments on continuous maize (Zea mays L.) in Iowa, which have generated gradients of SOC, we evaluated the legacy effects of N fertilizer inputs on the fate of added N. Across the historical N fertilizer rates, which ranged from 0 to 269 kg N ha−1 yr−1, we applied isotopicallylabeled N fertilizer at the empirically-determined site-specific agronomic optimum rate (202 kg N ha−1 at the central location and 269 kg N ha−1 at the southern location) and measured fertilizer recovery in crop and soil pools, and, by difference, environmental losses. Crop fertilizer N recovery efficiency (NREcrop) at physiological maturity averaged 44% and 14% of applied N in central Iowa and southern Iowa, respectively (88 kg N ha−1 and 37 kg N ha−1, respectively). Despite these large differences in NREcrop, the response to historical N rate was remarkably similar across both locations: NREcrop was greatest at low and high historical N rates, and least at the intermediate rates. Decreasing NREcrop from low to intermediate historical N rates corresponded to a decline in early-season fertilizer N recovery in the relatively slow turnover topsoil mineral-associated organic matter pool (0-15 cm), while increasing NREcrop from intermediate to high historical N rates corresponded to an increase in early-season fertilizer N recovery in the relatively fast turnover topsoil particulate organic matter pool and an increase in crop yield potential. Despite the variation in NREcropalong the historical N rate gradient, we did not detect an effect of historical N rate on environmental losses during the growing season, which averaged 34% and 69% of fertilizer N inputs at the central and southern locations, respectively (69 kg N ha−1 and 185 kg N ha−1, respectively). Our results suggest that, while beneficial for SOC storage over the long term, fertilizing at the agronomic optimum N rate can lead to significant environmental N losses. . "Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize." Agriculture, Ecosystems & Environment 265 (2018): 544-555. A B S T R A C TNitrogen fertilizer management can impact soil organic C (SOC) stocks in cereal-based cropping systems by regulating crop residue inputs and decomposition rates. However, the impact of long-term N fertilizer management, and associated changes in SOC quantity and quality, on the fate of N fertilizer inputs is uncertain. Using two 15-year N fertilizer rate experiments on continuous maize (Zea mays L.) in Iowa, which have generated gradients of SOC, we evaluated the legacy effects of N fertilizer inputs on the fate of added N. Across the historical N fertilizer rates, which ran...

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“…Such results often lead to fertilizer overapplication in agricultural systems (Liu et al 2010) and then to N losses from leaching and denitrification. While gross rates of mineralization are higher and may better correlate with plant N uptake (Osterholz et al 2016), they are rarely measured at the temporal and spatial scales that are needed to resolve the complex processes that regulate bioavailable N. In addition, many natural ecosystems exhibit a ''missing sink'' phenomenon wherein soils store more N than can be accounted for by N budgeting (Bernal et al 2012;Yanai et al 2013;van Groenigen et al 2015). This suggests there are other pathways of N storage and production that are not adequately represented by standard laboratory measures of N availability.…”

Section: Introductionmentioning

confidence: 99%

Minerals in the rhizosphere: overlooked mediators of soil nitrogen availability to plants and microbes

et al. 2018

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Despite decades of research progress, ecologists are still debating which pools and fluxes provide nitrogen (N) to plants and soil microbes across different ecosystems. Depolymerization of soil organic N is recognized as the rate-limiting step in the production of bioavailable N, and it is generally assumed that detrital N is the main source. However, in many mineral soils, detrital polymers constitute a minor fraction of total soil organic N. The majority of organic N is associated with clay-sized particles where physicochemical interactions may limit the accessibility of N-containing compounds. Although mineralassociated organic matter (MAOM) has historically been considered a critical, but relatively passive, reservoir of soil N, a growing body of research now points to the dynamic nature of mineral-organic associations and their potential for destabilization. Here we synthesize evidence from biogeoscience and soil ecology to demonstrate how MAOM is an important, yet overlooked, mediator of bioavailable N, especially in the rhizosphere. We highlight several biochemical strategies that enable plants and microbes /doi.org/10.1007/s10533-018-0459-5 to disrupt mineral-organic interactions and access MAOM. In particular, root-deposited low-molecularweight exudates may enhance the mobilization and solubilization of MAOM, increasing its bioavailability. However, the competitive balance between the possible fates of N monomers-bound to mineral surfaces versus dissolved and available for assimilation-will depend on the specific interaction between mineral properties, soil solution, mineral-bound organic matter, and microbes. Building off our emerging understanding of MAOM as a source of bioavailable N, we propose a revision of the Schimel and Bennett (Ecology 85:591-602, 2004) model (which emphasizes N depolymerization), by incorporating MAOM as a potential proximal mediator of bioavailable N.123 Biogeochemistry (2018) 139:103-122 https:/

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Can mineralization of soil organic nitrogen meet maize nitrogen demand?

Cited by 63 publications

References 63 publications

Nitrogen Fertilizer Suppresses Mineralization of Soil Organic Matter in Maize Agroecosystems

Nitrogen Fertilizer Suppresses Mineralization of Soil Organic Matter in Maize Agroecosystems

Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize

Minerals in the rhizosphere: overlooked mediators of soil nitrogen availability to plants and microbes

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