Land use and management effects on volcanic soils in West Sumatra, Indonesia

Abstract

In this study, we aimed to assess the influence of land use and management on the fertility characteristics and pedogenic indicators of volcanic soils. Our study area was a mountainous area located in West Sumatra, Indonesia, where local farmers intensively cultivate vegetables by applying high amounts of chemical fertilizers and agrochemicals. Some negative impacts of conventional management were observed in the vegetable fields: soil acidification and loss of organic matter, with descended soil pH and increased acidity as well as decreased contents of exchangeable bases and with decreased amount of organic C. These impacts were not effectively mitigated by positive factors such as increased P availability and decreased capacity for P fixation. Continued cultivation over the years compounded the effects of these changes. Organic farming was advantageous in terms of soil fertility maintenance as it alleviated negative impacts compared to conventional farming. Natural fallow was effective in replenishing soil fertility as indicated by a significant increase in organic C, total N, and exchangeable Ca and Mg contents compared to the vegetable fields. The degree of replenishment was enhanced with a longer period under fallow; however, the natural fallow decreased P availability and increased P fixation capacity. Calliandra calothyrsus fallow further accelerated soil acidification, regardless of the rapid increase in the organic C and exchangeable bases contents. The adverse effects of Calliandra fallow were associated with the formation of humus–aluminum complexes to an extent that it changed from Sil-andic to Alu-andic Andosols.