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23-134-0
Soil organisms in organic and conventional systems
SOIL ORGANISMS IN ORGANIC AND CONVENTIONAL CROPPING SYSTEMS
Wagner Bettiol1,2*; Raquel Ghini1,2; José Abrahão Haddad Galvão1; Marcos Antônio VieiraLigo1; Jeferson Luiz de Carvalho Mineiro1
1Embrapa Meio Ambiente, C.P. 69 - CEP: 13820-000 - Jaguariúna, SP.2CNPq Fellow. *Corresponding author <[email protected]>
ABSTRACT: Despite the recent interest in organic agriculture, little research has been carried out in this area. Thus, the objective of this study was to compare, in a dystrophic Ultisol, the effects of organic and conventionalagricultures on soil organism populations, for the tomato (Lycopersicum esculentum) and corn (Zea mays)crops. In general, it was found that fungus, bacterium and actinomycet populations counted by the number ofcolonies in the media, were similar for the two cropping systems. CO evolution during the cropping season
was higher, up to the double for the organic agriculture system as compared to the conventional. The numberof earthworms was about ten times higher in the organic system. There was no difference in the decompositionrate of organic matter of the two systems. In general, the number of microartropods was always higher in theorganic plots in relation to the conventional ones, reflectining on the Shannon index diversity. The higherinsect population belonged to the Collembola order, and in the case of mites, to the superfamily Oribatuloidea. Individuals of the groups Aranae, Chilopoda, Dyplopoda, Pauropoda, Protura and Symphyla were occasionallycollected in similar number in both cropping systems. Key words: soil microorganisms, organic agriculture, microartropods, cropping systems, environmental impacts
ORGANISMOS DO SOLO EM SISTEMAS DE CULTIVO ORGÂNICO E CONVENCIONAL
RESUMO: Apesar do crescente interesse pela agricultura orgânica, são poucas as informações de pesquisadisponíveis sobre o assunto. Assim, num Argissolo Vermelho-Amarelo distrófico foram comparados os efeitosde sistemas de cultivo orgânico e convencional, para as culturas do tomate (Lycopersicum esculentum) e domilho (Zea mays), sobre a comunidade de organismos do solo e suas atividades. As populações de fungos,bactérias e actinomicetos, determinadas pela contagem de colônias em meio de cultura, foram semelhantespara os dois sistemas de produção. A atividade microbiana, avaliada pela evolução de CO manteve-se
superior no sistema orgânico, sendo que em determinadas avaliações foi o dobro da evolução verificada nosistema convencional. O número de espécimes de minhoca foi praticamente dez vezes maior no sistemaorgânico. Não foi observada diferença na taxa de decomposição de matéria orgânica entre os dois sistemas. De modo geral, o número de indivíduos de microartrópodos foi superior no sistema orgânico do que nosistema convencional, refletindo no maior índice de diversidade de Shannon. As maiores populações deinsetos foram as da ordem Collembola, enquanto para os ácaros a maior população foi a da superfamíliaOribatuloidea. Indivíduos dos grupos Aranae, Chilopoda, Dyplopoda, Pauropoda, Protura e Symphyla foramocasionalmente coletados e de forma similar entre os sistemas. Palavras-chave: microbiota do solo, agricultura orgânica, microartrópodos, sistemas de cultivo, impacto ambiental
INTRODUCTION
the use of highly soluble fertilizers, pesticides and growthregulators must be excluded in this system (Paschoal,
Contamination of the water-soil-plant system with
1995). Not only does the system have to satisfy the need
pesticides and fertilizers, in addition to breaking up the
for reducing the environmental negative-impact problems
soil structure due to inadequate use of machinery and
caused by intensive agriculture, it must also be
implements, is one of the main problems caused by
economically competitive. In comparing the organic and
intensive agriculture. The implementation of integrated
the conventional cropping systems, an important step is
cropping systems and the reduction of the external
to establish which social, economic and ecological factors
energy requirements have been suggested to minimize
influence the production systems the most. Besides, a
these problems. The organic cropping system is defined
knowledge of those factors allows for a better
as a production system that is sustainable in time and
understanding of how the production systems are
space, by means of management and protection of the
natural resources, without the use of chemicals that are
With respect to the biological activity, in studies
aggressive to humans and to the environment, retaining
to compare the conventional, integrated and organic
fertility increases, soil life and biological diversity. Thus,
cropping systems, Bokhorst (1989) found that the number
Scientia Agricola, v.59, n.3, p.565-572, jul./set. 2002
of worms in a soil planted with sugar beets was five times
before liming: pH (CaCl ) 4.4; OM 0.6%; P (resin) 1 µg
higher in the organic system than in other systems, and
cm-3; K 0.5; Ca 7; Mg 7; H + Al 28; CEC 43 and S 15
that the percentage of wheat and potato roots infected
mmol dm-3 of soil; and V 35%. The studies were
with arbuscular mycorrhizae was twice as high in the
conducted from January 1993 to September 1995.
organic as compared to the conventional and integrated
The experiment was set up as randomized blocks
systems. Gliessman et al. (1990, 1996), working with
with six replicates, and plots measuring 25 x 17 m. Tomato
similar objectives, compared conventional and organic
planting pits were spaced 0.5 m apart with 1.20 m between
strawberry cropping systems in areas where farmers
rows. Each plot was split in two halves, the first 12.5 x 17
became organic producers, and verified an increase in
m-half being planted with the variety Débora and the other
the number of plants infected with mycorrhizae. Swezey
planted with the variety Santa Clara. Therefore, each of
et al. (1994) found higher microbial biomass in the soil
the twelve rows contained 17 planting pits for each variety.
and in arbuscular mycorrhizae in the organic system than
The edging between plots was 10 m wide and was planted
in the conventional, in an area being changed from
with sorghum. Two tomato plants were transplanted per
conventional into an organic apple growing area. All these
pit. The tomato crop was conducted using the stake
studies emphasize the biological elasticity in the organic
system, with one or two stems/plant. The number of stems
systems as a fundamental characteristic, influencing the
was determined based on the successful establishment of
the seedlings. Furrow irrigation and plant pruning were
With regard to soil organisms, Brussaard et al.
(1988, 1990) verified that the total biomass of soil
The entire area received 4.2 t ha-1 lime and 2 kg
organisms was higher for the integrated than for the
per meter, 110 and 12 days before planting, respectively.
conventional cropping system, with figures averaging 907
Fertilization in the organic system employed 2.5 L of
kg C ha-1 and 690 kg C ha-1, respectively. Of these
organic compost (pH=6.4; C=29.6%; N=1.6%; P O =1.8;
biomasses, bacteria accounted for over 90%, fungi
K O=0.17% and U=25.3%) plus 130 g of single
represented approximately 5% and protozoa were less
superphosphate/pit; additionally, 2.5 L of organic
than 2% of the total biomass. El Titi & Ipach (1989) studied
compost, 60 g of single superphosphate, and 60 g of
the effect of a cropping system with low input rate index
dolomitic lime/pit were applied as sidedressing; plants
as well as the conventional system on the soil fauna
were sprayed twice a week with biofertilizer (Bettiol et al.,
components and observed there were smaller populations
1997), at concentrations of 5 or 10%. In the conventional
of nematodes pathogenic to plants, higher worm biomass,
system, fertilization consisted of 200 g 4-14-8 (NPK)/pit
and larger populations of collembolans and Mesostigmata
and, after planting, a sidedressing application of 30 g N,
mites in the system with low input index. Collembola is a
33 g K and 10.5 g P/pit; 52 days after planting and
microarthropod related to the soil’s capacity to suppress
beyond, plants were sprayed once a week with foliar
Rhizoctoniasolani (Lartey et al., 1994). Rickerl et al. (1989)
fertilizer [5-8-0,5 (NCaB)] at a rate of 3 mL L-1.
found that populations of this organism were 29% larger
In the conventional system, 0.15g/pit of active
in soils under minimum tillage as compared to soils under
ingredient of the insecticide carbofuram were applied
conventional tillage. Ladd et al. (1994) verified that the C
before planting. According to the procedures utilized by
biomass of microbial populations was greater in soils under
conventional local growers, a blend of insecticides,
crop rotation than in soils under continuous monoculture;
fungicides and miticides was sprayed twice a week, after
greater in soils where plant residues were incorporated or
planting. Active ingredients of fungicides sprayed during
remained on the soil surface than where they were
the crop cycle were metalaxyl, mancozeb, chlorothalonil,
removed; and smaller in a nitrogen-fertilized soil than in
copper oxychloride, kasugamycine, cuprous oxide, methyl
non-fertilized ones. This information is important because
thyophanate, iprodione, benomyl, cymoxamil, maneb and
these are characteristics that contribute to soil biological
monohydrate zinc sulphate, at the rates recommended
equilibrium, nutrient mineralization and suppressive
by the manufacturers. Insecticides used were
capacity toward plant pathogens, among others, making
deltamethrin, permethrin, methomyl, methamidophos,
the system less dependent on external input.
acephate, avermectin and cartap, also at the
The objective of this work was to evaluate the
influence of the organic and the conventional cropping
Extracts of black pepper, Eucalyptus, garlic and
systems, for tomato and corn, on the community of soil
fern; Bordeaux mixture, and biofertilizer were applied
twice a week (Bettiol et al., 1997; Abreu Junior, 1998) tocontrol diseases and pests in the organic system. These
MATERIAL E METHODS
applications were performed according to the programadopted by organic producers in the region.
The experiment was carried out in Jaguariúna,
Weed control was carried out by mechanical
SP, Brasil, latitude 22° 41' S, longitude 47° W Gr., and
weeding and with the herbicide glyphosate (directed
an altitude of 570 m, on a dystrophic Ultisol, with the
spray) on post-planting in the conventional system, and
following chemical properties of the 0-0.2 m topsoil layer,
with mechanical weeding in the organic system. Scientia Agricola, v.59, n.3, p.565-572, jul./set. 2002
Soil organisms in organic and conventional systems
After harvesting the tomato the area was planted
animals to leave the soil. Samples remained in the extractor
with ‘BR 201’ corn; sowing occurred 178 days after
for 72 hours. An alcohol:glycerin (1:1) aqueous solution was
planting the tomatoes. The organic system plots received
used for specimen preservation. After extraction, the animals
an application of 4 m3 of organic compost and single
were counted and separated into groups with the use of a
superphosphate at the rate of 20 g per meter; in addition,
stereoscopic microscope. Mites and other smaller animals
the biofertilizer was sprayed at 10% as sidedressing. In
were fixed on permanent slides for identification. Data were
the conventional system fertilization consisted of 500 kg
expressed as number of individuals per 785 cm3 soil.
ha-1 of the 4-14-8 NPK rate applied pre-planting and 15 g
Shannon’s diversity index (Shannon & Weaver, 1949) was
m-1 urea as sidedressing. Weed control used the herbicide
calculated for a better understanding of the variations in the
paraquat (directed spray) in the conventional system, and
mechanical weeding was used in the organic.
Organic matter decomposition rate estimate: The
After harvesting the corn, ‘Débora’ tomatoes were
decomposition rate was estimated via loss of organic
again cultivated, as previously described. Transplantation
content from leaf litter confined in nylon bags, 20 x 20
was made 401 days after the initial tomato planting.
cm, with a 1 mm mesh, where 10 g of elephant grassdried at 60°C for three days. The field-collected samples,
Soil Microorganisms
were collected every 20 days and transported to the
A sample composed of 20 sub-samples of soil
laboratory, dried at 105°C for 24 hours and ashed at
taken at the planting row from the 0-7 cm-depth layer was
600°C for 4 hours. The loss of organic matter estimate
obtained for each plot. Samples were placed in plastic
was calculated using the equation described by Santos
bags and immediately transported to the laboratory.
& Whitford (1981), which corrects for the adhesion of soil
Assessments were performed within 24 hours after
Evaluation of earthworms in the soil: The first
Populations of fungi, bacteria and actinomycetes:
evaluation was carried out 81 days before the first
The populations of fungi, bacteria and actinomycetes were
planting, i.e., before plowing and liming. A hand excavator
quantified through the serial-dilution method, followed by
was used to collect samples; two samples were collected
plating in culture medium. Martin’s culture medium (Tuite,
from each plot, up to a depth of 20 cm, with 20 cm
1969) added of 100 mg mL-1 streptomycine was used for
diameter. Shortly after planting the tomatoes, and 90 days
fungi; for bacteria, the agar nutrient medium added of
later, samples were taken at about 40 cm depth, with a
nistatin (42 mg L-1) was used; for the actinomycetes, the
diameter of 10 cm. Three samples were collected from
alkalized agar-water medium was utilized. Aliquots (0.1
the compost: one from the pile surface; another at a layer
mL) from three dilutions, for each soil sample, were
up to 35 cm, and the third at a depth of 90 cm. The worm
transferred to the culture media in three replications.
populations were determined 370, 407, and 471 days
Assessments were performed by counting the number of
colonies per Petri dish and expressed as colony-formingunits/g of dry soil (CFU g-1 dry soil). RESULTS AND DISCUSSION
Total respiratory activity: Total microbial
respiration was evaluated according the method
described by Grisi (1978). Soil samples (200 g) were
actinomycetes were similar for the two cropping systems
incubated for 10, 20, and 30 days within tightly sealed
over the entire period of study, with populations of fungi
containers holding 10 mL of a 0.5 mol L-1 (10 mL) KOH
varying from 104 to 105, whereas populations of bacteria and
solution. At 10-day intervals, the solution was substituted
actinomycetes varied from 105 to 107 CFU g-1 dry soil (Figure
and titrated with 0.1 mol L-1 of HCl. Incubation was
1). Similar results were obtained by Castro et al. (1993),
conducted in the dark, at 25°C. This parameter was
when several types of soybean management were
expressed as g CO (g dry soil-1) (day-1). Since the more
compared, and by Cattelan & Vidor (1990) on soils
substantial changes happened in the first days, only
cultivated with different crop rotation systems. Grigorova &
readings up to the tenth day were used to determine
Norris (1990) justified not adopting this method for
mean values. For the statistical analysis, data were
evaluating soil microorganisms, because only a small
transformed into square root (x + 0.5) and subjected to
fraction of microbial biomass could be cultivated on a
analysis of variance and Duncan’s mean comparison test.
selective medium. However, Cattelan & Vidor (1990)
Soil microarthropods: Collecting was made with a
demonstrated the effectiveness of the method in studies with
Uhland-type, stainless steel auger 5 cm in diameter and 10
different cropping systems. In spite of a similar behavior in
cm in height, totaling four samples per plot. Samples were
regard to microbial populations, starting 145 days after
placed in plastic bags and taken to the laboratory. Collecting
planting the tomatoes, the bacteria populations (Figure 1 C)
was between 8:00 and 10:30 h, 82 days before and 325
were higher in the organic system as compared to the
days after the first tomato seeding, for a total of 16
conventional. This could be due to soil plant cover, like
evaluations. Extraction was according to Tullgren’s modified
Cattelan & Vidor (1990) who found a smaller bacterial
method, which uses heat and desiccation to force the
population on naked as compared to cultivated soil. Scientia Agricola, v.59, n.3, p.565-572, jul./set. 2002
Soil total respiratory activity continued higher in the
organic system during the crop cycles, showing in some
evaluations twice as much as the evolution observed in
the conventional system (Figure 2). Differences were found
during the intermediate period, that is, between 142 and
400 days after planting. There were no statistical
Log10 CFU/g of soil 4,2
differences between treatments at the initial periods or at
the end. The higher respiratory rate in the organic system
could be due to the addition of an exogenous source of
organic matter to the soil and the consequent stimulationof heterotrophic microorganisms (Lambais, 1997).
Observed organic matter decomposition rates
ranged from 15 to 45% of organic carbon loss in a 20-day
period. Rodrigues et al. (1997) observed, in corn cultivatedduring the summer, values reaching 70% of carbon loss
Log10 CFU/g of soil
in a period of 30 days. There was no difference among
results from the organic and the conventional systems
(Figure 3). However, regardless of the system, there was
an influence of time on the organic matter decomposition
rate was, although no interaction between time and the
treatments was found. This suggests that variations found
during the study period could be related to the humidity
and temperature fluctuations that occur in the field, thus
Log10 CFU/g of soil
providing no evidence that the adopted management forms
The CO release method used in this study to
Days after planting
evaluate respiratory activity favors the microorganism
Figure 1 - Dynamic population of fungi, bacteria and actinomycetes
population, since soil manipulation can eliminate the
in soil from organic (- - -) and conventional ( ) cropping
majority of the microarthropod community. Several
systems for tomato and corn. CFU: Colony Forming Units. A=Fungi; B=Actinomycetes; C=Bacteria. The data
authors have, in microcosmos studies, demonstrated the
represent the mean of six replicates. The bars indicate
role microarthropods in soil organic matter decomposition
process. A low fungivore density (Collembola) has astimulating effect on microbial respiration, whereas high
densities inhibited microorganism respiration Barsdate et
al, 1974; Hanlon & Anderson, 1979).
Mites and insects, belonging to various families,
were the two main groups of arthropods found in the soil
in 1993 and 1994 (Tables 1 and 2). In general, rates and
numbers of individuals from these groups were higher in
the organic cropping system, reflecting on Shannon’s
diversity indices, which were higher in the organic system
on all sampling dates (Figure 4), but not on the soil
organic matter decomposition (Figure 3).
The largest populations of insects were from the
Order Collembola, and the number of individuals found in
Figure 2 - CO evolution from soil microorganisms of organic-
the organic system was three times as high as that in the
and conventional systems for tomato and corn crops.
conventional system, during the first nine months (Table
Results were obtained though soil incubation at 25°C
1). During the following six months, the number of
for 10 days. For each planting time, data followed thesame letter did not differ (Duncan 5%).
collembolans remained 20% higher in the organic croppingsystem than in the conventional (Table 2). These data
because these organisms are, for the most part,
agree with El Titi & Ipach (1989), who verified larger
mycophagous, modifying the community of fungi. Because
populations of collembolans for the low-input system than
in this work the practices in the organic system stimulated
for the conventional. Collembolans contribute to the soil’s
the community of collembolans, it can be inferred that
abilitity of suppressing plant pathogens such as
these organisms are responsible, at least in part, for the
Rhizoctonia solani, Fusarium oxysporum f. sp.
suppression ability in soils enriched with organic matter. vasinfectum, and Pythium (Wiggins & Curl, 1979; Curl et
Still, in regard to insects, the number of individuals was
al., 1985a, b; Rickerl et al., 1989; Lartey et al., 1994),
low for the rest of the orders (Tables 1 and 2). Scientia Agricola, v.59, n.3, p.565-572, jul./set. 2002
Soil organisms in organic and conventional systems
Decomposition rate (%)
1 1 8 - 1 3 9 - 2 3 4 - 2 5 5 - 2 7 0 - 2 9 2 - 4 5 1 - 4 7 1 - 5 0 1 -
D a y s a f t e r p l a n t i n g
Figure 3 - Organic matter decomposition rate soil of organic and conventional cropping systems. Shannon´s diversity index
1 1 8 1 3 9 1 6 7 2 1 4 2 3 4 2 5 5 2 7 0 2 9 2 3 1 2 3 3 2
D a y s a f t e r p la n t in g
Figure 4 - Shannon´s diversity index for soil microarthropods of the organic and conventional cropping systems.
During the first nine months of evaluation (Table
populations of collembolans and Gamasida mites in the
1), for both cropping systems, the largest mite population
low-input system than in the conventional.
was of the superfamily Oribatuloidea, followed by the
Due to the more abundance of microarthropods
in the organic system, it was believed that the organic
Passalozetoidea, all in the suborder Oribatida and with
matter decomposition rate would be higher in this system,
similar behavior between cropping systems. In the
because these organisms contribute for organic matter
suborder Gamasida the most abundant population was
degradation and stimulate microbial activity in the soil
Laelapidae and in Actinedida the most abundant was
(Nosek, 1981). Accordingly, when the presence of
Pygmephoridae, both more numerous in the organic
Oribatida and Collembola in litterbags incorporated into the
system. Populations in the suborders Acaridida and
organic and the conventional systems was evaluated, a
Ixodida were very small. In the six subsequent months
larger number of individuals in the litterbags was found for
(Table 2), when only the families of mites were quantified,
the organic system (Melo & Ligo, 1999), indicating that this
the largest population was of Scheloribatidae followed by
system contributes for an increase in biological diversity.
Galumnidae, with similar behavior between the systems.
Since the presence of these organisms in larger numbers
The expressive number of individuals in the families
was not accompanied by a higher decomposition of
Galumnidae and Scheloribatidae for both cropping
organic matter, one can say that the differences in
systems is due to the characteristic these families exhibit
arthropod density found in the soil between the organic
toward occupying space in agroecosystems. In the orders
and the conventional systems did not reflect on the
Actinedida and Gamasida, families Cunaxidae and
organic matter decomposition rate, as evaluated by the
Laelapidae were the largest, respectively. In general, mite
litterbag method. The community of microarthropods in the
population densities in the classes Gamasida and
soil might have, among other factors, influenced microbial
Actinedida were higher in the organic system. The fact
activity, since the organic system showed a higher
that the Gamasida showed high numbers is possibly due
microbial activity potential than the conventional system.
to a large Collembola population, because these
The influence of the soil fauna on the organic matter
organisms are a source of food for this class of mites. El
decomposition rate of forest soils is well documented, but
Titi & Ipach (1989) verified the existence of larger
this is not true for agricultural ecosystems (Crossley et al.,
Scientia Agricola, v.59, n.3, p.565-572, jul./set. 2002
Table 1 - Number of soil microarthropods in the tomato organic (O) and conventional (C) cropping systems.
Data expressed in number of individuals per 785 mL soil and represent the mean of six replicates. Scientia Agricola, v.59, n.3, p.565-572, jul./set. 2002
Soil organisms in organic and conventional systems
Table 2 - Number of soil microarthropods in the corn organic (O) and conventional (C) cropping systems.
Data expressed in number of individuals per 785 mL soil and represent the mean of six replicates. Scientia Agricola, v.59, n.3, p.565-572, jul./set. 2002
1989). In agroecosystems the effect of the fauna on the
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AAB BIOFLUX Advances in Agriculture & Botanics- International Journal of the Bioflux Society Effects of cold stress on some Apricot ( Prunus armeniaca L.) cultivars in different phenological stages Mehdi Rouhani Nia, Alireza Motallebi-Azar, and Habib Davati-Kazemnia Department of Horticultural Sciences, Faculty of Agriculture, University of Tabriz, Corresponding author:
afara cu zuzan ! - Community supported by miniBB forum software scripttransparenta si accesul la informatiile publice. Va multumim ca ne cititi , Redactia. # Postat: 12 Oct 2006 13:42 Citat intinerirea echipei de la primarie este imperios necesara in perspectiva aderari la u.e.schimbati ofosilele lacome post decembriste spre binele orasului nostru drag. # Postat: 13 Oct 2006 17:44 Citat afara c