Propriedades físicas e químicas de um solo submetido a diferentes sistemas de manejo da capoeira ao longo do tempo.

Abstract

In the scenario of the Northeast of the state of Pará, the secondary forest is a dominant and fundamental element for the maintenance of agricultural activity and income generation. However, the reduced fallow times in this region, where agriculture is based on slash and burn, has led to the unsustainability of the productive system, because the 2 to 5 year fallow period used in the region is not sufficient to recuperate the quality of the soil. The continuous loss of nutrients associated to physical degradation of the soil caused by this type of management hampers the farmer from using the same area, resulting in itinerant crops and unbalanced swidden cultivation. The negative effects in socio economic and environmental terms resulting from this practice has motivated the researches in order to design a model using more sustainable from the management of the bushes. Being studied for more than 17 years under long term experiment comparing the effects of land preparation (slash and burning the underwood or “capoeira” ) after 3-4 years of fallow and two periods of cultivation in the same area direct planting used on bushy areas based on slash and trituration, has contributed to transform this technology into a productive force for family farming, however the results from these researches are from short evaluation periods (up to 4 years after implantation of the system). Thereof, this study will focus in the behavior of the soil in relation to some of its physical and chemical properties throughout 15 years of use of slash and trituration technology in bushy areas of the Municipality of IgarapéAçu, located in the Northeast of the state of Pará, in Entisol Typic. Three forms of land preparation was evaluated: 1- slash and burn of vegetation in fallow; 2- slush and trituration of vegetation in fallow to be used as vegetative cover of the soil; and, 3- slash, trituration and incorporation of vegetation to the soil, with and without NPK , and a natural bushy area as the control plot. The experimental design consisted of random blocks, with 6 treatments and 3 repetitions, in factorial experiment 4X4 with split plots. The factors consisted, respectively, of 4 years (1995, 1996, 1998 e 2010) and 4 layers (0-10; 10-20; 20-30 e 30-50 cm). The soil samples were analyzed at the Soil Laboratory of Embrapa Amazônia Oriental, according to methodology used by Embrapa (1997), and compared using Tukey test at 5%. The results indicate that the system based on slash and trituration of the bush and the use of mineral fertilization presents greater potential for maintenance of the physical and hydric quality of the soil in relation to burning the secondary vegetation over time; the management systems with or without burning the vegetation are similar in terms of availability of nutrients and organic matter in the soil over the years; over time, the treatment with incorporation of triturated vegetal biomass plus and fertilization offers a better alternative to replace burning when preparing the land.