Maize//soybean intercropping promotes activation of soil phosphorus fractions by secreting more phosphatase in red soil under different phosphorus application rates

Abstract

Abstract Aims Rational intercropping plays an important role on improving Phosphorus(P) uptake and utilization. This study aimed to investigate the effects of intercropping on the activation of soil P fractions and available P in acid soil. Methods The field experiments were conducted for two consecutive years to investigate the effects of maize intercropping with soybean at different P application rates (0, 60, 90, and 120 kg P2O5 ha− 1) on soil P fractions and P turnover. Results Compared with the monoculture maize, intercropping significantly increased maize P uptake by 43.6%~74.3% and 45.5%~76.8% in two years, while the intercropping advantage gradually weakened with the increasing of P levels. Intercropping maize promoted the activation of soil P pools, which increased labile P pools by 32.5%~38.4% and 14.4%~82.1%, while reducing non-labile P pools by 7.4%~10.9% and 6.6%~11.6% compared with monoculture maize. Meanwhile, intercropping could deplete NaOH-Po, conc. HCl-Pi, conc. HCl-Po and Residual-P fractions, and increase Resin-P, NaHCO3-Pi, NaHCO3-Po by 4.3%~41.2%, 21.1%~84.6% and 9.7%~98.8%, respectively. In addition, intercropping significantly increased alkaline phosphatase activity (ALP) by 21.2%~42.6% and 19.9%~28.6%, and significantly increased acid phosphatase activity (ACP) by 13.8%~27.1% and 9.5%~13.4% under different P rate. Structural equation model (SEM) showed that both ACP and ALP plays curtail role increased available P directly or indirectly through their effects on organic P turnover. Conclusions These result highlight the importance that intercropping maize with soybean increases soil P bioavailability by transforming organic P pools (NaOH-Po and conc. HCl-Po) into soluble phosphate (Resin-P, NaHCO3-Pi and NaOH-Pi) by facilitating the secretion of phosphatase.