[Improvement effects of quicklime and calcium magnesium phosphate fertilizer on acidified soil cultivating Codonopsis tangshen.] / ç”ŸçŸ³ç°å’Œé’™é•ç£·è‚¥å¯¹é ¸åŒ–å·å šå‚åœŸå£¤çš„æ”¹è‰¯æ•ˆæžœ.

To solve the problem of soil acidification in the cultivation of Codonopsis tangshen, laboratory experiments were carried out to investigate C. tangshen seed germination, seedling growth and soil exchangeable acid, microbial community structure after applying quicklime (QL) and calcium magnesium phosphate fertilizer (CMP). The results showed that QL and CMP treatments significantly improved the survival rate of C. tangshen seedlings from 147.7% to 326.7% and from 270.1% to 311.2%, respectively. The maximum increase rates of the height of C. tangshen seedlings were 516.7% and 546.3%, and that of root length were 798.0% and 679.2% in the treatments of QL and CMP, respectively. 1‰-4‰ QL or CMP treatments increased the relative chlorophyll content, antioxidant enzyme activity and the content of soluble protein of C. tangshen seedlings, decreased the content of malondialdehyde and superoxide anion radical of seedlings, increased soil pH by 0.88-2.02 units and 0.23-1.19 units, and decreased the exchangeable aluminum content in soil by 53.0%-95.3% and 17.6%-81.3%, respectively. Soil bacterial and actinomycetic abundances were significantly higher in 2‰-4‰ QL or CMP treatments than that in the control. Soil fungal abundance was significantly lower in the QL treatment of 2‰ and CMP treatment of 4‰. 1‰-4‰ QL or CMP treatments significantly increased fresh weight of C. tangshen tubers by 40.5%-78.5% and 28.4%-78.8%, respectively. In conclusion, the suitable quantity of QL and CMP for acidified soil (pH=4.12, ρb=1.15 g·cm-3, tillage layer=15 cm) amendment were 1.73-3.45 t·hm-2 and 3.45-6.90 t·hm-2, and QL and CMP amendment could fit the optimum soil pH (5.5-6.5) for the growth of C. tangshen seedlings.

Water management impacts the soil microbial communities and total arsenic and methylated arsenicals in rice grains.

The bioavailability of the metalloid arsenic (As) in paddy soil is controlled by microbial cycling of As and other elements such as iron (Fe) and sulfur (S), which are strongly influenced by water management in paddy fields. In this study, we evaluated how water management affects As bioavailability by growing rice plants in a geogenic As-contaminated soil. We determined As speciation in soil porewater and the diversity of the associated microbial community. Continuous flooding enhanced the release of Fe and As and increased arsenite (As(III)) and methylated As species concentrations in the rice grain compared with aerobic treatment. Total inorganic and organic As in the grain was 84% and 81% lower, respectively, in the aerobic treatment compared with the continuous flooding treatment. The amounts of Fe(III)-reducing bacteria (FeRB) increased in the flooded rhizosphere soil. The abundance of FeRB in the soil correlated with the dissolution of Fe and As. Among the As-transformation genes quantified, the aioA gene for As(III) oxidation and arsM gene for As(III) methylation were most abundant. The arsM copy number correlated positively with the levels of dsrB (dissimilatory (bi) sulfite reductase ß-subunit), suggesting that dissimilatory sulfate-reducing bacteria (SRB) may play an important role in dimethylarsenate (DMAs(V)) production in soil. Our results show that decreased populations of rhizosphere FeRB and SRB contributed to a lower bioavailability of As, and decreased production of methylated arsenicals under oxic conditions.