Uptake of Nutrients in a Plantation ofAcacia mangiumin Relation to Decrease in Soil Amounts

Abstract

Abstract Amounts of total nitrogen, phosphorus, potassium, calcium, magnesium, manganese, and sodium in the humus layer and plant-available or exchangeable nutrients in the top 30 cm of the soil were determined before planting and in a 45-month-old plantation of Acacia mangium. Amounts were lower in the plantation than before planting owing to plant uptake and leaching. However, for potassium and calcium the difference was much smaller than the amounts in the plantation biomass, indicating that the plants had taken up nutrients from soil depths below 30 cm or had utilized other sources of nutrients. The other main sources of nutrients were mineralization of dead logs, big branches, and roots, none of which had been included in the humus sampling, and chemical weathering of minerals. The supply of plant nutrients through atmospheric input was low, and there was a negligible input of nutrients dissolved in laterally flowing water because the investigated plot was situated near the water divide. The investig...