File Name: inorganic and organic components of soil .zip
Soil Sci. Plant Nutr.
Shashank Tewari. Kumar Upendra Akshay. Deepika Agrawal.
This study aimed to identify how the ratio of inorganic-to-organic components in animal manure compost AMC affected both lead immobilization and microbial activity in lead-contaminated soil. The residual fraction under sequential extraction increased with the inorganic fraction in the AMC; however, in those AMCs, the levels of microbial enzyme activity were the same or less than those in the control soil.
Lead is one of the most common and harmful heavy-metal soil contaminants worldwide, particularly near mines and shooting ranges. Lead contamination in the soil of such sites poses a risk to human and animal health as well as plant growth. Thus, its mobility and bioavailability should be reduced by appropriate treatments.
In addition, the rehabilitation of soil ecosystems that have undergone destruction by lead contamination should be accomplished through the remediation of such soil.
Since contamination in these sites is extensive and asset values are extremely low, chemical immobilization capable of transforming lead into less soluble phases is a cost-effective remediational approach.
Thus, various immobilization materials have been studied and developed [ 1 — 7 ]. Animal manure compost AMC , which is the most abundantly found organic waste material in Japan, can immobilize heavy metals and improve plant growth and microbial activity [ 8 — 16 ] by supplying nutrients to plant and soil biota. Therefore, in addition to lead immobilization, the application of AMC to lead-contaminated soil can help rehabilitate soil ecosystems, which inorganic immobilization materials cannot [ 17 ].
In particular, the presence of both inorganic and organic components in AMC makes it complicated to understand lead immobilization. Lead immobilization by AMC can be separated into indirect and direct mechanisms. The typical indirect mechanisms of lead immobilization are explained by the pH increase owing to the alkalinity of the inorganic component in AMC; this pH increase can promote the precipitation of lead carbonate and hydroxide minerals, resulting in a reduction of lead mobility and bioavailability [ 1 , 20 ].
The direct mechanisms of lead immobilization by AMC have been considered to be the reaction of the lead with the inorganic and organic components in AMC. Phosphorus, sulfate, and iron in the inorganic component and humic substances in the organic component in AMC seem to be the sources responsible for the reaction with lead [ 10 , 18 , 21 — 23 ].
Katoh et al. They indicated that the inorganic component in AMC could immobilize lead more effectively than its organic components [ 24 ]. These results imply that the inorganic component in AMC has a crucial role in lead immobilization, and AMC with a higher inorganic content is more suitable. However, to rehabilitate microbial activity, the organic component in AMC is also required since it supplies sufficient nutrients to soil microorganisms [ 17 ].
This component, however, may negatively affect lead mobility; water-soluble organic matter in AMC reacts and forms complexes with lead ions, resulting in enhancements in lead mobility.
Therefore, a suitable ratio of inorganic and organic components in AMC should be clarified to reduce the mobility and bioavailability of lead and enhance the microbial activities in the soil.
AMC has a wide range of the inorganic-to-organic component ratios [ 25 ]; however, to our knowledge, the optimal ratio of inorganic-to-organic components in AMC for lead immobilization and the rehabilitation of microbial activity have not been studied. We investigated the mobility and bioavailability of the lead, lead phases, and microbial activities in soil amended with the AMCs of various inorganic-to-organic component ratios. The inorganic fraction was derived from swine manure compost and the acid-insoluble organic fraction was derived from cattle manure compost.
These fractions can immobilize lead more effectively than other AMCs owing to the high content of phosphorus and mature organic matter in the inorganic and acid-insoluble organic fractions, respectively [ 24 ]. We aimed to identify how the ratio of inorganic-to-organic components in AMC affected the mobility and bioavailability of lead, lead phase, and microbial activity.
On the basis of the obtained results, we discuss the optimal ratio of the inorganic and organic components in AMC to immobilize lead and rehabilitate microbial activity in soil. The selected physicochemical properties of the soil used are shown in Table 1. The soil had a sandy loam texture.
The total lead content of the soil was 4. Commercial swine and cattle manure composts were used herein to obtain the inorganic and acid-insoluble organic fractions, respectively. We selected these composts since each fraction of the compost can immobilize lead more effectively than other composts [ 24 ]. The fractionation followed the method described by Katoh et al.
The pH of each fraction was adjusted to 7 to match that of the soil. Table 2 shows the selected chemical properties of each fraction [ 24 ]. Soil without AMC was also prepared as a control. Three replicates were prepared for each treatment. Soil samples were collected at 0, 7, 30, 90, and days; the samples were freeze-dried and analyzed to determine the levels of water-soluble lead and water-soluble organic carbon.
The soil sampled on day was analyzed to assess lead phases by sequential extraction and microbial enzyme activities. Herein, the level of water-soluble lead was employed as an indicator of lead mobility and bioavailability in the soil, because its water-soluble form is easily mobile and utilized by plant and soil biota. At days 7, 14, 30, 60, , and , the glass beaker containing 0.
The collected NaOH was titrated with 0. Soil texture was determined using the hydrometer method [ 26 ]. The total carbon and nitrogen contents in the soil were determined using a carbon, hydrogen, and nitrogen elemental analyzer MT-6; Yanaco New Science Inc.
The total lead, phosphorus, aluminum, and iron contents in the soil were determined by acid digestion with HNO 3 and HCl using a microwave. A sequential extraction procedure was performed on the soil samples in accordance with the procedure described by Tessier et al. All of the extracted or digested solutions were passed through a 0. Three different microbial enzyme activities—dehydrogenase, urease, and saccharase—were measured in the soil sample. The dehydrogenase activity was determined in accordance with the method described by Tabatabai [ 29 ] using triphenyltetrazolium chloride.
The urease activity was monitored using the method described by Kandeler and Gerber [ 30 ] by measuring the produced after the incubation of soil with urea. The saccharase activity was determined in accordance with the method described by Frankenberger and Johanson [ 31 ].
Statistical analyses were performed using JMP Ver. An analysis of variance was used to measure microbial enzyme activities. The pH in the control soil was not significantly changed and ranged from 7.
Moreover, the soil pH levels in all the AMCs were not significantly different from that in the control, indicating that the soil pH did not affect the enhancement or reduction in the lead mobility and bioavailability in the soil with AMC. Figure 1 a shows the amount of water-soluble lead in the soil with AMC.
The amount of water-soluble organic carbon in the soil is shown in Figure 1 b. Figure 3 shows the lead fraction results under sequential extraction. The composition of the control soil was as follows: The addition of AMC with a higher ratio of inorganic fraction resulted in a greater enhancement in the residual percentage.
However, the water-soluble lead level decreased as the incubation time increased in soil with both composts. These observations would be explained by the higher level of water-soluble organic matter and its sorption and decomposition in the soil thereby increasing the incubation time. The water-soluble organic matter can easily form complexes with lead ions, and its complexes could enhance the lead mobility in the soil [ 17 , 32 , 33 ].
The water-soluble organic matter was derived from the compost containing humic and fulvic acids with relatively low molecular weight [ 34 , 35 ]. These organic compounds are also readily decomposable and sorbed on the soil surface [ 36 , 37 ].
According to the result for CO 2 emission Figure 2 , the amount of CO 2 emission was lower than that of water-soluble organic carbon-decrease from day 0 to day , suggesting that some of the water-soluble organic matter derived from the compost was decomposed and some of it was sorbed in the soil with the increase in the incubation period.
It has been known that the compost amendment induced the very short-term leaching pulses of lead after the application [ 38 ], and lead was redistributed to the soil component by the decomposition of dissolved organic matter [ 39 ]. These results suggest that the organic component in the AMC does not considerably contribute to the immobilization of lead and suppression of lead mobility and bioavailability.
This was comparable with the results of Schwab et al. Farrell et al. The water-soluble organic matter derived from the compost is utilized as a nutrient source by microorganisms; thus, the addition of AMC with high organic matter content would induce the rehabilitation of microbial activity owing to the large amount of readily decomposable organic matter.
The inorganic fraction used herein contained a considerable amount of phosphorus, which results in the precipitation of lead phosphate minerals such as pyromorphite [ 24 ]. Pyromorphite is thermodynamically stable with a solubility product of [ 45 ].
This is supported by the results of Walker et al. These results suggest that the phosphorus in the inorganic component of AMC could immobilize lead-precipitating lead phosphate minerals even if the AMC contained more organic than inorganic components. This may be because the magnitude of lead immobilization by the inorganic component of AMC suppressed the magnitude of the facilitation of lead mobility by the organic component in AMC. This was attributed to incomplete immobilization.
Scheckel et al. The higher amount of water-soluble organic matter formed complexes with lead dissolved from the exchangeable and carbonate fractions, resulting in an enhancement in the level of water-soluble lead in the early stage of incubation.
With the increasing incubation time, water-soluble organic matter was decomposed and the level of water-soluble lead decreased below that in the control soil. Various inorganic percentages are used in the AMC, ranging from 7.
The ranges of the inorganic fraction of AMC in this study fall within this range. The importance of an inorganic component for the immobilization of heavy metals including lead in soil is pointed out by other researchers [ 21 , 47 , 48 ].
This is consistent with the result of Katoh et al. These findings suggest that AMCs cannot immobilize both lead and restore microbial activity. In soil treated with fully organic AMC, the readily soluble lead fraction in sequential extraction did not change in comparison with that in the control soil, whereas the organic fraction in sequential extraction was enhanced.
The authors declare that there is no conflict of interests regarding the publication of this paper. The authors are grateful to Professor F. Li and Professor T. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Journal overview. Special Issues. Academic Editor: Ezio Ranieri. Received 20 Nov Accepted 15 Dec Published 06 Jan Abstract This study aimed to identify how the ratio of inorganic-to-organic components in animal manure compost AMC affected both lead immobilization and microbial activity in lead-contaminated soil.
Introduction Lead is one of the most common and harmful heavy-metal soil contaminants worldwide, particularly near mines and shooting ranges. Materials and Methods 2.
16.2A: Soil Composition
See the Latest Publications. Browse All Publications. Download PDF. Phosphorus P is a naturally occurring element that exists in minerals, soil, living organisms and water. Plant growth and development require phosphorus, like nitrogen, in large amounts. Phosphorus is essential for early root development and hastens plant maturity. Note that phosphorus is the least mobile of the major plant nutrients.
It seems that you're in Germany. We have a dedicated site for Germany. The major components of most soils are inorganic. These constituents are derived from the weathering of rocks and minerals or from subsequent reaetions and interactions of the weathering products. Large amounts of inorganic colloids are essential in soils if they are to support luxurious plant growth.
Plants obtain inorganic elements from the soil, which serves as a natural medium for land plants. Soil is the outer, loose layer that covers the surface of Earth. Soil quality, a major determinant, along with climate, of plant distribution and growth, depends not only on the chemical composition of the soil, but also the topography regional surface features and the presence of living organisms. Components of soil : The four major components of soil are shown: inorganic minerals, organic matter, water, and air. The amount of each of the four major components of soil depends on the quantity of vegetation, soil compaction, and water present in the soil. A good, healthy soil has sufficient air, water, minerals, and organic material to promote and sustain plant life. The organic material of soil, called humus, is made up of microorganisms dead and alive , and dead animals and plants in varying stages of decay.
Most soils consist of four components and three phases. The four components include inorganic solids, organic solids, water, and air. Inorganic.
Understanding the effects of external organic and inorganic components on soil fertility and quality is essential for improving low-yielding soils. Results showed that the fertilized treatments significantly improved rice yields over the first three experimental seasons. Compared with the NPK treatment, organic amendments produced more favorable effects on soil productivity. Notably, the NPKM treatment exhibited the highest levels of nutrient availability, microbial biomass carbon MBC , activities of most enzymes and the microbial community.
This paper was primarily devoted to understand the interactions of soil aggregates, organic carbon C and carbon cycle enzymes in aggregates under different fertilization managements, aiming to identify the effects of organic and inorganic fertilizer amendments on soil organic C accumulation and the activities of carbon cycle enzymes within aggregates in Vertisol. A Vertisol soil following 4-year compost and inorganic fertilizer amendments, i. An increased amounts of carbon cycle enzymes in aggregates or 0—20 cm bulk soil were also observed in FRM plots. Compared to FR, FRM significantly strengthened the structural stability of macroaggregates and the intimate connection between enzyme activities and macroaggregates. As a recommended measure, supplementation with organic manure such as compost strengthened the process of mutual promotion between carbon cycle enzymes and macroaggregates, and the synergistic effect would be highly beneficial to soil organic C sequestration.
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