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Biochar: A Sustainable Approach for Improving Plant Growth and Soil Properties

Authors:
  • Bipin Tripathi Kumaon Institute of Technology, Dwarahat, India
  • B T Kumaon Institute of Technology, Dwarahat
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Chapter
Biochar: A Sustainable Approach
for Improving Plant Growth and
Soil Properties
JyotiRawat, JyotiSaxena and PankajSanwal
Abstract
Soil is the most important source and an abode for many nutrients and micro-
flora. Due to rapid depletion of agricultural areas and soil quality by means of
ever-increasing population and an excessive addition of chemical fertilizers, a
rehabilitated attention is a need of the hour to maintain sustainable approaches in
agricultural crop production. Biochar is the solid, carbon-rich material obtained
by pyrolysis using different biomasses. It has been widely documented in previous
studies that, the crop growth and yield can be increased by using biochar. This
chapter exclusively summarizes the properties of biochar, its interaction with soil
microflora, and its role in plant growth promotion when added to the soil.
Keywords: biochar, pyrolysis, soil microflora, nutrients, plant growth promotion
. Introduction
Crop growth and productivity are strongly influenced by various biotic and abiotic
stresses such as pests, weeds, drought, high salinity, extreme temperature, etc. and
the soil quality [1]. Soil is also contaminated by heavy metals through various human
activities [2], which affect plant growth and development and ultimately brings low
yielding cropping systems. Mining is one of the important sources of heavy metal con-
tamination in soil [3, 4]. The strength of soil is directly related to nutrient availability.
Plants require a number of soil nutrients like nitrogen (N), phosphorus (P), and potas-
sium (K) for their growth, but soil nutrient levels may decrease over time after crop
harvesting, as nutrients are not returned to the soil. In India, the soil of many regions is
not only deficient in macronutrients like NPK but also in secondary nutrients
(e.g. sulfur, calcium, and magnesium) and micronutrients (e.g. boron, zinc, copper,
and iron) [5]. Thus, to fulfill the shortage, a large amount of chemical fertilizers is
added to the soil; however, only a small percent of water-soluble nutrients are taken up
by the plants and the rest are converted into insoluble forms, making continuous appli-
cation necessary. Finally, the extensive use of chemical fertilizers has led to the dete-
rioration of the environment causing infinite problems. It not only lowers the nutrient
composition of the crops but also degrades the soil fertility in the long run [6, 7].
Besides fertilizers, pesticides are also the basic evil for agriculture, and the adverse
effects of pesticides on the environment are truly responsible for influencing the
microbial properties of soil. High inputs of fertilizers and pesticides and their long
persistence in the soil adversely affect the soil microflora, thereby disturbing soil
Biochar - An Imperative Amendment for Soil and the Environment
health and significantly reducing the total bacterial and fungal biomass [8]. Due to
long-term treatment with inorganic fertilizers (N and NPK) and/or organic manures,
a shift in structural diversity and dominant bacterial groups in agricultural soils has
been recorded by Wu etal. [9]. Biofertilizers, on the other hand, can reenergize the
soil by improving the soil fertility and hence can be used as a powerful tool for sus-
tainable agriculture, rendering agro-ecosystems more stress-free. Additionally, the
application of organic amendments to soils, from a remedial point of view, has typi-
cally been justified by their relatively low cost, which normally requires other forms
of disposal (burial in a landfill, incineration, etc.). Soil amendments must possess
properties such as high binding capacity and environmental safety and should have
no negative effect on the soil structure, soil fertility, or the ecosystem on the whole
[10]. The use of biochar has been accepted as a sustainable approach and a promising
way to improve soil quality and remove heavy-metal pollutants from the soil [11].
Biochar is a carbon-rich organic material, an organic amendment, and a
by-product derived from biomass by pyrolysis under high-temperature and low-
oxygen conditions. Biochar is produced through a process called pyrolysis, which
basically involves heating of biomass (such as wood, manure, or leaves) in complete
or almost complete absence of oxygen, with oil and gas as co-products. However,
the quantity of these materials produced depends on the processing conditions.
Recently, it has been reported that biochar obtained from the carbonization of
organic wastes can be a substitute that not only influences the sequestration of soil
carbon but also modifies its physicochemical and biological properties [12, 13].
Biochar has the potential to produce farm-based renewable energy in an eco-
friendly way. Specifically, the quality of biochar depends on several factors, such as
the type of soil, metal, and the raw material used for carbonization, the pyrolysis
conditions, and the amount of biochar applied to the soil [14]. In addition, the
biochar amendment to the soil proved to be beneficial to improve soil quality and
retain nutrients, thereby enhancing plant growth [15]. Since biochar contains
organic matter and nutrients, its addition increased soil pH, electric conductivity
(EC), organic carbon (C), total nitrogen (TN), available phosphorus (P), and the
cation-exchange capacity (CEC) [16]. Earlier, Verheijen etal. [17] reported that the
biochar application affected the toxicity, transport, and fate of various heavy metals
in the soil due to improved soil absorption capacity. The presence of plant nutrients
and ash in the biochar and its large surface area, porous nature, and the ability to act
as a medium for microorganisms have been identified as the main reasons for the
improvement in soil properties and increase in the absorption of nutrients by plants
in soils treated with biochar [18]. Chan etal. [19] reported that biochar application
decreased the tensile strength of soil cores, indicating that the use of biochar can
reduce the risk of soil compaction. A lot has already been discussed on the benefits
of inoculation of rhizobacteria in soil, but the addition of biochar can also provide
more nutrients to the soil, thus benefiting the agricultural crops. The mixing of the
plant growth-promoting microorganisms with biochar was referred to as the best
combination for growth and yield of French beans by Saxena etal. [20].
Addition of biochar in the soil can be extremely useful to improve the soil
quality, as well as to stimulate the plant growth, and thus, biochar can play an
important role in developing a sustainable system of agriculture. Several uses and
positive effects of biochar amendment have currently been considered as an effec-
tive method to reclaim the contaminated soil [21] and to achieve high crop yields
without harming the natural environment. The positive influence of biochar on
plant growth and soil quality suggests that using biochar is a good way to overcome
nutrient deficiency, making it a suitable technique to improve farm-scale nutrient
cycles. Therefore, a complete focus is been made to explore the positive effects of
biochar amendment on soil stability and plant growth promotion.
Biochar: A Sustainable Approach for Improving Plant Growth and Soil Properties
DOI: http://dx.doi.org/10.5772/intechopen.82151
. Biochar production and properties
Biochar is made up of elements such as carbon, hydrogen, sulfur, oxygen, and
nitrogen as well as minerals in the ash fraction. It is produced during pyrolysis, a
thermal decomposition of biomass in an oxygen-limited environment. Biochar is
black, highly porous, and finely grained, with light weight, large surface area and
pH, all of which have a positive effect on its application to soil. To address the major
concern on quality of agricultural soil degradation, biochar is applied to the soil in
order to enhance its quality. Biochar is stabilized biomass, which may be mixed into
soil with intentional changes in the properties of the soils atmosphere to increase
crop productivity and to mitigate pollution. The raw material (biomass) used and
processing parameters dictate the properties of the biochar.
. Biomass as a raw material
A wide range of organic materials are suitable as feedstock for the produc-
tion of biochar. Biochar can be produced with raw materials such as grass, cow
manure, wood chips, rice husk, wheat straw, cassava rhizome, and other agricul-
tural residues [22, 23]. It was reported that the production of biochar with high
nutrients depends on the type of raw material used and pyrolysis conditions [24].
Biochar is produced from the residual biomasses such as crop residues, manure,
wood residues, and forests and green wastes using modern pyrolysis technology.
Agricultural wastes (bark, straw, husks, seeds, peels, bagasse, sawdust, nutshells,
wood shavings, animal beds, corn cobs and corn stalks, etc.), industrial wastes
(bagasse, distillers’ grain, etc.), and urban/municipal wastes [25, 26] have been
extensively used, thus also achieving waste management through its production
and use [27].
Feedstocks currently used on a commercial scale include tree bark, wood chips,
crop residues (nut shells, straw, and rice hulls), grass, and organic wastes including
distillers’ grain, bagasse from the sugarcane industry, mill waste, chicken litter,
dairy manure, sewage sludge, and paper sludge [2830]. A 40wt.% yield of biochar
from maize stover was obtained by Peterson etal. [31].
The biomass used for the production of biochar is mainly composed of cellulose,
hemicellulose, and lignin polymers [32]. Among these, cellulose has been found to
be the main component of most plant-derived biomasses, but lignin is also impor-
tant in woody biomass.
. Biochar production
Biochar can be manufactured on a small scale using low-cost modified stoves
or kilns or through large-scale, cost-intensive production, which utilizes larger
pyrolysis plants and higher amounts of feedstocks. Biochar is produced from
several biomass feedstocks through pyrolysis as discussed above, generating oil
and gases as by-products [33]. The dry waste obtained is simply cut into small
pieces to less than 3cm prior to use. The feedstock is heated either without oxygen
or with little oxygen at the temperatures of 350–700°C (662–1292°F). Pyrolysis is
generally classified by the temperature and time duration for heating; fast pyrolysis
takes place at temperatures above 500°C and typically happens on the order of
seconds (heating rates 1000°C/min). This condition maximizes the genera-
tion of bio-oil. Slow pyrolysis, on the other hand, usually takes more time, from
30min to a few hours for the feedstock to fully pyrolyze (heating rates 100°C/min)
and at the same time yields more biochar. The temperature range remains
250–500°C [34].
Biochar - An Imperative Amendment for Soil and the Environment
The type of biochar produced depends on two variables: the biomass being
used and the temperature and rate of heating. High and low temperatures have
an unequivocal effect on char yields. It has been noticed that at low temperature
(<550°C), biochar has an amorphous carbon structure with a lower aromaticity
than the biochar produced at high temperature [35]. High temperature leads to
lower char yield in all pyrolysis reactions [36]. Peng etal. [37] reported the effect of
charring duration on the yield of biochar; yield showing a decrease with increasing
duration at the same temperature. The pyrolysis process seriously affects the quality
of biochar and its potential value to agriculture in terms of agronomic performance
or in carbon sequestration. The yield of biochar from slow pyrolysis of biomass has
been stated to be in the range of 24–77% [38, 39] (Figure ). The pyrolysis process
can be shown as follows:
Biomass
(
Solid
)
→ Biochar + Liquid or oil
(
tars, water, etc.
)
+ Volatile gases
(
CO
2 , CO, H
2
)
(1)
. Physical, chemical and biological properties of biochar
Biochar is a stable form of carbon and can last for thousands of years in the soil
[40]. It is produced for the purpose of addition to soil as a means of sequestering
carbon and improving soil quality. The conditions of pyrolysis and the materials
used can significantly affect the properties of biochar. The physical properties of
biochar contribute to its function as a tool for managing the environment. It has
been reported that when biochar is used as a soil amendment, it stimulates soil fer-
tility and improves soil quality by increasing soil pH, increasing the ability to retain
moisture, attracting more useful fungi and other microbes, improving the ability of
Figure 1.
Biochar production from different biomasses.
Biochar: A Sustainable Approach for Improving Plant Growth and Soil Properties
DOI: http://dx.doi.org/10.5772/intechopen.82151
cation exchange, and preserving the nutrients in the soil [41]. Biochar reduces soil
density and soil hardening, increases soil aeration and cation-exchange capacity,
and changes the soil structure and consistency through the changes in physical and
chemical properties. It also helps to reclaim degraded soils. It has shown a greater
ability to adsorb cations per unit carbon as compared to other soil organic matters
because of its greater surface area, negative surface charge, and charge density [42],
thereby offering the possibility of improving yields [43]. Samples with a sufficient
amount of stable carbon can be added to the soil to be sequestered; a high sorption
surface of biochar can characterize it as a soil additive, competent of halting risk
elements in soil.
The physical characteristics of biochar are directly and indirectly related to how
they affect soil systems. Soils have their own physical properties depending on the
nature of mineral and organic matter, their relative amounts, and how minerals
and organic matter are related. When biochar is present in the soil mixture, its
contribution to the physical nature of the system is significant, affecting the depth,
texture, structure, porosity, and consistency by changing the surface area, pore and
particle-size distribution, density, and packing [44]. The influence of biochar on
physical properties of soil directly affects the growth of plants, since the depth of
penetration and accessibility of air and water in the root zone is determined mainly
by the physical composition of the soil horizons. This affects the soils response to
water, its aggregation, and work ability in soil preparation, dynamics, and perme-
ability when swelling, as well as the ability to retain cations and response to changes
at ambient temperature. The smaller the pores on biochar, the longer they can retain
capillary soil water. The addition of biochar can reduce the effects of drought on
crop productivity in drought-affected areas due to its moisture-retention capacity.
It has been shown that it eliminates soil constraints that limit the growth of plants,
and neutralizes acidic soil because of its basic nature [45]. Carbon dioxide and
oxygen occupy air-filled spaces on the pores of biochar or can be chemosorbed on
the surface. As biochar can contain nutrients, microorganisms, and syngases, it can
also retain fertilizers in the soil longer than other soils and prevent it from leaching
into water sources such as rivers and lakes.
As far as its chemical properties are concerned, biochar reduces soil acidity by
increasing the pH (also called the liming effect) and helps the soil to retain nutri-
ents and fertilizers [46]. The application of biochar improves soil fertility through
two mechanisms: adding nutrients to the soil (such as K, to a limited extent P, and
many micronutrients) or retaining nutrients from other sources, including nutri-
ents from the soil itself. However, the main advantage is to retain nutrients from
other sources. In most cases, the addition of biochar only has a net positive effect
on the growth of crops if nutrients from other sources, such as inorganic or organic
fertilizers, are used. Biochar increases the availability of C, N, Ca, Mg, K, and P to
plants, because biochar absorbs and slowly releases fertilizers [47]. It also helps to
prevent fertilizer drainage and leaching by allowing less fertilizer use and reducing
agricultural pollution in the surrounding environment [48]. Biochar alleviates the
impact of hazardous pesticides and complex nitrogen fertilizers from the soil, thus
reducing the impact on the local environment.
Good healthy soil should include a wide and balanced variety of life forms,
including bacteria, fungi, protozoa, nematodes, arthropods, and earthworms.
Recently, biochar has been reported to increase the microbial respiration of the soil
by creating space for soil microbes [49], and in turn the soil biodiversity and soil
density increased. Biochar also served as a habitat for extra-radical fungal hyphae
that sporulated in micropores due to lower competition from saprophytes and
therefore served as an inoculum for arbuscular mycorrhizal fungi [50]. It is
believed that biochar has a long average dwelling time in soil, ranging
Biochar - An Imperative Amendment for Soil and the Environment
from 1000 to 10,000years, with an average of 5000years [5153]. However, its
recalcitrance and physical nature present significant impediment to the evaluation
of long-term stability [43]. The commercially available soil microbes which can be
used for inoculation include Azospirillum sp., Azotobacter sp., Bacillus thuringiensis,
B. megaterium, Glomus fasciculatum, G. mosseae, Pseudomonas fluorescens, Rhizobium
sp., and Trichoderma viride [54].
. Biochar as a soil amendment
The issues as food security, declining soil fertility, climate change, and profit-
ability are the driving forces behind the introduction of new technologies or new
farming systems. The amendment of soils for their remediation aims at reducing the
risk of pollutant transfer to waters or receptor organisms in proximity. The organic
material such as biochar may serve as a popular choice for this purpose because its
source is biological and it may be directly applied to soils with little pretreatment
[55]. There are two aspects which make biochar amendment superior to other
organic materials: the first is the high stability against decay, so that it can remain in
soil for longer times providing long-term benefits to soil and the second is having
more capability to retain the nutrients. Biochar amendment improves soil quality
by increasing soil pH, moisture-holding capacity, cation-exchange capacity, and
microbial flora [56].
The addition of biochar to the soil has shown the increase in availability of
basic cations as well as in concentrations of phosphorus and total nitrogen [57, 58].
Typically, alkaline pH and mineral constituents of biochar (ash content, including
N, P, K, and trace elements) can provide important agronomic benefits to many
soils, at least in the short to medium term. When biochar with a higher pH value
was applied to the soil, the amended soil generally became less acidic [59]. Acidic
biochar could also increase soil pH when used in soil with a lower pH value. The pH
of biochar, similar to the other properties, is influenced by the type of feedstock,
production temperature, and production duration.
Another valuable property of biochar is suppression of emissions of greenhouse
gases in soil. It has also been demonstrated by Zhang etal. [60] that the emissions
of methane and nitrous oxide were reduced from agricultural soils, which may
have additional climate mitigation effects, since these are potent greenhouse gases.
Spokas etal. [61] reported reduced carbon dioxide production by addition of dif-
ferent concentrations of biochar ranging from 2 to 60% (w/w), suppressed nitrous
oxide production at levels higher than 20% (w/w), and ambient methane oxidation
at all levels over unamended soil.
Several studies have shown the control of pathogens by the use of biochar in
agricultural soil. Bonanomi etal. [62] reported that biochar is effective against both
air-borne (e.g. Botrytis cinerea and different species of powdery mildew) and soil-
borne pathogens (e.g. Rhizoctonia solani and species of Fusarium and Phytophthora).
The application of the biochar derived from citrus wood was capable of controlling
air-borne gray mold, Botrytis cinerea on Lycopersicon esculentum, Capsicum annuum
and Fragaria × ananassa. Although there is a shortage of published data on the
effects of biochar on soil-borne pathogens, evidence given by Elmer etal. [63] has
shown that the control of certain pathogens may be possible. The addition of bio-
char in 0.32, 1.60, and 3.20% (w/w) to asparagus soils infested with Fusarium has
augmented the biomass of asparagus plants and reduced Fusarium root rot disease [63].
Similarly, Fusarium root rot disease in asparagus was also reduced by biochar
inoculated with mycorrhizal fungi [64]. A study of suppression of bacterial wilt in
tomatoes showed that biochar obtained from municipal organic waste reduced the
Biochar: A Sustainable Approach for Improving Plant Growth and Soil Properties
DOI: http://dx.doi.org/10.5772/intechopen.82151
incidence of the disease in Ralstonia solanacearum infested soil [65]. Ogawa [66]
advocated the use of biochars and biochar amended composts for controlling the
diseases caused by bacteria and fungi in soil. The disease suppression mechanism
has been attributed to the presence of calcium compounds, as well as improvements
in the physical, chemical, and biological characteristics of the soil.
The prevention of ‘diffuse water pollution’ through ammonium sorption or the
mediation of the dynamics of a soil solution containing nitrate, phosphorus, and
other nutrients has been extensively studied. The application of biochar to soil can
influence a wide range of soil constraints such as high availability of Al [67], soil
structure and nutrient availability [24], bioavailability of organic [68] and inor-
ganic pollutants [69], cation-exchange capacity (CEC), and retention of nutrients
[70, 71]. Biochar can also adsorb pesticides, nutrients, and minerals in the soil,
preventing the movement of these chemicals into surface water or groundwater and
the subsequent degradation of these waters from agricultural activity.
Xie etal. [72] reported that biochar amendment enhanced soil fertility and crop
production, particularly in soils with low nutrients. However, in soils with high
fertility, no noticeable increase in production was noticed, and some studies even
reported inhibition of plant growth. The observations of Taghizadeh-Toosi etal.
[73] indicated that ammonia adsorbed by biochar could be later released to the soil.
Saarnio etal. [74] showed that biochar application along with fertilizers can lead
to better plant growth, but sometimes a negative effect was also observed without
fertilization due to reduced bio-availability through sorption of nitrogen. It has
been shown that application of biochar in the soil has a positive to neutral and even
negative impact on crop production. Hence, it is crucial that the mechanisms for
action of biochar in the soil be understood before its application.
The consequence of biochar addition on plant productivity depends on the
amount added. Recommended application rates for any soil amendment should
be based on extensive field testing. At present, insufficient data are available for
obtaining general recommendations. In addition, biochar materials can vary greatly
in their characteristics, so the nature of the particular biochar material (e.g. pH and
ash content) also influences the application rate. Several studies have reported a
positive effect of using biochar on crop yields with rates of 5–50 tonnes per hectare
with appropriate nutrient management. The experiments conducted by Rondon
etal. [75] resulted in a decrease in crop yield in a pot experiment with nutrient
deficient soil amended with biochar at the rate of 165 tonnes per hectare. An
experiment conducted in the United States showed that peanut hull and pine chip
biochar, applied to 11 and 22 tonnes per hectare, could reduce corn yields below
those obtained in the control plots with standard fertilizer management [76]. Thus,
the control of the rate of application of biochar is necessary to prevent the negative
impact of biochar.
. Stimulation of soil microflora and plant growth
There are several reports which show that biochar has the capability to stimulate
the soil microflora, which results in greater accumulation of carbon in soil. Besides
adsorbing organic substances, nutrients, and gases, biochars are likely to offer a
habitat for bacteria, actinomycetes and fungi [64]. It has been suggested that faster
heating of biomass (fast pyrolysis) will lead to the formation of biochar with fewer
microorganisms, smaller pore size, and more liquid and gas components [77].
The enhancement of water retention after biochar application in soil has been
well established [78], and this may affect the soil microbial populations. Biochar
provides a suitable habitat for a large and diverse group of soil microorganisms,
Biochar - An Imperative Amendment for Soil and the Environment
although the interaction of biochar with soil microorganisms is a complex phenom-
enon. Many studies reported that addition of biochar along with phosphate solubi-
lizing fungal strains promoted growth and yield of Vigna radiata and Glycine max
plants, with better performances than control or those observed when the strains
and biochar are used separately [20, 79, 80].
The use of biochar increased mycorrhizal growth in clover bioassay plants by
providing the suitable conditions for colonization of plant roots [81]. Warnock
etal. [82] summarized four mechanisms by which biochar can affect functioning of
mycorrhizal fungi: (i) changes in the physical and chemical properties of soil,
(ii) indirect effects on mycorrhizae through exposure to other soil microbes, (iii) plant-
fungus signaling interference and detoxification of toxic chemicals on biochar, and
(iv) providing shelter from mushroom browsers. Carrots and legumes grown on
steep slopes and in soils with less than 5.2 pH showed significantly improved growth
by the addition of biochar [83]. It was found that biochar increased the biological N2
fixation (BNF) of Phaseolus vulgaris [75] mainly due to greater availability of micro-
nutrients after application of biochar. Lehmann etal. [58] reported that biochar
reduced leaching of NH4+ by supporting it in the surface soil where it was available
for plant uptake. Mycorrhizal fungi were often included in crop management strate-
gies as they were widely used as supplements for soil inoculum [84]. When using
both biochar and mycorrhizal fungi in accordance with management practices, it is
obviously possible to use potential synergism that can positively affect soil quality.
The fungal hyphae and bacteria that colonize the biochar particles (or other porous
materials) may be protected from soil predators such as mites, Collembola and
larger (>16μm in diameter) protozoans and nematodes [8587].
Biochar can increase the value of non-harvested agricultural products [88] and
promote the plant growth [58, 89]. A single application of 20tha1 biochar to a
Colombian savanna soil resulted in an increase in maize yield by 28–140% as com-
pared with the unamended control in the 2nd to 4th years after application [90].
With the addition of biochar at the rate of 90gkg1 to tropical, low-fertile ferralsol,
not only the proportion of N fixed by bean plants (Phaseolus vulgaris) increased
from 50% (without biochar) to 72%, but also the production of biomass and bean
yield were improved significantly [75]. When biochar was applied to the soil, a
higher grain yield of upland rice (Oryza sativa) was obtained in northern Laos
sites with low P availability [91, 92]. Many of these effects are interrelated and may
act synergistically to improve crop productivity. Often there has been a reported
increase in yields, which is directly related to the addition of biochar as compared to
the control (without biochar) [58]. However, in some cases, growth was found to be
depressed [93].
The direct beneficial effects of biochar addition for the availability of nutri-
ents are largely due to the higher content of potassium, phosphorus, and zinc
availability and, to a lesser extent, calcium and copper [58]. Few studies have
examined the potential for amending biochar in soil to impact plant resistance to
pathogens. With reference to soil pathogens principally concerned with the effect
of AM fungal inoculations on asparagus tolerance to the soil borne root rot patho-
gen Fusarium, Matsubara etal. [94] demonstrated that charcoal amendments had
a suppressive effect on pathogens. One more study that supported these earlier
findings stated that biochar made from ground hardwood added to asparagus
field soil led to a decrease in root lesions caused by Fusarium oxysporum,
F. asparagi, and F. proliferatum compared to the non-amended control [95].
Biochar reduces the need for fertilizer, which results in reduction in emissions
from fertilizer production, and turning the agricultural waste into biochar also
reduces the level of methane (another potent greenhouse gas) caused by the
natural decomposition of waste.
Biochar: A Sustainable Approach for Improving Plant Growth and Soil Properties
DOI: http://dx.doi.org/10.5772/intechopen.82151
. Mixing biochar with other amendments
Mixing biochar with other soil amendments such as manure, compost, or lime
before soil application can improve efficiency by reducing the number of field
operations required. Since biochar has been shown to sorb nutrients and protect
them from leaching [70, 96], mixing of biochar may improve the efficiency of
manure and other amendments. However, Kammann etal. [97] acknowledged in
their recent review that very few studies that directly combined organic amend-
ments with biochars were available. They found that co-composted biochars had
a remarkable plant growth-promoting effect as compared to biochars when used
pure, but no-systematic studies have been done to understand the interactive effects
of biochars with non-pyrogenic organic amendments (NPOAs). Biochar can also
be mixed with liquid manures and used as slurry. Additionally, combined biochar
and compost applications have numerous advantages over mixing of biochar or
compost with soil separately. These benefits, according to Liu etal. [98], include
more efficient use of nutrients, biological activation of biochar, an enhanced
supply of plant-available nutrients by biological nitrogen fixation, reduction of
nutrient leaching, and the contribution of combined nutrients in comparison to a
single application of compost and biochar. Diminutive biochars are most likely best
suited for this type of application. Biochar was also mixed with manure in ponds
and potentially reduced losses of nitrogen gas were recorded same as when it was
applied to soil [99, 100].
. Conclusion
The problem of the depletion of agricultural land as a result of the pressure
caused by the ever-growing population necessitated the sustainable practice of crop
production. It was suggested to use biochar as a means of remediating contaminated
agricultural soil, improving soil fertility by reducing the acidity, and increasing the
availability of nutrients. Thus, addition of biochar to the soil can be one of the best
practices to overcome any biotic stress in soil and to increase the crop productiv-
ity. The positive effects of biochar on the interactions between soil-plant-water
caused better photosynthetic performance and improved nitrogen and water use
efficiency. Hence, it can be concluded by this comprehensive review that biochar
has the potential to improve the properties of soil, microbial abundance, biological
nitrogen fixation, and plant growth. Therefore, it is recommended to use biochar as
a soil amendment for long-term carbon sink restoration.
Biochar - An Imperative Amendment for Soil and the Environment

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms
of the Creative Commons Attribution License (http://creativecommons.org/licenses/
by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly cited.
Author details
JyotiRawat1, JyotiSaxena2* and PankajSanwal2
1 Department of Biotechnology, Kumaun University, Bhimtal Campus, Nainital,
India
2 Biochemical Engineering Department, B.T.Kumaon Institute of Technology,
Dwarahat, India
*Address all correspondence to: saxenajyoti30@gmail.com

Biochar: A Sustainable Approach for Improving Plant Growth and Soil Properties
DOI: http://dx.doi.org/10.5772/intechopen.82151
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... Biochar also reduces nitrous oxide, carbon dioxide, and methane from agricultural land. Different concentrations of biochar ranging from 2 to 60% (w/w) can reduce the emission of nitrous oxide higher than 20% (w/w) (Rawat et al. 2019). It also increases the water holding capacity, cation exchange capacity, total nitrogen, and phosphorous (Lehmann et al. 2003). ...
... It has also been reported that biochar improves the nitrogen fixation in Phaseolus vulgaris (Rondon et al. 2007). Biochar also protects fungal hyphae and beneficial microbes from attacks of mites, protozoans, and nematodes (Rawat et al. 2019). Biochar amended soil can suppress the growth of pathogen through its antagonist effect and with indirect interaction through induction of systemic resistance in plants. ...
... It can resist the growth of soil borne as well as air borne pathogen that causes powdery mildew (Bananomi et al. 2015). The biochar prepared from citrus wood can control the gray mold (Botrytis cinerea) on tomato and pepper (Rawat et al. 2019). Similarly, biochar obtained from the grounded hardwood prevents the root lesion (causal organism Fusarium oxysporum) in asparagus (Elmer et al. 2011). ...
Chapter
Biochar is carbon rich, porous substance produced under limited or no supply of oxygen. Pristine biochar is considered as a sustainable, beneficial, and low-cost product employed for soil conditioning, agricultural production, and pollutant removal. It is a promising product having a wide array of applications including catalytic reaction, carbon sequestration, pollution mitigation, and sustainable agriculture. The production of biochar is a sustainable practice to treat and valorize solid waste. Without any activation or modification, pristine biochar has lower surface area, porosity, and surface functional groups. To enhance the physicochemical and functional properties of pristine biochar, modification of biochar is done via physical, chemical, and biological methods. This chapter provides an overview of pristine biochar, including its production, modification, differences between pristine and engineered/modified biochar and multi-dimensional applications. Additionally this chapter covers knowledge gaps and perspectives in the domain of biochar technology and application.KeywordsPyrolysisCarbon sequestrationBiocharWastewaterHydrochar
... Most studies have found that biochar application improves soil fertility, increases crop yields, reduces greenhouse gas emissions and increases soil carbon stocks [53,54]. It was further demonstrated that biochar can be used as a soil additive because its structure allows it to bind and retain water in the soil. ...
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Spent coffee ground is a massively produced coffee industry waste product whose reusage is beneficial. Proximate and ultimate and stochiometric analysis of torrefied spent coffee ground were performed and results were analyzed and compared with other research and materials. Spent coffee ground is a material with high content of carbon (above 50%) and therefore high calorific value (above 20 MJ·kg−1). Torrefaction improves the properties of the material, raising its calorific value up to 32 MJ·kg−1. Next, the phytotoxicity of the aqueous extract was tested using the cress test. The non-torrefied sample and the sample treated at 250 °C were the most toxic. The sample treated at 250 °C adversely affected the germination of the cress seeds due to residual caffeine, tannins and sulfur release. The sample treated at 350 °C performed best of all the tested samples. The sample treated at 350 °C can be applied to the soil as the germination index was higher than 50% and can be used as an alternative fuel with net calorific value comparable to fossil fuels.
... However, the key factors affecting vegetable growth and quality are not always constant. They are influenced by vegetable species and soil conditions (Jyoti et al. 2018). In this study, the average comprehensive benefit improvement of the pak choi was 123%. ...
Article
The properties of biochar determine its ability to alleviate soil acidity and improve plant growth; however, its key properties remain unclear. Therefore, the purpose of this study was to screen the key characteristics of biochar that strongly influence soil acidity and plant growth to obtain a better estimation of biochar characteristics that is suitable for acid soil amelioration. Pak choi was selected as the experimental plant in this pot trial. Soil acidity and pak choi biomass were used to estimate the effect of biochar derived from different organic wastes on acid soil amelioration. Pearson’s correlation combined with a random forest model analysis was applied to investigate the relationship between the characteristics of biochar and soil acidity or plant growth. The results showed that the presence of biochar altered the soil pH by − 0.2 to 1.7 unit and pak choi biomass yield by − 6% to 314%. The Ca, Mg, and P contents (importance = 34.6%), basic surface functional groups, and BET surface area significantly affected the soil acidity. The properties of biochar, including the Fe content, dissolved organic carbon (DOC), electrical conductivity (EC), and micropores, played pivotal roles in promoting pak choi growth, and the importance of the above properties reached to 53.9% according to random forest model analysis. In addition, all biochars used in this study improved soil fertility by 48.26–113.04%, and the comprehensive benefits of pak choi improved by 34.14–180.11%, especially for sheep dung biochar and bone powder biochar. Biochars with rich pores, abundant Ca, Mg, P, and Fe, high DOC and EC, and basic surface functional groups are favorable for acid soil improvement and pak choi growth. Applying biochar to acid soils may be a promising way to improve the comprehensive benefits of soil fertility and vegetable production.
... Biochar is generally characterized by a large specific surface area, high porosity and degree of stability, and well-developed pore structure (Edeh et al. 2020). Biochar has been recognized as a long-term promising solution in improving water infiltration, aeration, porosity, soil water retention, hydraulic conductivity, and reducing ineffective evaporation (Rawat et al. 2019;Li et al. 2020). In addition, soil amended with biochar directly improved soil thermal conductivity, soil water and nutrient retention, crop yield, and water use efficiency (WUE) (El-Naggar et al. 2019;Gao et al. 2020;Ma et al. 2020;Obia et al. 2020). ...
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Purpose Environmentally friendly mulching material and appropriate tillage practice are needed to solve plastic film residues in agricultural production in ridge-furrow rainwater harvesting technology (RFRHT) in the Loess Plateau in China. Materials and methods A field experiment in randomized block design was conducted to (1) investigate the runoff coefficient for three ridge widths (30, 45, and 60 cm) using three ridge mulching materials (ridges compacted with soil (RCS), maize straw biochar-soil mixture (SBM), and cow dung biochar-soil mixture (DBM)); (2) the effects of three ridge widths using three ridge mulching materials on soil moisture, temperature, nutrients, fodder yield, quality, and water use efficiency (WUE) of sainfoin and conventional flat planting (FP) as a control, during two consecutive sainfoin-growing years: 2017 and 2018. Results The predicted runoff coefficient for RCS30, RCS45, RCS60, SBM30, SBM45, SBM60, DBM30, DBM45, and DBM60 (subscripts 30, 45, and 60 referred to ridge widths) was 0.31, 0.33, 0.34, 0.26, 0.30, 0.31, 0.22, 0.24, and 0.25, respectively, over 2 years. DBM had a higher concentration of total nitrogen and organic matter compared to SBM, while SBM had a higher concentration of Olsen phosphorus and available potassium compared to DBM. The higher runoff coefficient and soil moisture in SBM led to higher fodder yield, WUE, and condensed tannin content of sainfoin, compared to DBM. Compared to FP, in RCS, fodder yield and WUE of sainfoin decreased by 8.8–17.8% and 0.6–2.6 kg ha⁻¹ mm⁻¹, respectively. Condensed tannins concentration of sainfoin for RCS, SBM, and DBM increased by 4.1 −9.0%, 11.4 −21.8%, and 9.4 −15.2%, respectively. Fodder yield in SBM and DBM increased by 14.3 −19.5% and 7.1 −10.0%, respectively, while WUE in SBM and DBM increased by 6.7 −8.5 and 4.7 −5.5 kg ha⁻¹ mm⁻¹. Conclusion Ridges compacted with biochar-soil mixture, especially with maize straw biochar-soil mixture, increased fodder yield, WUE, and condensed tannin content of sainfoin. The optimum ridge width in SBM and DBM for sainfoin production was 46–49 and 41 cm, respectively.
... Despite this, the long-term beneficial impacts of biochar and fertilizers on farmlands may be limited by weak soil structure and weathering, which makes them more vulnerable to erosion and nutrient leaching (Ding et al., 2016). According to reviews by (Guo et al., 2016;Mulabagal et al., 2017;Rawat et al., 2019), amending soils with biochar (a by-product of the pyrolysis of plant biomass in a low-oxygen environment) reduces nutrient leaching and improves soil cation exchange capacity, soil organic matter, microbial biomass, pH, and soil moisture retention. Smallholder farmers in Northern Ghana use legume-cereal intercrop systems with organic residue inputs, although yield responses are generally limited by the aforementioned soil issues. ...
... Despite this, the long-term beneficial impacts of biochar and fertilizers on farmlands may be limited by weak soil structure and weathering, which makes them more vulnerable to erosion and nutrient leaching (Ding et al., 2016). According to reviews by (Guo et al., 2016;Mulabagal et al., 2017;Rawat et al., 2019), amending soils with biochar (a by-product of the pyrolysis of plant biomass in a low-oxygen environment) reduces nutrient leaching and improves soil cation exchange capacity, soil organic matter, microbial biomass, pH, and soil moisture retention. Smallholder farmers in Northern Ghana use legume-cereal intercrop systems with organic residue inputs, although yield responses are generally limited by the aforementioned soil issues. ...
... Biochar is a carbon-derived material that is produced from the thermochemical conversion of biomass or waste biomass in the absence or low oxygen content and used as a soil amendment [5]. It can also be used for carbon sequestration or for improving soil productivity [5][6][7][8][9][10]. Some studies have shown that charcoal in boreal soils increases nitrogen consumption and tree growth [11,12]. ...
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Ammoniacal nitrogen (N-NH3) is one of the pollutants that has adverse effects on the environment and is present in most effluents generated by mining operations. Therefore, mining companies must manage it to keep it below the regulated discharge criteria to avoid environmental contamination. In this context, the present study aims to valorize N-NH3 in the form of ammonium sulphate ((NH₄)₂SO₄) for the manufacture of biochar pellets used as growth substrates for the production of forest seedlings. The biochar was first produced by fast pyrolysis, at 320 °C, and different recipes of pellets were then prepared to evaluate their hardness, binder type and content, humidity and durability. The optimal granule chosen was composed of biochar, corn starch and canola oil. Six combinations of different compositions were then prepared as substrates for black spruce growth: (1) Peat (P); (2) Peat and bulk biochar (PB); (3) Peat and bulk biochar impregnated with ammonium sulfate (PBAS); (4) Peat and biochar pellets impregnated with water (PBPeW); (5) Peat and biochar pellets impregnated with an ammonium sulfate solution (PBPeAS); (6) Peat, biochar pellets impregnated with ammonium sulfate and perlite (PBPeASPer). The effects of these sub-strates on the growth of black spruce seedlings, as well as fertilizer leaching, were measured. The results show that seedling biomass is equivalent to the control for the granular treatment, but higher biomass was obtained with bulk biochar (PB). This shows that a quarter of peat could be replaced by biochar to obtain similar or even better results of biomass yield and, consequently, solve part of the supply issue. As to plant nutrition, no tendency was observed for the experiments apart from the higher proportion of Ca in spruce needles. The prepared biochar-based pellet substrate appears to not only be advantageous for spruce production but also for other uses such as golf courses, forestry producers and horticultural nurseries using conventional fertilizers and peat as growing media. In addition, these approaches could help the Abitibi-Témiscamingue region in Québec, Can-ada to build a local circular economy.
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Soil amendment with nanobiochar (a novel nanomaterial) may benefit crop production by modulating water-holding capacity, increasing biotic interactions, and providing an additional source of macro- and micronutrients. We reported nano-biochar-induced changes in carrot agronomic, ionomic, and nutriomic profiles. Root-zone application of nanobiochar at four levels [0 (control), 0.1 (S1), 0.3 (S3), and 0.5% (S5)] was performed at sowing and foliar spray of nanobiochar suspension [0 (control), 1 (F1), 3 (F3), and 5% (F5)] after 30 days of germination. The combined application of soil and foliar nanobiochar induced more growth and improved pigments in the shoot and storage root of the carrot. Results indicated maximum improvements (+ 3–4 folds) in shoot agronomic traits at S3F3. This trend was also evident in the case of chlorophyll content (both a and b), some primary and specialized metabolites (sugars, free amino acids, phenolics, flavonoids), and P, N, and K content in leaves which were maximum at S3F3. The chlorophyll a, b, and carotenoids in shoot showed 2-, 2-, 4-fold, and anthocyanin, β-carotene, and lycopene in roots showed 2-, 2-, and 3-fold increase at S3F3, and it showed a fold increase in than control. While carrot root weight (4-fold increase than at control) was maximum at S3F1. The root nutriomic profile revealed the highest N, P, and K content and root pigments (lycopene, beta-carotene, and anthocyanins) at S3F1, while the least values were associated with control plants. These results showed that nanobiochar could be used as sustainable fertilizer due to its beneficial effects and high nutritional content.
Chapter
The dependence on fertilizers and pesticides to enhance agricultural outputs owing to the demands of a growing human population creates the need for soil maintenance to sustain agriculture. Various activities are responsible for the maintenance of soil quality. Among the wide range of conventional agricultural practices, biochar is one of the best biosorption agents that has received much attention recently due to its high adsorption capacity toward various environmental contaminants. It plays a key role in agriculture sustainability by removing pollutants from soil and enhancing crop productivity along with soil fertility. In addition, biochar enhances the efficiency of agricultural soil such as bulk density, moisture content, water holding capacity, hydraulic conductivity and aggregated stability, increased microbial community, and reduced nutrient loss. Along with, biochar mitigates and/or removes hazardous substances in the agricultural soil. The effects of biochar on soil properties vary widely depending on the characteristics of the soil and the biochar. The aim of this chapter is to provide a current state of knowledge regarding the effects of biochar on agricultural sustainability, application of biochar for soil treatment, and future research directions for long‐term use of biochar.
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Disposal of potato waste at landfills results in nutrient losses and pollution of air and groundwater. Biochar from the waste could minimise carbon dioxide (CO2) emission, increase storage of carbon (OC) and recycle nutrients in soil. This study determined effects of biochar from cull potato (CP) and pine bark (PB) on CO2 emission and available nitrogen (N), phosphorus (P), and potassium (K) in contrasting soils. Biochar pyrolysed at 350 °C (CP350; PB350) and 650 °C (CP650; PB650), and feedstocks were applied to Luvisol and Ferralsol soils at rates equivalent to 10 Mg C ha−1 and incubated at 25 °C. The carbon dioxide (CO2-C) was captured in 1 M NaOH and the solution was back-titrated with 0.5 M HCl after 3, 7, 14, 21, 28, 42, 56, and 84 days. A similar experiment was conducted, with destructive sampling, including after 112 and 140 days, for analysis of ammonium-N, nitrate-N, and available P and K. Biochar increased CO2 in the Luvisol but decreased it in the Ferralsol when compared with the feedstocks and the control. Higher CO2 was emitted from PB biochar than from CP in the Luvisol. Ammonium-N increased in the Luvisol, reaching a peak after 14 days, and decreased after 42 days, while, in the Ferralsol, it decreased to below detection after 21 days. Nitrate-N increased with decline in ammonium-N, except in CP, in both soils. Available P increased within 14 days and declined after 28 days, with generally higher levels in the Ferralsol. Available K increased with addition of CP and its biochar, with greater availability at higher pyrolysis temperatures for both soils throughout the incubation. The findings showed that application of CP biochar causes emission of CO2 to increase in Luvisol and decrease in Ferralsol, while available K increase, with no effects on N availability, relative to control soils.
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The leather industry sector is one of the leading industries playing a significant role in the generation of foreign currency in Ethiopia. However, the environmental management for this industry is generally ignored. As a result, chromium (Cr) accumulates in vegetable tissues at toxic concentrations. The present pot experiment was therefore conducted to investigate the effect of biochar application on the selected properties of chromium polluted soils and uptake of lettuces grown in polluted soils. Biochar produced from maize stalk was applied at the rates of 0, 5 and 10t/ha on soils artificially polluted with Cr at the levels of 0, 10 and 20ppm. The study showed a significant (P<0.01) increase in pH, electrical conductivity, organic carbon, total nitrogen, available phosphorous, cation exchange capacity and exchangeable bases due to application of biochar. Moreover, uptake of nitrogen, phosphorous and potassium were significantly (P<0.01) increased by addition of biochar. A significant (P<0.01) reduction in the uptake of Cr due to application of biochar was also observed in heavily Cr polluted soils (20ppm). Therefore, application biochar is very imperative to increase soil fertility, enhance nutrient uptake, ameliorate Cr polluted soils and reduce the amount of carbon produced due to biomass burning.
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Increasing energy demand, environmental pollution, and soaring CO2 emissions necessitate the exploitation of renewable sources of energy. Lignocellulosic biomass is a naturally abundant resource that can be considered as one of the promising environment-friendly renewable energy options. Biochar is a carbon-rich, porous solid produced by the thermal decomposition of biomass under anoxic conditions and at moderate temperatures; it is suitable for soil remediation and with some functionalization can be converted into functional materials, finding applications in catalysis for biofuel production. Biochar can be produced on a scale ranging from large industrial facilities to individual farms since it is a solid residue formed in the pyrolysis of biomass. How to use it effectively is a critical question for improving economic viability and environmental sustainability of biomass conversion technologies. Biochar production and applications for soil remediation and pollutant removal has been discussed and reviewed extensively. However, there are limited critical reviews on the biochar formation mechanism, functionalization of biochar materials for catalysis and biofuel production applications. Therefore, this study reviewed the current literature on the activities and advantages of biochar derived materials used in biofuel production. The preparation methods and prevailing reaction conditions affecting the catalytic activity of the biochar derived material along with their reusability aspect are discussed in this review.
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Use of biochar for soil fertility improvement is gaining popularity due to its potential to improve soil quality, increase crop yield, and sequester carbon from the atmosphere-biosphere pool into the soil. A 40-day pot experiment was carried out to investigate the effects of corncob biochar and compost applied alone (at a rate of 2%, w/w) or in combination (1% of each, thus 1% compost + 1% biochar) on soil physicochemical properties, growth, and yield of maize on two soils of contrasting pH and texture collected from the Rainforest and Coastal Savannah agroecological zones of Ghana. Biochar and compost applied alone or in combination significantly increased soil pH, total organic carbon, available phosphorus, mineral nitrogen, reduced exchangeable acidity, and increased effective cation exchange capacity in both soils. Additionally, combined application and single application biochar or compost additions increased the plant height, stem girth, and dry matter yields of two maize (local (“ ewifompe ”) and hybrid ( Obaatanpa )) varieties used in the study. The study showed that biochar applied alone or in combination with compost offers the potential to enhance soil quality and improve maize yield.
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Understanding the key roles of biochar properties on microbial activity in different soil types are essential to know the conditions of biochar to reach the desired benefits, and how can the trade-offs between various environmental and the biological effects of biochar. Focused on certain key functions of biochar, this review synthesizes the biochar-microbe interaction mechanisms pertinent to those questions, covering. The microbial community modification by biochar, via alteration of nutrient availability and soil characters, and the electron transfer between microbial cells and contaminants facilitated by biochar. In generally biochar and soil beneficial microorganism interaction cannot be determined in a single conclusion as biochar can affect soil beneficial microorganism positively and as well as negatively. This study provided evidence that beneficial soil microorganism improvements were directly or circuitously affected by biochar incorporation into soil results from the combination of a direct effect that is dependent on the type of char and a microbiome shift in root-associated beneficial bacteria. Therefore, in order to use in biochar for soil amendment, biochar feedstock, soil type, microorganism species, pyrolysis temperature must be considered.
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Biochar (BC), known as the new black gold, is a stable, novel carbonaceous by-product that is synthesized through pyrolysis of biological materials in the absence of O2. Recently, an emerging interest in the application of BC as a robust soil amendment has given rise to a broad research area in science and technology. It is considered a promising remediation option for heavy metal (HM)-contaminated soils to reduce HM bioavailability to plants. Remediation efficacy of BC depends on the porosity, composition, pyrolysis temperature, feedstock, and residence time of pyrolysis. This review article aimed to present an overview of BC use in the immobilization of HMs, i.e., Cd, As, Pb, Zn, Ni, Cu, Mn, Cr, and Sb, in contaminated soils. The remaining uncertain factors, including the specific soil HM immobilization mechanisms, long-term beneficial effects, and potential environmental risks associated with BC application are analyzed. Future research must be conducted to ensure that the management of environmental pollution is in accord with ecological sustainability and adaptation of the black gold biotechnology on a commercial basis for immobilization of HMs in contaminated soils.
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Excessive fertilization is a common agricultural practice that has largely reduced soil nutrient retention capacity and led to nutrient leaching in China. To reduce nutrient leaching, in this study, we evaluated the application of biochar, compost, and biochar-compost on soil properties, leaching water quality, and cucumber plant growth in soils with different nutrient levels. In general, the concentrations of nutrients and heavy metals in leaching water were higher under high-nutrient conditions than under low-nutrient conditions. Both biochar and compost efficiently enhanced soil cation exchange capacity (CEC), water holding capacity (WHC), and microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP), reduced the potential leaching of nutrients and heavy metals, and improved plant growth. The efficiency of biochar and compost in soil CEC, WHC, MBC, MBN, and MBP and plant growth was enhanced when applied jointly. In addition, biochar and biochar-enhanced compost efficiently suppressed plant-parasitic nematode infestation in a soil with high levels of both N and P. Our results suggest that biochar-enhanced compost can reduce the potential environmental risks in excessively fertilized vegetable soils.
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Biochar is nowadays largely used as a soil amendment and is commercialized worldwide. However, in temperate agro-ecosystems the beneficial effect of biochar on crop productivity is limited, with several studies reporting negative crop responses. In this work, we studied the effect of 10 biochar and 9 not pyrogenic organic amendments (NPOA), using pure and in all possible combinations on lettuce growth (Lactuca sativa). Organic materials were characterized by 13C-CPMAS NMR spectroscopy and elemental analysis (pH, EC, C, N, C/N and H/C ratios). Pure biochars and NPOAs have variable effects, ranging from inhibition to strong stimulation on lettuce growth. For NPOAs, major inhibitory effects were found with N poor materials characterized by high C/N and H/C ratio. Among pure biochars, instead, those having a low H/C ratio seem to be the best for promoting plant growth. When biochars and organic amendments were mixed, non-additive interactions, either synergistic or antagonistic, were prevalent. However, the mixture effect on plant growth was mainly dependent on the chemical quality of NPOAs, while biochar chemistry played a secondary role. Synergisms were prevalent when N rich and lignin poor materials were mixed with biochar. On the contrary, antagonistic interactions occurred when leaf litter or woody materials were mixed with biochar. Further research is needed to identify the mechanisms behind the observed non-additive effects and to develop biochar-organic amendment combinations that maximize plant productivity in different agricultural systems.
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The dependence on chemical fertilizers in agriculture leads to environmental hazards, destruction of biological communities and poorer soil quality. Addition of biochar in soil alters overall soil properties, encourages microbiota and increases nutrients' holding and absorption capacity; hence can be used to improve soil fertility for sustainable agriculture. Cow dung (CD), pine wood (PW) and pine needles (PN) found abundantly in the Himalayan region were selected for preparing biochar. Since phosphate solubilizing fungi have also been cited in the literature to enhance plant growth, the Penicillium sp. K4 strain was added along with biochar. A pot experiment with mung bean plants with eight different treatments was conducted. Generally, all the treatments showed a significant increase in growth and yield compared to plants grown in untreated soil. However, the biochar prepared from pine needles was found to be the best. It was observed that addition of biochar to soil influenced the overall growth of plants positively but the inoculation of Penicillium sp. K4 with biochar improved this effect further. Hence, it can be concluded that the addition of bio-inoculant in biochar can be a useful practice for enhancing crop productivity.
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Soil microorganisms play a main role in the nutrient cycle and they also play an important role in soil health. This article studies the influence of three rates of biochar (0.5, 1 and 3%) in comparison with control (0 biochar) in two different soils (Valečov and Čistá) on soil microbiota activities. The biochar was prepared from 80% of digestate from Zea mays L. and 20% of cellulose fibres by pyrolysis (470°C, 17 min). The biochar ability to influence microbial processes in soil was determined by respiration and nitrification tests. There were no significant differences between basal respiration of control samples and biochar-amended samples. Basal respiration in the Valečov soil reached average amounts from 1.32 to 1.52 mg CO<sub>2</sub>/h/100 g. In the Čistá soil, basal respiration reached average amounts from 1.40 to 1.49 mg CO<sub>2</sub>/h/100 g. No significant differences were proved also in nitrification tests of both soils. Nitrifying potential was the highest in 3% rate of biochar amendment. There were no negative changes in the measured soil parameters. CO<sub>2</sub> efflux was not higher in biochar-amended soil.
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Biochar is considered to be a potential soil amendment. However, its implications for soil physical and hydraulic properties have not been widely discussed. Changes in the soil physical environment influence the numerous services that soils provide. This paper (i) reviewed the impacts of biochar on soil compaction, mechanical, structural, hydraulic, and thermal properties; (ii) discussed factors affecting biochar performance; and (iii) identified research areas. Biochar generally reduces soil bulk density by 3 to 31%, increases porosity by 14 to 64%, and has limited or no effects on penetration resistance. Biochar increases wet aggregate stability by 3 to 226%, improves soil consistency, and has mixed effects on dry soil aggregate stability. It increases available water by 4 to 130%. Saturated hydraulic conductivity decreases in coarse-textured soils, and increases in fine-textured soils following biochar application. Studies on other properties are few but suggest that biochar reduces tensile strength and particle density, alters water infiltration, moderates soil thermal properties, and has minimal effect on soil water repellency. Sandy soils appear to respond more to biochar than clayey soils. Biochar effectiveness increases as the amount of biochar applied increases. A decrease in biochar particle size can increase water retention but may reduce saturated flow. Field-scale and long-term studies assessing all soil physical properties under different scenarios of biochar management are needed. Overall, biochar generally improves the soil physical environment, but long-term field studies are lacking to conclusively ascertain the extent of biochar effects. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved