scholarly journals Different root exudates C/N ratios accelerate CO2 emission from paddy soil

2021 ◽  
Author(s):  
Guan Cai ◽  
Muhammad Shahbaz ◽  
Tida Ge ◽  
yajun Hu ◽  
Baozhen Li ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Root Exudates ◽  
Paddy Soil ◽  
Co2 Emission ◽  
Extracellular Enzymes ◽  
High Energy ◽  
Organic N ◽  
C Mineralization ◽  
Organic C ◽  
Stoichiometric Ratios

Root exudates can greatly modify microbial activity and soil organic matter (SOM) mineralization. However, the mechanism of root exudation and its stoichiometric ratio of C/N controlling upon paddy soil C mineralization are poorly understand. In this study, we used a mixture of glucose, oxalic acid, and alanine as root exudate mimics, employing three C/N stoichiometric ratios (CN6, CN10, and CN80) to explore the underlying mechanisms involved in C mineralization. The input of root exudates enhanced CO2 emission by 1.8–2.3-fold than that of the control. Artificial root exudates with low C/N ratios (CN6 and CN10) increased the metabolic quotient (qCO2) by 12% over those obtained at higher stoichiometric ratios (CN80 and C-only), suggesting a relatively high energy demand for microorganisms to acquire organic N from SOM by increasing N-hydrolase production. The stoichiometric ratios of enzymes (β-1,4-glucosidase to β-1,4-N-acetyl glucosaminidase) promoting organic C degradation compared to those involved in organic N degradation showed a significant positive correlation with qCO2; the stoichiometric ratios of microbial biomass (MBC/MBN) were positively correlated with carbon use efficiency. This suggests that root exudates with higher C/N ratios entail an undersupply of N for microorganisms, triggering the release of N-degrading extracellular enzymes. This in turn decreases SOM mineralization, implying the C/N ratio of root exudates to be a controlling factor. Our findings show that the C/N stoichiometry of root exudates controls C mineralization by the specific response of the microbial biomass through the release of C- and N-releasing extracellular enzymes to adjust for the microbial C/N ratio.

Effects of different stoichiometric ratios on mineralisation of root exudates and its priming effect in paddy soil

2020 ◽  
Vol 743 ◽  
pp. 140808
Author(s):  
Linsen Du ◽  
Zhenke Zhu ◽  
Yanting Qi ◽  
Dongsheng Zou ◽  
Guolin Zhang ◽  
...  
Keyword(s):  
Root Exudates ◽  
Paddy Soil ◽  
Priming Effect ◽  
Stoichiometric Ratios

scholarly journals Wheat Straw Incorporation Affecting Soil Carbon and Nitrogen Fractions in Chinese Paddy Soil

Agriculture ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 803
Author(s):  
Wei Dai ◽  
Jun Wang ◽  
Kaikai Fang ◽  
Luqi Cao ◽  
Zhimin Sha ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Wheat Straw ◽  
Paddy Soil ◽  
Rice Paddy ◽  
Water Soluble ◽  
Microbial Biomass N ◽  
Rice Grain ◽  
Organic C ◽  
Straw Incorporation ◽  
N Fractions

Soil organic carbon (SOC) and nitrogen (N) fractions greatly affect soil health and quality. This study explored the effects of wheat straw incorporation on Chinese rice paddy fields with four treatments: (1) a control (CK), (2) a mineral NPK fertilizer (NPK), (3) the moderate wheat straw (3 t ha−1) plus NPK (MSNPK), and (4) the high wheat straw (6 t ha−1) plus NPK (HSNPK). In total, 0–5, 5–10, 10–20, and 20–30 cm soil depths were sampled from paddy soil in China. Compared with the CK, the HSNPK treatment (p < 0.05) increased the C fraction content (from 13.91 to 53.78%), mainly including SOC, microbial biomass C (MBC), water-soluble organic C (WSOC), and labile organic C (LOC) in the soil profile (0–30 cm), and it also (p < 0.05) increased the soil N fraction content (from 10.70 to 55.31%) such as the soil total N (TN) at 0–10 cm depth, microbial biomass N (MBN) at 0–20 cm depth, total water-soluble N (WSTN) at 0–5 and 20–30 cm depths, and total labile N (LTN) at 0–30 cm depth. The primary components of soil LOC and LTN are MBC and MBN. Various soil C and N fractions positively correlated with each other (p < 0.05). The HSNPK treatment promoted the soil MBC, WSOC, and LOC to SOC ratios, and also promoted MBN, WSTN, and LTN to soil TN ratios at a depth of 0–20 cm. To summarize, the application of HSNPK could maintain and improve rice paddy soil quality, which leads to increased rice grain yields.

scholarly journals Mulching with pruned fronds promotes the internal soil N cycling and soil fertility in a large-scale oil palm plantation

2021 ◽  
Author(s):  
Greta Formaglio ◽  
Edzo Veldkamp ◽  
Muhammad Damris ◽  
Aiyen Tjoa ◽  
Marife D. Corre
Keyword(s):  
Microbial Biomass ◽  
Soil Fertility ◽  
Oil Palm ◽  
Large Scale ◽  
Management Practices ◽  
N Cycling ◽  
Organic N ◽  
Soil N ◽  
Total N ◽  
Organic C

AbstractIntensive management practices in large-scale oil palm plantations can slow down nutrient cycling and alter other soil functions. Thus, there is a need to reduce management intensity without sacrificing productivity. The aim of our study was to investigate the effect of management practices on gross rates of soil N cycling and soil fertility. In Jambi province, Indonesia, we established a management experiment in a large-scale oil palm plantation to compare conventional practices (i.e. high fertilization rates and herbicide weeding) with reduced management intensity (i.e. reduced fertilization rates and mechanical weeding). Also, we compared the typical management zones characterizing large-scale plantations: palm circle, inter-row and frond-stacked area. After 1.5 years of this experiment, reduced and conventional management showed comparable gross soil N cycling rates; however, there were stark differences among management zones. The frond-stacked area had higher soil N cycling rates and soil fertility (high microbial biomass, extractable C, soil organic C, extractable organic N, total N and low bulk density) than inter-row and palm circle (all p ≤ 0.05). Microbial biomass was the main driver of the soil N cycle, attested by its high correlation with gross N-cycling rates (r = 0.93–0.95, p < 0.01). The correlations of microbial N with extractable C, extractable organic N, soil organic C and total N (r = 0.76–0.89, p < 0.01) suggest that microbial biomass was mainly regulated by the availability of organic matter. Mulching with senesced fronds enhanced soil microbial biomass, which promoted nutrient recycling and thereby can decrease dependency on chemical fertilizers.

Different forms and rates of nitrogen addition show variable effects on the soil hydrolytic enzyme activities in a meadow steppe

Soil Research ◽  
2020 ◽  
Vol 58 (3) ◽  
pp. 258
Author(s):  
Chengliang Wang ◽  
Baoku Shi ◽  
Wei Sun ◽  
Qingcheng Guan
Keyword(s):  
Microbial Biomass ◽  
Enzyme Activities ◽  
Hydrolytic Enzyme ◽  
Soil Enzyme ◽  
Organic N ◽  
Microbial Biomass C ◽  
N Addition ◽  
Meadow Steppe ◽  
Soil Enzyme Activities ◽  
Organic C

The effects of mixed inorganic and organic nitrogen (N) addition on soil enzyme activities and the underlying mechanism remain unclear, especially in complex field conditions. We conducted a mesocosm experiment with two rates of N addition (10 and 20 g N m–2 year–1) and four ratios of N addition (inorganic N:organic N = 10:0, 7:3, 3:7 and 1:9) and measured enzyme activities, soil physicochemical properties, microbial biomass and vegetation indicators. Generally, soil enzyme activities involved in carbon (C), N and phosphorus cycling increased with the increase of N addition rate. Compared to the single inorganic N addition treatment, enzyme activities were highest under mixed N addition treatments, especially medium organic N addition. The variations in soil enzyme activities across different treatments were tightly linked to the soil microbial biomass C, dissolved organic C and soil pH. These findings provide a good understanding of the response trends of soil hydrolytic enzyme activities in a meadow steppe to changes in N deposition rate and form.

C:N:P stoichiometry regulates soil organic carbon mineralization and concomitant shift of microbial community in paddy soil

2020 ◽  
Author(s):  
Zhenke Zhu ◽  
Xiaomeng Wei ◽  
Tida Ge ◽  
Jinshui wu ◽  
Andreas Richter
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Keystone Species ◽  
C Mineralization ◽  
Microbial Activities ◽  
P Fertilization ◽  
C:N:P Stoichiometry ◽  
Stoichiometric Ratios ◽  
Soc Mineralization

&lt;p&gt;Soil carbon (C), nitrogen (N), and phosphorus (P) contents and their stoichiometric ratios play modifying the microbial metabolism of C. Microbial populations vary in their strategies for C and nutrient acquisition to maintain the microbial biomass C:N:P balance. However, the regulation of soil C mineralization and microbial activities by stoichiometric ratios in input substrates becomes unpredictable in flooded soils because of the frequent redox fluctuations and general oxygen limitation. Stoichiometric control on input substrate (glucose) and soil organic carbon (SOC) mineralization were assessed by a manipulation experiment based on N or P fertilization in paddy soil. Glucose mineralization increased by nutrient addition up to 11.6% with combined N and P applications compared with addition without nutrients. During 100-days incubation, about 4.5% of SOC was mineralized in all five treatments, being increased by glucose and reduced by P fertilization. Glucose and SOC mineralization increased exponentially with the dissolved organic carbon (DOC):NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;-N, DOC:Olsen P, and microbial biomass (MB)C:MBN ratios. The glucose mineralization was negatively associated with the MBC:MBP ratio, suggesting that P addition relieved P limitation for microorganisms and increased microbial activities of labile C mineralization. The shift of bacterial community structure was significantly affected by the soil available and microbial biomass C:N:P stoichiometric ratios. The decrease of negative associations between bacterial taxa in the P-added soil indicated that microbial competition for nutrients was alleviated. 16S rRNA amplicon sequencing showed that combined C and nutrients application stimulated the Clostridia and &amp;#946;-Proteobacteria (r strategists) and increased the enzyme activities of &amp;#946;-glucosidase and &amp;#946;-acetyl-glucosaminidase. In contrast, after 100-day incubation, when the available substrate was exhausted, Syntrophus (K strategist) was found as the keystone species. Hence, soil microbial communities shifted their keystone species to acquire necessary elements to maintain the microbial biomass C:N:P stoichiometric balance in response to the change of resource C:N:P stoichiometry.&lt;/p&gt;

scholarly journals Rhizosphere priming of two near-isogenic wheat lines varying in citrate efflux under different levels of phosphorus supply

2019 ◽  
Vol 124 (6) ◽  
pp. 1033-1042 ◽  
Author(s):  
Qiao Xu ◽  
Xiaojuan Wang ◽  
Caixian Tang
Keyword(s):  
Microbial Biomass ◽  
Root Exudates ◽  
Root Exudation ◽  
Mineral Dissolution ◽  
Microbial Biomass C ◽  
Inorganic N ◽  
Organic C ◽  
Extractable P ◽  
Water Extractable ◽  
Citrate Efflux

Abstract Backgrounds and Aims The rhizosphere priming effect (RPE) has been explained from the perspective of microbial responses to root exudates and nutrient availability. This study introduced a chemical process that could also contribute to RPE: root exudates (organic acid ligands) could liberate mineral-protected carbon (C) in soil for microbial degradation. Methods Wheat (Triticum aestivum L.) near-isogenic lines varying in citrate efflux were grown for 6 weeks in a C4 soil supplied with either low (10 μg g–1) or high P (40 μg g–1). Total below-ground CO2 was trapped and partitioned for determination of soil organic C decomposition and RPE using a stable isotopic tracing technique. Mineral dissolution was examined by incubating soil with citric ligand at a series of concentrations. Key Results High P increased RPE (81 %), shoot (32 %) and root biomass (57 %), root-derived CO2-C (20 %), microbial biomass C (28 %) and N (100%), soil respiration (20 %) and concentrations of water-extractable P (30 %), Fe (43 %) and Al (190 %), but decreased inorganic N in the rhizosphere. Compared with Egret-Burke, wheat line Egret-Burke TaMATE1B with citrate efflux had lower inorganic N, microbial biomass C (16 %) and N (30 %) in the rhizosphere but greater RPE (18 %), shoot biomass (12 %) and root-derived CO2-C (low P 36 %, high P 13 %). Egret-Burke TaMATE1B also had higher concentrations of water-extractable P, Fe and Al in the rhizosphere, indicating the release of mineral-protected C. In addition, citrate ligand facilitated Fe and Al release from soil, with their concentrations rising with increasing ligand concentration and incubation time. Conclusions While high P supply increased microbial growth and RPE possibly due to higher total root exudation, citrate efflux from the root might have facilitated the liberation of mineral-bound C, leading to the higher RPE under Egret-Burke TaMATE1B. Mineral dissolution may be an important process that regulates RPE and should be considered in future RPE research.

BIOLOGICAL PROPERTIES OF SOME PRINCE EDWARD ISLAND SOILS: RELATIONSHIP BETWEEN MICROBIAL BIOMASS NITROGEN AND MINERALIZABLE NITROGEN

1987 ◽  
Vol 67 (2) ◽  
pp. 333-340 ◽  
Author(s):  
M. R. CARTER ◽  
J. A. MACLEOD
Keyword(s):  
Microbial Biomass ◽  
N Mineralization ◽  
Prince Edward Island ◽  
Organic N ◽  
Microbial Biomass N ◽  
Soil N ◽  
Mineral N ◽  
Organic C ◽  
Mineralization Potential ◽  
N Mineralization Potential

The mineral N flush, a measure of microbial biomass N, and the N mineralization potential (No) were determined in eight representative agricultural soils (Humo-Ferric Podzols and Gray Luvisols) of Prince Edward Island. The acidic (pH 5.0–5.8) soils, varying in texture from loam to loamy sand had an organic C range of 0.75–2.74%. Both mineral N flush (4–38 μg N g−1 soil) and the percentage soil organic N in the mineral N flush (0.4–2.0%) were relatively low compared to other studies. This observation was related to the generally low pH range of these soils. Potentially mineralizable soil N (No) ranged from 44 to 247 μg N g−1 and accounted for 4.5–13.3% of the total soil organic N. The No was closely related to the mineral N flush (r2 = 0.94) but poorly related to percent organic matter (r2 = 0.26) or organic N (r2 = 0.38). The results indicate that for these soils of similar properties, with low levels of residual mineral N, the mineral N flush could be utilized as an indirect measure of the soil N mineralization potential. Key words: Biomass C, mineral N flush, N mineralization potential, Podzolic soil, Luvisolic soil

scholarly journals Nitrogen and Carbon Mineralization Dynamics of Manures and Composts

HortScience ◽  
2000 ◽  
Vol 35 (2) ◽  
pp. 209-212 ◽  
Author(s):  
T.K. Hartz ◽  
J.P. Mitchell ◽  
C. Giannini
Keyword(s):  
Festuca Arundinacea ◽  
Carbon Mineralization ◽  
Plant Residue ◽  
Organic N ◽  
N Recovery ◽  
Net N Mineralization ◽  
C Mineralization ◽  
Mineral N ◽  
Organic C ◽  
Manure Compost

Nitrogen and carbon mineralization rates of 19 manure and compost samples were determined in 1996, with an additional 12 samples evaluated in 1997. These organic amendments were mixed with a soil: sand blend at 2% by dry weight and the amended blends were incubated at constant moisture for 12 (1996) or 24 weeks (1997) at 25 °C. Net N mineralization was measured at 4- (1996) or 8-week (1997) intervals, C mineralization at 4-week intervals in 1997. Pots of the amended blends were also seeded with fescue (Festuca arundinacea Shreb.) and watered, but not fertilized, for 17 (1996) or 18 weeks (1997); N phytoavailability was estimated from fescue biomass N and mineral N in pot leachate. An average of 16%, 7%, and 1% of organic N was mineralized in 12 weeks of incubation in 1996, and an average of 15%, 6%, and 2% in 24 weeks of incubation in 1997, in manure, manure compost, and plant residue compost, respectively. Overall, N recovery in the fescue assay averaged 11%, 6%, and 2% of total amendment N for manure, manure compost, and plant residue compost, respectively. Mineralization of manure C averaged 35% of initial C content in 24 weeks, while compost C mineralization averaged only 14%. Within 4 (compost) or 16 weeks (manure), the rate of mineralization of amendment C had declined to a level similar to that of the soil organic C.

Microbial and biochemical changes induced by rotation and tillage in a soil under barley production

1993 ◽  
Vol 73 (1) ◽  
pp. 39-50 ◽  
Author(s):  
D. A. Angers ◽  
N. Bissonnette ◽  
A. Légère ◽  
N. Samson
Keyword(s):  
Alkaline Phosphatase ◽  
Organic Matter ◽  
Microbial Biomass ◽  
Phosphatase Activity ◽  
Alkaline Phosphatase Activity ◽  
Soil Layer ◽  
Red Clover ◽  
Organic C ◽  
Top Soil ◽  
Total Organic C

Crop rotations and tillage practices can modify not only the total amount of organic matter (OM) in soils but also its composition. The objective of this study was to determine the changes in total organic C, microbial biomass C (MBC), carbohydrates and alkaline phosphatase activity induced by 4 yr of different rotation and tillage combinations on a Kamouraska clay in La Pocatière, Quebec. Two rotations (continuous barley (Hordeum vulgare L.) versus a 2-yr barley–red clover (Trifolium pratense L.) rotation) and three tillage treatments (moldboard plowing (MP), chisel plowing (CP) and no-tillage (NT)) were compared in a split-plot design. Total organic C was affected by the tillage treatments but not by the rotations. In the top soil layer (0–7.5 cm), NT and CP treatments had C contents 20% higher than the MP treatment. In the same soil layer, MBC averaged 300 mg C kg−1 in the MP treatment and up to 600 mg C kg−1 in the NT soil. Hot-water-extractable and acid-hydrolyzable carbohydrates were on average 40% greater under reduced tillage than under MP. Both carbohydrate fractions were also slightly larger in the rotation than in the soil under continuous barley. The ratios of MBC and carbohydrate C to total organic C suggested that there was a significant enrichment of the OM in labile forms as tillage intensity was reduced. Alkaline phosphatase activity was 50% higher under NT and 20% higher under CP treatments than under MP treatment and, on average, 15% larger in the rotation than in the continuous barley treatment. Overall, the management-induced differences were slightly greater in the top layer (0–7.5 cm) than in the lower layer of the Ap horizon (7.5–15 cm). All the properties measured were highly correlated with one another. They also showed significant temporal variations that were, in most cases, independent of the treatments. Four years of conservation tillage and, to a lesser extent, rotation with red clover resulted in greater OM in the top soil layer compared with the more intensive systems. This organic matter was enriched in labile forms. Key words: Soil management, soil quality, organic matter, carbohydrates, microbial biomass, phosphatase

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