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

In the Amazon region, shifting cultivation with slash buming which is practiced by at least 500,000 small farmers, has been considered one of the main activities responsible for deforestation. To considerably reduce deforestation rates the leveI of sustainability of the shifting cultivation systems, has to be increased and technologies perrnitting an increase in the period used for cultivation of an area to three or more years need to be employed. Thus, the present study had the following objectives: I) to evaluate the effects of tire-free land preparation on crop performance and nitrogen dynarnics; 2) to evaluate the importance of chemical ferti!izer use in systems without the use of tire 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 l G-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 soi! ± NPK fertilization. Rice was planted followed by cowpea and cassava in two consecutive cropping periods. Yield characteristics of the crops as well as the nitrogen dynamics in the soil and the nitrogen uptake by the crops were evaluated. Furtherrnore, 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.