Revista Ciência Agronômica, v. 50, n. 3, p.

502-509, jul-set, 2019

Centro de Ciências Agrárias - Universidade Federal do Ceará, Fortaleza, CE Technical Article
www.ccarevista.ufc.br ISSN 1806-6690

Seed distribution by punch seeder in family farming 1

Distribuição de sementes por uma semeadora puncionadora para agricultura familiar

Rafaela Paula Melo2*, Daniel Albiero3, Aline Castro Praciano4, Leonardo de Almeida Monteiro4 and Angel
Pontin Garcia3

ABSTRACT - Family farming seeks to use less-aggressive agricultural practices, however, there is little machinery available
that is suitable for the reality of this sector. This has led to the use of technically incorrect practices, which have contributed
to the impoverishment, compaction and desertification of agricultural soils. Punch seeders are seen as a promising alternative
for carrying out sowing in family farming, as they employ localised seed distribution with less disturbance of the soil and the
consequent preservation and conservation of its structure. The aim of this study was to evaluate the quality of seed distribution
by a punch seeder used in family farming. The experiment was carried out in a soil classified as a Red-Yellow Argisol.
Descriptive statistics were used to evaluate the quality of seed distribution by the punch system. Statistical Process Control
was adopted to evaluate quality control in the seed distribution process. The results showed that the performance of the punch
seeder was similar to that of the precision pneumatic seeder, with 90.2% acceptable spacing. As demonstrated by the SPC study
that showed the process to be compatible with quality standards, the punch seeder is therefore a viable alternative in the sowing
process for family farming, since an improvement in sowing quality, with a precision of 88.4% was obtained. The punch system
resulted in less soil disturbance when compared to the disc harrow and manual seeder, and proved to be an effective solution
for conservation agriculture.
Key words: Quality control. Punch system. Seeding.

RESUMO - A agricultura familiar busca utilizar práticas agrícolas menos agressivas, entretanto existem poucas máquinas
adequadas à realidade deste segmento, isso tem levado ao uso de práticas tecnicamente incorretas, que vem contribuindo para
o empobrecimento, compactação e desertificação dos solos agrícolas. Diante disso, as semeadoras puncionadoras apresentam-
se como uma possibilidade promissora para realizar o processo de semeadura para agricultura familiar, visto que realiza
a distribuição de semente de forma pontual, contribuindo para a menor mobilização do solo e consequente preservação e
conservação da estrutura do mesmo. O objetivo do trabalho foi avaliar a qualidade de distribuição de sementes por uma
semeadora puncionadora para a agricultura familiar. O ensaio foi realizado em um solo classificado como Argissolo Vermelho-
amarelo. Foi utilizada a estatística descritiva para avaliar a qualidade da distribuição de sementes pelo sistema puncionador.
O Controle Estatístico do Processo foi adotado para avaliar o controle de qualidade do processo de distribuição de sementes.
Os resultados demostraram que a semeadora puncionadora apresentou desempenho semelhante à semeadora de precisão
pneumática, obtendo 90,2% de espaçamentos aceitáveis, sendo uma alternativa viável para realizar o processo de semeadura
para a agricultura familiar, fato comprovado pelo estudo do CEP que indicou a adequação do processo de semeadura aos
padrões de qualidade, pois obteve 88,4% de precisão no processo, possibilitando a elevação da qualidade de semeadura. O
sistema puncionador proporcionou menor mobilização do solo quando comparado ao sulcador de disco e semeadora manual,
mostrando-se como uma solução eficaz para a agricultura conservacionista.
Palavras-chave: Controle de qualidade. Punção. Semeadura.

DOI: 10.5935/1806-6690.20190059
*Author for correspondence
Received for publication in 27/07/2017; approved in 14/09/2018
1
Parte da Tese de Doutorado da primeira autora, apresentada no Programa de Pós-Graduação em Engenharia Agrícola/DENA/UFC.
2
Instituto de Desenvolvimento Rural, Universidade da Integração Internacional da Lusofonia Afro-Brasileira-UNILAB, Redenção, Ceará, Brasil,
rafaelapaula@unilab.edu.br (ORCID ID 0000-0001-7416-9317)
3
Faculdade de Engenharia Agrícola, Universidade Estadual de Campinas/UNICAMP, Campinas-SP, Brasil, daniel.albiero@gmail.com (ORCID
ID 0000-0001-6877-8618), angel.garcia@feagri.unicamp.br (ORCID ID 0000-0002-8163-6638)
4
Departamento de Engenharia Agrícola, Centro de Ciência Agrárias, Universidade Federal do Ceará/UFC, Fortaleza-CE, Brasil, alinecastro.
praciano@gmail.com (ORCID ID 0000-0002-9688-7202), aiveca@ufc.br (ORCID ID 0000-0003-3703-8072)
 R. P. Melo et al.

INTRODUCTION MATERIAL AND METHODS

Family farming plays a prominent role in The work was carried out in the experimental
agricultural production in the country, and mechanised area of the Department of Agricultural Engineering at the
agriculture is therefore important for the development of Centre for Agrarian Sciences of the Federal University of
the sector. However, of the available equipment, a large Ceará, Pici Campus. The soil in the area is classified as a
part is difficult to operate and maintain, and is unsuitable Red-Yellow Argisol with a sandy-loam texture as per the
or inappropriate for the conditions of the family farmer, recommendations of the Empresa Brasileira de Pesquisa
besides often having poor operating quality (VIANNA; Agropecuária (2006).
REIS; MACHADO, 2014). Table 1 shows values for the physical characteristics
As such, it is necessary to develop equipment of the soil in the experimental area. The mean cone index
aimed at family farming, using technology that can help for the area varied between 0.8 and 1.1 MPa.
to increase the quality of work, as well as develop and During the experiment with the seeder, a distance
adapt new machines that enable these farmers to increase of 45 metres was marked out for longitudinal distribution
their production and productivity (STEFANELLO et al., of the seeds, with a distance of 5 metres being ignored in
2014). the evaluation for the seed dispensing system to stabilise.
For Milagres et al. (2015), it is necessary that the To evaluate seed distribution, a method of manual digging
design of mechanisms to carry out the seeding process was used; the holes were opened at random every one
are not always limited to the same conditions, it being metre, and a centimetre rule was used to evaluate the
important to consider other factors, such as soil type, water distribution process. The methodology described by
content, etc. In this respect, Teixeira et al. (2009), point Montgomery (1991) was used to determine the minimum
out that there are few machines suitable for the reality number of samples for data normality, employing
of family farming. This has led to the use of technically operating characteristic graphs of bicaudal distribution at
incorrect practices, and has contributed significantly to 5% significance. After evaluating the preliminary data, a
minimum sample size of 30 was determined. The number
the impoverishment of agricultural soils and a reduction
of seeds was counted for each metre of the sowing row
in productivity.
under evaluation, i.e. each seed represented one sample;
It is therefore important to implement new therefore, for each distribution band, 100 seeds were
technologies that seek a model of agricultural production collected to guarantee data normality. In total, five rows
where the conservation and management of natural were sown, giving a total of 500 samples. Seed spacing
resources prevail. Seeders using a punch system can be an was evaluated as per the recommendations of Kurachi
alternative for family farming in Ceará, since they allow (1989).
less turning of the soil and mulch, which helps to conserve
A seeder with a punch system was used to
the soil, a requirement that is essential to conservation perform the test (Figure 1). This system is driven by a
agriculture (FRABETTI et al., 2011).
camshaft which, when rotated, activates the hole-making
Punch seeders function by opening holes and system, producing a hole for depositing the seed. The
then depositing the seeds; these seeders therefore systeem was adjusted to obtain a spacing of 140 mm
deposit seeds in a localised way, which increases the between seeds, following the recommendations for
possibility of raising the yield of crops that are sensitive maize crops (EMPRESA BRASILEIRA DE PESQUISA
to uniform plant distribution, besides positioning the AGROPECUÁRIA, 2010). A horizontal perforated-disc
seeds in the ground with greater precision (ALBIERO mechanism was employed to dispense the seeds.
et al., 2015). The disturbed area was determined by means of a
Research has been developed to design punch profilometer containing 50 vertical rods, each 64 cm in
seeders for family farming that carry out sowing in length and spaced 1 cm apart. The mean values for the
equidistant holes, with the aim of providing a distribution area disturbed by the punch system, the disc harrow and
system that is reliable, accurate, easy to maintain and the manual seeder (ratchet) were compared.
operate, and of increasing the profit of the farmer The forward speed of the seeder was set to 0.53 m s-1,
(FRABETTI et al., 2011). which is compatible with a commercial rototiller.
In view of the above, the aim of this study was to During the trial, the hopper of the seeder was
evaluate the quality of seed distribution by a punch seeder consistantly operated at 50% of its volumetric capacity, as
used for family farming. recommended by Mialhe (1996).

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 Seed distribution by punch seeder in family farming

Table 1 - Physical properties of the experimental área

Soil Db (kg dm-3) M (g 100g-1) CS (g kg-1) FS (g kg-1) Clay (g kg-1) Silt (g kg-1) OM (g kg-1)
Sandy-Loam 1.61 5.54 435 371 118 76 1.69
Db: Bulk density; M: Moisture; CS: Coarse Sand; FS: Fine Sand; OM: Organic Material

Figure 1 - Prototype of the punch seeder with the punch displaying normality and to verify the stability of the
system for depositing the seeds process. The SPC evaluation was based on the C p and
Cpk number indices, as per Equation 2.

CP = USL-LSL/6s (2)

Where:
Cp is the process capability index;
USL is the upper specification limit;
LSL is the lower specification limit;
σ is the standard deviation.
The effective capacity of the process (Cpk) was
based on Equations 3, 4 and 5.

Cpk = min (CPs1 Cpi) (3)

CPs = USL-µ/3.σ (4)

CPi = µ-LSL/3.σ (5)

The wheel slip index of the seeder was measured
following the methodology recommended by Mialhe Where:
(1996), counting the number of turns made by the wheel
of the prototype seeder over a distance of 40 metres. The μ is the mean value of the process.
slip index of the seeder was determined from Equation 1. According to Chao (1974), given two random
independent variables, each normally distributed, if the
(1)
variances of these variables are not inter-dependent, it is
Where: possible to use the characteristics of the F distribution as
a test of hypothesis, employing the F ratio given below.
Sl is the slippage; In this test the difference between mean values using the
Pt is the perimeter travelled by the driven tyre of the F statistic considers that the various treatment groups
machine; comprise one total group, with the variance of the total
sample being partitioned into variance within the group
N is the number of runs made along the experimental row;
and variance between groups; this method is found in the
Cl is the working length of the experimental row. Analysis of Variance (ANOVA).
A completely randomised experimental design According to Snedecor and Cochran (1989),
was used to test the prototype. Descriptive statistics were ANOVA is a statistical method that develops from the
used to analyse the following parameters: mean, standard assumption that different populations have different
deviation, and the coefficients of variance, symmetry estimates of variance. According to Montgomery (1991),
and kurtosis. From the coefficients of symmetry and provided that the F ratio is at 5% significance, the most
kurtosis the normality of the studied data was determined powerful test for comparing mean values is the Least
as per the recommendations of Montgomery (2004). The Significant Difference Test (LSD), which investigates all
MINITAB v 16 statistical software used was in trial the differences between pairs of mean values. This test
mode for thirty days. consists in calculating the differences between all the
Statistical Process Control (SPC) was used existing pairs of mean values using a combination of all
to evaluate the seed distribution process for data treatments (SNEDECOR; COCHRAN, 1989).

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 R. P. Melo et al.

RESULTS AND DISCUSSION performance and less than 50% of poor performance.

To evaluate the number of acceptable spacings, Frabetti et al. (2011), evaluating the performance
the limits to the frequency class ranges recommended of a punch seeder prototype in the direct sowing of
by Kurachi (1989) were used; the author states that the maize, obtained 95.08% regularity in seed distribution,
mean value obtained is within the acceptable spacings by the authors also found that a system for opening holes
classifying values that are less than 0.5.Xreferential as double by means of wheels positioned in a V formation with
spacings, values that are within the 140 to 1.5.referential dispensers coupled to the wheel, is a viable solution for a
limits as acceptable, and values greater than 1.5.Xreferential localised system of sowing maize.
as errors. As the seeder was adjusted to give a spacing of In Table 3 can be seen the descriptive-statistic data
140 mm between seeds, spacings of 70 to 210 mm were of the spacings obtained when evaluating the longitudinal
considered normal, double for values less than 70 mm and distribution of seeds.
errors for those over 210 mm.
It can be seen that the punch seeder had a mean
A speed of 0.53 m s-1 was used to carry out the spacing of 151.19 mm between seeds, a standard deviation
test. This speed allows the prototype to obtain maximum of 35.27 mm and a coefficient of variation of 23.28%. The
efficiency in the field, in addition to meeting the needs spacing values are evidently greater than those for which
of the family farmer, since any two-wheeled tractor can the seeder was adjusted, indicating an irregularity during
develop this operating speed. Albiero et al. (2012), working the seed distribution process.
with a seeder for family farming at a speed of 0.25 m s-1,
concluded that this speed enables a field capacity that is The slip index of the wheels was 9%, which
compatible with small Brazilian farms. contributed to the above result (mean value of 151.19 mm),
as the seeder was adjusted so that a hole was punched
Table 2 shows the evaluation of double spacings, every 140 mm to distribute the seeds. Furlani et al. (2008)
acceptable spacings and errors obtained in the field with and Corrêa Júnior et al. (2010) agree with this assertion,
the seeder prototype. since they point out that the slip index of the wheels is
As can be seen, the punch seeder achieved 4.2% directly related to the effective performance of the seeder.
double spacings, 90.2% acceptable spacings and 5.6% Another factor that contributed to the seeder not
errors, thereby obtaining an excellent seed-distribution achieving the desired spacing was the large distance
index. Santos et al. (2011), evaluating the spatial analysis between the seed dispenser and the ground; this was
of maize-seed distribution by a precision seeder, used the due to the position of the camshaft, which was under the
percentage of seeds distributed in the range of acceptable dispensing mechanism. It was necessary for the height of
spacings to classify distribution efficiency, considering the seed dispensing system to be raised so to avoid contact
seeders that distribute from 90 to 100% of the seeds between the two components. Siqueira, Casão Júnior and
within the range of acceptable spacings to be of optimal Araújo (2002) point out that the closer to the ground the
performance, those that distribute from 75% to 90% of the seed is ejected from the dispensing mechanism, the more
seeds of good performance, from 50% to 75% of regular efficient is the longitudinal seed distribution.

Table 2 - Evaluation of double spacings, acceptable spacings and erors of the punch seeder
Evaluation of the spacing between seeds
Double Acceptable Errors
21 (4.2%) 451 (90.2%) 28 (5.6%)

Table 3 - Basic descriptive statistics for the longitudinal distribution of seeds of the punch seeder in a Red-Yellow Argisol
Descriptive statistics of seed distribution
M SD Var Min Max
Observations CV % Sym Kur
----------------------------------- mm -----------------------------------
500 151.19 35.27 1244 40 290 23.28 -0.50 1.23
M: Mean; SD: Standard Deviation; Var: Variance; Min: Minimum; Max: Maximum; CV: Coefficient of Variation; Sym: Symmetry; Kur: Kurtosis

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 Seed distribution by punch seeder in family farming

It can be seen in Table 3 that the data under Figure 3 shows the analysis of the effective seed-
evaluation displayed a normal distribution, since, distribution capacity of the punch seeder. Effective
according to Montgomery (2004), if the coefficients capacity can be classified from the errors; therefore, for a
of symmetry and kurtosis are within the range of -2 to Cpk <0.33 there is one error in every two samples, when
2, the data can be considered normal. The author also the Cpk ≥ 0.51 there is one error in every eight samples,
recommends SPC to evaluate normal processes, since this with a Cpk ≥ 1 one error is considered to occur every
tool is widely used to evaluate variability and to determine 400 samples, and for a Cpk ≥ 1.5, error-occurrence is
the problem areas of repetitive processes, as is the case of considered low, with a possible error rate of 1 in every
the seeding process. Fernandes, Costa and Souza (2011) 150,000 evaluated samples (ELSMAR, 2009).
agree with this assertion, since the authors state that
SPC assists in quality control during the various stages
of a process, especially repetitive processes, as it aims Figure 3 - Analysis of the effective seed-spacing capacity
to guarantee the stability and continuous improvement
of the process. Figure 2 shows the control chart for seed
spacing of the punch seeder.

Figure 2 - Control chart for seed spacing of the punch seeder

generated by the MINITAB v 16 software

It can be seen that the value for effective capacity

(Cpk) was 0.55, therefore one error was obtained for every
8.62 samples, equal to a process accuracy of 88.4%, with
11.6% of errors.
For the graph in question, when analysing
the process using the specifications of Ribeiro and
Caten (2011), the analysis of the effective capacity
of the process is classified as having failed, since the
Note that the average spacing was 151.5 mm and value of Cpk is less than 1.00, and it can be seen that
that some samples exceeded the specified control limits; the distribution process exceeded the specified limits
as such, the process is considered unstable. However, (USL=210 mm and LSL=70 mm), this was due to the
Albiero et al. (2012) and Melo et al. (2013) point out influence of specific circumstances, such as the slip
that if only 5% of the samples are outside the control index of the seeder.
limits, the process can be considered stable, the authors
Quality control is therefore an important tool
defining an error index of around 10% as being optimal,
in agricultural operations, and can help in making
considering that during field operations there is a lot of
decisions that contribute to increases in productivity,
variability.
since the correction and elimination of waste and
Under agricultural conditions these indices are errors gives a reduction in costs and a consequent
considered good, since agricultural processes are far from increase in productivity, with innumerable advantages
having the same control as industrial processes, where all for competitiveness in the field (CHIODEROLI et al.,
the conditions and factors that can interfere in the process 2012).
are controlled (MELO et al., 2016).
Table 4 shows basic descriptive statistics for the
Therefore, it can be said that as the process provided area disturbed by the manual seeder (ratchet), disc harrow
stability, the punch seeder showed satisfactory results, and punch, where it can be seen that the mean value for the
with the samples not exceeding the 5% (25 samples) area disturbed by the ratchet was 0.0153 m2, 0.0081 m2 for
established by the author. the punch and 0.0735 m2 for the disc harrow.

506 Rev. Ciênc. Agron., v. 50, n. 3, p. 502-509, jul-set, 2019

 R. P. Melo et al.

Table 4 - Descriptive statistics for the area disturbed by the hole-making system for seed deposition, of a manual seeder
(ratchet), disc harrow and punch
Descriptive statistics of the hole-making systems for seed deposition in the soil
M SD Min Max
Obs CV % Sym Kur
------------------------------- mm -------------------------------
Ratchet 10 0.0153 0.0088 0.0137 0.0165 5.76 -0.60 -0.45
Punch 10 0.0081 0.0008 0.0071 0.0095 10.99 0.35 -1.51
Disc harrow 10 0.0735 0.0076 0.0652 0.0857 10.39 0.64 -0.99
Obs: Observation; M: Mean; SD: Standard Deviation; Min: Minimum; Max: Maximum; CV: Coefficient of Variation; Sym: Symmetry; Kur: Kurtosis

From the above, it can be seen that the largest area of principle: when penetrating the soil, it opens to form the
soil was disturbed by the disc harrow. It is important to note hole and is removed from the ground with the system
that soil disturbance is associated with the working depth still open, which contributes to greater soil disturbance,
of the mechanism, since Modolo et al. (2013), evaluating whereas the punch system is removed from the ground
the area disturbed by disc and rod harrows, concluded with the system closed, thereby disturbing a smaller area
that the rod harrow caused greater soil disturbance when compared to the manual seeder.
compared to the disc harrow, and attributed this result to
It should be noted that there was less soil
the greater working depth of the mechanism.
disturbance with the punch system when compared to
It can be seen that the coefficients of symmetry the disc harrow and the ratchet, showing that, as stated
and kurtosis (Table 4) are within the values established by by Frabetti et al. (2011), this system results in less soil
Montgomery (2004), since both are in the range of -2 to disturbance; the authors affirm that seeders equipped
2, with the data considered to show a normal distribution, with a punch system for seed deposition turn the soil less
thereby permitting an analysis of variance of the data. compared to seeders that use rod or disc harrows.
Table 5 shows the analysis of variance for the area Seeders that have a punch system can be used
disturbed by the manual seeder (ratchet), disc harrow and as an alternative for family farming in Ceará, since the
punch. soils found in this region are characterised as shallow,
It was found from the F-test, that at 5% which, due to their morphological, chemical and physical
significance, there was a significant difference between characteristics, helps to make them susceptible to erosive
the mean values of the disturbed areas. As there was a processes.
difference between the mean values under evaluation, From the tests carried out to evaluate the
the mean-value test for the area disturbed by the manual performance of the punch seeder, it was found that the
seeder (matraca), disc harrow and punch is shown in punch system has an excellent seed distribution index, as
Table 6 below. it achieved the same index as a pneumatic seeder, with
A statistical difference can be seen for the LSD test 90% of the seeds being within the acceptable range. This
at 5% significance; however, the disc harrow showed a can be verified by the SPC study that demonstrated the
greater area of disturbance. It can be seen that the mean sowing process to be compatible with quality standards,
value for the manual seeder (ratchet) was superior to that showing that a seeder equipped with a punch system can
of the punch system, despite also depositing seeds in a be an alternative in family farming, since it proved to be
localised way. This can be explained by its operating an accurate and reliable system. Furthermore, it resulted

Table 5 - Analysis of variance of the area disturbed by the manual seeder (ratchet), harrow and punch

ANOVA
Source of Variation DF SS MS F P
Factor 2 0.0257151 0.0128575 642.92 0.000
Error 27 0.0005400 0.0000200
Total 29 0.0262550
DF: Degrees of freedom; SS: Sum of Squares; MS: Mean Squares

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 Seed distribution by punch seeder in family farming

Table 6 - Mean-value test for the area disturbed by the ratchet, disc harrow and punch
Mean-value test
Hole-making system Number of samples Mean values for the disturbed área (m2)
Harrow 10 0.0735 a
Ratchet 10 0.0153 b
Punch 10 0.0081 c
*Mean values followed by the same letter do not differ statistically by the LSD test at a level of 5%

in the least soil turning, since the localised system for CHAO, L. L. Statistics: methods and analyses. 2nd. ed. New
depositing the seeds in holes results in less disturbance of York: McGraw-Hill, 1974. 359 p.
the area, which helps to conserve the soil, a requirement CHIODEROLI, C. A. et al. Perdas de grãos e distribuição de
which is essential to conservation agriculture; the demand palha na colheita mecanizada de soja. Bragantia, v. 71, n. 1,
for power to activate the implements was also reduced, p. 112-121, 2012.
helping to reduce fuel consumption.
CORRÊA JÚNIOR, D. et al. Influência da velocidade de
deslocamento no desempenho de uma semeadora-adubadora
de tração animal. Global Science and Technology, v. 3, n. 3,
CONCLUSIONS p. 50- 58, 2010.
EMPRESA BRASILEIRA DE PESQUISA AGROPECUÁRIA.
1. A seeder with punch system is a viable alternative for Centro Nacional de Pesquisa de Solos. Sistema brasileiro de
sowing in family farming, since it obtained a distribution classificação de solos. 2. ed. Rio de Janeiro, 2006. 306 p.
performance similar to that of a precision pneumatic
EMBRAPA MILHO E SORGO. Plantio. 6. ed. 2010. (Embrapa
seeder; Milho e Sorgo. Sistema de produção,1). Disponível em: < http://
2. It can be concluded from the Statistical Process Control www.cnpms.embrapa.br/publicacoes/milho_1_ed/plantespaca.
(SPC) analysis, that the process of the punch seeder is htm>. Acesso em: 24 set. 2016.
stable and that is has a satisfactory Process Capacity ELSMAR. FMEA. 2009. Disponível em: <http://wWww.elsmar.
(CPk), with 88% sowing accuracy; com>. Acesso em: 24 ago. 2016.

3. The punch mechanism resulted in less soil disturbance, FERNANDES, A. E. S.; COSTA, C. E. S.; SOUZA, E. S. O. O
proving to be an effective solution when considering the uso de controle estatístico de processo na gestão de qualidade.
principles of conservation agriculture. Estudo de caso: Grupo Coringa - AL. Inovação, Gestão e
Produção, v. 3, n. 6, p. 1-10, 2011.
FRABETTI, D. R. et al. Desenvolvimento e avaliação do
desempenho de uma semeadora puncionadora para plantio
ACKNOWLEDGEMENTS direto de milho. Revista Brasileira de Engenharia Agrícola e
Ambiental, v. 15, n. 2, p. 199-204, 2011.
The authors wish to thank the Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior (CAPES) FURLANI, C. E. A. et al. Semeadora-adubadora: exigências
and the Fundação Cearense de Apoio ao Desenvolvimento em função do preparo do solo, da pressão de inflação do pneu
Científico e Tecnológico (FUNCAP) for granting the e da velocidade. Revista Brasileira Ciências do Solo, v. 32,
doctoral scholarship. n. 1, p. 345-352, 2008.
KURACHI, S. A. H. et. al. Avaliação tecnológica de
semeadoras e/ou adubadoras: tratamento de dados de ensaios
e regularidade de distribuição longitudinal de sementes.
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