Shifting cultivation in decline: An analysis of soil fertility and weed pressure in intensified cropping systems in Eastern Amazon

THOMAS ABRELL; KRISHNA NAUDIN; FELIX J.J.A. BIANCHI; DEBORA VEIGA ARAGAO; PABLO TITTONELL; MARC CORBEELS

AGRICULTURE, ECOSYSTEMS AND ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2024 vol. 360

0167-8809

Reconciling forestpreservation and agricultural production is a major challenge. In Brazil,environmental laws have been introduced to reduce forest degradation associatedwith the expansion of agriculture. However, these laws are constrainingsmall-scale family farmers who rely on cassava produced in shiftingcultivation. Faced by scarcity of land, farmers are reducing the fallow periodson their farms. In this study, our hypothesis was that the reduction of thefallow period in shifting cultivation systems leads to a depletion of soilfertility and an increase in weed pressure. In the Brazilian Eastern Amazonregion, soil fertility and weed infestation indicators were assessed in 36cassava fields under shifting cultivation with different land-use histories.The frequency of cultivation of the fields in the past 10 years ranged from 1to 7 and averaged 3.7 ± 2.3. The results show that the most frequentlycultivated fields had lower soil fertility, indicated by lower soil organiccarbon, total nitrogen and exchangeable potassium and pH. In addition, laborinput for weeding and weeding frequency increased with the frequency ofcultivation of the fields, indicating that weed pressure increased withintensified crop cultivation and shorter fallow periods. The findings of thisstudy make clear that the current trend of reducing the fallow period in theEastern Amazon is a threat to the sustainability and productivity of the localshifting cultivation systems. There is an urgent need for alternativeproduction systems that allow for a better weed control and that contribute torestoring and maintaining soil fertility.