Addition Of Organic Matter Research Articles

Analysis of soil fertility status on rice (Oryza sativa L.) planted land in Polewali District, Polewali Mandar Regency

Rice is the main food commodity in Indonesia. The main abiotic factor affecting rice productivity is soil fertility. This study aimed to determine the soil fertility status (SFS) of paddy fields in Polewali District, Polewali Mandar Regency, West Sulawesi. The research was conducted by surveying soil characteristics supported by soil chemical analysis at the Laboratory of Soil Science and Environmental Conservation, Faculty of Agriculture, Universitas Muslim Indonesia. The research was conducted in Polewali District, with the survey area consisting of 4 land map units (LMU). Soil fertility status was determined based on the criteria of each soil fertility parameter, namely: soil pH, organic C-content, cation exchange capacity, available P, Potassium content, and base saturation. The results showed that the SFS in Polewali District was classified as low. Only the base saturation parameters in LMU-2 and LMU-3 were classified as high. In addition, all parameters were only classified as very low to medium at all LMUs. Low C-organic content and very low P and K content are the main limiting factors for SFS. Recommended land management to improve soil fertility is the addition of organic matter that can increase total nitrogen and C-organic in the soil and the application of manure. Keywords: Soil fertility status, paddy fields, rice plants

Production of high-quality seedlings of Handroanthus spongiosus (Bignoniaceae), native to a seasonally dry tropical forest

Studies of the use of alternative substrates have enabled producing seedlings of various species with high quality and low cost. The objective of this work was to evaluate the best cultivation conditions for production of Handroanthus spongiosus seedlings. The seeds were collected from five different populations in the state of Pernambuco, Brazil, and cultivated in six substrates: soil, sand, soil + vermiculite, soil + goat manure, soil + vermiculite + goat manure, and soil + goat manure + 30% biochar. We evaluated the emergence, shoot and root length, stem base diameter, shoot and root dry mass, and Dickson quality index. The substrates with addition of organic matter favored increased shoot length, stem diameter and dry mass. The incorporation of goat manure and biochar in the substrates favored the quality of the H. spongiosus seedlings.

Remediation of petroleum hydrocarbon contaminated soils by nZVI coupled with electrokinetic activation of persulfate

This paper explores the use of nanoscale zero-valent iron (nZVI) coupled with electrically activated persulfate (nZVI-EK/PS) for remediating petroleum hydrocarbon-contaminated soil. The effects of persulfate (PS) dosage, nZVI dosage, and soil organic matter content on the remediation of petroleum hydrocarbons were investigated. The study concludes that persulfate (PS) and nanoscale zero-valent iron (nZVI) are the primary factors influencing the remediation of petroleum hydrocarbons in the nZVI-EK/PS system. The optimal reaction conditions of PS = 170 mmol and nZVI = 17 mmol increased the efficiency of petroleum hydrocarbon treatment to 40.45%, with the highest removal efficiency of petroleum hydrocarbons observed at position S2, reaching 48.5%. With the addition of organic matter at 5%, the efficiency of petroleum hydrocarbon treatment reached 50.08%, representing a 9.68% enhancement in the nZVI-EK/PS system. Furthermore, potential mechanisms for the degradation of petroleum hydrocarbons by the nZVI-EK/PS system were identified using gas chromatography-mass spectrometry (GC-MS). The degradation order of different components was found to be esters < alkenes < alkanes < phenols.

In vitro growth of different chrysanthemum cultivars on murashige and skoog medium modified with some organic additives

Mass in vitro propagation of chrysanthemum plants requires large amounts of Murashige and Skoog (MS) media. In order to increase efficiency of MS media usage, the addition of organic materials and the selection of cultivars need to be studied. This study aimed to obtain the best modified MS media and cultivars for in vitro propagation of chrysanthemums. This research was conducted from July to September 2023 at tissue culture laboratory of Politeknik Negeri Jember. This study used Completely Randomized Design with two factors. The first factor was the chrysanthemum cultivars, i.e. Naweswari Agrihort and Suciono Agrihort. The second factor was the modified MS media, i.e. MS, ½MS + 50 g/l banana, ½MS + 50 ml/l coconut water and ½MS + 50 g/l sweet potato. Each combination of treatments was thrice repeated. Observation variables were plant height, time of shoot emergence, the number of shoots and the number of leaves. Data analysis was carried out using ANOVA and DMRT. The best modified media was ½MS + 50 g/l sweet potato that showed significantly higher plant compared to other treatments. The addition of the tested organic materials could reduce MS media usage by 50%.

Evaluation of Soil Micronutrients in Madagali Local Government Area of Adamawa State, Nigeria

This study was carried out to evaluate soil micronutrients in Madagali Local Government area. The importance of micronutrients in plant nutrition is high, and they should not be neglected, although they are needed in minor quantities. Twenty (20) soil samples from each selected five wards were collected which gave a total of one hundred samples used for the study. The collected soil samples were analyzed in the laboratory using appropriate methods and were subjected to descriptive statistics to ascertain their variability across the study area. Based on the laboratory outcome, iron was high with the mean values 5.11mg/kg and 4.86mg/kg for surface and sub-surface, while molybdenum was low with the mean of 0.06mg/kg and 0.04mg/kg. On the other hand, molybdenum (Mo) had the highest which was 75.6% coefficient of variation, while iron (Fe) had the lowest percentage of 30.27% coefficient of variation for surface soils. In sub-surface, manganese (Mn) had the highest percentage value which stood at 59.28% while zinc had the lowest percentage of 28.42% coefficient of variation. To achieve maximum crop production in the study area, it was recommended that addition of organic matter, liming and proper soil management practices should be adopted.

Response of Soil CO2 Emission to Addition of Biochar and Dissolved Organic Carbon along a Vegetation Restoration Gradient of Subtropical China

Biochar, as a soil amendment, has been widely confirmed to increase soil carbon sequestration. However, how biochar addition affects soil carbon changes during the vegetation restoration process is still unclear, which constrains our ability to explore biochar’s application in the technology of soil carbon sequestration in forests. We conducted an incubation experiment on biochar and dissolved organic matter (DOM) addition to soil at three stages of revegetation (degraded land (DS), plantation forest (PS), and secondary natural forest (NS) in Changting County in Fujian province, China) to investigate the effects of vegetation restoration, biochar, DOM, and their interaction on soil CO2 emission and its relative mechanisms. We found that the accumulative release of CO2-C in the NS and PS soils was 7.6 and 6.8 times higher, respectively, in comparison to that from the DS soil. In the DS, biochar addition significantly increased the accumulative release of CO2-C, soil pH, NH4+-N content, qCO2, phenol oxidase, and peroxidase activities. Peroxidase activities were positively correlated with the accumulative release of CO2-C, and oxidase was the most important direct factor influencing the accumulative release of CO2-C in the DS. However, the accumulative release of CO2-C, soil NH4+-N content, qCO2, β-glucosidase, and N-acetylglucosaminidase activities was significantly reduced after the application of biochar in the PS and NS. These two hydrolases were positively associated with the accumulative release of CO2-C, and hydrolase was the most vital direct factor influencing the accumulative release of CO2-C from the PS and NS soils. The positive effect of DOM addition on CO2 emission under biochar application declined with a vegetation restoration age increase. Our results indicated that biochar could alter microbial physiological processes, inhibit qCO2 and hydrolase activities, and further decrease CO2 emission in relatively fertile soil from the PS and NS; but in the relatively barren soil from the DS, biochar might promote CO2 emission by stimulating microorganisms to enhance qCO2 and oxidase activities.

Linking bacterial life strategies with the distribution pattern of antibiotic resistance genes in soil aggregates after straw addition

Straw addition markedly affects the soil aggregates and microbial community structure. However, its influence on the profile of antibiotic resistance genes (ARGs), which are likely associated with changes in bacterial life strategies, remains unclear. To clarify this issue, a soil microcosm experiment was incubated under aerobic (WS) or anaerobic (AnWS) conditions after straw addition, and metagenomic sequencing was used to characterise ARGs and bacterial communities in soil aggregates. The results showed that straw addition shifted the bacterial life strategies from K- to r-strategists in all aggregates, and the aerobic and anaerobic conditions stimulated the growth of aerobic and anaerobic r-strategist bacteria, respectively. The WS decreased the relative abundances of dominant ARGs such as QnrS5, whereas the AnWS increased their abundance. After straw addition, the macroaggregates consistently exhibited a higher number of significantly altered bacteria and ARGs than the silt+clay fractions. Network analysis revealed that the WS increased the number of aerobic r-strategist bacterial nodes and fostered more interactions between r-and K-strategist bacteria, thus promoting ARGs prevalence, whereas AnWS exhibited an opposite trend. These findings provide a new perspective for understanding the fate of ARGs and their controlling factors in soil ecosystems after straw addition. Environmental implicationsStraw soil amendment has been recommended to mitigate soil fertility degradation, improve soil structure, and ultimately increase crop yields. However, our findings highlight the importance of the elevated prevalence of ARGs associated with r-strategist bacteria in macroaggregates following the addition of organic matter, particularly fresh substrates. In addition, when assessing the environmental risk posed by ARGs in soil that receives crop straw, it is essential to account for the soil moisture content. This is because the species of r-strategist bacteria that thrive under aerobic and anaerobic conditions play a dominant role in the dissemination and accumulation of ARG.

Dynamics of Water-Soluble Metals in Soil Moistened with Citrus Wastewaters Depends on Soil Reaction and Organic Acids

The demand for water for civil and industrial use is diminishing the availability of such a valuable environmental resource for agricultural purposes. Thus, for the next generation, it is imperative to find alternative water sources for crop irrigation. The citrus agroindustry utilizes a large amount of water for processing fruit (e.g., essential oil extraction, fruit washing). Wastewaters produced by citrus industry (CWWs) are rich in organic matter and mineral nutrients, thus making them potentially usable for crop irrigation. Conversely, due to their high content of organic acids and low pH, they may increase the availability of soluble metals, in the form of both plant nutrients and contaminants. The aim of this study was to evaluate the effect of CWWs on the dynamics of soil water-soluble metals and pH. To this end, CWWs from the processing of lemons, oranges, and tangerines at three different doses were used. CWWs were analyzed to investigate type and amount of organic acids. Soil water-soluble metals (Na, Mg, Al, K, Ca, Fe, Co, Ni, Cu, Zn, and Cd) and pH were determined at days 1, 3, 7, 21, and 28 after the addition of CWWs. Citric, ascorbic, oxalic, tartaric, acetic, and malic acids were found in CWWs, with citric acid being two orders of magnitude more concentrated than the other acids. After the addition of CWWs, soil pH promptly decreased from 7.2 to at least 5.3 depending on the type and concentration of CWWs. Concurrently, the concentration of almost all investigated metals sharply increased within 7 days after the addition of CWWs. Then, it decreased, reaching values similar to that of the control. The increase in metals availability as a consequence of pH decrease was ascribed to different causes: the exchange reaction between H+ and cations adsorbed onto colloid surfaces, the addition of organic matter by CWWs that stimulated microbial activity, and the quantity and type of organic acids added via CWWs. In conclusion, the obtained results suggest that the use of citrus wastewater for irrigation purposes could be a valid solution, with them being rich in plant nutrients and easily mobilized elements such as Ca, Mg, K, and Na. Further research is needed to refine the understanding of the impact of CWWs in the long term and to develop targeted strategies for managing industrial wastewater in agriculture.

Effects of modified organic material addition on soil and microbial communities in ecologically restored engineering slopes of the Qinghai-Tibetan plateau: A mesocosm study

Organic material plays an essential role in the ecological restoration of different types of surfaces with engineering damage in extremely fragile environments. An outdoor mesocosm experiment was conducted to explore the effects of modified organic material on chemical, physical properties and microbial communities of reconstructed soil in ecologically restored engineering slopes of the Qinghai-Tibetan plateau. The physical and chemical properties of the soil indicate that the addition of modified organic materials significantly improves soil nutrients. In this area, organic carbon increased by 1.87 g·kg−1 in the frame beam slopes compared with the control area, and the potassium content doubled. In addition, modified organic material effectively induced soil metabolism responses, mainly promoting the activities of soil enzymes like amylase, cellulase, urease, sucrase, and alkaline phosphatase. Moreover, addition of modified organic material noticeably changed the abundance and structure of microbial communities in soils. The enhanced concentrations of the signal molecules N-acylated-L-homoserine lactone and auto inductor peptide indicated that addition of modified organic materials significantly influenced quorum-sensing in soil microbial communities. There are differences in the soil improvement effects of different types of slopes, among which the frame grid beam has the best effect. These findings demonstrate the effect and underlying mechanisms of the addition of incorporating modified organic materials, primarily sodium carboxymethyl cellulose and anionic polyacrylamide, into the soil of engineering slopes. These results have extensive application prospects for ecological restoration in strict environments.

Effects of soil on the development, survival, and oviposition of Culex quinquefasciatus (Diptera: Culicidae) mosquitoes

BackgroundWater quality is known to influence the development and survival of larval mosquitoes, which affects mosquito-borne pathogen transmission as a function of the number of mosquitoes that reach adulthood and blood feed. Although water properties are known to affect mosquito development, few studies have investigated the link among soil properties, water quality, and mosquito development. Given the large number of ground-breeding mosquito species, this linkage is a potentially important factor to consider in mosquito ecology. In this study, we explored the effects of different soils on multiple life history parameters of the ground-breeding mosquito species Culex quinquefasciatus (Diptera: Culicidae).MethodsCx. quinquefasciatus larvae were reared in water combined with different soil substrates (sandy, silt, or clay loam textures) at increasing soil to water volume ratios, with and without the addition of organic matter (fish food). Gravid mosquitoes were offered different soil–water extracts to investigate soil effects on oviposition preference.ResultsWithout the addition of organic matter, larval survival and development differed significantly among waters with different soil textures and volumes of substrate. Mosquitoes in water with clay loam soil survived longer and developed further than mosquitoes in other soil waters. Larvae survived for longer periods of time with increased volumes of soil substrate. Adding organic matter reduced the differences in larval survival time, development, and pupation among soil–water extracts. Adult female mosquitoes oviposited more frequently in water with clay loam soil, but the addition of organic matter reduced the soil effects on oviposition preference.ConclusionsThis study suggests soil composition affects larval mosquito survival and development, as well as the oviposition preference of gravid females. Future studies could differentiate abiotic and biotic soil features that affect mosquitoes and incorporate soil variation at the landscape scale into models to predict mosquito population dynamics and mosquito-borne pathogen transmission.Graphical

Clay and organic compost as quality conditioners of a sandy soil in the brazilian semiarid

Due to natural and anthropic pressures of semiarid regions, like sandy texture, organic matter (OM) deficiency, water scarcity and inadequate management, we carried out an experiment under greenhouse conditions, to evaluate the effects of clay and OM addition on the quality of a sandy soil of the Brazilian semiarid. The experiment lasted 75 days, testing four clay contents (10 and 31% natural soils, 15% by clay addition to a sandy soil and 26% by mixing clay subsoil to a sandy topsoil) in the absence and presence of organic compost (7.5g.kg-1). For biological parameters, sorghum plants were used for biometric and mineral composition analysis, in addition to assessing microbial activity (BSR, MBC, and qCO2). The results showed significant differences in soil microporosity and total porosity; the field capacity and permanent wilting point correlated linearly with clay content and OM addition; potencial and exchangeable soil acidity decreased significantly in the presence of compost. Sorghum plants showed higher values of biometric attributes and lower levels of nutrients in the presence of compost. The microbial activity did not show significant differences in terms of clay content or compost addition. The cluster analysis correlated the mixed soils (26%) to the lowest clay content soil (10%), and the clay addition (15%) to the highest clay content soil (31%), showing potential as soil conditioner in association with compost, as it might promote changes in the soil quality properties of semiarid regions.

Immobilisation of anaerobic digestate supplied nitrogen into soil microbial biomass is dependent on lability of high organic carbon materials additives

Anaerobic digestate is a nutrient rich slurry by-product derived from biogas production, often used as a fertiliser due to its high nitrogen content. However, nitrogen losses from its application can lead to environmental pollution. In a laboratory experiment, the addition of high organic carbon materials to digestate-amended soil as a potential means to stimulate microbial immobilisation of digestate supplied nitrogen was investigated. Soil was incubated in pots for 5 months with digestate (equivalent to 250 kgN ha−1). The impact of adding carbon into the digestate (equivalent to 540 kgC ha−1) as either glycerol, straw, woodchip, or biochar on soil microbial and chemical parameters was quantified. Glycerol amended soils had significantly higher microbial biomass compared to digestate alone during the first month and at 30 days after application had a 4x higher on average microbial N. The digestate + straw treatment resulted in a 2.5x significantly greater nitrogen immobilisation compared to digestate alone after 3 months of incubation. The digestate + woodchip had a 2× higher mean microbial N after 5 months, whilst the biochar amendment did not stimulate significant nitrogen immobilisation at any time. These results suggest that mixing a labile to moderately labile organic carbon amendment, such as straw, with digestate has the greatest potential to reduce nitrogen losses following digestate application through microbial immobilisation.

Assessment of rapid initiators and long-lasting nutrients for developing biological permeable reactive barriers to treat mine-contaminated groundwater

ABSTRACT The formation of mine-contaminated groundwater as a result of acidic mine drainage from the oxidation of sulfur-containing minerals entering the groundwater. Biological permeable reactive barrier (Bio-PRB) technology is excellent for the remediation of mine-contaminated groundwater. Usually, the organic substrates utilized in Bio-PRB are a combination of rapid initiators, which are readily bioavailable, and long-lasting nutrients, which are more difficult to degrade. Herein, we investigated the effectiveness of three rapid initiators and three long-lasting nutrients to remove sulfate from simulated mine-contaminated groundwater via simulated column experiments. The rapid initiators comprised crude glycerol, sodium acetate, and industrial syrup (IS), and the long-lasting nutrients included biodiesel emulsified oil, soybean oil emulsified oil, and high-carbon alcohol emulsified oil (HO). Microorganisms were stimulated using IS to create a sulfate reduction system owing to its high total organic carbon content (24.30 g L−1), achieving optimal sulfate removal rate (1.69 mmol dm−3 d−1). The fastest (2.93 mmol dm−3 d−1) and highest (88%) sulfate removal rates were achieved using HO, which is probably associated with the ability of HO to provide the most suitable C/N ratio (111.75) and induce the growth of sulfate-reducing bacteria (SRB) for substrate degradation. Conversely, a high concentration of sulfate reduction products inhibited SRB growth in the HO column. The addition of organic materials promoted SRB growth and various organic substrate–degrading bacteria. Furthermore, the competitive growth of methanogens (86.6%) may be responsible for the decrease in the relative abundance of SRB during the later stages of the experiment in the HO column.

PENGEMBANGAN BIBIT PORANG DARI BEBERAPA SUMBER DENGAN BERBAGAI MEDIA TUMBUH MELALUI TEKNIK POTTING MIX PADA TANAH ENTISOL

Porang plants (Amorphophallus muelleri Blume) are herbaceous plants that are commonly found growing wild in forested areas, under bamboo clumps, along riverbanks, on mountain slopes, amidst dense and humid vegetation. Porang propagation from corms and cormels requires a considerable amount of time, around 7-9 months. Therefore, there is a need for the development of porang seedlings through easy vegetative propagation methods that can be implemented at the farmer level. This research utilized Entisol soil originating from Andalan Village, Bayan Subdistrict, North Lombok Regency. The research was conducted using an experimental method. The treatments were arranged using a Completely Randomized Design (CRD) involving 4 seed sources (porang cormels/bulbils, split corms, porang leaves, and porang stems) with 3 treatments, namely no treatment, biochar, liquid organic fertilizer, PGPR, and Trubus plant growth regulator. The analysis of variance results showed that the application of various growing media (biochar, liquid organic fertilizer, and PGPR) influenced changes in soil properties and the growth of porang seedlings. The growth of porang seedlings was influenced in the split corm and cormel techniques. Further tests indicated that the cormel technique, specifically in terms of plant height and stem diameter, was affected by the addition of organic materials compared to the absence of organic material application

Soil physical properties in a oxisol under a syntropic agroforestry system: row versus inter-row

Synthropic agroforestry systems are agricultural systems designed to reconcile agricultural production with environmental conservation. However, the benefits related to soil physical properties of these systems have only been documented for the planting rows. Thus, the physical behavior of the soil in the inter-rows remains unknown. The objective of this paper was to characterize the physical properties of the soil in the rows and inter-rows of a syntropical agroforestry system - SAS. For this, infiltration capacity (mini-disk infiltrometer) and soil resistance to penetration (STOLF Penetrometer) were measured in five ramdomly located blocks involving the rows and inter-rows. The results showed that there were no significant differences between row and inter-rows for both variables. The high species diversity, continuous addition of organic matter to the soil via pruning, the absence of heavy machinery use, and the vigorous growth of exotic grasses in the inter-row are the likely factors that explain the absence of differences reported here. We conclude that the rows and inter-rows of a SAS behave similarly in relation to the attributes evaluated. This demonstrates that such systems are highly beneficial for food production as well as maintaining soil physical properties.

Synergistic application of Pseudomonas strains and compost mitigates lead (Pb) stress in sunflower (Helianthus annuus L.) via improved nutrient uptake, antioxidant defense and physiology

Lead (Pb) is one of the most dreadful non-essential elements whose toxicity has been well reported worldwide due to its interference with the major plant functions and its overall yield. Bioremediation techniques comprising the application of beneficial microorganisms have gained attention in recent times owing to their ecofriendly nature. Addition of organic matter to soil has been reported to stimulate microbial activities. Compost application improves soil structure and binds toxic contaminants due to its larger surface area and presence of functional groups. Furthermore, it stimulates soil microbial activities by acting as C-source. So, in current study, we investigated the individual and synergistic potential of two lead (Pb)-tolerant Pseudomonas strains alongwith compost (1% w/w) in sustaining sunflower growth under Pb contaminated soil conditions. Lead chloride (PbCl2) salt was used for raising desired Pb concentration (500 mg kg−1). Results revealed that Pb stress drastically affected all the measured attributes of sunflower plant, however joint application of rhizobacteria and compost counteracted these adverse effects. Among them, co-application of str-1 and compost proved to be significantly better than str-2, as its inoculation significantly improved shoot and root lengths (64 and 76%), leaf area and leaves plant−1 (95 and 166%), 100-achene weight (200%), no. of flowers plant−1 (138%), chl ‘a’, ‘b’ and carotenoid (86, 159 and 33%) contents in sunflower as compared to control treatments. Furthermore, inoculation of Pseudomonas fluorescens along with compost increased the NPK in achene (139, 200 and 165%), flavonoid and phenolic contents (258 and 185%) along with transpiration and photosynthetic rates (54 and 72%) in leaves as compared to control treatment under Pb contamination. In addition, Pb entry to roots, shoots and achene were significantly suppressed under by 87, 90 and 91% respectively due to integrated application of compost and str-1 as evident by maximum Pb-immobilization efficiency (97%) obtained in this treatment. Similarly, bioconcentration factors for roots, shoots and achene were found to be 0.58, 0.18 and 0.0055 with associated translocation factor (0.30), which also revealed phytostabilization of Pb under combined application of PGPR and compost. Since, phytoremediation of heavy metals under current scenario of increasing global population is inevitable, results of the current study concluded that tolerant PGPR species along with organic amendments such as compost can inhibit Pb uptake by sunflower and confer Pb tolerance via improved nutrient uptake, physiology, antioxidative defense and gas exchange.

Enhancing soil properties, soil-borne diseases control, and quality through selecting high C/N agricultural waste during reductive soil disinfestation for continuous tobacco cropping

The addition of organic matter is crucial for achieving successful reductive soil disinfestation (RSD) for flue-cured tobacco cultivation. However, the effects of diverse organic materials and their application rates on soil-borne disease control and yield enhancement remain poorly understood. To address this, field experiments were conducted at two sites. Two organic materials, G and D, were employed with varying application rates (CK, G/D0.8, G/D1.0, and G/D1.2). The results demonstrated that adding these organic materials enhanced soil physicochemical properties, including pH, alkaline nitrogen, available phosphorus, available potassium, organic matter, and the C/N ratio. Furthermore, the relative abundance of Phytophthora nicotianae and Fusarium spp., with associated soil-borne diseases, was significantly reduced. Particularly, the G1.2 treatment exhibited a remarkable reduction in the relative abundance of the two pathogenic bacteria by over 20% at both experimental sites. Moreover, this treatment contributed to a reduction in disease incidence by over 21% and severity by over 72%. Increasing the application rates of these organic materials also enhanced nutrient content, agronomic traits, and biomass accumulation of flue-cured tobacco plants, improving the chemical composition of tobacco leaves and economic outcomes in cured-tobacco leaves. Notably, the G1.2 treatment at both experimental sites significantly enhanced the economic indices of tobacco leaves, respectively increasing the yield and output value by 10.6 kg ha−1 and 159.9 US$·ha−1. Overall, applying 15 t ha−1 (G1.2 treatment) of solid organic material during RSD was the optimal choice for sterilization, elimination of harmful substances, and enhancement of the economic characteristics of flue-cured tobacco.

Effects of Straw Returning and Biochar Addition on Greenhouse Gas Emissions from High Nitrate Nitrogen Soil After Flooding in Rice-vegetable Rotation System in Tropical China

In rice-vegetable rotation systems in tropical areas, a large amount of nitrate nitrogen accumulates after fertilization in the melon and vegetable season, which leads to the leaching of nitrate nitrogen and a large amount of N2O emission after the seasonal flooding of rice, which leads to nitrogen loss and intensification of the greenhouse effect. How to improve the utilization rate of nitrate nitrogen and reduce N2O emissions has become an urgent problem to be solved. Six treatments were set up [200 mg·kg-1 KNO3 (CK); 200 mg·kg-1 KNO3 + 2% biochar addition (B); 200 mg·kg-1 KNO3+1% peanut straw addition (P); 200 mg·kg-1 KNO3 + 2% biochar + 1% peanut straw addition (P+B); 200 mg·kg-1 KNO3 + 1% rice straw addition (R); 200 mg·kg-1 KNO3 + 2% biochar+1% rice straw addition (R+B)] and cultured at 25℃ for 114 d to explore the effects of organic material addition on greenhouse gas emissions and nitrogen use after flooding in high nitrate nitrogen soil. The results showed that compared with that in CK, adding straw or combining straw with biochar significantly increased soil pH (P<0.05). The B and P treatments significantly increased the cumulative N2O emissions by 41.6% and 28.5% (P<0.05), and the P+B, R, and R+B treatments significantly decreased the cumulative N2O emissions by 14.1%, 24.7%, and 36.7% (P<0.05), respectively. The addition of straw increased the net warming potential of greenhouse gases (NGWP). The addition of coir biochar significantly reduced the effect of straw on NGWP (P<0.05). The combined application of straw and biochar decreased NGWP, and P+B significantly decreased NGWP, but that with R+B was not significant (P>0.05). Adding straw or biochar significantly increased soil microbial biomass carbon (MBC) (P<0.05), and that of P+B was the highest (502.26 mg·kg-1). The combined application of straw and biochar increased soil microbial biomass nitrogen (MBN), and that of P+B was the highest. The N2O emission flux was negatively correlated with pH (P<0.01) and positively correlated with NH4+-N and NO3--N (P<0.01). The cumulative emission of N2O was negatively correlated with MBN (P<0.05). There was a significant negative correlation between NO3--N and MBN (P<0.01), indicating that the reduction in NO3--N was likely to be held by microorganisms, and the increase in the microbial hold of NO3--N also reduced N2O emission. In conclusion, the combined application of peanut straw and coconut shell biochar could significantly inhibit N2O emission and increase soil MBC and MBN, which is a reasonable measure to make full use of nitrogen fertilizer, reduce nitrogen loss, and slow down N2O emission after the season of Hainan vegetables.

Labile organic matter promotes nitrogen retention in natural and constructed gulf coast marshes

Coastal marshes mitigate allochthonous nitrogen (N) inputs to adjacent marine habitat; however, their extent is declining rapidly. As a result, marsh restoration and construction have become a major foci of wetland management. Constructed marshes can quickly reach similar plant biomass to natural marshes, but biogeochemical functions like N removal and retention can take decades to reach functional equivalency, often due to lags in organic matter (OM) pools development in newly constructed marshes. We compared denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in a 32 year-old constructed marsh and adjacent reference marsh in the Northern Gulf of Mexico. Marsh sediments packed into 3 mm “thin discs” were subjected to three OM quality treatments (no OM addition, labile OM, or recalcitrant OM) and two N treatments (ambient nitrate or elevated nitrate) during a 13 day incubation. We found that OM addition, rather than marsh type or nitrate treatment, was the most important driver of nitrate reduction, increasing both denitrification and DNRA and promoting DNRA over denitrification in both marshes. Fungal and bacterial biomass were higher in the natural marsh across treatments, but recalcitrant OM increased fungal biomass in the constructed marsh, suggesting OM-limitation of fungal growth. We found that constructed marshes are capable of similar denitrification and DNRA as natural marshes after 30 years, and that labile OM addition promotes N retention in both natural and constructed marshes.Graphical Conceptual figure highlighting the findings of this experiment. Under control treatment with no C addition (bottom panel), constructed and natural marshes have similar rates of both DNRA and denitrification. The natural marsh has higher fungal and bacterial biomass, while fungal biomass is not detectable in the constructed marsh. Under labile OM additions (upper left panel), rates of both DNRA and denitrification are increased and DNRA becomes favored over denitrification in both marshes. Recalcitrant OM additions (upper right) increase denitrification, but do not affect DNRA or % denitrification. The addition of recalcitrant OM also increases the detectability of fungal biomass in the constructed marsh.

Adsorption of the fungicide carbendazim on activated carbon: analysis of isotherms, kinetics, rapid small-scale column tests, and impacts of the presence of organic matter

Abstract The adsorption of the fungicide carbendazim (CBZ) on granular activated carbon (GAC) made from bovine bone was investigated in deionized water (DW) and DW with the addition of natural organic matter (DWNOM). The study included tests of isotherms, kinetics, and rapid small-scale column tests (RSSCT). The Freundlich model represented better the adsorption of the fungicide in both matrices, while the pseudo-second-order model fitted better in DW. The isotherm and kinetic studies showed the interference of NOM in the adsorption of CBZ through changes in the parameters of the applied models. In RSSCT, the breakthrough time was faster in DWNOM than in DW. Nevertheless, the CBZ concentrations of both matrices were considered statistically similar for most contact times in RSSCT. In the fixed-bed experiments, the organic matter did not cause significant changes in the adsorption of CBZ in GAC. The NOM presence may have improved the efficiency of GAC in adsorbing CBZ in kinetic and RSSCT tests. There is no knowledge of a similar approach to studying the adsorption of CBZ on GAC in Brazil, mainly using fixed-bed studies. In this way, the present work contributes to a better understanding of the adsorption of carbendazim through the methods used.