The experimental mixed cropping plantation two years after installation: a provisional balance for agriculture.

Shifting cultivation is the norm in Amazonia, because the soils are extremely poor. Mixed cropping in under discussion as a means of making agriculture self-sustaining and reducing clearance of primary forest. Mixed cropping systems involving different test (fertilizer input, inoculation with VA-mycorrhizal fungi spores, management of the spontaneous vegetation and of the cover crop (Pueraria phaseoloides) are being tested in a former experimental rubber plantation with the objective of achieving sustainability. The paper presents the useful plants of the four mixed cropping systems; 1. rubber, cupuacu, peach palm, papaya;2. cupuacu, peach palm, Brazil nut, urucum, manioc; 3. rubber, cupuacu, coonut, orange, parica, manioc, beans, maize; 4. rubber, parica, ma-hogny, andiroba; and of four conventional monocultures (rubber, cupuacu, peach palm and orange). The plants inoculated with VA-mycorrhizal spores had better growth in the nursery, and higher survival rates after planting out. However, the possible beneficial effects of mycorrhizal fungi were not detected in the field. The incidence of diseases and pests in the mixed systems is the same as in the monocultures, because the plants in those systems have not yet reached a height sufficient to form pathogen barriers. The crop yields, in particular palm hearts, have equalled the local average in newly deforested areas. It emerged that production without input of chemical fertilizer is practicaly impossible on deforested areas after to three years cultivation...