Chemical properties of soils under different cultivation systems in the Amazon

Abstract

The most well-known farming systems are: the traditional farming system, widely used by family farmers and the more intensive farming system, which uses monocultures. Both have different characteristics, with advantages and disadvantages. As an alternative for small producers, we have agroforestry systems, which consist of a search for profitability together with sustainable land use. Depending on the system to be adopted in the crops, different characteristics may be observed in the soils in which these systems will be implanted. Therefore, the present work aimed to evaluate the chemical attributes of soils under different land use systems, in the municipality of São Francisco do Pará, with the purpose of characterizing them chemically. Soil collection was carried out in December 2006, in 7 (seven) sample areas, as follows: three agroforestry systems - SAF1 (coconut orchard and agricultural crops such as watermelon and manioc); SAF 2 (coconut orchard, cupuaçuzeiros and cashew trees); SAF 3 (composed of rubber trees, soursop and cupuaçuzeiros). Two annual crops: Roça 1 (planting cassava by cutting and burning without fertilization system (2006); Roça 2 (planting corn and manioc fertilized (2006); Pasture planted in old cultivation of cassava, without fertilization and Secondary Forest - approximately 20 years of age.The soil pH values ​​ranged from 4.3 (SAF 3) to 5.4, characterizing acidic to very acidic soils. 1.5 mg dm^-3) to very high (43.10 mg dm^-3) .The very high value is probably related to the residual effect, as the SAF 3 is found in an old rubber plantation that received periodic fertilizations. average value of organic carbon concentration was higher for Secondary Forest with 11.78 g/kg and lower for SAF 1 with 6.45 g/kg. The lowest organic matter concentration value was registered in SAF 1 with 11, 11 g/kg and the highest in the Secondary Forest (FS) with 20.10 g/kg. The values ​​for magnesium varied from 0.28 cmol_c dm^-3 in SAF 3 at 0.47 cmol_c dm^-3 in the secondary forest. The concentration values ​​were 'low' for potassium and 'average' for calcium. Therefore, the values ​​of chemical attributes found in the analyzed soils are characterized by medium nutrient levels and high acidity. Possibly in areas with higher values, the burning system and the supply of fertilizers are due. Another important point can be seen in the low technological level applied to SAF’s.