Combined application of manure and phosphorus fertilizer improved aggregate stability and phosphorus availability by improving soil organic carbon stock in coastal saline-alkaline soil

Abstract

Purpose The high salt content in soil decreases soil structure and fertility. We inquired the effects of manure combined phosphorus (P) fertilizer on the soil organic carbon (SOC) stock, soil aggregate stability and P availability in coastal saline-alkali soil. Methods A 2-year field experiment was arranged with manure and P fertilization in saline-alkaline soil of Yellow River Delta including: four manure treatments (C0, C1, C2 and C3, which was 0, 500, 1000 and 2000 kg C ha− 1, respectively) under two P fertilization levels (P1 and P2, which was 105 and 75 kg P ha− 1, respectively). Results Compared with C0 treatment, soil available P (AP) and microbial P in C2 treatment was significantly increased under the two P levels (p < 0.05). Under same C treatment, optimized P application did not significantly reduce soil AP pool. Under the two P levels, compared with C0 treatment, the mean weight diameter and > 0.25 mm aggregates proportion were significantly increased in C2 treatment (p < 0.05). As the binder for macroaggregates formation, SOC stock was increased by 5.98% and 5.11% in P1C2 and P2C2 treatments, respectively. And humus content increased with manure application. The fulvic acid (FA) content in C3 treatment was highest. However, the humin (HU) content in C2 treatment was highest. This might be because the increase of FA improved the activity of microorganisms and decomposed part of HU. Soil physicochemical properties were increased with manure application. Conclusions Appropriate manure and optimized P fertilizer was conducive P availability, increased aggregate stability and SOC stock.