Fire-free land preparation as an alternative to slash-and-burn agriculture in the bragantina region, eastern Amazon: crop performance and phosphorus dynamics.

Shifting cultivation is the most important agricultural land-use system in the Amazon region and the slash-and-bum practice is the traditional method for land preparation used by small farmers. During slash and buming, however, high amounts of nutrients are lost through volatilization. This fact, exacerbate by reduced fallow time, decreases the total nutrient stock offallow systems and compromises the system's sustainability. The objectives of this study were: I) to evaluate the effects of fire-free land preparation on crop performance and phosphorus dynamics; 2) to evaluate the importance of the use of chemical fertilizer in systems without the use of fire and 3) to select rice, maize, cowpea and cassava cultivars suitable for mulch systems. The studies were conducted in the community of Cumaru in the municipality of Igarapé Açu (Pará, Brazil) on two neighboring sites with 4-year-old (FV4y) and 10-year-old fallow vegetation (FVIOy). Three treatments for land preparation were tested with and without fertilizer. The treatments were: I) buming ± NPK fertilization; 2) mulching ± NPK fertilization; 3) incorporation of the fallow vegetation biomass into the soil ± NPK fertilization. Rice was planted followed by cowpea and cassava in two consecutive cropping periods. Yield characteristics of the crops as well as the phosphorus dynamics in the soil and uptake by the crops were evaluated. Furthermore, screening experiments were set up to evaluate the yield characteristics of a total of 8 rice, 18 maize, 21 cowpea and 5 cassava cultivars under mulch conditions with and without fertilizer application...Doctoral Dissertation (Doctor of Agricultural Sciences) - George-August-University Göttingen, Göttingen