Soil Carbohydrate Content Research Articles

Effect of continuous planting on Casuarina equisetifolia rhizosphere soil physicochemical indexes, microbial functional diversity and metabolites.

Continuous planting has a severe impact on the growth of Casuarina equisetifolia. In this study, the effects of three different long-term monocultures (one, two and three replanting) on the physicochemical indexes, microbial functional diversity, and soil metabolomics were analyzed in C. equisetifolia rhizosphere soil. The results showed that rhizosphere soil organic matter content, cation exchange capacity, total and available nitrogen, total and available phosphorus, and total and available potassium contents significantly decreased with the increasing number of continuous plantings. The evaluation of microbial functional diversity revealed a reduction in the number of soil microorganisms that rely on carbohydrates for carbon sources and an increase in soil microorganisms that used phenolic acid, carboxylic acid, fatty acid, and amines as carbon sources. Soil metabolomics analysis showed a significant decrease in soil carbohydrate content and a significant accumulation of autotoxic acid, amine, and lipid in the C. equisetifolia rhizosphere soil. Consequently, the growth of C. equisetifolia could hinder total nutrient content and their availability. Thus, valuable insights for managing the cultivation of C. equisetifolia and soil remediation were provided.

The Mineral Biochar Alters the Biochemical and Microbial Properties of the Soil and the Grain Yield of Hordeum vulgare L. under Drought Stress

Biochar improves soil physical, biochemical, and microbial properties, leading to the amelioration of soil fertility, which, in turn, results in better growth and yield in crop plants. The current study aimed to evaluate whether using different levels of biochar can enhance soil characteristics and plant attributes. Accordingly, an experimental study was conducted in 2022 using a randomized complete block design with four replications (n = 4) in the experimental glasshouse of the University of Zanjan, in which two regimes of irrigation (D0, full irrigation as the control; D1, water scarcity was applied immediately after the flowering stage for two weeks) and four levels of natural mineral biochar (0% as the control treatment, 0.25, 0.5, and 1% of soil weight) were applied. The results indicated that drought substantially decreased the organic carbon content of the soil and the grain yield while increasing the available phosphorous, soil carbohydrate content, and microbial biomass of the soil. Biochar could considerably alter the means of the studied soil quality parameters and the barley grain yield. Adding biochar could be considered a valid strategy to increase the resistance of plants to drought.

Soil carbohydrate and aggregation as affected by carbohydrate composition of paper mill biosolids

Paper mill biosolids (PB) are recognized as a valuable source of carbon for the physical improvement of arable soils. However, little is known about the composition of carbohydrates of these materials and their breakdown in soil, which contributes to soil structural stability. The objectives of this study were to characterize the carbohydrates in PB and to determine under controlled conditions and in the field the soil carbohydrate content and water-stable aggregation. The field experiment consisted of PB applied every year (2000–2008) at 0, 30, and 60 Mg wet weight·ha−1 to annual row crops with soils collected after 3, 6, and 9 yr. The other experiment consisted of PB added at 50 Mg wet weight·ha−1 to two soils, a clay and a sandy loam, and incubated at 25 °C and 60% water-filled pore space for 16 wk. The PB differed in their content in galactose, mannose, and arabinose for total fraction and sum of carbohydrates for water-soluble fraction. In the field, repeated annual PB application increased most of soil total carbohydrates (sum and individuals) after 3 yr and the proportion of >1 mm stable aggregates. The incubation study confirmed results obtained in the field, where the PB richest in carbohydrates induced the highest increases in soil total carbohydrates in both soil types. Soil total and microbial (galactose and mannose)-derived carbohydrates were closely correlated with the percentage of large aggregates, while with water-soluble carbohydrates, they are highly correlated to the amount of microbial carbohydrates applied, thus further contributing to improve soil C quality.

Effect of long-term fertilization on bacterial community in a sandy loam soil and its relation to organic carbon accumulation

Fertilization can affect the transformation of soil organic carbon (SOC) and soil microbial community composition. However, thus far, how SOC accumulation in association with bacterial community is still unclear. We collected arable soils (aquic inceptisol) from a long-term fertilization experiment (20 years) including compost (CM), inorganic nitrogen + phosphorus + potassium (NPK), half compost N plus half inorganic fertilizer N (HCM), NP, NK, PK, and untreated (Control). We investigated the relationship between the SOC accumulation rate and bacterial community composition measured by high-throughput sequencing. The highest SOC accumulation rate was observed in the compost treatments. Furthermore, compost and balanced NPK treatments increased soil carbohydrate content significantly (P < 0.05), while no such enhancement was observed following NK and PK application. Compared with the Control, fertilization substantially reduced the effective diffusion coefficient of oxygen in soil. Meanwhile, fertilization lowered the relative abundance (RA) of Bacteroidetes but increased the RA of Proteobacteria. Compost application increased the RA of Firmicutes, while inorganic fertilizers reduced it. The RA of Proteobacteria and Firmicutes were significantly and positively correlated with the SOC and carbohydrate content and the SOC accumulation rate (P < 0.05). SOC accumulation was also accompanied with the reduction in the effective diffusion coefficient of oxygen in soil. Our results indicated that poor aeration may induce a shift in the microbial community composition and a transition from aerobic to anaerobic degradation of SOC, thereby favoring SOC accumulation.

Changes in soil nutrient content and enzymatic activity under conventional and zero-tillage practices in an Indian sandy clay loam soil

For 3 years we studied the impact of different tillage practices on biological activity, major nutrient transformation potential in a sandy clay loam soil and crop yield in a Himalayan subtemperate region. Field agroecosystems with a rotation of two grain crops per year (lentil-finger millet) received four different tillage practices: zero–zero (ZZ), conventional–conventional (CC), zero–conventional (ZC), and conventional–zero (ZC) tillage. Most of the chemical parameters were influenced by the type of tillage practice. ZZ increased the soil organic carbon (SOC) content in the upper soil layer from 6.8 to 7.5 mg g−1 soil. Similarly available N was increased by 6.1% in ZZ over CC. Under zero tillage soil generally had higher P and K content than under other tillage practices. Soil carbohydrate content was also increased from 3.1 to 4.9 mg g−1 and dehydrogenase activity was also increased significantly under continuous zero-tillage practice. Alkaline phosphatase, protease, and cellulase were most sensitive to changes due to tillage management. Alkaline phosphatase and protease activity was greater (by 9.3–48.1%) in the zero-tillage system over conventional practice. In contrast, cellulase activity was more (by 31.3–74.6%) in conventional practice than other management practices. We suggest that, by understanding the effects of tillage on soil biological properties, soil quality and agricultural sustainability of subtemperate hill agro-ecosystems may be improved.

Carbohydrates in hot water extracts of soil aggregates as influenced by long-term management

Microbial carbohydrates are immediate by-products of microbial metabolism and play an important role in the formation and stabilization of soil structure. The effect of long-term management on soil carbohydrate content and monosaccharide composition was investigated in five Danish sandy loams under organic and conventional management with animal manure and mineral fertilizers. Hot-water (80°C) extraction was used to measure the distribution and composition of carbohydrates in aggregate size. Carbohydrates released to hot water were determined after hydrolysis as reducing sugars equivalent to glucose. The monosaccharide composition in hot-water extracts was analyzed as the corresponding alditol acetates. Sites with a history of long-term continuos management practices were used. Three treatments from the >100 year Askov long-term field experiment were used to show results of contrasting fertilization on soil carbohydrate content. These were all grown to a four-course crop rotation. Total carbohydrate content was significantly influenced by long-term management practices, with a significantly higher carbohydrate content in soils fertilized with either mineral fertilizers or animal manure (1200 to 800 mg C kg− 1 DM aggregate) than in an unfertilized soil (600 to 500 mg C kg− 1 DM aggregate). These results were as true for micro-aggregates (<0.25 mm) as for the 0.5–1.0 mm and 4.0–8.0 mm fractions. The organically managed soil (>40 years) was sited at a commercial farm with forage crop rotations, organic manure and no use of crop protection chemicals. These results showed significantly higher levels of carbohydrate both in micro-aggregate and macro-aggregates (1200 to 900 mg C kg− 1 DM aggregate) than an adjacent conventionally managed soil with annual cash crop, mineral fertilizers and use of crop protection chemicals (960 to 760 mg C kg− 1 DM aggregate). Carbohydrate C content generally increased as aggregate size decreased in both soils. Monosaccharide distribution was generally similar among three aggregate size classes studied. In all soils the content of monosaccharide was highest in microaggregates and lowest in macro-aggregates. Mannose and galactose were normally the most common monosaccharides in the hot-water extracts of aggregate fractions, indicating a predominantly microbial origin.

Plant residue biochemistry regulates soil carbon cycling and carbon sequestration

Substrate composition is one of the most important factors influencing the decomposition of plant residues in soils. The interaction of organic residue biochemistry with residue decomposition rates, soil aggregation and soil humus composition was determined in a laboratory experiment. Addition of seven different organic residues (2% w/w alfalfa, oat, canola, clover, soybean, corn and prairie grasses) to a Webster soil resulted in a rapid, transient increase in aggregate mean weight diameters (MWD) when incubated for 9 d with residues with low phenolic acid content (alfalfa, canola and clover) and was inversely correlated with soil carbohydrate content ( r=−0.63). More pronounced improvement in aggregate size was noted upon increased incubation to 84 d with organic residues higher in phenolic acid content (corn, prairie grasses, oat and soybean) and was related to soil phenolic acid ( r=0.65) and soil carbohydrate content ( r=0.70). Total plant residue phenolic acid content was related to MWD measured after incubation for 84 d by a quadratic response and plateau function ( r=0.96) and the MWD quadratically increased with an increase in vanillin-vanillic acid concentrations in the plant residues ( r=0.997). Soil organic C after 84 d was related to the MWD ( r=0.82) and the residue's vanillin-vanillic acid content ( r=0.86), suggesting that C remaining in the soil following decomposition maybe related to the specific phenolic acid content. The results suggest that transient aggregate stability initiated by microbial decomposition of the carbohydrate and amino acid content of the residue, is then strengthened by the interaction with phenolic acids such as vanillin or vanillic acid released by microbial decomposition from residues structural components.

Relations entre stabilité de l'agrégation et matière organique totale et soluble à l'eau chaude dans des sols ferrallitiques argileux (Congo, Brésil)

Organic matter (OM) generally plays an important role in soil aggregate stability. The objective of this work was to characterize the hot water-extractable OM and its role in the aggregate stability of clayey ferrallitic soils under different land use management. The macroaggregate (&gt;200 µm) stability of these soils was determined before (AS) and after hot-water extraction (ASe). The contents in total organic carbon and in carbon present as carbohydrates, as well as the sugar composition, were determined on the bulk soils and their hot-water extracts.The carbon and macroaggregate contents decreased upon land-clearing and cultivation, but to a lesser extent when some cultural practices were used. Whatever the situation considered, the hot-water extract always presented a higher carbohydrate content than the bulk soil. The high values of ratios r = (galactose + mannose)/(arabinose + xylose) suggested that a large proportion of carbohydrates was of microbial origin. There were significant correlations between AS and the carbon content of bulk soils or hot-water extracts, and between AS and the soil carbohydrate content. On the opposite, whatever the soil sample studied, no significant difference could be found between AS and ASe, showing that hot-water extractable OM had thus no clear aggregating role in these soils. Key words: Organic matter, macroaggregate stability, hot-water extraction, carbohydrates, ferrallitic soils

Hydraulic conductivity in soils irrigated with wastewaters of differing strengths: Field and laboratory studies

Application of wastewater can decrease the hydraulic conductivity of soils, and so reduce future loading rates. A possible mechanism for this decrease is blockage of soil pores by microbial growth and extracellular carbohydrate production. Our objective was to determine whether wastewater characteristics that increased microbial biomass and carbohydrate also decreased soil hydraulic conductivity. In field trials, irrigation of secondary-treated wastewater for 7 years onto a sandy soil increased carbohydrate, but had no effect on microbial C or unsaturated hydraulic conductivity, relative to non-irrigated soil. Irrigation of tertiary-treated wastewater for 5 years onto an allophanic soil had no significant effect on these soil characteristics. Effects on soil properties of wastewater with differing carbon : nitrogen (C : N) ratio were examined in the laboratory on repacked cores of the allophanic soil over 14 weeks. Unsaturated hydraulic conductivity decreased significantly in cores irrigated with the high C: N wastewater. These cores also exhibited an increase in soil carbohydrate content, microbial biomass, and respiration relative to cores irrigated with water. This study has demonstrated that the land treatment of industrial wastewaters of high C: N ratio and high biochemical oxygen demand could be problematic, even on freely draining soils.

Changes in microbial biomass C, soil carbohydrate composition and aggregate stability induced by growth of selected crop and forage species under field conditions

SUMMARYThe effects of growth of various crop and forage species on microbial biomass C, soil carbohydrate content and monosaccharide composition, and mean weight diameter (MWD) were investigated in two field experiments. One experiment was conducted over one growing season (4 months) whereas the other had been conducted for three consecutive growing seasons (32 months). In the four‐month experiment, aggregate stability (estimated as MWD) of soil from experimental plots followed the order Italian ryegrass &gt; prairie grass &gt; phacelia = pea = maize. At the 32‐month site the order was perennial ryegrass &gt; annual ryegrass &gt; perennial white clover = barley. At both sites crops with the greatest root mass and root length density had the greatest effect on increasing MWD. In all cases, rhizosphere soil had a significantly higher microbial biomass and MWD than non‐rhizosphere soil. However, organic C, total content of acid‐hydrolysable carbohydrate and content of individual monosaccharides in acid hydrolysates were similar in rhizosphere and non‐rhizosphere soil.The fraction of soil carbohydrate extractable with hot water (representing about 6‐8% of the total carbohydrate content) was significantly higher in the rhizosphere soil. This fraction has a galactose plus mannose over arabinose plus xylose ratio of 2.1–2.3 indicating that it was predominantly of microbial origin. It is suggested that the carbohydrate fraction extractable with hot water is made up of exocellular microbial polysaccharides that are involved in stabilizing soil aggregates in the rhizosphere. By comparison with arable crop species, grass species have a larger root mass and root length density, and therefore a higher microbial biomass and larger production of carbohydrate extractable with hot water. As a result they have a more marked effect on improving soil aggregate stability.

Direct determination of total soil carbohydrate content

A direct procedure for the determination of total soil carbohydrate content and a classic determination after acid hydrolysis, both employing the phenol-sulphuric acid method, are compared. The direct procedure enables simultaneous determination of mono-, oligo- and polysaccharides without prior hydrolysis. This procedure is reproducible and takes only a short period of time. The correlation between the proposed method and the classic one with hydrolysis was high (r2=0.9843; n=11; p=0.05).

EFFECTS OF CROPPING ON CARBOHYDRATE CONTENT AND WATER-STABLE AGGREGATION OF A CLAY SOIL

In a previous study, the mean weight diameter of water-stable aggregates of a clay soil was increased by up to 50% after two growing seasons under barley and alfalfa compared to fallow or corn. The objective of the present study was to determine whether rapid changes in water-stable aggregation under different crops were related to changes in soil carbohydrate content. Compared to fallow or corn, cropping to barley and alfalfa for 2 yr did not affect the soil C and N contents but significantly increased carbohydrate content by up to 25%. The correlation (r = 0.63, P = 0.001) between aggregate mean weight diameter and carbohydrate content suggested that at least part of the change in water-stable aggregation was related to carbohydrates. Treatment of the soil with sodium periodate prior to wet-sieving confirmed the partial involvement of carbohydrates in the stabilization of aggregates by crops. The remainder of the crop effect on aggregation was removed by sodium tetraborate which suggests that more-humified, though ill-defined, organic substances were also involved. Key words: Carbohydrates, aggregate stability, barley, alfalfa, corn, periodate

Population Dynamics of Chlamydomonas sajao and Its Influence on Soil Aggregate Stabilization in the Field

Chlamydomonas sajao, a single-celled, eucaryotic microalga, was inoculated onto replicated field plots cropped to corn at two rates (5 x 10 and 5 x 10 log-phase cells ha) to assess colonization, reproduction, and persistence, changes in soil carbohydrate content, and wet stability of 0.92- to 1.68-mm-sized aggregates from the surface 2- to 3-mm soil veneer. The most-probable-number technique and extraction and fluorometric quantification of chlorophyll were used as indices of microalgal abundance. Cell numbers ranged up to 6.9 x 10 g of soil by most probable number and were significantly greater on high-rate than on low-rate and control plots over a 10-week period. Chlorophyll content and most probable number were positively correlated (r = 0.64) for the high-rate plots but not for low-rate plots or the controls. Increased wet aggregate stability measurements (33 to 77%) for the high-rate plots during the growing season were significantly greater than for low-rate and control plots, which were not different from each other. The work leads support to the hypothesis that mass-cultured palmelloid microalgae are a feasible means for conditioning soil biologically.

MEASUREMENT OF THE POLYSACCHARIDE CONTENT OF SOILS

The polysaccharide content of two soils, measured by precipitating and weighing the microbial gums from the fulvic acid fraction of soil organic matter, and by colorimetric analyses using anthrone, was increased appreciably during the incubation of samples with straw. Applications of nitrogen and phosphorus altered only slightly the amount of polysaccharides present. The polysaccharide content of the amended soils increased rapidly during the first week of incubation and then levelled off.Peptization of the soil with dilute alkali prior to acid hydrolysis substantially increased the carbohydrates measured with anthrone. The anthrone reagent which measures primarily hexoses indicated a soil carbohydrate content of 10–15 per cent occurring in a range of Saskatchewan soils. Thirty-five per cent more carbohydrate carbon was found using the less specific phenol-sulphuric acid reagent.The acetone precipitated fraction from the fulvic acids accounted for only 10 per cent of the soil carbohydrates and contained a large proportion of ash and other non-carbohydrate materials. The total acid-soluble base-soluble fraction, fulvic acids, contained 15–25 per cent; the remainder was distributed in the alkali insoluble humin — 55–70 per cent and the humic acid fraction 4–12 per cent.