scholarly journals Effects of mowing dominant grasses on root exudation and soil nitrogen cycling in a natural sod culture apple orchard  

2021 ◽  
Author(s):  
Enda Zhou ◽  
Mingchuan Gou ◽  
Bo Yu ◽  
Chao Sun ◽  
Jiali He ◽  
...  
Keyword(s):  
Root Exudates ◽  
Soil Nitrogen ◽  
Root Exudation ◽  
Amoa Gene ◽  
Apple Orchard ◽  
N Cycling ◽  
Microbial Biomass N ◽  
N Content ◽  
T1 And T2 ◽  
Dominant Grasses

We evaluated the effects of mowing dominant grasses on root exudation and soil nitrogen (N) cycling by assessing metabolomics analysis of root exudates, microbial metabolism, the abundance of N-cycling-related prokaryotes, and different forms of N concentrations in soil. The treatments included Polygonum aviculare L. mowing (T1), Digitaria sanguinalis (L.) Scop. mowing (T2), and no mowing as the controls (CK1 and CK2). The results showed that compared with the no mowing control (CK1 and CK2), T1 and T2 root exudates contained 223 (178 up-regulated, 45 down-regulated) and 183 (40 up-regulated, 143 down-regulated) differential metabolites, respectively. The average well colour development (AWCD) could reflect the microbial metabolic activity. The AWCD values of T1 were increased while that of T2 decreased on the 2<sup>nd</sup> day after mowing. The variation in root exudates was the main reason for the change in soil AWCD values and carbon utilisation of T1 and T2 on the 2<sup>nd</sup> day after mowing. Mowing increased soil microbial biomass N content significantly in the T1 and T2 topsoil. The NO<sub>3</sub><sup>–</sup>-N and NH<sub>4</sub><sup>+</sup>-N contents in the 0–10 cm soil increased on the 2<sup>nd</sup> day after T1 mowing with an increase in the nitrogenase iron protein gene (nifH), glutamate dehydrogenase gene (gdh), ammonia monooxygenase gene (amoA) of ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB) abundance. However, NO<sub>3</sub><sup>–</sup>-N content decreased on the 2<sup>nd</sup> day after T2 mowing following a decrease in AOA-amoA and AOB-amoA gene abundance. The results of this study will facilitate the optimisation of sod culture orchard N management, reduction of N fertiliser input, and improvement of N utilisation efficiency.  

Nitrogen availability from peat amendments used in boreal oil sands reclamation

2010 ◽  
Vol 90 (1) ◽  
pp. 165-175 ◽  
Author(s):  
S S Hemstock ◽  
S A Quideau ◽  
D S Chanasyk
Keyword(s):  
Soil Nitrogen ◽  
Seasonal Variability ◽  
Oil Sands ◽  
Nitrogen Availability ◽  
Organic N ◽  
Soil Reclamation ◽  
Microbial Biomass N ◽  
Net Nitrification ◽  
Resin Core ◽  
Net Mineralization

Following surface mining, peat is typically used as an organic amendment to cap reconstructed soils in the Athabasca oil sands region of Alberta. Yet, very little is known about its ability to provide available nitrogen (N) in these soils. Hence, the overall objective of this study was to measure soil nitrogen (N) availability throughout the year in five peat amendments. Specific objectives were: (1) to examine seasonal variability in soil labile N pool sizes (nitrate, ammonium, dissolved organic N, and microbial biomass N), and (2) to determine in situ net nitrification, ammonification, and mineralization rates using the resin-core technique. Results from this field incubation method indicated a strong seasonal variability in net mineralization rates, with maximum positive values in the fall, and low or negative rates in winter. Net ammonification rates, which were significantly correlated to soil moisture content, were significantly smaller and showed smaller seasonal fluctuations and fewer differences among peat materials than net nitrification rates. Furthermore, the contribution of net nitrification to total net mineralization rates was characteristically higher than what is typically observed in undisturbed boreal forest soils. Taken together, results indicate that net nitrification processes may control nitrogen availability in these reclaimed soils.Key words: Soil nitrogen, soil reclamation, nitrification, mineralization, boreal soils

scholarly journals Stoichiometry constrains microbial response to root exudation- insights from a model and a field experiment in a temperate forest

2013 ◽  
Vol 10 (2) ◽  
pp. 821-838 ◽  
Author(s):  
J. E. Drake ◽  
B. A. Darby ◽  
M.-A. Giasson ◽  
M. A. Kramer ◽  
R. P. Phillips ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Microbial Biomass ◽  
Field Experiment ◽  
Microbial Activity ◽  
Root Exudates ◽  
Microbial Respiration ◽  
Root Exudation ◽  
N Availability ◽  
Rhizosphere Soils ◽  
Wide Range

Abstract. Plant roots release a wide range of chemicals into soils. This process, termed root exudation, is thought to increase the activity of microbes and the exoenzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The nitrogen (N) content of microbial biomass and exoenzymes may introduce a stoichiometric constraint on the ability of microbes to effectively utilize the root exudates, particularly if the exudates are rich in C but low in N. We combined a theoretical model of microbial activity with an exudation experiment to test the hypothesis that the ability of soil microbes to utilize root exudates for the synthesis of additional biomass and exoenzymes is constrained by N availability. The field experiment simulated exudation by automatically pumping solutions of chemicals often found in root exudates ("exudate mimics") containing C alone or C in combination with N (C : N ratio of 10) through microlysimeter "root simulators" into intact forest soils in two 50-day experiments. The delivery of C-only exudate mimics increased microbial respiration but had no effect on microbial biomass or exoenzyme activities. By contrast, experimental delivery of exudate mimics containing both C and N significantly increased microbial respiration, microbial biomass, and the activity of exoenzymes that decompose low molecular weight components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exoenzymes that degrade high molecular weight SOM (e.g., polyphenols, lignin). The modeling results were consistent with the experiments; simulated delivery of C-only exudates induced microbial N-limitation, which constrained the synthesis of microbial biomass and exoenzymes. Exuding N as well as C alleviated this stoichiometric constraint in the model, allowing for increased exoenzyme production, the priming of decomposition, and a net release of N from SOM (i.e., mineralization). The quantity of N released from SOM in the model simulations was, under most circumstances, in excess of the N in the exudate pulse, suggesting that the exudation of N-containing compounds can be a viable strategy for plant-N acquisition via a priming effect. The experimental and modeling results were consistent with our hypothesis that N-containing compounds in root exudates affect rhizosphere processes by providing substrates for the synthesis of N-rich microbial biomass and exoenzymes. This study suggests that exudate stoichiometry is an important and underappreciated driver of microbial activity in rhizosphere soils.

Plants colonized by AM fungi regulate further root colonization by AM fungi through altered root exudation

1999 ◽  
Vol 77 (6) ◽  
pp. 891-897 ◽  
Author(s):  
Alexandra Pinior ◽  
Urs Wyss ◽  
Yves Piché ◽  
Horst Vierheilig
Keyword(s):  
Root Exudates ◽  
Glomus Mosseae ◽  
Glomus Intraradices ◽  
Root Colonization ◽  
Root Exudation ◽  
Axenic Culture ◽  
Am Fungi ◽  
Hyphal Growth ◽  
Gigaspora Rosea ◽  
Stimulation Of

The effect of root exudates from non-mycorrhizal and mycorrhizal cucumber (Cucumis sativus L.) plants colonized by one of three arbuscular mycorrhizal fungi (Gigaspora rosea Nicolson & Schenck, Glomus intraradices Smith & Schenck, or Glomus mosseae (Nicolson & Gerdemann) Gerd. & Trappe) on hyphal growth of Gi. rosea and G. intraradices in axenic culture and on root colonization by G. mosseae in soil was investigated. Root exudates from non-mycorrhizal cucumber plants clearly stimulated hyphal growth, whereas root exudates from all mycorrhizal cucumber plants tested showed no stimulation of the hyphal growth of Gi. rosea and only a slight stimulation of the hyphal growth of G. intraradices. Moreover, root exudates from all mycorrhizal cucumber plants inhibited root colonization by G. mosseae compared with the water-treated controls. These results suggest that plants colonized by AM fungi regulate further mycorrhization via their root exudates.Key words: Glomales, Gigaspora rosea, Glomus intraradices, Glomus mosseae, root exudates, regulation.

The use of 15N-enriched feed to label pig excreta for N cycling studies

2004 ◽  
Vol 84 (1) ◽  
pp. 43-48 ◽  
Author(s):  
Martin H. Chantigny ◽  
Denis A. Angers ◽  
Candido Pomar ◽  
Thierry Morvan
Keyword(s):  
Swine Manure ◽  
Matter Content ◽  
N Cycling ◽  
Organic N ◽  
Dry Matter Content ◽  
Pig Slurry ◽  
Mineral N ◽  
N Content ◽  
Heterogeneous Distribution ◽  
N Concentration

Isotopic labelling can help improve our knowledge of the fate of manure N in agroecosystems. Our objective was to investigate the labelling dynamics of excreta N by feeding a pig with a 15N-enriched diet (2.808 atom % 15N) and to establish the implications of using the labelled excreta for N cycling studies. Pig urine and feces were collected and pooled each day for 20 d following the start of 15N-feeding. Each of the 20 excreta samples were analyzed for pH, dry matter content, C and N contents, and 15N distribution between the mineral and organic N pools. Sub-samples of each excreta sample were incubated for 84 d, and the 15N abundance of N mineralized after 7, 21 and 84 d of incubation was determined. The 15N concentration in pig excreta increased sharply during the first 3 d of 15N-feeding and slowly thereafter. The 15N concentration in excreta decreased rapidly when an unlabelled feed was served after 12 d of 15N-feeding. On the first day and after 9 d of 15N-feeding, the mineral and the organic N pools of the collected excreta had similar 15N content. However, from day 2 to 9 of 15N-feeding, the 15N abundance of excreta mineral N was 0.1 to 0.3 atom % lower than in the organic N pool. During incubation of the excreta samples, the 15N content of the mineralized N was 0.1 to 0.4 atom % lower after 84 d than after 21 d of incubation, indicating a heterogeneous distribution of 15N between the rapidly and the slowly mineralizable N pools of pig excreta. Despite some heterogeneity, the measured differences in 15N enrichment among the various excreta N pools were generally less than 15% for the first 9 d of 15N-feeding, and less than 5% afterwards. The labelled excreta were thus considered appropriate for short-term studies on the fate of manure N in the soil-plant system, especially for excreta collected after 9 d of 15N-feeding. Key words: 15N labelling, animal feeding, swine manure, pig slurry

Soil-plant nitrogen dynamics following incorporation of a mature rye cover crop in a lettuce production system

1995 ◽  
Vol 124 (1) ◽  
pp. 17-25 ◽  
Author(s):  
L. J. Wyland ◽  
L. E. Jackson ◽  
K. F. Schulbach
Keyword(s):  
Microbial Biomass ◽  
Cover Crop ◽  
Microbial Biomass N ◽  
N Availability ◽  
N Content ◽  
N Transformations ◽  
Total N ◽  
Mineralizable N ◽  
Biomass N ◽  
Bare Soils

SUMMARYWinter non-leguminous cover crops are included in crop rotations to decrease nitrate (NO3-N) leaching and increase soil organic matter. This study examined the effect of incorporating a mature cover crop on subsequent N transformations. A field trial containing a winter cover crop of Merced rye and a fallow control was established in December 1991 in Salinas, California. The rye was grown for 16 weeks, so that plants had headed and were senescing, resulting in residue which was difficult to incorporate and slow to decompose. Frequent sampling of the surface soil (0–15 cm) showed that net mineralizable N (anaerobic incubation) rapidly increased, then decreased shortly after tillage in both treatments, but that sustained increases in net mineralizable N and microbial biomass N in the cover-cropped soils did not occur until after irrigation, 20 days after incorporation. Soil NO3-N was significantly reduced compared to winter-fallow soil at that time. A 15N experiment examined the fate of N fertilizer, applied in cylinders at a rate of 12 kg 15N/ha at lettuce planting, and measured in the soil, microbial biomass and lettuce plants after 32 days. In the cover-cropped soil, 59% of the 15N was recovered in the microbial biomass, compared to 21% in the winter-bare soil. The dry weight, total N and 15N content of the lettuce in the cover-cropped cylinders were significantly lower; 28 v. 39% of applied 15N was recovered in the lettuce in the cover-cropped and winter-bare soils, respectively. At harvest, the N content of the lettuce in the cover-cropped soil remained lower, and microbial biomass N was higher than in winter-bare soils. These data indicate that delayed cover crop incorporation resulted in net microbial immobilization which extended into the period of high crop demand and reduced N availability to the crop.

scholarly journals Identification of Root-Secreted Compounds Involved in the Communication Between Cucumber, the Beneficial Bacillus amyloliquefaciens, and the Soil-Borne Pathogen Fusarium oxysporum

2017 ◽  
Vol 30 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Yunpeng Liu ◽  
Lin Chen ◽  
Gengwei Wu ◽  
Haichao Feng ◽  
Guishan Zhang ◽  
...  
Keyword(s):  
Fusarium Oxysporum ◽  
Root System ◽  
Root Exudates ◽  
Bacillus Amyloliquefaciens ◽  
Root Colonization ◽  
Plant Root ◽  
Root Exudation ◽  
Soil Borne Pathogens ◽  
Split Root System ◽  
Cucumber Roots

Colonization of plant growth–promoting rhizobacteria (PGPR) is critical for exerting their beneficial effects on the plant. Root exudation is a major factor influencing the colonization of both PGPR and soil-borne pathogens within the root system. However, the tripartite interaction of PGPR, plant roots, and soil-borne pathogens is poorly understood. We screened root exudates for signals that mediate tripartite interactions in the rhizosphere. In a split-root system, we found that root colonization of PGPR strain Bacillus amyloliquefaciens SQR9 on cucumber root was significantly enhanced by preinoculation with SQR9 or the soil-borne pathogen Fusarium oxysporum f. sp. cucumerinum, whereas root colonization of F. oxysporum f. sp. cucumerinum was reduced upon preinoculation with SQR9 or F. oxysporum f. sp. cucumerinum. Root exudates from cucumbers preinoculated with SQR9 or F. oxysporum f. sp. cucumerinum were analyzed and 109 compounds were identified. Correlation analysis highlighted eight compounds that significantly correlated with root colonization of SQR9 or F. oxysporum f. sp. cucumerinum. After performing colonization experiments with these chemicals, raffinose and tryptophan were shown to positively affect the root colonization of F. oxysporum f. sp. cucumerinum and SQR9, respectively. These results indicate that cucumber roots colonized by F. oxysporum f. sp. cucumerinum or SQR9 increase root secretion of tryptophan to strengthen further colonization of SQR9. In contrast, these colonized cucumber roots reduce raffinose secretion to inhibit root colonization of F. oxysporum f. sp. cucumerinum.

scholarly journals Spatial variability of total soil nitrogen and sulphur content at two conventionally managed fields

2008 ◽  
Vol 54 (No. 10) ◽  
pp. 413-419 ◽  
Author(s):  
V. Vaněk ◽  
J. Balík ◽  
J. Šilha ◽  
J. Černý
Keyword(s):  
Spatial Variability ◽  
Crop Yield ◽  
Soil Nitrogen ◽  
Coefficient Of Variation ◽  
Sulphur Content ◽  
N Content ◽  
Total N ◽  
Total Soil ◽  
Positive Correlations ◽  
Total Soil Nitrogen

Spatial variability of total soil nitrogen and sulphur content has been observed in two plots (I – 54 ha and II – 32 ha). Soil samples were taken from the topsoil in a regular grid, which was localised by GPS (individual sampling points were 80 m apart); subsequently total soil N and S contents were analysed. The average N content in plot I was 0.16%; in plot II it was 0.12%. The content of S in plots I and II was 0.09% and 0.08%, respectively. Spatial variability of total N differed in separate parts of the plots. A higher variability was recorded in plot I, where the coefficient of variation (<I>CV</I>) was 15.7%, whereas in plot II it was only 11.1%. However, sulphur showed only little variability, and thus its coefficient of variation was low (2.5 a 2.3% in plots I and II, respectively). A positive and mostly conclusive relationship has been observed between the N content of soil and the crop yield. This effect was more significant in plot II. The S content in soil showed no correlation with yield. Furthermore, positive correlations were observed between field altitude, soil moisture and crop yield in both plots.

Sorghum hybrid differences in grain yield and nitrogen concentration under low soil nitrogen availability. I. Hybrids with similar phenology

1998 ◽  
Vol 49 (8) ◽  
pp. 1267 ◽  
Author(s):  
A. Kamoshita ◽  
R. C. Muchow ◽  
M. Cooper ◽  
S. Fukai
Keyword(s):  
Leaf Senescence ◽  
Soil Nitrogen ◽  
N Uptake ◽  
Genotypic Variation ◽  
Grain Filling ◽  
N Availability ◽  
N Content ◽  
Available N ◽  
N Concentration ◽  
Application Rates

In Australia, grain sorghum [Sorghum bicolor (L.) Moench] hybrids are often grown under conditions of low soil nitrogen (N) availability with suboptimal levels of N fertiliser supplied. However, little is known about the traits that contribute to sorghum hybrid performance in environments with low available N. We examined plant traits that may contribute to adaptation of sorghum to low soil N conditions, and the influence of genotype × N environment interactions on yield and grain N concentration. Two experiments were conducted using 3–6 hybrids with similar phenology. Three N fertiliser application rates (0, 60, and 240 kg/ha) were used in Expt 1, and 2 application rates (0 and 60 kg/ha) were used in Expt 2. Hybrid yield was associated with plant N content at maturity. The ability of a hybrid to take up N continuously during grain filling, under N limiting conditions, was identified as an important component contributing to high yield. In the non-fertilised treatment of Expt 2, where plants suffered the most severe N limitation before anthesis (e.g. total plant N content at anthesis <3 g/m2), hybrid yield was associated with biomass production and duration of effective grain filling. The dependence of the expression of the higher N uptake trait on N availability and other environmental factors resulted in genotype × environment interactions for yield. Differences among hybrids in leaf senescence and grain growth rate had little effect on yield. Genotypic variation for grain N concentration was consistent across experiments for hybrids with and without the staygreen attribute. In Expt 2 the magnitude of leaf senescence and amount of N mobilised from leaf to grain were greater at 60 kg N/ha than in the non-fertilised treatment. In addition, the staygreen hybrid 72389–1-1–3/QL36 had a slower rate of leaf senescence, took up larger amounts of N after anthesis, and had higher grain N concentration (1·07%) than the senescent hybrids ATx623/RTx430 (0·95%) and QL41/69264–2-2–2 (0·90%).

An altered root exudation pattern through mycorrhization affecting microconidia germination of the highly specialized tomato pathogen Fusarium oxysporum f. sp. lycopersici (Fol) is not tomato specific but also occurs in Fol nonhost plants

2007 ◽  
Vol 85 (3) ◽  
pp. 347-352 ◽  
Author(s):  
Stephan Scheffknecht ◽  
Marc St-Arnaud ◽  
Thanasan Khaosaad ◽  
Siegrid Steinkellner ◽  
Horst Vierheilig
Keyword(s):  
Fusarium Oxysporum ◽  
Root Exudates ◽  
Glomus Mosseae ◽  
Arbuscular Mycorrhizal Fungus ◽  
Root Exudation ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Tomato Pathogen

The effect of root exudates from plants colonized or noncolonized by the arbuscular mycorrhizal fungus Glomus mosseae on microconidia germination of Fusarium oxysporum f. sp. lycopersici (Fol) was studied. Root exudates from the Fol-host tomato and root exudates from Fol nonhost plants were tested. Root exudates from all tested plants stimulated microconidia germination. Mycorrhization increased the stimulatory effect exhibited by the root exudates from the Fol host tomato and from all Fol nonhost plants, showing that similar changes occur in the root exudates of all plants after mycorrhization.

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