Pools and distributions of soil phosphorus in China

We have investigated the pools and distributions of soil phosphorus (P) in the top 50 cm of soil in China by using a combination of total and available P information from more than 2400 soil profiles and a map of soil types at a resolution of 1:1,000,000. Our estimates indicate that the average total P density and available P density in China are about 8.3 × 10 2 g/m 3 and 5.4 g/m 3 , respectively. The total national soil P pool in the surface half meter is 3.5 Pg (10 15 g). The available P density ranges from 0.7 g/m 3 in the Lithosols to 16.7 g/m 3 in the Irrigated Silting Soils. The total P density ranges from 1.2 × 10 2 g/m 3 in the Lithosols to 19 × 10 2 g/m 3 in the Frigid Desert Soils. The ratio of available P to total P density ranges from 0.6 × 10 −3 in Aeolian Soils to 21.6 × 10 −3 in Coastal Solonchaks. The available P content and its vertical distribution show a complex pattern among soil orders of different development stages, possibly indicating the important role of biota's control over soil available P content. There are large variations of P content in different climatic regions. The tropical and subtropical region has the lowest available P density (4.8 g/m 3 ) and the second lowest total P density (8.2 × 10 2 g/m 3 ) among all climatic regions. The large variation in the soil P content suggests that further study is needed to investigate climatic and land‐use controls over the soil P content.