Abstract:

To explore the regulatory effects of applying commercial organic fertilizer from fermented chicken manure on rice yield and soil physicochemical properties in a double-cropping rice system, a paired field experiment was conducted in sandy loam paddy fields derived from river alluvium in eastern Hunan Province. The treatments consisted of conventional chemical fertilizer and commercial organic fertilizer from fermented chicken manure (4.5 t/hm² per season). The effects of continuous organic fertilizer application on rice yield, soil physicochemical properties, and enzyme activities were systematically analyzed. The results showed that, compared with the control plots, although the organic fertilizer treatment did not significantly increase double-cropping rice yield (the increase range between 11%-15%), it significantly improved the soil physical structure: the soil bulk density decreased by 15%-16% in early rice season, and the stability of soil aggregates was significantly increased by 21%-61% (P<0.05). The contents of various soil carbon components showed an increasing trend. In Lutang Village, the total soil organic carbon content was significantly increased by 12% and 19% in early and late rice seasons, respectively; the contents of active organic carbon components (dissolved organic carbon and particulate organic carbon) increased by 29%-67%, and the mineral-bound organic carbon content increased by 14%-65%. The increase in available nutrient content showed spatiotemporal heterogeneity. In Lutang Village, the total nitrogen and alkali-hydrolyzable nitrogen contents were significantly increased by 26% and 21%, respectively, in the early rice season; in Fengyu Village, the alkali-hydrolyzable nitrogen and available potassium contents were increased by 21% and 11%, respectively, in the late rice season (P<0.05). The response of soil enzyme activity to organic fertilizer application varied with the experimental site and rice season. In Fengyu Village, the activities of urease, acid phosphatase, and β-1,4-glucosidase were significantly increased by 93%-149% in the late rice season, while in Lutang Village, β-1,4-glucosidase activity was decreased by 23%-35% in both early and late rice seasons. Correlation analysis showed that rice yield was significantly positively correlated with soil organic carbon, available potassium, and mineral-bound carbon (Pearson correlation coefficient was 0.420-0.634), but was significantly negatively correlated with β-1,4-glucosidase activity (Pearson correlation coefficient was -0.506). In conclusion, commercial organic fertilizer from fermented chicken manure positively enhances soil fertility in double-cropping rice systems by improving soil physical structure, increasing soil organic carbon content, and modulating enzyme activities, though its effects are influenced by native soil properties and rice season.

Key words: soil aggregate stability, enzyme activity, carbon composition, soil nutrients, soil properties