Sugarcane Soil Research Articles

Registry of mermithid (Mermithidae) parasites of spittlebug nymphs (Hemiptera: Cercopidae) in sugarcane crops in Veracruz, Mexico

SObjective: To make known the presence of parasite mermithids of the spittlebug nymph in different sugarcanelocalities of the state of Veracruz, Mexico.Design/methodology/approach: The nematodes were collected in sugarcane soils after observation of theemergence of the pest from the spittlebug nymphs (in situ), while some others were obtained after collectingspittlebug nymphs in the field and the pest’s emergence in the laboratory. The death of the nematodes wasprovoked with hot water (sterile distilled, 60 °C), and they were measured and stored in Eppendorf tubes of 1.5mL in formaldehyde 4% and kept in refrigeration at 4 °C.Results: This report is presented as evidence of pest mermithids that emerge from the spittlebug nymph hostin sugarcane crops in eight localities of the state of Veracruz. Although their identification at the species levelcould not be done, the length of each mermithid found was recorded, as well as its relationship with the host.Limitations on study/implications: When the presence of mermithids was verified and their location wasidentified in diverse localities, the opportunity of continuing with the collection of specimens was justified andtheir identification could be formally performed, as well as the implementation of biological control studieswith the use of these native nematodes; also, the exploration of their roles in the control of nymphs from thesugarcane crop.Findings/conclusions: The presence of mermithid parasites of spittlebug nymphs in the sugarcane crop ineight localities in the mountainous region of Veracruz was verified in situ. Their emergence was classifiedinitially on nymphs of the spittlebug (Hemiptera: Cercopidae) that belong to the genera Aeneolamia and Prosapia

Denitrifying microbial genes quantification attests inference for potential N2O emissions in sugarcane soils by enzymatic bioanalysis

This study evaluated the relationships and sensitivity of denitrifying microbial gene abundance, as well as the activities of soil enzymes β-glucosidase (GLU) and arylsulfatase (ARYL), to assess the quality of sugarcane soils managed with vinasse (V), filter cake (FC), and mineral fertilizer (MF). Composite soil samples were collected using a systematic sampling approach that included two soil classes (Ferralsol and Acrisol), two textures (clayey and sandy), three management systems (V, V+FC, and MF), two sampling seasons (rainy and dry), and three replicates, totaling 72 samples. Analysis of soil organic carbon (SOC), and macro- and micronutrients differentiated the Ferralsol and Acrisol samples into distinct groups based on agricultural management (Global R = 0.554) and showed some overlap based on soil texture (Global R = 0.369). The number of nirK, nirS, and nosZ I gene copies per gram of soil, determined by Real-Time Quantitative PCR (qPCR) based on genomic DNA isolated from the 72 soil samples, was higher in the rainy season compared to the dry season (P<0.05). None of the genes evaluated revealed a consistent response to different sugarcane soil managements, showing specific response patterns for each soil class and texture. In the Ferralsol, the activities of GLU and ARYL increased in the following order: V < MF < V+FC, regardless of soil texture (sandy or clayey) and sampling season. The average activity of the two enzymes in both V+FC and MF treatments was 1.8 times higher in sandy soil and 3.9 times higher in clayey soil compared to soil managed with vinasse. In the Acrisol, no significant differences among the treatments were observed. Statistical analyses revealed negative correlations (P<0.05) between the number of copies of the nirK and nosZ I genes and GLU and ARYL activities in the soil during both seasonal periods analyzed. The number of copies of these two microbial genes was also negatively correlated with the soil organic matter in the rainy season. Thus, the indications of sugarcane soil quality based on enzymatic analyses were corroborated by the lower abundance of genes associated with denitrification process. The findings of this study open the possibilities to infer about the potential for N2O emission from these sugarcane soils based on GLU and ARYL activities.

Relative to rainforests and grasslands, banana and sugarcane soils have half the microbial biomass and highly distinct bacterial and fungal communities

Soil microbial communities mediate a range of ecosystem services and are impacted by land use. The Wet Tropics region of north Queensland, Australia, is a biodiversity hotspot with some of the world's oldest rainforests, but also has large areas converted for agriculture. We explored soil abiotic and biotic characteristics in 86 sites across four of the key land uses in this area: banana production, sugarcane production, grassland, and rainforest. Furthermore, we characterised sites where wild bananas were found in rainforests to bridge the associations found in natural and agricultural areas. Soil abiotic and biotic characteristics were found to differ between landuses, with commercial banana soils being the most distinct. Commercial banana and sugarcane soils had less soil carbon, and banana soils were also less acidic and had higher zinc and nitrate levels than other landuses. Interestingly, banana and sugarcane soils had half the microbial biomass of other landuses, including wild banana. The diversity of soil bacterial and fungal communities was also highly distinct in commercial banana soils, with significantly larger relative abundances of Fusarium oxysporum, a fungal species complex that includes important plant pathogens. Differences in soil biotic characteristics between landuses were significantly correlated with soil carbon, nitrogen, phosphorus, and pH. Our results demonstrate that land management can profoundly impact soil microbial communities, with potential consequences for ecosystem functioning.

HOW DOES NATURE AFFECT COMPETITIVENESS AND INNOVATION?

The aim is to strengthen the understanding of nature as an attribute of competitiveness and innovation from a regional perspective. A dialectical relationship is used to consider competitiveness, innovation, and nature as interconnected and not separated dimensions. The expansion of the sugarcane frontier in the south of the Brazilian state of Goiás is taken as empirical evidence. The method compares two municipalities, Mineiros and Goiatuba, with similar economic structures but located respectively in unfavorable and favorable environments. While Mineiros is less competitive than Goiatuba, the challenge of producing sugarcane in soils with higher erodibility stimulated investments in knowledge creation. Keywords: Competitiveness, Regional Innovation, Nature, Sugarcane, Brazil.

Protective role of reactive aluminum phases to stabilize soil organic matter against long-term cultivation in the humid tropics under volcanic influence

ABSTRACT Cultivation can cause rapid depletion of soil organic matter (SOM), particularly in the humid tropics. Understanding the factors controlling SOM storage is a key step toward effective soil management for sustainable crop production. While clay + silt content is known to be an important factor for soil organic carbon (SOC) storage, recent studies have shown greater importance of oxalate-extracted Al (Alo; roughly corresponds to short-range-order aluminosilicate minerals and organo-Al complexes) and Fe (Feo). However, the extent to which these mineralogical factors control the response of SOM pool to land-use changes remains unclear, especially in the tropics. This study aimed to clarify the factors regulating SOM content in croplands compared to secondary forests or home gardens in Negros Occidental, Philippines. Along two line transects having a wide range of Alo contents, soil samples were collected at a depth of 0 − 10 cm from sugarcane sites (n = 33; long-term continuous cultivation of >70 years) that were paired with either secondary forests (n = 10) or home gardens (n = 20). Sugarcane sites had significantly lower SOC and total nitrogen (N) contents than secondary forest and home garden sites, whereas there was no clear difference between the latter two land uses. Both SOC and total N contents showed significant positive correlations with Alo content and, to a much less extent, with Feo content, but not with clay + silt content. The slope of the regression line between SOC and Alo was indifferent between sugarcane and the other two land uses, while the intercept was significantly lower in the sugarcane sites. These results suggest the protective role of Alo phases in both agricultural and forest soils and the presence of unprotected SOM (e.g. plant litter) in the latter sites. Furthermore, δ13C analysis suggested that the proportion of forest (C3 plant) derived carbon remaining in the sugarcane soils ranged between 10% and 50% and increased with Alo content. Together, our study showed indirect evidence of Alo-induced stabilization of SOM against long-term cultivation under the humid tropical environment.

Soil dissipation and efficacy on itchgrass of soil-applied residual herbicides pendimethalin and clomazone in Louisiana sugarcane.

Sugarcane (Saccharum sp.) growers in Louisiana report that the widely used soil residual herbicide, pendimethalin, is less effective at controlling itchgrass (Rottboellia chochinchinensis), possibly through accelerated dissipation from repeated applications. Some growers have started to use another herbicide, clomazone, in place of pendimethalin for itchgrass control when pendimethalin does not provide the necessary control. Little is known about the dissipation of these two herbicides, especially when applied together, in diverse sugarcane soils in Louisiana. Thus, the objective of the research was to measure the dissipation of pendimethalin and clomazone in soils having high itchgrass pressure. Soil samples from five fields were fortified (4 μg g-1) with clomazone and pendimethalin and monitored over the course of 163 days under laboratory conditions. Herbicide levels were determined by extracting the herbicides from soil with acetonitrile and analyzing the extracts with high performance liquid chromatography (HPLC). The results indicate that clomazone is persistent in the soils studied, with a degradation half-life (DT50) of ≥79 days. Pendimethalin dissipates more rapidly in soil with a DT50 ranging from 7 to 59 days. All itchgrass plants showed injury to herbicide but many grew out of symptoms, and responses were not consistent between soil types. Pendimethalin dissipation varied greatly between soil types, yet clomazone was generally persistent in each soil tested. However, when these soils were seeded with itchgrass, pendimethalin was more effective at controlling itchgrass than clomazone. Although persistent in the soils tested, the leaching potential of clomazone may limit its long-term effectiveness. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Productivity and Energy Utilization in Sugarcane Soil Tillage Systems

Productivity and Energy Utilization in Sugarcane Soil Tillage Systems

Contribution of the ratoon sugarcane with planting years to river pollution evidenced from the four-year watershed observation

Non-point source pollution water erosion caused by sugarcane planting on sloping land is a serious environmental problem in tropical and subtropical regions. The adjustment of sugarcane planting patterns (ratio of perennial to new planting areas) will affect slope soil erosion. However, the relationship between the contribution of sugarcane land to river pollution load and the planting years of ratoon sugarcane remains unclear. To quantitatively analyse the contribution of sugarcane fields to eroded sediment nitrogen (N) and phosphorus (P) loads into the river in different ratoon years and growing seasons, this study was conducted in the intensive sugarcane cultivation area of the southern subtropical Guangxi Nala sub watershed, using the specific compound specific stable isotope (CSSI) traceability technology and real-time monitoring in the watershed. The changes of N and P loading of sugarcane soil erosion and sediment into the river was determined at different ratoon years (RS0-RS3) in addition to the related influencing factors. The results showed that the influence of different ratoon years on the N and P input loads of eroded sediment from sugarcane fields was significantly greater than that of runoff. The contribution of different ratoon sugarcane planting years (including root density) to the loads of sediment N and P into the river was 67.1 % (p < 0.01), which was 2.8 times that of runoff (24.3 %) (p < 0.05). With increasing ratoon sugarcane planting years, the N and P loads of sediment into the river from the sugarcane land decreased significantly; the ratoon sugarcane planting years showed a highly significant negative correlation with the N loads of sediment into the river from the sugarcane fields (p < 0.01), and a significant negative correlation with P (p < 0.05) was observed. Newly planted sugarcane contributed the most to the N and P sediment loads into the river at the seedling stage and the least at the maturity stage. Therefore, in the intensive sugarcane planting areas, to effectively control erosion-induced non-point source pollution, perennial sugarcane planting areas should be rationally in the newly planted sugarcane fields, especially at the seedling stage, to increase land surface cover.

Developing Vis–NIR libraries to predict cation exchange capacity (CEC) and pH in Australian sugarcane soil

In sugarcane growing areas of Queensland Australia, management of soil condition requires information about soil chemical properties (i.e., cation exchange capacity [CEC], and pH), because they are used to make fertiliser recommendations. While laboratory analysis is cost prohibitive the development of visible near–infrared (Vis–NIR) spectroscopy libraries might be useful. The aims of this study was to compare: i) linear (i.e., Partial least squares regression [PLSR]) and machine learning (i.e., Cubist, Random Forest [RF] and Support vector machine [SVM]) algorithms in terms of their calibration strength (i.e., coefficient of determination (R2); ii) depth-specific (i.e., topsoil [0 – 0.3 m], subsurface [0.3 – 0.6 m], subsoil [0.6 – 0.9 m] and deep subsoil [0.9 – 1.2 m]) and multi-depth libraries; iii) prediction R2, agreement (Lin’s concordance correlation coefficient [LCCC]) and accuracy (ratio of performance to interquartile [RPIQ]); and iv) minimum number of calibration sample locations (i.e., n = 400, 350, …, 50). For depth-specific calibration for CEC, strong calibration R2 was achieved for the subsurface (i.e., RF [0.95], Cubist [0.93], PLSR [0.88] and SVM [0.81]), and for pH, the largest R2 was for deep subsoil (i.e., RF [0.91], followed by PLSR [0.80], Cubist [0.79] and SVM [0.56]), with subsurface, and deep subsoil similar, with topsoil R2 smaller. In terms of model prediction of depth-specific, Cubist was superior to PLSR, RF and SVM for CEC, and PLSR was the best for pH. For example, agreement for topsoil CEC was substantial for Cubist (0.80) and PLSR (0.80), but moderate for RF (0.69) and poor for SVM (0.59). For subsurface (0.9), subsoil (0.91) and deep subsoil (0.92), the agreements were perfect for CEC using Cubist. In terms of multi-depth calibration for CEC it was strong for RF (R2 = 0.94), Cubist (0.92), PLSR (0.81) and SVM (0.72), but for prediction agreement, Cubist (LCCC = 0.92) was perfect, with PLSR (0.85), RF (0.84) and SVM (0.83) substantial. This was also the case for pH (0.84) substantial. However, there are efficiencies in developing a multi-depth calibration. Moreover, the minimum number of calibration sample sites required was 300 (i.e., 1,200 samples) (1.78 sites/ha). The results have implications for using a Vis–NIR library to replace traditional soil laboratory analysis and for fertiliser recommendations for sugarcane soil.

Parasitic Nematodes of Sugarcane: A Major Productivity Impediment and Grand Challenges in Management.

Sugarcane is an important cash crop grown in 137 countries, accounting for 80% of global sugar production. It supports the livelihood of more than 100 million people and up to 25% of the rural population in some countries. Plant-parasitic nematodes are one significant constraint in sugarcane production and can lead to a loss of up to 30% in productivity. More than 300 species of parasitic nematodes have been discovered in sugarcane soil. Owing to limited data, the potential damage to sugarcane crops caused by parasitic nematodes is often underestimated. The main nematodes present in sugarcane fields are root-lesion (Pratylenchus spp.), spiral (Helicotylenchus spp.), root-knot (Meloidogyne spp.), dagger (Xiphinema spp.), stunt (Tylenchorhynchus spp.), ring (Criconemella spp.), and stubby (Paratrichodorus spp.). Among these, Meloidogyne javanica and Pratylenchus zeae are the most damaging nematode species. Management of nematodes is a challenging task as there are no clear symptoms of their presence, and they often come in multiple species with varying levels of pathogenicity. Moreover, the management options available are not always effective. Integrated nematode management is a sustainable strategy for controlling nematode infestations. It involves using all possible methods to suppress the parasitic nematode population in a compatible manner and reduce it below economic threshold levels. This article focuses on the challenges of managing nematodes in sugarcane and highlights the opportunity for implementing a sustainable nematode management strategy.

Exploring rhizobacteria of wild sugarcane (Saccharum spontaneum L.) and their plant growth promoting potential

In this study, the rhizospheric soil of wild sugarcane from three different salt-affected soils of the eastern Indo-Gangetic Plains was sampled. Rhizospheric bacteria from S. spontaneum were isolated and they were characterized for growth-promoting traits with molecular identification. A total of 49 isolates were isolated from three S. spontaneum rhizosphere soils from different places. These isolates were shown to have differential tolerance to NaCl concentrations up to 2000 mM. Owing to their host habitat and poor nutrient availability, these bacteria were found to have excellent tolerance to high NaCl concentrations along with having multiple plant growth traits. Apart from salt tolerance, these isolates were screened for EPS production, phosphate solubilization, zinc solubilization, siderophore production and ammonia production and based on multiple plant growth-promoting traits, twenty isolates were taken for molecular identification and further in vivo screening. These twenty S. spontaneum rhizospheric microbes belonged to the classes Gammaproteobacteria, Firmicutes (Bacilli) and Actinomycetia, representing six genera and 15 species. In vivo growth promotion studies indicated that some of these isolates could improve germination and growth in rice seedlings. The results of this study signify the possibility of utilizing wild crop microbiomes to nurture cultivated crops under adverse growing conditions.

Hybrid pathways of denitrification drive N2O but not N2 emissions from an acid-sulphate sugarcane soil

AbstractAcid-sulphate sugarcane soils in the subtropics are known hot-spots for nitrous oxide (N2O) emissions, yet the reduction of reactive N2O to non-reactive dinitrogen (N2) via specific pathways remains a major uncertainty for nitrogen (N) cycling and loss from these soils. This study investigated the magnitude and the N2O:N2 partitioning of N2O and N2 losses from a subtropical acid-sulphate soil under sugarcane production using the 15N gas flux method, establishing the contribution of hybrid (co- and chemo-denitrification) and heterotrophic denitrification to N2O and N2 losses. Soils were fertilised with potassium nitrate, equivalent to 25 and 50 kg N ha−1, watered close to saturation then incubated over 30 days. An innovative, fully automated incubation system coupled to an isotope-ratio mass-spectrometer enabled real time analysis of 15N2O and 15N2 at sub-diel resolution. Peak losses of N2O and N2 reached 6.5 kg N ha−1 day−1, totalling &gt; 50 kg of N2O+N2-N ha−1. Emissions were dominated by N2, accounting for more than 57% of N2O+N2 losses, demonstrating that the reduction of N2O to N2 proceeded even under highly acidic conditions. Over 40% of N2O, but only 2% of N2 emissions, were produced via hybrid pathways. These findings demonstrate hybrid pathways are generally limited to N2O production, likely driven by high organic matter content and low soil pH, promoting both biotic, and abiotic nitrosation. Regardless of the underlying process, the magnitude of the N2O emissions demonstrates the environmental, but also the potential agronomic significance, of hybrid pathways of N2O formation for N loss from fertilised acid-sulphate soils.

Biocontrol ability of Bacillus velezensis T9 against Apiospora arundinis causing Apiospora mold on sugarcane.

Sugarcane (Saccharum officinarum L.) may be infected with Apiospora, which can produce the toxin 3-nitropropionic acid (3-NPA) during improper transportation and storage. The consumption of sugarcane that contains 3-NPA can lead to food poisoning. Therefore, this study sought to explore a novel biocontrol agent to prevent and control Apiospora mold. Bacteria were isolated from the soil of healthy sugarcane and identified as Bacillus velezensis T9 through colony morphological, physiological and biochemical characterization and molecular identification. The inhibitory effect of B. velezensis T9 on Apiospora mold on sugarcane was analyzed. Assays of the cell suspension of strain T9 and its cell-free supernatant showed that T9 had significant in vitro antifungal activities against Apiospora arundinis and thus, would be a likely antagonist. Scanning electron microscopy and transmission electron microscopy showed that treatment with T9 significantly distorted the A. arundinis mycelia, perforated the membrane, contracted the vesicles, and decomposed most organelles into irregular fragments. A re-isolation experiment demonstrates the ability of T9 to colonize the sugarcane stems and survive in them. This strain can produce volatile organic compounds (VOCs) that are remarkably strong inhibitors, and it can also form biofilms. Additionally, the cell-free supernatant significantly reduced the ability of A. arundinis to produce 3-NPA and completely inhibited its production at 10%. Therefore, strain T9 is effective at controlling A. arundinis and has the potential for further development as a fungal prevention agent for agricultural products.

Carbon Dioxide and Nitrous Oxide Emissions from a Typical Sugarcane Soil in the Cauca River Valley, Colombia

Sugarcane is an important crop for tropical countries and to accurately inventory its greenhouse gas (GHG) emissions baseline measurements are needed. In Colombia, sugarcane is one of the most important crops in terms of cultivated area and, paradoxically, scientific information reporting GHG emissions based on field measurements is almost nonexistent. The objective of this work was to quantify the direct emissions of carbon dioxide (CO2) and nitrous oxide (N2O) in the sugarcane-soil system of the Cauca river valley, Colombia. For this purpose, a field experiment was established in a typic haplustert soil cropped with sugarcane. The effects of nitrogen (N) fertilization and sampling site on its GHG emissions were tested using the closed static chamber method over a period of 211 days. The main cumulative emissions were 765.14 ± 34.1 g CO2–C m−2 and 125.4 ± 22.6 mg N2O–N m−2. Overall, GHG emissions were modified by N fertilization, the sampling site, and their interaction. Nitrogen fertilization with urea increased mean and cumulative CO2 and N2O emissions, especially at the row sampling site. This paper highlights the importance of considering these factors when the quantification of GHGs or a reduction of their associated uncertainties are required. This work reportss the first GHG emissions data for a typical sugarcane agroecosystem in Colombia.

Nutrient availability and stoichiometry mediate microbial effects on soil carbon sequestration in tropical forests

The persistence of soil organic carbon (SOC) is primarily driven by microbial metabolic activities; however, how microbial effects on SOC sequestration are affected by soil nutrient status remains unclear. Here, we conducted a one-year-long in situ soil incubation experiment using mesh bags (with a mesh size of 38 μm, allowing bacterial colonization and fungal hyphal penetration while preventing root penetration). This experiment involved incubating fertile sugarcane soil and infertile sand across an elevational gradient, characterized by diverse climatic and biotic conditions within a tropical forest. Biomarkers, such as phospholipid fatty acids, carbon-, nitrogen-, and phosphorus-acquiring hydrolases, glomalin-related proteins, and amino sugars, were measured to characterize the production and accumulation of microbial biomass, exo-enzymes, extracellular glycoproteins, and microbial necromass. These measurements aimed to elucidate their respective contribution to the sequestration of SOC. We found that Gram-negative bacteria dominated the microbial community composition in fertile soil, and the higher nutrient availability was related to the production and accumulation of microbial necromass via promoting microbial biomass turnover, thus enhancing the accumulation of SOC in fertile soil. This process was negatively associated with phosphorus availability and carbon- and phosphorus-acquiring enzyme activities in fertile soil. In contrast, the SOC accumulation was positively correlated with nitrogen availability and stoichiometry (including C:N and C:P), as well as moisture content in infertile sand. However, more resources were preferentially allocated to stress-tolerant fungi and Gram-positive bacteria under nutrient deficiency in infertile sand used for microbial biomass maintenance, nutrient acquisition, and environmental adaption which further aggravated the consumption of SOC, resulting in SOC loss after one year of field incubation. Our results suggest that microbial effects on SOC persistence are highly context-dependent and nutrient availability-induced changes in microbial communities and microbial resource-allocation strategies are key processes for understanding and predicting the fate of carbon in tropical forest soils.

Meyerozyma caribbica Isolated from Vinasse-Irrigated Sugarcane Plantation Soil: A Promising Yeast for Ethanol and Xylitol Production in Biorefineries.

The production of fuels and other industrial products from renewable sources has intensified the search for new substrates or for the expansion of the use of substrates already in use, as well as the search for microorganisms with different metabolic capacities. In the present work, we isolated and tested a yeast from the soil of sugarcane irrigated with vinasse, that is, with high mineral content and acidic pH. The strain of Meyerozyma caribbica URM 8365 was able to ferment glucose, but the use of xylose occurred when some oxygenation was provided. However, some fermentation of xylose to ethanol in oxygen limitation also occurs if glucose was present. This strain was able to produce ethanol from molasses substrate with 76% efficiency, showing its tolerance to possible inhibitors. High ethanol production efficiencies were also observed in acidic hydrolysates of each bagasse, sorghum, and cactus pear biomass. Mixtures of these substrates were tested and the best composition was found for the use of excess plant biomass in supplementation of primary substrates. It was also possible to verify the production of xylitol from xylose when the acetic acid concentration is reduced. Finally, the proposed metabolic model allowed calculating how much of the xylose carbon can be directed to the production of ethanol and/or xylitol in the presence of glucose. With this, it is possible to design an industrial plant that combines the production of ethanol and/or xylitol using combinations of primary substrates with hydrolysates of their biomass.

Microbial carbon functional responses to compaction and moisture stresses in two contrasting Australian soils

Soil compaction combined with water deficit may cause a significant decrease in microbial functions. Two texture-contrast sugarcane soils were exposed to the combined stresses of compaction and drought, and microbial responses were investigated going into stress (phase I) as well as their response coming out of stress (phase II). We artificially applied a gradient of bulk densities (0.9–1.5 g cm−3) and water-filled pore space (WFPS, 21–100%) to simulate compaction and drought conditions. PCA results clearly demonstrated the separation of impacts of soil types and the moisture treatments. Additionally, it is evidenced that soil texture can strongly regulate soil microbial response to compaction, as finer texture provides a better local environment for soil microbial community growth, supported by two folds higher microbial biomass carbon content and significantly higher CO2 respiration in Nitisol (clayey soil) than Planosol (sandy soil). The Structural Equation Modelling (SEM) analysis showed a strongly direct negative effect (path coefficient= −0.59 to −0.61, p < 0.01) of WFPS on the labile C at Phase I and Phase II in both Nitisol than Planosol. Further, soil moisture would govern microbial respiration cross soil types, particularly after removal of compactions which supported by the SEM result (path coefficient= −0.36 to −0.47, p < 0.05). Results from this study have implied the importance in considering the combined effects of soil texture and moisture in assessing compaction impacts and developing associated management regimes.

Effects of bagasse biochar application on soil organic carbon fixation in manganese-contaminated sugarcane fields

BackgroundIn recent years, there have been several studies on the remediation of heavy metal pollution in soil by the application of biochar. However, little attention has been paid to understanding the effects and underlying mechanisms of biochar on soil carbon sequestration in manganese-contaminated farmlands. Therefore, in this study, bagasse biochar was applied to the soil in different proportions (0%, 0.5%, 2%, and 5%) and the test was conducted indoors for 100 days at a constant temperature. Soil physical and chemical properties, organic carbon mineralization, organic carbon components, and enzyme activities were analyzed in this study.ResultsIn this study, when compared with the control, the application of 0.5%, 2%, and 5% bagasse biochar to the manganese-contaminated sugarcane field soil effectively reduced the cumulative CO2 emissions, i.e., decreased by 123.18 mg·kg−1, 208.28 mg·kg−1, and 287.79 mg·kg−1, respectively. Among the different treatment groups, the highest decrease in cumulative CO2 emissions was observed in the 5% bagasse biochar-treated soil when compared with the control. The application of bagasse biochar increased the soil microbial biomass carbon content by 12.72 mg·kg−1, 13.71 mg·kg−1, and 15.10 mg·kg−1, respectively when compared with the control. The soil nutrients and enzyme activities significantly increased with the increase in biochar application amount.ConclusionsThe application of bagasse biochar to manganese-contaminated sugarcane soil field effectively inhibited the mineralization of soil organic carbon, improved the carbon sequestration potential of manganese-contaminated sugarcane field soil, and provided a theoretical basis for the carbon sequestration mechanism in manganese-contaminated farmland soil.Graphical

Assessment of microbial respiration in sugarcane soil with different nitrogen's dosage

Assessment of microbial respiration in sugarcane soil with different nitrogen's dosage

Beneficial shift of rhizosphere soil nutrients and metabolites under a sugarcane/peanut intercropping system.

Intercropping systems have been studied as a sustainable agricultural planting pattern to increase soil quality and crop yields. However, the relationships between metabolites and soil physicochemical properties remain poorly understood under sugarcane/peanut intercropping system. Thus, we determined the rhizosphere soil physicochemical properties, and analyzed rhizosphere soil metabolites and root metabolites by metabolomics method under monoculture and intercropping patterns of sugarcane and peanut. The results showed that pH, the contents of total phosphorus (P), total potassium (K), available nitrogen (N), available phosphorus (P), and available potassium (K) were higher in rhizosphere soil of intercropping peanut than monoculture peanut, and the content of total P was higher in rhizosphere soil of intercropping sugarcane than monoculture sugarcane. Sugarcane/peanut intercropping also significantly increased the activities of acid phosphatase and urease in rhizosphere soil. The metabolomics results showed that 32 metabolites, mainly organic acids and their derivatives (25.00%), nucleotides and their metabolites (18.75%), were detected in root and rhizosphere soil samples. In the MP-S (rhizosphere soil of monoculture peanut) vs. IP-S (rhizosphere soil of intercropping peanut) comparison, 47 differential metabolites (42 upregulated) were screened, including glycerolipids (19.15%), organic acids and their derivatives (17.89%), and amino acids and their metabolites (12.77%). In the MS-S (rhizosphere soil of monoculture sugarcane) vs. IS-S (rhizosphere soil of intercropping sugarcane) comparison, 51 differential metabolites (26 upregulated) were screened, including heterocyclic compounds (15.69%), glycerolipids (11.76%), and organic acids and their derivatives (9.80%). The metabolite species from MP-S, MS-S, IP-S, and IS-S were similar, but some metabolite contents were significantly different, such as adenine, adenosine, maltotriose, thermozeaxanthin-13 and PE-NMe (20:0/24:0). Adenine and adenosine were detected in root and rhizosphere soils, and their levels were increased in the intercropping treatment, which were mainly related to enhanced purine metabolism in root and rhizosphere soils under the sugarcane/peanut intercropping system. Importantly, adenine and adenosine were significantly positively correlated with total P and total K contents, acid phosphatase and urease activities, and pH. This study clarified that the sugarcane/peanut intercropping system could improve soil nutrients and enzymes and was related to purine metabolism.