Dissolved organic nitrogen in contrasting agricultural ecosystems

Christou, M.; Avramides, Elizabeth J.; Roberts, John Park; Jones, Davey L.

doi:10.1016/j.soilbio.2005.01.025

Cited by 91 publications

(47 citation statements)

References 20 publications

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“…The WEOC:TDN ratio provides a hint of the quality of WEOM where the decline in WEOC:TDN ratio is usually associated with increased bioavailability of WEOM (Cookson et al, 2008). In the present study, the values of WEOC:TDN ranged from 7.28 to 9.30, lower than the reported range of 16 ± 4 for arable soils by Christou et al (2005). Concentrations of WEOC and TDN may differ depending upon the type of extracting solution used, presenting a challenge when comparing WEOM pools across studies (Carrillo-Gonzalez et al, 2013).…”

Section: Discussioncontrasting

confidence: 75%

Soil Organic Carbon Pools as Early Indicators for Soil Organic Matter Stock Changes under Different Tillage Practices in Inland Pacific Northwest

2017

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Soil organic matter (SOM) is essential for sustaining soil health and crop productivity. However, changes in SOM stocks in response to agronomic practices are slow and show years later when it is too late for adjustments in management. Identifying early indicators of SOM dynamics will allow early management decisions and quick remedial action. The objectives of this study were to evaluate long-term effects of tillage intensity and timing on SOM pools and determine the most responsive SOM pools to tillage practice. Soil from a long-term (53 years) winter wheat (Triticum aestivum L.)-spring pea (Pisum sativum L.) rotation and undisturbed grass pasture (GP) in inland Pacific Northwest (iPNW) was sampled to evaluate the effect of four tillage systems [no-till (NT), disk/chisel (DT/CT), spring plow (SP), and fall plow (FP)] on soil organic carbon (SOC, proxy for SOM), total nitrogen (TN), particulate organic matter carbon (POM-C) and nitrogen (POM-N), permanganate oxidizable carbon (POXC), water extractable organic carbon (WEOC), total dissolved nitrogen (TDN), KCl-extractable nitrogen (KEN), microbial biomass carbon (MBC) and nitrogen (MBN), basal respiration (BR), carbon mineralization (Cmin), and metabolic quotient (qCO 2 ). GP had higher levels of SOC pools than cultivated treatments. On average, tillage significantly decreased SOC and TN by 28 and 26%, respectively, compared to GP. Among the cultivated soils, tillage had no significant effect on SOC and TN, except for DT/CT that had slightly higher SOC than FP (P = 0.08). On the contrary, NT and DT/CT significantly (P < 0.05) increased levels of POM-C, POM-N, POXC, WEOC, MBC, BR, Cmin, and qCO 2 over FP or SP. However, tillage did not affect TDN, MBN, and KEN. The C-pools (POM-C, POXC, MBC, WEOC, BR, and Cmin) were more strongly correlated with SOM than the N-pools (TDN, MBN, and KEN), with an exception to POM-N. Under wheat-pea rotation in the iPNW, reduced tillage systems (NT and DT/CT) have a potential to maintain or increase SOM, which can be assessed early through its physical (POM), chemical (POXC, WEOC), and microbiological (MBC, BR, Cmin) indicators. POXC and WEOC were the most sensitive indicators of tillage-induced changes in SOM dynamics.

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Section: Discussioncontrasting

confidence: 75%

Soil Organic Carbon Pools as Early Indicators for Soil Organic Matter Stock Changes under Different Tillage Practices in Inland Pacific Northwest

2017

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“…The WEN is made of organic and inorganic N, and their proportion can be affected by the extraction protocol (Christou et al, 2005;Jones and Willet, 2006;Ros et al, 2009), but includes water extractable organic N (Ros et al, 2009), which is considered sensitive to cropping systems and management practices (Haynes, 2005). Further, thanks to its dual organic and inorganic nature, WEN (1) continuously interchanges among different organic and inorganic N forms, (2) is affected by microbial activity and processes such as fixation in organic compounds, mineralisation of organics, nitrification/denitrification, solubilisation, plant absorption, adsorption/desorption processes on organic and inorganic colloids (Kalbitz et al, 2000;Nannipieri and Eldor, 2009), and (3) is restored by organic matter inputs and root exudates.…”

Section: Effect Of Soil Management On the Content Of Different C And mentioning

confidence: 99%

Carbon and nitrogen in soil and vine roots in harrowed and grass-covered vineyards

Agnelli

Bol

Trumbore

et al. 2014

Agriculture, Ecosystems & Environment

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a b s t r a c tTo examine the effects of vineyard soil management on soil C and N content and quality, we studied harrowed and grass-covered vineyards on a soil developed on plio-pleistocene, marine sediments. A soil naturally covered by grasses adjacent to the vineyards served as control. To reach this goal, we assessed (1) the distribution of C and N and their 13 C and 15 N signatures in different soil organic matter pools, (2) the amount of C and N as live and dead vine fine roots and their 13 C, 15 N and 14 C signatures, and (3) the stocks of C and N forms accumulated at two soil-depth intervals (0-50 and 50-100 cm).Independent of the soil management, the vines increased the total organic C and total N content in the deeper soil horizons because of root turnover and rhizodeposition processes. In the upper horizons, a greater organic matter accumulation was fostered by the presence of the grass cover and the absence of tillage. The grass cover favoured the organic C storage mainly in the form of particulate and highly stabilised organic matter (humic acids and humin), and reduced the soil N content by plant uptake, whereas the harrowing produced a greater abundance of fulvic acids, which were mainly ascribed to oxidative processes enhanced by the soil tillage. In both vineyard soils, decaying vine roots represented an important source of organic C and N, especially in the deepest horizons. Indeed, isotope analyses revealed a more intense degradation of the dead vine roots in the deeper soil portion, where they likely constituted the main substrate for soil microorganisms. In the deepest horizons of the grass-covered vineyard, the greater mean residence time of the decaying vine roots and the lower root production were attributed to the easily available energetic substrates supplied by grass root turnover and rhizodeposition, which were preferentially used by microorganisms. This fact fostered a larger C accumulation in the grass-covered than in the harrowed vineyard.

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“…animal manure based, low-input or organic agriculture), amino acids may represent a large N input (El-Naggar et al, 2009) and an important plant-available N pool (Jones et al, 2002). Under such circumstances, a significant proportion of total N in the soil solution consists of dissolved organic N, including both free amino acids and complex, humic-rich soluble organic matter which has relatively low bioavailability (Christou et al, 2005). The distribution of free amino acids in soil may show considerable spatial heterogeneity due to, e.g.…”

Section: Introductionmentioning

confidence: 99%

Interactions between uptake of amino acids and inorganic nitrogen in wheat plants

2012

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Abstract. Soil-borne amino acids may constitute a source of nitrogen (N) for plants in various terrestrial ecosystems but their importance for total N nutrition is unclear, particularly in nutrient-rich arable soils. One reason for this uncertainty is lack of information on how the absorption of amino acids by plant roots is affected by the simultaneous presence of inorganic N forms. The objective of the present study was to study absorption of glycine (Gly) and glutamine (Gln) by wheat roots and their interactions with nitrate (NO − 3 ) and ammonium (NH + 4 ) during uptake. The underlying hypothesis was that amino acids, when present in nutrient solution together with inorganic N, may lead to down-regulation of the inorganic N uptake, thereby resulting in similar total N uptake rates. Amino acids were enriched with double-labelled 15 N and 13 C, while NO − 3 and NH + 4 acquisition was determined by their rate of removal from the nutrient solution surrounding the roots. The uptake rates of NO − 3 and NH + 4 did not differ from each other and were generally about twice as high as the uptake rate of organic N when the different N forms were supplied separately in concentrations of 2 mM. Nevertheless, replacement of 50 % of the inorganic N with organic N was able to restore the N uptake to the same level as that in the presence of only inorganic N. Co-provision of NO − 3 did not affect glycine uptake, while the presence of glycine down-regulated NO − 3 uptake. The ratio between 13 C and 15 N were lower in shoots than in roots and also lower than the theoretical values, reflecting higher C losses via respiratory processes compared to N losses. It is concluded that organic N can constitute a significant N-source for wheat plants and that there is an interaction between the uptake of inorganic and organic N.

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Dissolved organic nitrogen in contrasting agricultural ecosystems

Cited by 91 publications

References 20 publications

Soil Organic Carbon Pools as Early Indicators for Soil Organic Matter Stock Changes under Different Tillage Practices in Inland Pacific Northwest

Soil Organic Carbon Pools as Early Indicators for Soil Organic Matter Stock Changes under Different Tillage Practices in Inland Pacific Northwest

Carbon and nitrogen in soil and vine roots in harrowed and grass-covered vineyards

Interactions between uptake of amino acids and inorganic nitrogen in wheat plants

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