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CORRELATION BETWEEN CLAY CONTENT AND SEED DEPTH IN NO-TILLAGE CORN (Zea mays L.) / CORRELAÇÃO ENTRE O CONTEÚDO DE ARGILA E A PROFUNDIDADE DE DEPOSIÇÃO DAS SEMENTES MILHO (Zea mays L.) EM PLANTIO DIRETO

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Abstract

The region of Campos Gerais, in the State of Paraná, is leader in grain yields and state-of-the-art no-tillage farming. The widely adopted no-tillage system tends to increment soil variability. There are several studies about spatial variability of soil characteristics affecting grain yield, but not enough attention has been given to the variability resulting of human actions. The objective of this study was to evaluate the correlation of soil clay content and the depth of placement of corn seeds on areas under no-till systems management. The four selected cornfields areas for the study are property of local farm cooperatives associates. The points for evaluation were defined considering the local mapping of soil texture. Clay content varied from 94 to 489 g kg-1 on Plot 1; from 222 to 414 g kg-1 on Plot 2; from 269 to 509 of rows to be considered for plant distribution and seed depth analyses. The coefficient of variation (CV) of plant distribution was between 23 and 56%. For seed depth, the CV was between 18 and 34%. The regression analysis showed high coefficients of determination (r2) for plots 1 and 2 (r2=0,85 and 0,83). The clay content was generally higher on plots 3 and 4. In this case, the analysis of variance was not significant, and the coefficients of determination were low (r2=0,22 and 0,01). Results indicate that clay content values may be used to delimit g kg-1 on plot 3; and from 368 to 698 g kg-1 on plot 4. The type of planter determined the number management zones on the field, where the depth of seed placing in the planting process can be regulated in different ways. Keywords: Soil Texture, Planting Process, Management Zones
Recebido:
Jan/08
CORRELATION BETWEEN CLAY CONTENT AND SEED DEPTH IN NO-TILLAGE
CORN (Zea mays L.)
CORRELAÇÃO ENTRE O CONTEÚDO DE ARGILA E A PROFUNDIDADE DE DE-
POSIÇÃO DAS SEMENTES MILHO (Zea mays L.) EM PLANTIO DIRETO
ABSTRACT
The region of Campos Gerais, in the State of Paraná, is leader in grain yields and state-of-the-art
no-tillage farming. The widely adopted no-tillage system tends to increment soil variability. There
are several studies about spatial variability of soil characteristics affecting grain yield, but not
enough attention has been given to the variability resulting of human actions. The objective of this
study was to evaluate the correlation of soil clay content and the depth of placement of corn seeds
on areas under no-till systems management. The four selected cornelds areas for the study are
property of local farm cooperatives associates. The points for evaluation were dened consider-
ing the local mapping of soil texture. Clay content varied from 94 to 489 g kg-1 on Plot 1; from 222
to 414 g kg-1 on Plot 2; from 269 to 509 of rows to be considered for plant distribution and seed
depth analyses. The coefcient of variation (CV) of plant distribution was between 23 and 56%. For
seed depth, the CV was between 18 and 34%. The regression analysis showed high coefcients
of determination (r2) for plots 1 and 2 (r2=0,85 and 0,83). The clay content was generally higher
on plots 3 and 4. In this case, the analysis of variance was not signicant, and the coefcients of
determination were low (r2=0,22 and 0,01). Results indicate that clay content values may be used
to delimit g kg-1 on plot 3; and from 368 to 698 g kg-1 on plot 4. The type of planter determined the
number management zones on the eld, where the depth of seed placing in the planting process
can be regulated in different ways.
Keywords: Soil Texture, Planting Process, Management Zones5
1 Eng. Agrícola, Prof. Dr., Laboratório de Mecanização Agrícola (Lama), Curso de Agronomia, Universidade
Estadual de Ponta Grossa (UEPG). E-mail: lama1@uepg.br
2 Eng. Agrônomo, Mestrando, Lama/UEPG. E-mail: pwguepg@yahoo.com.br
3 Eng. Agrônomo, MSc, Fundação ABC/Para Pesquisa e Divulgação Técnica. E-mail:
mecaniza@fundacaoabc.org.br
PEDRO HENRIQUE WEIRICH NETO1
PAULO WILLIAM GARBUIO2
LEANDRO MARIA GIMENEZ3
MARCELO JOSÉ COLET4
BioEng, Campinas, v.2, n.1, p.001-007, jan/abr., 2008
RESUMO
A região dos Campos Gerais do Paraná é reconhecida pelo pioneirismo e estado de arte do
sistema plantio direto no Brasil, que associado a outras tecnologias de produção, condições de
solo e clima, propicia a obtenção de altos rendimentos das culturas de grãos. Entretanto, a va-
riabilidade espacial que naturalmente ocorre nos solos desta região é acentuada pelo emprego
do plantio direto. Existem vários estudos sobre o efeito da variabilidade espacial de atributos do
solo no rendimento das culturas, mas pouca atenção tem-se dado à variabilidade resultante da
ação antrópica. O objetivo deste trabalho foi avaliar a correlação do conteúdo de argila do solo e
a profundidade de deposição de sementes de milho em áreas sob plantio direto. As quatro áreas
de produção selecionadas para este trabalho são propriedades de associados de cooperativas
agrícolas locais. Os pontos para avaliação foram denidos considerando o mapeamento local da
textura do solo. O conteúdo de argila variou de 94 a 489 g kg-1 na área 1; de 222 a 414 g kg-1 na
área 2; de 269 a 509 g kg-1 na área 3; e de 368 a 698 g kg-1 na área 4. O número de linhas a ser
considerado para distribuição de plantas e profundidade de semeadura foi equivalente ao número
de linhas da semeadora utilizada. O coeciente de variação (CV) da distribuição de plantas ob-
servado variou de 23 a 56 %. Para a profundidade de semeadura, o CV variou entre 18 e 34%.
A análise de regressão para profundidade de semeadura em função do teor de argila apresentou
coecientes de determinação (r2) para as áreas 1 e 2 igual a 0,85 e 0,83, respectivamente. O
teor médio de argila foi geralmente maior nas áreas 3 e 4. Neste caso, a análise de variância não
foi signicativa e os coecientes de determinação foram baixos (r2=0,22 e 0,01). Os resultados
indicam que os valores de conteúdo de argila do solo podem ser indicativos para delimitar zonas
de manejo, onde a regulagem de profundidade de deposição de sementes de milho pode ser em
taxa variável.
INTRODUCTION
The region of Campos Gerais, in the
State of Paraná, is leader in grain yields and
state-of-the-art farming technology. No-tillage
system is widely adopted, and precision agri-
culture techniques are gradually being estab-
lished. Precision Agriculture (PA) is dened as
a production management system; it is based
on process optimization, and considers spatial
variability and correlated factors (MOLIN, 1997).
The division of the crop eld in smaller
areas, or management zones, based on vari-
ables that affect grain yield is an alternative to
minimize the effects of variability. Some studies
show a correlation between grain yield and soil
physical characteristics (SWAN et al., 1987;
BAKHSH et al., 2000).
The planting process is a source of vari-
ability, and the control over this process is a form
of PA accessible to most farmers. Accuracy and
precision during the planting process increase
production rates and reduce the input
Palavras-chaves: Textura do Solo, Processo de Semeadura, Zona de Manejo.
of seeds and fertilizers.
The structure of the plant is important in
the interception of solar radiation, and is a direct
result of plant population and distribution on
the eld (MEROTTO JUNIOR et al., 1998, and
FANCELLI & DOURADO NETO, 2000). SILVA
& FREITAS (1994) observed that the distance
measured in number of plants was more impor-
tant than in metric units for pollination effective-
ness.
In a study of the planting process, LIU
et al. (2004) observed better correlation of corn
yield to emergence variability, than to plant distri-
bution variability, do not forgetting that problems
in plant emergence can provoke a decrease
on plant population. Several studies describe
some form of correlation between corn yield
and heterogeneity of emergence (NAFZIGER
et al., 1991; MEROTTO JUNIOR et al., 1998).
The temporal dissimilarity of plantlet emergence
may cause losses up to 3.0 Mg per
P.H.WEIRICH NETO, P.W. GARBUIO, L.M.GIMENEZ, M.J. COLET.
BioEng, Campinas, v.2, n.1, p.001-007, jan/abr., 2008
hectare (MEROTTO JUNIOR et al., 1998).
The higher the depth of seed placement,
the higher the consumption of energy for emer-
gence, implying negative influences by the
lower temperatures of the soil and lower levels
of oxygen; conversely, the lower the depth of
placing implies higher susceptibility of the seeds
to water decits. Plants emerging at distinct
speeds, in addition to the initial stress, are likely
to face lower photosynthetic rates due to shad-
ing or having its pollination process affected
(NAFZIGER et al., 1991).
Positive linear correlation between corn
seed depth and emergence time in favorable
temperatures was observed by GUPTA et al.
(1988). PRADO et al. (2001) did not nd sig-
nicant differences in corn emergence speed at
varying seed depths, with water supply. YORI-
NORI et al. (1996) found inverse proportionality
between seed depth and emergence speed of
popcorn seeds.
The literature reports several interesting
planting depths; FANCELLI & DOURADO NETO
(2000) state it is 3 to 5 cm for clay soils, and 4
to 6 cm for sandy soils. WEIRICH NETO (2004)
found the “mathematical optimum” seed depth;
seeds placed above or below the optimum took
longer to emerge.
Seed depth is an important variable,
though very difcult to control. SATTLER (1992)
has developed a device to control seed depth
at planting. In no-tillage, there are common im-
pediments such as residues, irregular surface
and large variability of soil resistance (JANKE &
ERBACH, 1985; MORISON JUNIOR & GERIC,
1985).
Different seed depths and ridge-opening
depths for different water contents in the soil
were observed by FEY (2000). BATEMAN
(1972) found higher standard deviations for
deeper projected depths.
The objective of this study was to evalu-
ate the correlation of soil clay content and the
depth of corn seed placing on areas under no-till
systems management.
MATERIAL AND METHODS
Four properties (plots) were selected: Plot
1, 30 ha, is located at 50º 10’ 00’’ W and 25º 10’
00’’ S; Plot 2, 25 ha, is located at 50º 03’ 00’
W and 25º12’ 00’’S; in Ponta Grossa. Plot 3,
22 ha, is located in Castro, at 49º56’00’’W and
24º51’00’’S. Plot 4, 26 ha, is located in Tibagi,
at 50º08’00’’W and 24º20’00’’S.
The points for evaluation were dened
considering the local mapping of soil texture.
Seed depth and plant distribution was evaluated
at each point. To evaluate seed depth place-
ment, the seedlings were cut close to the soil ten
days after emergence, and after carefully taking
out the roots, the distance from the cut to the
seed was measured, employing ten replications
by each sowing row. The number of sowing rows
of the planter determined the number of rows to
be considered for plant distribution analyses,
and the length was the minimum enough.
Four distinct planters were employed; in
the area 1 a John Deere planter, and in the areas
3, 4, and 5 a Semeato machine. On each area,
the seeding was performed in the same day, em-
ploying the same machine, same operator, and
the same adjustment. It was therefore expected
the same depth of seed placement, not taking in
consideration the likely spatial variability, which
may have soils texture, in particular clay content,
as the main reason.
The target adjustment for depth of place-
ment was 5, 5, 4, and 5 cm, respectively to areas
1, 2, 3, and 4. All machines were adjusted to
a nal population of 65.000 pl ha-1, and were
executed by the mangers of each area.
The variability on depth of placement can
reduce plant population, induce errors in the
plant management associated to plant growing
stages, and affect the pollination. Plant distribu-
tion was represented by population pressure,
or the area occupied by a single plant, in m2
or plants per hectare (SCHIMANDEIRO et al.
2006).
The data for seed depth and population
pressure was analyzed with descriptive statis-
tics. The analysis of variance for seed depth
considered each point as one treatment. The
relation between soil texture and seed depth
was analyzed with linear regression analyses.
The statistics for this study was calculated with
the software MINITAB 12.2.
The properties selected for this study be-
long to the project “Investigation on Precision
Agriculture Practices” of Fundação ABC. The
project was launched in 1998/1999 and includes
properties in the region of Campos Gerais, in
Paraná state.
BioEng, Campinas, v.2, n.1, p.001-007, jan/abr., 2008
RESULTS AND DISCUSSION
Table 1 displays the descriptive statistics
of clay content in the soil on the study plots.
In soil texture studies in Campos Gerais,
(1995) found clay content varying from 208 to
592 g kg-1, and WEIRICH NETO (2004) ob-
served an interval between 320 and 560 g kg-1,
with CV of 13%. It is clear that values on table 1
are typical to the Campos Gerais region.
Table 1 – Descriptive statistics of clay and sand content (depth 0-200 mm)
* coefcient of variation (CV)
Table 2 displays the descriptive statistics
of seed depths found on eld. There was a
higher variability of planting depth on plots 2
and 3, as the CV was higher (see Table 2). Al-
though a CV of 19% is statistically considered
average, when referring to planting depth of
corn seeds this value is considered low. Ac-
cordingly to CASÃO JUNIOR et al. (1998) and
CASÃO JUNIOR et al. (2000) found seed depth
CVs varying from 22.9 to 41.6%, and from 26.3
to 32.7%, respectively.
Table 2 – Descriptive statistics of planting depths (mm)
BioEng, Campinas, v.2, n.1, p.001-007, jan/abr., 2008
P.H.WEIRICH NETO, P.W. GARBUIO, L.M.GIMENEZ, M.J. COLET.
Initial climatic stress combined with vary-
ing seed depth may delay plantlet emergence,
causing qualitative and quantitative variability in
plant distribution.
Average seed depth in plot 3 was 37
mm, which lies within limits considering the soil
texture variation from medium to clay (Table 2).
Table 3 displays the descriptive statistics
of population pressure. The CVs of plots 1 and 4
are lower than in other plots. In plot 4, standard
deviation was low, and there was an average
of 73,850 plants per hectare. In this case, such
numbers are a result of crop management, as
the farmer aimed for a higher number of plants.
In plot 2, the CV was 55%, characterizing a very
high variability in plant distribution (Table 3).
An assessment of plant population
pressure in Campos Gerais shows CVs higher
than 55% in 3 out of 48 no-tillage cornelds
(SCHIMANDEIRO et al., 2006); such varia-
tion is extremely high when maximum yields
are expected. The source of missing or double
plants may be irregular planting speed, machine
adjustments, or biometric variations on the seed.
Except for the area 1, population pressure were
above the expected 65,000 pl ha-1.
Table 3 – Descriptive statistics of population pressure (pl ha-1)
The correlation of soil texture and seed
depth for plots 1 and 2 (Figures 1 and 2) shows
a close association between the two variables.
The analyses of variation of both regressions
were extremely signicant, with coefcients of
determination (R-squared) of 0.85 and 0.83%,
respectively. The relation is inversely propor-
tional: the higher the clay content in the soil,
the more supercial the seed was planted. In
plots 3 and 4 the analysis of variation was not
signicant, and the coefcients of regression
were low (Figures 3 and 4).
A tendency can be established consider
ing the values on variability (Table 1) and cor-
relation (Figures 1, 2, 3 and 4): the higher the
CV, the stronger the correlation between seed
depth and clay content in the soil. The minimum
values of clay content on plots 1 and 2 were
lower than on plots 3 and 4; a slight increase of
clay content to the lower values would result in
more severe variations to the soil structure, soil
resistance to penetration, water content.
BioEng, Campinas, v.2, n.1, p.001-007, jan/abr., 2008
On plots 3 and 4, the average clay content
values were higher; in this case, a variation of
the clay content would not have such strong
inuence to the soil structure. The adjustments
of the planter would have more inuence on the
process; even though there is no correlation
between seed depth and clay content on Plots
3 and 4 (Figures 3 and 4), there was an intense
variation of seed depth values, especially on
plot 3.
Soil clay content is an indicator for review-
ing the adjustment of the depth of placement of
corn seeds, as well as it can be an interesting
variable as it concerns crop productivity and
its tendency to inuence on the depth of seed
placement.
CONCLUSION
Two out of four study plots showed signi-
cant positive correlation between clay content
in the soil and seed depth. The plots where the
correlation was established had lower average
values and higher variability of clay content.
On an area, where signicant correlation
was observed, there was a lower population
pressure.
BioEng, Campinas, v.2, n.1, p.001-007, jan/abr., 2008
P.H.WEIRICH NETO, P.W. GARBUIO, L.M.GIMENEZ, M.J. COLET.
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