Influences of long-term fertilizations on phosphorus recovery efficiency of wheat in 6 dry upland soils of China

Based on long-term experiments in six upland soils (black soil, isotropic fluvo-aquic soil, fluvo-aquic soil, manural loess soil, red soil and yellow-brown soil), recovery efficiency of phosphorus (PRE) on wheat and its correlative parameters were analyzed to study the temporal and spatial changes of PRE on wheat under various long-term fertilizations. Results indicate that PREs on wheat in the isotropic fluvo-aquic soil, fluvo-aquic soil, manural loess soil and yellow-brown soil are increased annually by 0.80, 0.60, 1.30, and 0.44 percentage points with NPK application (chemical N, P and K fertilizers), respectively. PREs are increased by 0.25–1.72 percentage points with NPKM application (chemical N, P, K fertilizer combined with organic manure) on the four soils. For the black soil, PRE is unchanged during the long-term application of NPK, while that is increased annually by 0.50 percentage points with NPKM. However, PRE in red soil is decreased annually by 0.86 percentage points with long-term application of NPK, and unchanged with long-term application of NPKM. These results indicate that the application of organic manure is helpful to increase PRE in upland soils. The change rate of PRE is related with the fractions of soil phosphorus at the six sites. In isotropic fluvo-aquic soil, fluvo-aquic soil and manural loess soil, the main fraction of soil phosphorus is Ca-P, the PRE change rates of these soils are higher than those of black soil with the main fraction of organic-P and red soil with the main fraction of occluded-P. There are significant positive correlations between PRE and TP (total phosphorus) and soil pH respectively (P0.05).