Print version ISSN 1413-7054
Ciênc. agrotec. vol.36 no.3 Lavras May/June 2012
Desenvolvimento de matrizes clonais de cedro Australiano em diferentes substratos sob doses de fertilizantes
Bruno Peres BenattiI; Antonio Eduardo Furtini NetoII; Bruno da Silva MorettiIII; Eduardo de Castro StehlingIV; Thaiana Marinha Almeida de SousaIII
IUniversidade Federal de Lavras/UFLA - Cx. P. 3037 - 37200-000 - Lavras - MG - Brasil - firstname.lastname@example.org
IIUniversidade Federal de Lavras/UFLA - Departamento de Ciência do Solo/DCS - Lavras - MG - Brasil
IIIUniversidade Federal de Lavras/UFLA - Lavras - MG - Brasil
IVBela Vista Florestal - Campo Belo - MG - Brasil
In order to evaluate fertilizers doses in different substrates for growth and development of clonal matrices of Australian Red Cedar [Toona ciliata var. australis (F. Muell.) Bahadur], an experiment was conducted in a greenhouse. Five substrates were evaluate, with proportions by volume, the first consisting of 100% of Multiplant florestal®, the second of 50% vermiculite, 20% carbonized rice hulls, 20% soil and 10% coconut fiber, the third with 50% soil and 50% sand, the fourth was composed by 50% Multiplant florestal®, 10% soil and 40% coconut fiber and the fifth with 65% of Multiplant florestal®, 25% vermiculite and 10% carbonized rice hulls. The fertilizers doses applied were 0.0; 0.3; 0.6; 1.2; 2.4 of fertilization suggested by Malavolta (1980) for vases. The characteristics evaluated were: collar diameter of the matrices, production of dry mater by shoots, root system and total and accumulation of nutrients by shoot at the end of the experimental period of 150 days. The Australian Red Cedar plants have high nutritional requirements, as showed by the better development obtained with higher fertilizer doses than those suggested by Malavolta (1980). The substrate three provided the worst development to clonal matrices while the substrates 1, 4 and 5 provided the best environment for the development considering all the fertilizer doses and all variables.
Index terms: Toona ciliata, plant nutrition, fertilization.
Com o objetivo de avaliar diferentes substratos com taxas de fertilizantes para o crescimento e desenvolvimento de matrizes clonais de cedro australiano [Toona ciliata var. australis (F. Muell.) Bahadur], foi realizado um experimento em casa de vegetação. Foram avaliados cinco substratos, com as proporções em volume, sendo o primeiro composto por 100% Multiplant florestal®, o segundo de 50% Vermiculita, 20% casca de arroz carbonizada, 20% terra e 10% fibra de coco, o terceiro com 50% terra e 50% areia, o quarto com proporção de 50% Multiplant florestal®, 10% terra e 40% de fibra de coco e o quinto com 65% Multiplant florestal®, 25% vermiculita e 10% casca de arroz carbonizada. Para os níveis de fertilizantes aplicados, foram utilizadas 0.0; 0.3; 0.6; 1.2 e 2.4 da adubação sugerida por Malavolta (1980) para vasos. Foram avaliadas as características: diâmetro do colo das matrizes, produção de matéria seca de parte aérea, sistema radicular e total e o acúmulo de nutrientes na parte aérea das plantas ao final do período experimental de 150 dias. As plantas de cedro australiano apresentaram elevada exigência nutricional, visto que estimativas mostraram o melhor desenvolvimento das mesmas com doses superiores às sugeridas por Malavolta (1980). O terceiro substrato proporcionou o pior desenvolvimento para as matrizes clonais, enquanto os substratos 1, 4 e 5 proporcionaram os melhores ambientes para o desenvolvimento, considerando todas as doses de fertilizantes e todas as variáveis analisadas.
Termos para indexação: Toona ciliata, nutrição de planta, adubação.
Reforestation investments in Brazil have shown promising, because the country has adequate conditions for the development of several forest species. One specie that can be used is the Australian Red Cedar [Toona ciliata var. australis (F. Muell.) Bahadur], which has the same wood characteristics as Brazilian cedar, indicated for the manufacture of fine furniture and construction finishing , besides having rapid growth, reaching six meters tall at two years and eight months (BELA VISTA FLORESTAL, 2011).
This specie belongs to Meliaceae family, native to tropical regions of Australia and has shown good development in the southern region of Bahia and throughout the Bazilian southeast (PINHEIRO, 2003), where an average annual increase of between 20 and 30 cubic meters of wood per hectare per year can be estimated (MURAKAMI, 2008). Currently this specie is propagated by seed, resulting in heterogeneous plantings that hinders the management of the area. Moreover, the seed of the Australian Red Cedar is seasonal and of short viability (SOUZA et al., 2009).
An alternative that can be used is the vegetative propagation technique, obtaining clonal plants. Therefore, quality seedling production is one of the most important stages for the culture to ensure good growth and development in the field. Considering that the nutritional status of the clonal mother plant alters the rate of development, growth intensity and specific morphological characteristics (EPSTEIN; BLOOM, 2004), the nutritional requirements of Australian Red Cedar should be known. However, studies have not been done for the Australian Red Cedar that indicate what the appropriate nutrient levels are in the substrate of the clonal matrices, to show satisfactory performance.
For an evaluation of the nutritional status of plants, the use of a plant matter analysis (MALAVOLTA, 2006) comparing the values of elements with a standard sample, allows to diagnose and correct nutritional imbalances of plants (TRANI et al., 1983). However, to obtain a standard sample, studies are necessary to determine which values are appropriate, since each species has different needs for certain nutrients.
The objective of this study was to evaluate the growth and development, content and accumulation of nutrients in clonal matrices of the Astralian Red Cedar.
MATERIAL AND METHODS
The experiment was installed in a greenhouse located at the Fazenda Bela Vista Florestal, located in the municipality of Campo Belo - MG. It consisted of five substrates (Table 1) and five doses of fertilizers (0.0; 0.3; 0.6; 1.2; 2.4), corresponding to a 5X5 factorial with 5 replications in a completely randomized design. Each experimental plot was composed of one plant in each dibble-tube with a volume of 3.5 dm3 prepared with 200 cc of No. 01 crushed stone layer covered with shade net on this substrate.
The substrate preparation was conducted in a concrete mixer with a 400 dm3 capacity for better homogenization. The percentages of each substrate was measured based on volume. On this occasion doses of macronutrient fertilizers were added. The micronutrient fertilization was by solution in dibble-tubes.
The fertilizer doses were relative to a full dose of fertilizer per vase, as suggested by Malavolta (1980). The dose corresponding to 100% consists of 300, 200, 150, 75, 50 and 15 mg.dm-3 of nitrogen, phosphorus, potassium, calcium, sulfur and magnesium, respectively, and for micronutrient doses of 5.0; 0.5; 1.5; 5.0; 0.1; 3.6 mg.dm-3 of zinc, boron, copper, iron, molybdenum and manganese, respectively.
After the treatments were installed, the transplanting of seedlings, produced by mini-cuttings from a plant with the potential to become a clonal matrice was carried out. The substrates were kept under constant humidity with daily irrigation. The plants were conducted with pruning, used in clonal matrices for higher sprouting.
Measurements of the collar diameter of plants were made at 90 and 150 days after transplanting, marking the end of the experiment. During the experiment, pruning was done to form the architecture of these matrices and stored in Kraft paper bags, identified by treatment. At the end of the experiment, plants were separated into principal stem, leaves and root system, and the material was oven-dried at 65° C until constant weight. After this, the shoot dry matter (SDM) (that is made up by leaves, stem and cut material), root system (DMRS) and compound total dry matter (TDM) were determined. The leaves and stem were analyzed chemically in the laboratories of the Soil Science Departament in Federal University of Lavras.
With the nutrient concentration values of the plants and their dry matter production, we determined the accumulation of nutrients in the aerial part. The data were subjected to variance analysis and the means subjected to regression analysis and Scott Knott test at 5%, using the Sisvar statistical software (FERREIA, 2011).
RESULTS AND DISCUSSION
Collar diameter of clonal matrices
The evaluation of collar diameter of plants is one of the most important morphological factors that can be measured without the occurrence of any injury to the plants, besides being considered an important parameter in the seedling development after planting (GOMES, 2002).
All substrates showed an increase in the diameter as a function of the fertilizer dose applied (Table 2), with a posterior decrease in this variable. This behavior, as illustrated in Figure 1 can be explained by the "Mitscherlich law" that is based on the fact that with each successive increment in the fertilizer quantity, there is a lessening of production, reaching a point of maximum production and followed by a lower production, due to the toxicity caused by fertilizer (LOPES; GUILHERME, 2000).
For all fertilizer doses applied, the substrate that provided the smallest plant collar diameter was Substrate three. A similar result was obtained by Pio et al. (2004), in work with loquat, justifying the low substrate performance to excess water retention and low porosity. In order for the plant to have good development the substrate must present good aeration, drainage, retention and availability of water, the first two factors being related to macropores and the other two with micropores and specific surface of the substrate (FERREIA; DIAS- JUNIOR, 1997).
In the absence of fertilizers, independent of the clonal matrice collar diameter measurement times (90 or 150 days), Substrate 1 provided the best development to the plants, due to its favorable physical and chemical properties. Pio et al. (2005) evaluating the development of various substrates in the production of Jabuticaba seedlings concluded that a product based on pine bark (similar to Multiplant florestal®) provided better development.
With exception of Substrate 3, better development was estimated for all substrates when the fertilizer dose was above 120% of that recommended by Malavolta (1980), showing the high nutritional requirement for the specie under study. The high nutritional requirements of Australian Red Cedar is suggested by Moretti et al. (2011), more studies being recommended for an understanding of the appropriate fertilizer doses.
Dry matter production (DM)
For the SDM variable, except for Substrate 3, the plants obtained production similar to that of the collar diameter, and "Mitscherlich law" (Table 3). In Substrate 3 (50% soil, 50% sand) it was observed that the production of SDM, RSDM and TDM decreased with the increase in fertilizer doses (Figure 2). This result may be due to toxicity caused in the plant even in low doses, being progressive with dosage increase.
In the evaluation of TDM all plants presented a lower dry matter weight at the 240% rate (suggested by MALAVOLTA ,1980) compared with the 120% rate, suggesting that the 240% rate would be causing toxicity to the plant due the high fertilizer doses applied. These results show the importance of developing new experiments to define what should be the appropriate fertilizer dose for the clonal matrice of Australian Red Cedar.
Levels and accumulation of nutrients in clonal matrices.
Table 4 presents the nutrient levels and from this it was possible to quantify the nutrient accumulation in the shoot (Table 5) by the sum of the accumulation in the leaves, the pruned material of matrices and that accumulated in the stems.
It is evident by the nutrient accumulation data that with higher fertilizer doses, the accumulation of nutrients increases in the plant, but in some cases (Substrate 3) the inverse occurs, a lower accumulation with higher fertilizer doses applied, which can be explained by the low substrate aeration, providing an unfavorable environment to the root growth (PIO, 2005), resulting on a lower plant development and consequently poor nutrient accumulation.
Calcium, potassium and nitrogen are the nutrients that obtained the highest levels in the leaves of clonal matrices. The high calcium content, and consequently the high calcium requirement by Australian Red Cedar is pointed out by Souza et al. (2010), fertilizing at planting and in coverage being a necessary according to soil analysis. Potassium, in general, is the second nutrient most required by the culture (FAQUIN, 2005), and high levels of nitrogen in leaves, corroborate with the study by Moretti et al. (2011), with Australian Red Cedar plants in vases.
The nutrients that had higher accumulations were calcium, nitrogen and potassium. And the micronutrients that had the most accumulation in shoots of clonal matrices of Australian Red Cedar were iron, manganese, zinc and boron.
The Australian Red Cedar has high nutritional requirements, having its best development at higher fertilizers doses than those recommended for vases proposed by Malavolta (1980).
The substrate used for the development of clonal matrices of Australian Red Cedar has fundamental importance in its growth. The substrates composed of 100% Multiplant florestal® or 50% Multiplant florestal®, 10% soil and 40% coconut fiber or 65%Multiplant florestal®, 25% vermiculite and 10% carbonized rice hulls allowed the largest collar diameter of the clonal matrices.
The substrate composed of 100% Multiplant florestal® provided the highest shoot, root system and total dry matter production for the clonal matrices.
The substrate composed of 50% soil and 50% sand does not show desirable characteristics for a good development of clonal matrices of Australian Red Cedar.
The authors thank CNPq for providing scholarships and Viveiro Bela Vista Florestal for the use of the greenhouse and seedlings for this experiment.
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Received in march 21, 2012.
Approved in may 30, 2012.