Initial growth of Schizolobium parahybae in Brazilian Cerrado soil under liming and mineral fertilization

Os elevados precos e a escassez de madeiras nobres tornam necessario o uso de fontes alternativas de madeira, como guapuruvu (Schizolobium parahybae), especie arborea nativa da Mata Atlântica a qual apresenta rapido crescimento e alto potencial mercadologico; todavia, nao ha informacoes sobre seu cultivo no cerrado do Brasil; objetivou-se, neste sentido, analisar a contribuicao da adubacao mineral e da calagem no solo do cerrado sobre o crescimento inicial de Schizolobium parahybae. O delineamento foi em blocos casualizados, com 4 tratamentos (solo do cerrado; solo + calagem; solo + adubo; solo + adubo + calagem) e 15 repeticoes. As variaveis analisadas foram: altura de planta, diâmetro do caule, numero de folhas, massas secas totais da parte aerea, das folhas, da raiz e do caule e relacao raiz/parte aerea. Os dados obtidos foram submetidos a analise de variância, ao teste de Tukey e a analise de regressao. Observou-se, durante o crescimento inicial, que o Schizolobium parahybae pode ser cultivado em solo do cerrado brasileiro apenas com adubacao mineral sem a necessidade de calagem do solo.


Introduction
Forest production in Brazil mainly refers to Pinus and Eucalyptus plantations, with the largest sustainable production in the Southeast region, followed by South, Northeast, Midwest and North (ABRAF, 2013). However, high prices and the scarcity of hardwoods make it necessary the use of alternative sources of wood, such as the Guapuruvu [Schizolobium parahybae (Vell.) S. F. Blake].
Schizolobium parahybae is an arboreal species, native to the Atlantic Forest, which occurs from the state of Bahia until Santa Catarina (Carvalho et al., 2008). It has great cultivation potential in the South and Southeast regions of Brazil, for its fast growth (Brienza Júnior et al., 1991), capacity to recover riparian forests, and many purposes in which its wood and bark can be used, besides being considered as a promising source of cellulose pulp (Ferreira et al., 2007).
There are few reports in the literature on the cultivation of Schizolobium parahybae subjected to soil fertilization and liming, which are essential practices to obtain better cultivation conditions (Chaves et al., 2011;Leal et al., 2013). Adami & Hebling (2005) observed positive influence of phosphorus sources on the dry matter of parts of Schizolobium parahybae.
There is no information on the plantation of Schizolobium parahybae in the Brazilian Cerrado region. In order to use this native species in a commercial, rational way, it is necessary to develop cultivation techniques that make its production viable, especially in the beginning of the crop cycle.
Therefore, this study aimed to evaluate the initial growth of Guapuruvu (Schizolobium parahybae) in a Brazilian Cerrado soil under liming and NPK fertilization.

Material and Methods
The study was carried out in a protected environment, from June to December 2014, at the State University of Goiás (UEG), located in the municipality of Ipameri, GO,Brazil (17º 43' 19" S;48º 19' 35" W;773 m), where the climate is tropical, with dry winter and humid summer (Aw), according to Köppen's classification.
The soil was sieved (4-mm mesh), and 5 dm 3 of this sieved material were placed in plastic bags, applying 1.25 g of dolomitic limestone (RNV = 92%) per dm 3 of soil (value based on the soil chemical analysis) in the 30 experimental units corresponding to the treatments 2 and 4, which were incubated for the next 30 days. After this period, the plastic bags were opened and remained at rest for 2 days in order to evaporate the exceeding volume of water, maintaining the gravimetric water content close to field capacity.
In the treatments 3 and 4, soil chemical analysis data were used to determine the application of the NPK formulation (5-30-15), which corresponded to 1 g dm -3 for a soil volume of 5 dm 3 .
Then, the soil materials corresponding to each plot were transferred to black plastic pots with capacity for 5 dm 3 , perforated at the bottom perimeter and placed in a greenhouse.
The seedlings of Schizolobium parahybae used in the experiment were prepared with seeds obtained in the city of Pederneiras, São Paulo State, Brazil, from matrices homologated and registered by the Coordination of Integral Technical Assistance (CATI, SP).
Initially, seeds of Schizolobium parahybae underwent a process of dormancy break through immersion in boiling water at 95 ºC for 10 min and, immediately after, they remained immersed in water at room temperature for 48 h, as recommended by Bianchetti & Ramos (1981).
Then, seeding was performed in sand seedbed, which was daily watered thenceforth. At 15 days after seeding (DAS), when plants showed mean height of 9 cm, the seedlings were transplanted to plastic pots containing soil prepared according to the established treatments.
After transplanting the seedlings of Schizolobium parahybae, daily waterings were performed using a 1-L beaker, as suggested by Costa et al. (2006) for the control of soil moisture.
The following variables were biweekly measured from 15 to 60 days after transplantation (DAT): plant height, in cm, from the base to the apex of the plants, using a ruler; stem diameter, in mm, using a digital caliper; and number of leaves.
At 60 DAT (or 90 DAS), all the plants were separated into leaves, stems and roots, washed and dried in a forced-air oven at 65 ºC for 72 h until constant weight, in order to determine the following variables: total dry matter (TDM), in g; shoot dry matter (ShDM), in g; leaf dry matter (LDM), in g; root dry matter (RDM), in g; stem dry matter (StDM), in g; and the ratio between root and shoot matters (R/S).
The obtained results were subjected to the analysis of variance by F test (p < 0.01 and 0.05), and treatment means were compared by Tukey test (p < 0.05). In addition, regression analysis was performed for plant height and stem diameter as a function of the days after transplantation. Statistical analyses were performed using the program Assistat, Silva & Azevedo (2009). Table 1 shows the summary of the analysis of variance for plant height, stem diameter and number of leaves of Guapuruvu (Schizolobium parahybae), measured at 15, 30, 45 and 60 DAT. Plant height and stem diameter were significantly affected by the studied treatments in the analyzed periods (p < 0.01), according to the F test.

Results and Discussion
The parameter number of leaves was not significantly influenced by the studied treatments in any of the analyzed periods (Table 1). The mean value for this variable, between 15 and 60 DAT, was 1.3 leaves per plant. Likewise, Adami & Hebling (2005), studying P sources on the initial growth of Schizolobium parahybae, did not observe significant effects of the treatments on number of leaves.
The highest values of plant height were observed in Schizolobium parahybae plants subjected to the treatment with soil and mineral fertilization (T3), regardless of the analyzed period, which were 19.86, 21.99, 14.42 and 14.15% higher compared with plants in the treatment T4 (soil + fertilizer + liming), at 15, 30, 45 and 60 DAT, respectively ( Figure 1A). In addition, plants subjected to T1 (only Cerrado soil) and T2 (soil + liming), in all evaluation periods, showed the lowest values of plant height and did not differ significantly by Tukey test (p < 0.05) ( Figure 1A).
Stem diameter, among others, can be considered one of the most important variables in the study of wood-producing species. There were no significant differences for the means of stem diameter between plants subjected to the treatments T3 (soil + fertilizer) and T4 (soil + fertilizer + liming) at 15, 30, 45 and 60 DAT ( Figure 1B), indicating that fertilization alone can be sufficient to meet the nutritional requirements of Schizolobium parahybae during its initial growth.
As observed for plant height ( Figure 1A), the lowest values of stem diameter ( Figure 1B) were obtained in plants under the treatments T1 (Cerrado soil) and T2 (soil + liming), which suggests that the highest values of plant height and stem diameter occurred in the treatments T3 (soil + fertilizer) and T4 (soil + fertilizer + liming) were caused by the NPK fertilization, with no effect of soil liming on these variables.
According to Foloni et al. (2008), liming with the adequate dose of limestone neutralizes active soil acidity. However, in the present study, although the limestone dose was determined  These results show that Guapuruvu has certain tolerance to slightly acid soils, since the pH of the soil used in this study, before liming and NPK application, was equal to 5.2. This pH may have provided fertility values sufficient for the initial growth of the crop, as shown by Vale et al. (1996).
All data referring to plant height ( Figure 2A) and stem diameter ( Figure 2B) of Schizolobium parahybae, regardless of the treatment of soil nutritional correction, fitted to linear models and increased along the days after transplantation. However, the highest values of plant height and stem diameter were observed in plants subjected to the treatments 3 and 4 ( Figures 1A, 1B, 2A and 2B), possibly due to the NPK fertilization.
It is of great importance the knowledge on treatments that increase the growth speed of wood-producing plants, aiming to increment production in a shorter time, in order to fit and compete in the market, because the wood sector in Brazil is mainly composed of fast-growing forest plantations (Vidal et al., 2015).
The treatments of soil nutritional correction significantly affected total dry matter (p < 0.01), shoot dry matter (p < 0.01), leaf dry matter (p < 0.01), root dry matter (p < 0.05) and stem dry matter (p < 0.01) of Schizolobium parahybae, but no effect was observed on the root/shoot ratio ( Table 2). The mean value of root/shoot ratio was 0.7, i.e., the mass of roots of Schizolobium parahybae, at 60 DAT (90 DAS), was equivalent to 70% of the mass of shoots.

B.
T1 -Cerrado soil; T2 -soil + liming; T3 -soil + fertilizer; T4 -soil + fertilizer + liming. Means with the same letter for given period do not differ significantly T4 (soil + fertilizer + liming), which did not differ by Tukey test, while leaf dry matter ( Figure 3C) increased under the treatments T2 (soil + liming) and T4 (soil + fertilizer + liming), possibly because of the benefits of soil liming, such as the improvement in P mineralization, increase in mineralization, N nitrification (Chatzistathis et al., 2015).
The values of root dry matter ( Figure 3D) of Schizolobium parahybae cultivated in soils corrected with limestone (T2 and T4) were higher, probably due to a possible increase in pH, Ca, Mg and base saturation, as well as a reduction in H + Al, exchangeable Al and Al saturation, as observed by Auler et al. (2011).
Nevertheless, with respect to root dry matter ( Figure 3D), plants under the treatment with soil + fertilizer (T3) did not differ statistically from plants under liming treatments (T2 and T4), an additional evidence that NPK fertilization, in the absence of limestone, promoted favorable conditions for the initial growth of Schizolobium parahybae.
Stem dry matter -an important variable, since it refers to the part of Schizolobium parahybae of greatest commercial importance -was higher in plants under the treatment T3 (soil + fertilizer), followed by T4 (soil + fertilizer + liming), as shown in Figure 3E. This indicates that this species can be cultivated under the studied conditions, with no need for soil liming, in order to reduce production costs.
DF -Degrees of freedom; ns , ** and * Not significant and significant at p < 0.01 and p < 0.05, respectively; by F test; CV -Coefficient of variation  Table 2. Summary of analysis of variance for total dry matter (TDM), shoot dry matter (ShDM), leaf dry matter (LDM), root dry matter (RDM), stem dry matter (StDM) and root/shoot ratio (R/S) of Guapuruvu (Schizolobium parahybae) subjected to treatments of soil nutritional correction C. D.

E.
A. B.

Conclusion
During the initial growth, until 60 days after seeding, the Guapuruvu (Schizolobium parahybae) can be grown in soil from the Brazilian Cerrado with pH of 5.2, under only mineral fertilization, with no need for soil liming.