Comparação de métodos de plantio de Pinus spp.

Resumo

Survival and initial growth of three types of seedlings, with and without application of triple super phospate, were studied in Viçosa, Minas Gerais, Brasil, using Pinus oocarpa cubensis (Mexico), P. oocarpa (Honduras), P. insularis (Burma), P. cubensis (Costa Rica) and P. pseudostrobus var. oaxacana (Mexico).

The seedlings utilized, wich were planted in a flat area with clay soil of a terrace phase, were of the following types: 

a) Torrdo paulista (mud-balled stock)

b) Bare root

c) Bare root dipped in a clay-water suspension of 1,1:1 ratio by weight shortly after lifting.

Triple super phosphate was applied to one half of the seedlings of each type at a rate of 2 gms per planting hole for treatments (a) and (b) and 1 gm per seedling for treatment (c), applied in the suspension.

A randomized design with split plots and 4 replications was utilized, with a total of 120 seedlings per species or provenances being planted. Thus 200 seedlings of each of types (a), (b) and (c) described above were utilized, being observed to determine survival, initial height growth and root development.

The results obtained after 15 months from planting permit the following conclusions from this experiment:

1- In the absence of triple super phosphate, survival of seedling of all species or provenances was similar indepent of the type of planting stock utilized, with the exception of inus insularis. For this specie, bare root seedlings dipped in the clay-water suspension had a survival rate inferior to these planted bare root or balled stock.

2- Application of triple super phosphate in the clay-water suspension resulted in much lower survival for all the pines tested, possibly to development of extremely low pH values in the suspension.

3- Average height growth was greatest for Pinue oocarpa from Honduras, differing from the other pines tested

4- No differences in height growth were detected between the 2 types of seedlings tested, mud-balled stock and bare root stock, or between fertilized and non-fertilized plants.

Based on study of root systems it was noted that:

1- Root system of fertilized plants tended to weigh more than those of plants not fertilized.

2- Fertilization appeared to result in a more welldis- tributed root system.

3- Root system development appeared to be greater for bare root seedlings than for those planted as balled stock or dipped in the clay-water suspension, except for seedlings of Pinus cubensis.

In general terms, it can be said that, under conditions similar to those of this experiment, there are no counterindications to the bare root planting of Pines. Care should be taken in use of fertilizers as a par of the clay water suspension, when using dipped root techniques.