Excessive application of phosphorus (P) fertilizers to enhance crop yields is a common practice in regions with poor soil fertility and low agricultural productivity. However, such overuse often leads to significant P fixation and loss within the soil matrix, reducing nutrient use efficiency. The incorporation of green manure (GM) crops into cropping systems has emerged as a promising strategy to reduce chemical P fertilizer inputs while improving soil P availability. Despite this potential, the mechanisms by which GM crop growth and subsequent decomposition influence the transformation of soil P fractions in dryland agroecosystems remain poorly understood. To address this knowledge gap, a GM decomposition trial and a three-year field experiment were conducted on Loess Plateau, evaluating two P fertilizer levels (P0 and P120) and two GM crops-rapeseed (RS, Brassica napus L.) and black bean (BB, Phaseolus vulgaris L.). Annual P uptake by GM crops ranged from 23.0 to 36.9 kg P2O5 ha(-1) , with RS demonstrating significantly higher accumulation than BB (P < 0.05). After 120 days of decomposition, 13.6-30.9 kg P2O5 ha(-1) of the accumulated P was released, with RS exhibiting a faster decomposition rate than BB (P < 0.05). The incorporation of GM crops effectively substituted 11.3-25.8 % (average 18.6 %) of the conventional P fertilizer requirement. Compared with fallow (FW), GM treatments significantly increased labile P forms (NaHCO3-Pi and NaOH-Pi) and concurrently decreased more stable P fractions (HCld-P and HClc-Pi) under both fertilizer regimes. Overall, integrating GM crops into conventional dryland cropping systems significantly improved soil P availability by enhancing inorganic P fractions and reducing residual-P pools, thereby diminishing reliance on synthetic P fertilizers not only in the Loess Plateau but also in other comparable arid regions globally.