Artigo cobre x milho traduzido final

Development and yield of the maize in response to foliar fertilization with copper
ROGÉRIO
HIDALGO
BARBOSA1;
LUCIANE
ALMERI
TABALDI2*;
FÁBIO
RODRIGO
MIYAZAKI1; MÁRCIO PILECCO3; SAMIR OLIVEIRA KASSAB4; DAÍSA BIGATON5
1
Curso de Agronomia, Faculdade Anhanguera Educacional SA. Rua Manoel Santiago, 1155,
Vila São Luís, 79825-150, Dourados – MS.
2
Faculdade de Ciências Agrárias (FCA), Universidade Federal da Grande Dourados - UFGD
– Rodovia Dourados - Itahum, Km 12, Caixa Postal 533, Cidade Universitária, 79804-970,
Dourados/MS
3
Programa de Pós-Graduação em Zootecnia, FCA/UFGD - Rodovia Dourados - Itahum, Km
12, Caixa Postal 533, Cidade Universitária, 79804-970, Dourados/MS
4
Faculdade de Ciências Biológicas e Ambientais (FCBA), UFGD – Rodovia Dourados -
Itahum, Km 12, Caixa Postal 533, Cidade Universitária, 79804-970, Dourados/MS
5
Programa de Pós-Graduação em Agronomia, FCA/UFGD - Rodovia Dourados - Itahum, Km
12, Caixa Postal 533, Cidade Universitária, 79804-970, Dourados/MS
Maize under foliar fertilization with copper
Palavras-chave: Adubação, Micronutriente, Toxicidade, Zea mays.
Section of the article: Agrarian Science
*Correspondence to: Drª Luciane Almeri Tabaldi
Faculdade de Ciências Agrárias (FCA), Universidade Federal da Grande Dourados - UFGD –
Rodovia Dourados - Itahum, Km 12, Caixa Postal 533, Cidade Universitária, 79804-970,
Dourados/MS. E-mail: [email protected]
ABSTRACT
Soil applications of copper may not be effective under particular conditions of soil and
climate. Thus, the aim of this study was to evaluate the effects of foliar application of copper
on development and yield of DG-501 maize. The experiment was conducted between
December 2009 and April 2010, in conventional tillage. When plants were with six to eight
leaves, copper (0, 100, 200, 300, 400, 500 and 600g ha-1) was applied to the leaves.
Treatments were arranged in randomized complete block, with five replications. When 50%
of plants were in flowering, were evaluated the plant height, culms diameter, height of the
first ear insertion, leaf area and chlorophyll content. At harvest, it was evaluated diameter and
length of ear, yield and thousand grain weight. There was linear reduction in the plants height
and in the height of the first ear insertion with increasing copper doses. On the other hand, the
chlorophyll content, leaf area, diameter and length of ear, thousand grain weight and yield
increased at low doses and decreased at higher copper doses. Therefore, to achieve increase in
maize yield without detrimental effects on development, copper can be applied to the leaves
in doses not exceeding 100g ha-1.
Key words: Fertilization, Micronutrient, Toxicity, Zea mays.
INTRODUCTION
Maize (Zea mays L.) constitutes one of the main products of Brazilian agriculture, not
only in quantitative parameter but also in respect of its strategic significance, being the basis
for animal feed. Maize crop has a high yield potential (Gonçalves Jr. et al. 2008). According
to the Organization of Nations for Food and Agriculture (FAO), the production of maize in
the 2010/2011 crop should reach at 845 million tons, this number probably will be a world
record (FAO 2010). However, these yields are low, and are usually irregular (Palhares 2003).
It is considered that deficiencies in soil fertility may be listed as one of the main factors
responsible for the inability of maize cultivars manifest their full potential genetic production
(Ferreira et al. 2001; Carvalho et al. 2004).
It is known that the Cerrado soils are weathered and highly acidic, and that they
contain small amounts of nutrients that are essential for the cultivation of plants (Vendrame et
al. 2010). Moreover, in agreement with previous studies, micronutrient deficiencies in Brazil
have been presented more frequently in Cerrado soils (Luchese et al. 2004). Accordingly,
several studies are being directed to the use of micronutrients as way of increasing the
efficiency of production of plants and improve the economic returns to producers (Alam and
Raza 2001). Though required in small quantities by maize plants (Leite et al. 2003), copper
(Cu) is essential to complete its life cycle, and when provided in quantities below the
requirements, may to occur a decrease in yield (Luchese et al. 2004). Furthermore, Cu occurs
in enzymatic compositions of vital importance in plant metabolism, participates in the
photosynthesis, respiration, carbohydrate metabolism, nitrogen reduction and fixation, protein
metabolism and cell wall (Demirevska-kepova et al. 2004), and in plant resistance to disease
(Tomazela et al. 2006). On the other hand, Cu in high concentrations may play roles
cytotoxic, inducing stress, altering membrane permeability, protein synthesis and activity of
enzymes, causing leaf yellowing and growth retardation (Lewis et al. 2001; Vinit-Dunand et
al. 2002).
The providing of Cu to crops can be made directly into the soil, in the form of
fertilizer; in the plant via foliar fertilizer, or seed treatment (Luchese et al. 2004). Research
done by Galrão (1988, 1989) revealed that in field work with broadcast application of 2kg Cu
ha-1, in red-yellow oxisol, there was an increase in grain yields for wheat and soybeans crops.
Moreover, Cu application in maize seeds in doses of 1 to 6g kg-1 of seeds decreased the ability
of seed emergency, without affecting the dry weight of plants that emerged (Luchese et al.
2004).
In soil, more than 98% of the Cu of the solution is complexed as chelated with organic
compounds of low molecular weight (Faquin 1997). Besides, its greater availability is in the
range of pH 5.0 to 6.5. In view of these factors, soil applications may not be effective under
particular conditions of soil and climate, for example, high organic matter content or hot and
humid summer. In these cases, foliar application of Cu can avoid these problems.
With the need of an increase in agricultural yield, is essential the advance in studies of
nutritional requirements of different cultures and how nutrients are available to plants. Under
certain circumstances, a slight increase in the levels of certain nutrient can cause a significant
increase in crop yield. In that sense, for that occur an increase in maize yield is important that
studies show the nutritional real needs of that crop for each region, as well as their responses
to fertilization levels and the way in which nutrients are available. Thus, the aim of this study
was to evaluate the effect of foliar application of different doses of copper (Cu) on
development and yield of maize.
MATERIAL AND METHODS
The experiment was carried out at the Farm School of Faculdade Anhanguera
Educacional SA., in Dourados, MS, Brazil, located at 22º13’15”S of latitude, 54º48’21”W of
longitude and 430 m of altitude, from December 2009 to April 2010. The climate of
Dourados, according to Köppen (1948) is mesothermal humid, Cwa type, with temperature
and annual rainfall averages ranging from 20º to 24ºC and 1250-1500mm, respectively.
Soil from the cultivated area is classified as dystrophic red oxisol of clayey texture,
with the following chemical characteristics: 5.0 of pH in H2O; 25.09g dm-3 organic matter;
36.0mg dm-3 P; 0.0; 24.0; 46.0; 22.0; 53.0; 71.5 and 124.5mmolc dm-3 of Al+3, K, Ca, Mg,
H+Al, SB and CTC, respectively; 16.0; 2.1; 13.50 and 22.20mg dm-3 of Fe, Cu, Zn and Mn,
respectively, and 57.0% of saturation. Accumulation of rainfall during the execution of the
experiment was 603 mm and the average temperature of 25.3ºC (Max. 31.1ºC and Min.
18.7°C).
It was used seeds of triple hybrid maize DG-501 of early maturity, with characteristics
of grain semi-hard, yellow-orange and medium-sized plants. The seeds were sown in rows in
conventional tillage system after soil preparation. Seeds were treated with the imidacloprid
(52.5g ha-1) + thiodicarb (157.5g ha-1) insecticides and sown at a depth of 5 to 7cm, spaced
0.90m between rows and five plants per linear meter, corresponding to approximately 55,000
plants per hectare. Fertilization was applied at planting with 500kg per hectare of N-P-K with
the formulation 08-10-10, respectively.
Control of weeds and defoliating caterpillars was carried out 20 days after sowing
(DAS) using a backpack pump of 20L, adjusted to 150L ha-1, using the tembotrione herbicide
(100.8g ha-1) and the thiodicarb insecticide (120g ha-1).
Treatments were seven increasing doses of copper (0, 100, 200, 300, 400, 500 and
600g ha-1), by foliar application, distributed in a randomized complete block design with five
replications of 4 x 5m each (20m2). Pentahydrate sulfate copper (CuSO4.5H2O) (25% Cu) was
used as copper source.
The spraying was done when the maize plants were with six to eight leaves fully
developed, using backpack sprayer with steady flow, equipped with bar 1m, with two nozzles
spaced at 0.40m. It was used the spray tip of flat fan TeeJet XR11002, by applying 150L ha-1
of spray. Application was done by keeping the tips at 0.30m height, approximate, above the
top of the plant canopy.
When 50% of plants were in the flowering period, were evaluated at four plants per
plot, the plant height (using a tape line from the soil until insertion of the last leaf); the stem
diameter (measured with a digital caliper at 15cm soil) and the height of the first ear insertion
(using a tape line, measured of the base from the soil to insertion of the first ear); and
chlorophyll content (with Falker Clorofilog). After physiological maturity, at the time of
harvest, it was evaluated the diameter and length of the ear (with a caliper on four ears per
plot), the yield and thousand grain weight (using ears harvested at three meters central to the
plot, ignoring one meter from each side). At harvest, the grains had moisture between 1315%. Data were subjected to analysis of variance and when significance was found by F test,
data were subjected to regression analysis by 5% probability.
RESULTS AND DISCUSSION
The plant height is an indirect method for assessing crop performance (Tittonell et al.
2005). With increasing doses of copper (Cu) there was a linear reduction in the height of
maize plants and at the height of the first ear insertion (Fig. 1a and 1b). Genetic studies have
shown that these two characteristics show a high correlation with one another (Yan et al.
2010). The reduction in height is a factor that may contribute to the availability of assimilates
for grains filling and may when significant, affect yield. On the other hand, studies have
shown that smaller plants do not necessarily affect yield, especially in the absence of water
stress (Fortin and Pierce 1990).
Figure 1
It was suggested that the primary sites of growth inhibition by Cu are molecules of
chlorophyll of the pigment antenna of photosystem II (Liddon et al. 1993). Even without the
significant effect of Cu on the culms diameter (data not shown), shortening of internodes in
maize plants exposed to Cu may compromise the potential of this extra source of
photoassimilates located in the culms of the maize plant. This data contradict those reported
by Leite et al. (2003), who found that fertilization with Cu ranging from 0 to 16mg kg-1 soil
increased significantly the dry weight of shoots of maize plants grown in pots. According
Malavolta (2006), Cu concentrations in the experimental area were relatively high (2.1mg dm3
), suggesting high levels of organic carbon, since organic matter is a major source of this
nutrient in soil (Teixeira et al. 2003), explaining, probably, the lack of more significant effects
of Cu in maize plants.
On the other hand, the relative chlorophyll content and leaf area increased at low doses
and decreased at higher doses of copper (Fig. 2). Relative chlorophyll content and leaf area
showed maximum points at doses of 257.7 and 112.8g ha-1 of Cu, respectively (Fig. 2a and
2b). This increase in leaf area and chlorophyll content at low doses of Cu can maximize the
photosynthetic efficiency of maize plants, mainly by improving the interception of PAR, for
more efficient conversion of intercepted radiation into dry matter and photoassimilate
partition in the reproductive organs, resulting in higher yield. On the other hand, as the leaf is
the main source of assimilates to plant maize (Magalhães et al. 1995), the reduction in leaf
area and chlorophyll content in high doses of Cu suggests that the photosynthesis of maize
plants may have been harmed due to the adverse effects of Cu on chlorophyll molecule. These
data show the toxic effects of Cu at high concentrations, affecting the development and grain
production.
Figure 2
The same way as for leaf area and chlorophyll content, the data of diameter and ear
length (Fig. 2a and 2b, respectively), and thousand grain weight and yield (Fig. 3a and 3b,
respectively) showed quadratic response in function of Cu doses, where there was an increase
in low doses, with reduction at higher doses. Ear diameter and length had maximum points at
doses of 33.87 and 147.44g ha-1 Cu, respectively (Fig. 3a and 3b). Moreover, the points of
maximum for thousand grain weight and yield were at doses of 58.26 and 144.29g ha-1 Cu,
respectively (Fig. 4a and 4b). At the dose of 144.29g ha-1, Cu provided an increase of 8% in
the maize yield (Fig. 4b).
Figure 3
These results are related to the data of leaf area and chlorophyll content, indicating
that at low doses, Cu promotes an increase in growth and consequently on the yield of maize,
the opposite happening in high doses, when the Cu becomes toxic to culture. Luchese et al.
(2004) observed symptoms of toxicity in treatments with application of copper equal or
greater than 4g kg-1 seed.
Figure 4
These data suggest that the reduction in plant height of maize (Fig. 1a) at low doses of
Cu did not significantly affect the final yield in these plants, the same did not happening in
higher doses of Cu, where a decrease in parameters related to yield was observed. This
reduction may be related to the fact that excess Cu inhibits cell elongation, a complex process
dependent on cell turgor pressure, synthesis of wall components and growth regulators
(Alaoui-Sossé et al. 2004).
CONCLUSION
Under conditions that the experiment was carried out, it was possible to conclude that
to achieve increased yield in maize without detrimental effects on development, the copper
can be applied to the leaves in low doses, not exceeding 100g ha-1.
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RESUMO
Aplicações de cobre (Cu) no solo podem não ser efetivos sob condições particulares de solo e
clima. Assim, o objetivo deste trabalho foi avaliar os efeitos da fertilização foliar com Cu
sobre o desenvolvimento e produtividade do milho híbrido triplo DG-501. O experimento foi
desenvolvido no período entre dezembro de 2009 e abril de 2010, em sistema de plantio
convencional. Quando as plantas encontravam-se com 6-8 folhas totalmente desenvolvidas,
Cu (0; 100; 200; 300; 400; 500 e 600g ha-1) foi aplicado via foliar. Os tratamentos foram
arranjados em delineamento experimental de blocos casualizados, com cinco repetições.
Quando 50% das plantas apresentavam-se no período de florescimento, avaliaram-se a altura
de plantas, diâmetro de colmo, altura da inserção da primeira espiga, área foliar e teor de
clorofila. Na colheita, avaliou-se diâmetro e comprimento da espiga, produtividade e peso de
mil grãos. Houve redução linear na altura de plantas de milho e na altura de inserção da
primeira espiga com o aumento das doses de Cu. Por outro lado, os dados de índice relativo
de clorofila, área foliar, diâmetro e comprimento da espiga, peso de mil grãos e produtividade
aumentaram em baixas doses e diminuíram nas doses maiores de Cu. Portanto, para se obter
incremento em produtividade sem efeitos prejudiciais no desenvolvimento da cultura do
milho, o Cu pode ser aplicado via foliar em doses não excedendo 100g ha-1.
Palavras-chave: Adubação, Micronutriente, Toxicidade, Zea mays.
LEGENDS OF FIGURES
Figure 1. Plant height (a) and height of insertion of the first ear (b) of maize plants submitted
to increasing levels of copper to the leaves. Dourados – 2010.
Figure 2. Relative content of chlorophyll (a) and leaf area (b) of maize plants submitted to
increasing levels of copper to the leaves. Dourados – 2010.
Figure 3. Ear diameter (a) and ear length (b) of maize plants submitted to increasing levels of
copper to the leaves. Dourados – 2010.
Figure 4. Weight of 1000 grains (a) and yield (b) of maize plants submitted to increasing
levels of copper to the leaves. Dourados – 2010.
Figure 1
(a)
(b)
Figure 2
(a)
(b)
Figure 3
(a)
(b)
Figure 4
(a)
(b)