Variations of soil phosphatase activity and phosphorus fractions in ginger fields exposed to different years of chloropicrin fumigation

Purpose: Although soil fumigation efficiently controls soil-borne diseases, the effects of repeated soil fumigation on soil phosphorus (P) cycling are still largely unknown. Methods: In this study we conducted a field experiment to explore soil phosphorus availability in ginger fields with 0, 3, and 7 years (F0, F3, and F7) of annual chloropicrin (CP) fumigation history in Shandong Province of China. Soil samples (0–20 cm) were collected at four different times in 2019. Ginger yield, soil phosphatase (acid and alkaline) activities, and soil P fractions were measured. Results: Results showed that ginger rhizome yield was similar in F0 and F3 (70.0 t ha⁻¹), but significantly lower in F7 (37.5 t ha⁻¹). The acid phosphatase (AiP) activity was significantly higher in F0, while alkaline phosphatase (AlP) activity was the highest in F3. There was no significant difference in the available P (resin-P + NaHCO₃-P + NaOH-P) between F0 and F7, with 33.6 to 57.5% of total P (TP), while the available P was significantly lower in F3, being less than 30% of TP. Redundancy analysis (RDA) showed that the highest pH values in F3 contributed to the lowest soil P availability there. AiP activities showed highly positive effects on the soil labile P contents. Conclusion: Results suggested that more P fertilizers are needed after 3 years of CP fumigation to avoid soil P deficiency for ginger growth. The death of ginger became the main limitation for ginger production after 7 years of CP fumigation, at which time, comprehensive agricultural practices should be considered to control ginger soil-borne diseases.