Crescimento e nutrição de mudas de Pinus taeda L. no estado do Rio Grande do Sul

Abstract

The present study had as objective main to analyze the growth of seedlings of Pinus taeda L., by means of its morphologic variable, during its cycle of formation in fishery; to determine the Index of Quality of Dickson (IQD) of the produced changes; beyond verifying the concentration of nutrients in the aerial part of the seedlings during the production process. The work was developed in the commercial fishery of the Tecnoplanta Florestal Ltda., located in the city of Barra do Ribeiro - RS. The experiment was installed and lead in house of vegetation for about 60 days, during the period of 26 of October the 22 of December of 2006. After this period the seedlings had been taken the full sun, where they had remained up to 26 of April of 2007. Thirteen screens (5% of the production of the day of the company) composed for 1.260 seedlings had been used each one. The used substrate was composed for a mixture between rind of pinus and turf. The used seeds are proceeding from the Cambará Westwaco and the sowing was carried through mecaniclly in containers of polypropylene with capacity to store 50 cm ³ of substrate, and in the covering of the seeds it was used fine vermiculite. The germination on average occurred 15 days after the sowing. Seventy and four days the sowing the screens had after passed for the alternate operation. Two times per week in the period of 46 had been carried through fertirrigation the 90 days of age of the seedlings, and three times per week of 91 the 180 days after the sowing. To each 45 days, counted from the date of sowing, had been evaluated the height of the aerial part (H), col diameter (DC), relation height of the aerial part/col diameter (H/DC), aerial biomass (BA), root biomass (BR), relation root biomass /aerial biomass (BR/BA), index of quality of Dickon (IQD), root volume and the concentration of nutrients in the aerial part of the seedlings. The analysis statistics of the data was carried through by the statistical package SAS (Statistical Analysis System) version 8.2. In the end of the production cycle one observed the following average values for the variable: H=29,0 cm, DC=2,76 mm, H/DC= 10,7, BA= 1,763 g, BR=0,559 g, BR/BA= 0,3, IQD= 0,17and root volume= 7,31 mL. Also it was verified that the concentrations of N and P had diminished with the increase of the age of the seedlings. For macronutrients K, Ca, Mg and S had an oscillation trend, stabilizing its concentrations from the 90 days of age. The texts of Fe had increased with the age of the plants, supposedly had the great concentration of this element in the substrate and also to the vermiculite presence. It had increase in the concentrations of B, Cu, Mn and Zn up to 135 days after the sowing and reduction in these texts from this age. In the conditions where the seedlings had been produced, one concludes that: the seedlings of Pinus taeda L. had presented excellent development considering a cycle of formation of 180 days, and for this reason they can be used as model of formation of seedlings of the species in the State of the Rio Grande do Sul, since that the values of the variable and index reached in the present study are observed; the IQD verified for the seedlings of Pinus taeda L. can be used as parameter of evaluation of the quality of seedlings of the related species; the concentrations of the macronutrients in the end of the cycle of formation of the seedlings reflect the necessity of accomplishment of fertilization of expedition, mainly with elements N and P; the concentration of the micronutrients observed to the 180 days indicate that it does not have necessity of fertilization of expedition with the elements Fe, Mn, B, Zn and Cu; the use of a bigger container in the process of production of seedlings would raise the amount and the root volume of the dumb one. For future inquiries it is suggested: evaluation the field of the growth of the produced seedlings to confirm the validity of the parameters and index evaluated in the present study; accomplishment of studies on adequate fertilization of seedlings of Pinus taeda L., considering the concentration of nutrients observed in the present study; necessity of incorporation of fungi to the used substrate, therefore the symbiosis association between fungi and fine roots is essential in the process of absorption and nutrients cycle, mainly of element P