Landscape-scale assessment of soil response to long-term organic and mineral fertilizer application in an industrial oil palm plantation, Indonesia

摘要

Organic fertilizers improve soil fertility in oil palm plantations, based on small-scale (<30 ha), short-term (3-5 yr) studies, but the response is not equal across soil classes. Since organic fertilizers are costly to handle and apply, relative to mineral fertilizers, producers need to know where and how frequently to apply organic fertilizers to improve soil fertility. This study assessed the soil response to long-term mineral and organic fertilizer applications in an industrial oil palm plantation. A landscape-scale approach was developed to cope with unavailable historical soil data, variability in fertilizer application sequences and diverse soil classes across the plantation. Soil response to fertilizer application was inferred from (i) a one-off soil survey, (ii) record of fertilizer sequences, and (iii) knowledge of the biogeochemical processes underlying the measured soil response. Low-fertility Ferralsols responded significantly to continuous organic fertilizer application, with greater improvement in the loamy-sand uplands than sandy-loam lowlands. In the loamy-sand uplands discontinuing organic fertilizer applications significantly decreased the organic carbon concentration without reducing the pH, base saturation or nutrient concentrations, but organic carbon was protected from mineralization by slower drainage and fine texture in the sandy-loam lowlands. We conclude that organic fertilizers should be applied regularly to loamy-sand uplands to sustain soil fertility