Response of soil phosphatase activity and soil phosphorus fractions to the application of chloropicrin and azoxystrobin in ginger cultivation

Abstract

BACKGROUNDSoil fumigation can change soil nutrient cycling processes by affecting soil beneficial microorganisms, which is a key issue for soil fertility. However, the effect of combined application of fumigant and fungicide on soil phosphorus (P) availability remains largely unclear. We investigated the effects of the fumigant chloropicrin (CP) and the fungicide azoxystrobin (AZO) on soil phosphatase activity and soil P fractions in ginger production using a 28‐week pot experiment with six treatments: control (CK), a single application of AZO (AZO1), double applications of AZO (AZO2), CP‐fumigated soil without AZO (CP), CP combined with AZO1 (CP + AZO1) and CP combined with AZO2 (CP + AZO2).RESULTSAZO application alone significantly increased the soil labile P fractions (Resin‐P + NaHCO3‐Pi + NaOH‐Pi) at 9 weeks after planting (WAP) but decreased the soil phosphatase activity at 28 WAP. CP fumigation significantly reduced the soil phosphatase activity but increased the proportions of soil labile P fractions (Resin‐P + NaHCO3‐Pi + NaHCO3‐Po) to total P (TP) by 9.0–15.5% throughout the experiment. The combined application of CP and AZO had a synergistic effect on soil phosphatase activity and soil P fractions compared with a single application.CONCLUSIONAlthough AZO application and CP fumigation can increase soil available P in the short term, they might negatively affect soil fertility in the long run by inhibiting soil phosphatase activity. Soil microbial activities, especially microorganisms related to P cycling, may be responsible for the variations in soil P availability, but further research is needed. © 2023 Society of Chemical Industry.

Soil chemical fumigation alters soil phosphorus cycling: effects and potential mechanisms

“…For example, Huang et al (2020a;2020b) found that soil fumigation using chloropicrin and dazomet increased soil active P (H 2 O-P, NaHCO 3 -Pi and NaHCO 3 -Po) in the early stage of the culture (<7days). Wang et al (2023) also found that chloropicrin fumigation significantly increased the proportions of soil labile P fractions (Resin-P+NaHCO 3 -Pi + NaHCO 3 -Po) to total P across 28 weeks of ginger growth. However, the death of PSMs may reduce P-cycle related functional bacterial genes, and slow down the secretion of related phosphatase enzymes, which may arrest the mineralization of soil organic P. Both Huang et al (2020a;2020b) and Wang et al (2023) found that soil fumigation significantly reduced the phoC and phoD gene copy number, and related acid and alkaline phosphatase activities.…”

“…Wang et al (2023) also found that chloropicrin fumigation significantly increased the proportions of soil labile P fractions (Resin-P+NaHCO 3 -Pi + NaHCO 3 -Po) to total P across 28 weeks of ginger growth. However, the death of PSMs may reduce P-cycle related functional bacterial genes, and slow down the secretion of related phosphatase enzymes, which may arrest the mineralization of soil organic P. Both Huang et al (2020a;2020b) and Wang et al (2023) found that soil fumigation significantly reduced the phoC and phoD gene copy number, and related acid and alkaline phosphatase activities. This in turn can further slow down the mineralization processes of organic P released from the dead microbes, which then results in an accumulation of soil organic P (especially labile NaHCO 3 -Po) in the fumigated soils (Wang et al 2023).…”

“…These secreted organic acids may replace bound-P by forming complexes with Fe/Al/Ca-oxyhydroxides and releasing Pi into the soil solution (Lopez-Arredondo et al, 2014). Several previous studies, such as Wang et al (2023) and Li Q. et al (2022), have found that soil fumigation significantly reduces soil pH values, which provides indirect evidence for this hypothesis. However, some other studies such as Cheng et al (2021) and Zhang et al (2019a) have found that soil fumigation significantly increases soil pH values, possibly explained by soil fumigation significantly inhibiting soil nitrification processes (Yan et al, 2017).…”

“…However, the death of PSMs may reduce P-cycle related functional bacterial genes, and slow down the secretion of related phosphatase enzymes, which may arrest the mineralization of soil organic P. Both Huang et al (2020a;2020b) and Wang et al (2023) found that soil fumigation significantly reduced the phoC and phoD gene copy number, and related acid and alkaline phosphatase activities. This in turn can further slow down the mineralization processes of organic P released from the dead microbes, which then results in an accumulation of soil organic P (especially labile NaHCO 3 -Po) in the fumigated soils (Wang et al 2023). Similar decreases in soil phosphatase enzyme activities were also reported in several other studies (Klose & Tabatabai, 2002;Klose & Ajwa, 2004).…”

“…Huang et al (2020a) suggested that P fertilizer loads should be reduced at the early stages of crop growth immediately following fumigation (< 30 days). Wang et al (2023) suggested that reducing early P fertilization aggravates possible P deficiencies arising at later stages of crop growth, and therefore that additional P fertilization should be applied then.…”