[Dynamics of soil phosphorus adsorption-desorption in maize/soybean relay intercropping system in purple hilly area]

Field plot experiment was carried out to study the effect of phosphorus application on soil phosphorus adsorption-desorption characteristics under three cropping patterns including maize/soybean relay intercropping (M/S), maize monoculture (M), and soybean monoculture (S). Results showed that without phosphorus fertilization, the system crop yield under M/S was increased by 9.8% and 79. 1% compared with that of M and S, respectively, and the land equivalent ratio (LER) was 1.58. With phosphate fertilizer application, the system crop yield under M/S was increased by 10.4% and 80.3% compared with that of M and S, respectively, and the LER was 1.62. The system crop yields under M/S, M and S with phosphate fertilizer application were increased by 12.7%, 12. 2% and 17. 6%, respectively, compared with that without phosphorus fertilization. Among three cropping patterns, the soil buffer capacity (SBC) values were in the order of M/S>M >S regardless of phosphate fertilizer applied or not. The SBC values of M/S, M and S without phosphate fertilizer application were reduced by 19.6%, 30.3% and 12.0% compared with phosphate fertilizer application treatments, respectively. The soil desorption per absorption (b) values of the three cropping patterns with phosphate fertilizer application were in the order of M/S>M>S, and the b values increased by 10.9%, 39.1% and -9.6%, respectively, compared with non phosphate fertilizer application. The soil phosphorus maximum absorption (Qm) and soil phosphorus desorption rate also showed the same trend.