[Effects of Oyster Shell Powder and Lime on Availability and Forms of Phosphorus and Enzyme Activity in Acidic Paddy Soil].

Soil acidification improvement in the main grain production regions of southern China is an important issue to enhance the quality of cultivated land and promote grain yield. In order to explore the effects of oyster shell powder and lime on acidity and availability and inorganic forms of phosphorus in acidic paddy soil, a pot experiment was performed using oyster shell powder and lime amendments with dosages of 0.05%, 0.10%, and 0.15%. The results showed that both oyster shell powder and lime significantly (P<0.05) increased the pH and decreased exchangeable acid content of paddy soil. The improvement effects increased with the dosage of soil amendments. Under the same amendment dosage, the effects of lime on soil pH and acidity were higher than those of oyster shell powder. Both lime and oyster shell powder significantly increased the content of available P extracted using H2SO4-P, Bray-1 P, and Olsen-P techniques. The contents of inorganic P in soils decreased in the order of Fe-P>Al-P>Ca-P. The application of lime and oyster shell powder significantly increased the contents of Al-P and Fe-P in soil. Compared with the control treatment, lime and oyster shell power increased Al-P and Fe-P by 26.3%-37.4% and 7.9%-23.7%, respectively. However, there was no significant difference in Al-P content among treatments of the three amendment dosages. The contents of Fe-P and Ca-P in soils increased with an increased dosage of amendments. The activities of DHA, ALP, and IPP and the copy number of the phoD gene in soil increased with the application of lime and oyster shell powder, whereas the activities of ACP and the copy numbers of phoC and pqqC decreased. The application of lime and oyster shell powder at a rate of 0.10% and 0.15% significantly (P<0.05) increased the yield of rice. The lime and oyster shell powder treatments at the dosage of 0.15% increased rice yield by 34.2% and 46.8%, respectively, whereas the amendment had no significant effect on straw biomass of the rice crop. Correlation analysis showed that soil pH and the ALP activity were significantly positively correlated with inorganic P and available P contents, respectively. These results suggested that lime and oyster shell power could effectively increase the content of available phosphorus by eliminating soil acidity and improving the phosphatase activity, which played a positive role in increasing crop yield.

[Dynamic Effects of Direct Returning of Straw and Corresponding Biochar on Acidity, Nutrients, and Exchangeable Properties of Red Soil].

To compare the dynamic effects of straw and corresponding biochar on soil acidity, nutrients, and exchangeable capacity in red soil, a pot experiment was performed. The treatments included control (CK), rice straw (R1B0), rice straw biochar prepared at 350℃ (R1B1) and 550℃ (R1B2), rape stalk (R2B0), and rape stalk biochar prepared at 350℃ (R2B1) and 550℃ (R2B2). Straw at 1% and corresponding biochar were added to a strongly acidic red soil. The rice was planted as the experimental crop. Soils were collected at the seedling, tillering, filling and mature stages of rice growth, respectively. The changes in soil pH, exchangeable acidity, organic matter, nutrients (NH4+-N and NO3--N), and exchangeable cations in soils were measured. The results showed that soil pH, NH4+-N, and NO3--N concentrations decreased with the growth period of rice, while the organic matter content and cation exchange capacity (CEC) increased. Direct returning of straw and biochar could increase soil pH, organic matter content, and exchangeable cations content, and reduce the total amount of exchangeable acids. In the mature stage of rice, rice straw and rape stalk biochar at 350℃ increased the soil pH by 0.29 and 0.42, respectively, compared to the control treatment. Similarly, biochar decreased the exchangeable acidity and exchangeable Al3+ content significantly compared to the direct returning treatments of straw. The exchangeable acidity and exchangeable Al3+ contents of soils in R1B2 and R2B1 treatments decreased by 54.8% and 58.9%, respectively, compared to the control treatment. The soil organic matter (SOM) content and CEC in biochar treatments were significantly higher than those in direct returning treatments of straw. Overall, the effects of rape stalk biochar on soil properties were slightly stronger than those of rice straw. The correlation analysis showed that soil exchangeable acids had a significantly negative correlation with organic matter (R=-0.912, P<0.01), and CEC (R=-0.866, P<0.05). The CEC in soils was positively related to organic matter (R=0.833, P<0.05). Direct returning of straw and biochar applications can effectively improve soil acidity and increase nutrient contents. The effects of straw biochar on soils were stronger than the direct returning of straw in decreasing soil acidity, and increasing soil organic matter content and exchangeable capacity in acidic soils.

[Dynamic Effects of Different Biochars on Soil Properties and Crop Yield of Acid Farmland].

To investigate the dynamic effects of biochars produced from different biomass materials on farmland soil acidity, exchangeable cations, phosphorus nutrient, and crop yield, a field experiment was performed on acid paddy soil. Five types of biochars-rice straw biochar (RSB), maize straw biochar (MSB), wheat straw biochar (WSB), rice husk biochar (RHB), and bamboo charcoal (BCB)-were applied to farmland soil at mass fraction of 0.1%. No biochar addition was used as control treatment (CK). The soil physicochemical properties and crop yields were analyzed after harvesting rice, rapeseed, and corn crops. Results indicated that the addition of biochars could effectively increase soil pH and exchangeable cations and reduce exchangeable acid content, but the effects decreased with time. The biochars increased the content of exchangeable K+, Ca2+, and Mg2+ and decreased the exchangeable Na+ content in soils. The biochars increased the contents of organic matter (SOM), available phosphorus, total phosphorus, and inorganic phosphorus (Al-P and Fe-P). Compared with the control treatment, biochars significantly (P<0.05) increased the yields of rice, oil seed, and maize crops. Rice husk biochar (RHB) had the best effect in improving acid soil physicochemical properties and increasing crop yield.

Association of serum retinoic acid with depression in patients with acute ischemic stroke.

Retinoic acid (RA), produced by the metabolism of vitamin A, makes effects on depression and stroke. This study was aimed to evaluate the relationship between RA levels in serum and post-stroke depression (PSD). A single-center (Chengdu, China) prospective cohort study was conducted on patients with acute ischemic stroke. The RA serum level was measured at admission. The PSD was assessed in the 3-month follow-up. The RA-PSD relationship was evaluated with conditional logistic regression. In total, 239 ischemic stroke cases and 100 healthy controls were included. The median RA serum level in patients with ischemic stroke was 2.45 ng/ml (interquartile range [IQR], 0.72-4.33), lower(P<0.001) than 3.89 ng/ml of those in control cases ([IQR]: 2.62-5.39). The crude and adjusted odds ratios [OR] (and 95% confidence intervals [CI]) of PSD associated with an IQR increase for RA were 0.54 (0.44, 0.67) and 0.66 (0.52, 0.79), respectively. Higher ORs of PSD associated with reduced RA levels (