Tecnologia mecanizada em preparo de área sem queima no Nordeste paraense

Abstract

The no tillage on fallow vegetation technology uses of the secondary vegetation that expontaneously grows from existing roots and stumps from the traditional process of slash and burn preparation of that vegetation in the study region. This work was divided into two studies: the first evaluated of triturated material from two systems or trituration of biomass and one the second in which were evaluated: one alternative system of trituration (CT) (horizontal system), traditional system of slash and burn (CQ), slash burn remove and tillage (CQDG) and secondary vegetation after fallow, to evaluate physico-hydrical parameters during the land preparation. In the first study the decomposition and the release of nutrients by two triturators process was evaluated. The triturated material was classified in four categories of size in mm, (T1=1<T<7, T2=7<T<25, T3=25<T<35 e T4=T>35) and six qualitative categories, namely with bark, partially triturated, partially unweaved, completely unweaved, compacted and without form. Nutrient availability was determined in the prepared areas by these systems. The greatet release of nutrients was observed for materials T1 and T2 during the first ten months, with a maximum release of 70,25 kg ha-1 of nitrogen, 1,11 kg ha-1 of phosphorus, 1,8 kg ha-1 of potasium, 39,3 kg ha-1 of calcium, and 4,16 kg ha-1 of magnesium, for the size T2 obtained by the vertical system of trituration. Qualitatively, the most greatest nutrient release was observed for materials with bark residue with maximum release of 9,57 kg ha-1 of N, 0,3 kg ha-1 of P for material without form with high degree of. For this material was also observed the small least C/N relation 33,43 at the end of tenth month. Maximum values of release of K was of 2,09 kg ha-1, for Ca 12,38 kg ha-1, and for Mg 1,44 kg ha-1, observed for material with bark. Soil organic matter increased for both systems after one year, as did the availability of potassium at the layer of 0,05-0,1m. Phosphorus content increased only for the vertical system of trituration, while base saturation decreased for horizontal system of preparation. In the second study, physical properties of soil density, porosity and water retention curve were evaluated for study 1, (altenative systems with biomass trituration), whereas the same properties, along with others properties: preconsolidation pressure, resistence to penetration (RP) and medium geometric diameter of dry aggregates (DMG) were evaluated for study 2. In the area of study 1, the lowest soil density was observed for the treatment fallow, and the greatest for the system of preparation with vertical triturator, with a more compact layer between 0,2- 0,3 m. The available water varied from of 0,11 cm3 cm-3 for the horizontal system at surface layer to 0,128 cm3 cm-3 for the layer of 0,2-0,3 m. In study 2 differences were observed for DMG for the treatment CQDG, at 0,1-0,2 m depth. The pre consolidation pressure was not exceeded in the field at the layer of 0-0,1 m, nevertheless was exceeded at the layer of 0,1-0,2 m the values varying from 52,57 to 86,10 kPa. The soil density was greatest for fallow for all of the treatments, and lowest for CQDG, increasing during the period of analysis, but not differying to fallow treatment after 45 days of preparation. The same tendency was observed for the microporosity in that period; nevertheless for macroporosity and total porosity there were observed variations. This variation occurred at 0-0,1 m depth, at which CQDG differed from fallow. The greatest RP observed within the period of analysis was for fallow and CT, reaching a value of 2,08 MPa at the 0,2 m depth. Water availability, was highest for CQDG and CT (0,20 cm3 cm-3) and lowest for fallow (0,09 cm3 cm-3) at the soil surface. (0-0,1 m). At 0,1-0,2 m depth, it was 0,19 cm3 cm-3 for CQDG and CT, and 0,11 cm3 cm-3 for fallow.