NUTRIENT STORE AND EXPORT RATES OF EUCALYPTUS-UROGRANDIS PLANTATIONS IN EASTERN AMAZONIA (JARI)

Nutrient loss due to export of wood and bark of 4.5-year-old Eucalyptu s urograndis was studied in the Jari project, eastern Amazonia, Brazil . Results are based on estimates of biomass, above-ground nutrient sto re, and nutrient stores in the soil. Thirteen stands varying in site c onditions and the number of previous rotations (up to three), were stu died. Average nutrient losses due to export of wood and bark, as a per centage of the element store in the above-ground tree biomass, were: N , 65%; P, 54%; Ca, 76%; K, 57%; Mg, 61%. A comparison of export losses with the present soil stores of Ca, K and Mg cations shows that expor t is equal to or surpasses the remaining soil store to a depth of 100 cm. As a result of the last harvest, about 200-250 kg Ca and about 100 kg K ha(-1) were removed. In spite of uncertainties about other unkno wn inputs and outputs, one has to conclude that the next rotation may be endangered by acute deficiency of mineral nutrients, especially of Ca.