Spatial Distribution of Different Forms of Soil Phosphorus of a Pingguoli (Pyrus bretschneideri) Orchard in Yanji, China

The distribution of phosphorus in permanent cropping systems such as orchards soil differs from that of other agricultural soils because of the developed root system with a large biomass and long-life cycle of fruit trees. However, our understanding of soil phosphorus in orchards remains poor. This study applied chemical and spectroscopic analyses to compare differences in soil phosphorus between different slope positions and soil horizons of a Pyrus bretschneideri orchard. The results suggested that soil phosphorus of the Pyrus bretschneideri orchard exceeded that in wasteland. Moderately labile organic phosphorus and orthophosphate are the main forms of soil phosphorus in Pyrus bretschneideri orchard and play an important role in phosphorus cycle of Pyrus bretschneideri orchard soil, the continuous supplementation of them can meet the phosphorus nutrient needs of Pyrus bretschneideri trees. Moreover, Pyrus bretschneideri trees mainly obtain nutrients from horizons AB to B, there should be further focus to the depth of 20–80 cm of fertilizer application approximately in Haplic Luvisols.