Effects of different fertilization treatments on soil microbial functional diversity of dry tableland wheat field in south Shanxi Province.

Understanding the effects of different fertilization treatments on microbial functional diversity in loess tableland wheat soil in south Shanxi Province can provide the theoretical basis from the perspective of microbial functional diversity for chemical fertilizer reduction, wheat yield increase, and soil fertility improvement in dryland soil. We conducted a long-term field experiment with seven fertilization treatments in winter wheat cultivation area of loess tableland in south Shanxi Province, including straw charcoal fertilizer (SF), bacterial fertilizer (BF), organic fertilizer (OF), humic acid fertilizer (HF), monitoring fertilizer (MF), farmer fertilizer (FF) and no fertilizer (CK). We employed Biolog-ECO microplate technique to investigate the differences of carbon source utilization capacity and functional diversity of soil microorganisms. The results showed that all the fertilization treatments could improve the metabolic activity and functional diversity of soil microbial community. Carbon source utilization was the most efficient in SF, with the overall soil microbial utilization ability of the 31 carbon sources and the utilization ability of different guilds of carbon sources being improved. Functional diversity, richness, and dominance based on microbial carbon sources utilization were significantly higher in SF treatment than that under other five treatments, and the evenness was higher than BF. Results of principal component analysis (PCA) and biclustering heatmap analysis showed that different fertilization treatments had significant effects on the metabolic function of microbial community. SF treatment could promote the functional diversity of soil microbial community, especially for the utilization of carbohydrates, carboxylic acids and amino acids. In conclusion, straw charcoal fertilizer had positive effects on soil microbial activity in wheat soil of loess tableland in south Shanxi Province.

[Change characteristics of soil moisture and nutrients in rain-fed winter wheat field under different fertilization modes in Southern Shanxi of China during summer fallow period].

In 2009-2011, a field experiment was conducted in a rain-fed winter wheat field in Southern Shanxi of China to study the effects of different fertilization modes on the change characteristics of soil moisture and nitrate-N contents in 0-200 cm layer and of soil available phosphorus (Oslen-P) and potassium contents in 0-40 cm layer during summer fallow period (from June to September). Three fertilization modes were installed, i. e., conventional fertilization (CF), recommended fertilization (RF), and ridge film furrow planting (RFFP) combined with straw mulch. The results showed that the rainfall in summer fallow period could complement the consumed water in 0-200 cm soil layer in dryland wheat field throughout the growth season, and more than 94% of the water storage was in 0-140 cm soil layer, with the fallow efficiency ranged from 6% to 27%. The rainfall in summer fallow period caused the soil nitrate-N moving downward. 357-400 mm rainfall could make the soil nitrate-N leaching down to 100 cm soil layer, with the peak in 20-40 cm soil layer. Straw mulching or plastic film with straw mulch in summer fallow period could effectively increase the Oslen-P and available K contents in 0-40 cm soil layer, and the accumulative increment in three summer fallow periods was 16-45% and 36-49%, respectively. Among the three modes, the binary coverage mode of RFFP plus furrow straw mulching had the best effect in maintaining soil water and fertility. The accumulative water storage and mineral N in 0-200 cm soil layer in three summer fallow periods were up to 215 mm and 90 kg x hm(-2), and the accumulative Oslen-P and available K contents in plough layer were increased by 2.7 mg x kg(-1) and 83 mg x kg(-1), respectively, being significantly higher than those in treatments CF and RF. There were no significant differences in the change characteristics in the soil moisture and nutrients between treatments CF and RF.

[Screening, identification and phosphate-solubilizing characteristics of Rahnella sp. phosphate-solubilizing bacteria in calcareous soil].

Several strains of phosphate-solubilizing bacteria were isolated and screened from the crop rhizosphere of calcareous soil in Shanxi Province of China. After repeated isolation and purification, the strain W25 with strong phosphate-solubilizing activity was obtained, and identified as Rahnella sp., based on the morphological, physiological and biochemical properties and the analysis of 16S rRNA gene sequence. Further studies on the W25 showed that the maximum phosphate-solubilizing capability of the W25 on tricalium phosphate, aluminum phosphate and ferric phosphate reached 385.5, 110.4 and 216.6 mg x L(-1), respectively. In the liquid culture with aluminum phosphate and ferric phosphate, the solubilized phosphorous by the W25 was significantly negatively correlated with the liquid pH, with the correlation coefficient being 0.56 and 0.81, respectively. Among the carbon and nitrogen sources, glucose and ammonium nitrate were the optimum for the solubilization of tricalium phosphate by W25. The utilization of carbon source was in the order of glucose > lactose > sucrose > mannitose > starch, and that of nitrogen source was in the order of ammonium nitrate > ammonium chloride > ammonium sulfate > potassium nitrate > sodium nitrate. Different nitrogen sources had greater effects on the production of organic acids by W25. Formic acid and acetic acid would be produced when the nitrogen source was NH4+, oxalic acid and succinic acid would be produced when the nitrogen source was NO3(-), and citric acid would be extra produced when the ammonium nitrate was used as the nitrogen source.

[Effects of exogenous lead on the growth and lead accumulation characteristics of roadside dominant herbaceous plants in Shanxi Province].

A greenhouse pot experiment was conducted to study the effects of different concentration (0, 500, 1000, 1500 mg x kg(-1)) lead (Pb) on the growth and Pb absorption and accumulation of 14 roadside dominant herbaceous plants in Shanxi Province. With increasing Pb concentration in the pot, Amaranthus retroflexus and Sorghum bicolor x S. sudanese appeared obviously toxic symptoms, while the other 12 test plants had higher Pb tolerance, with no significant decrease in their plant height and biomass, compared with control. Chenopodium album and Psathyrostachys juncea had the lowest Pb content (averaged 12.70 and 11.33 mg Pb x kg(-1), respectively) in their aboveground part and the lowest Pb ratio (0.12 and 0.10, respectively) of aboveground part / root, being the potential low Pb-accumulation plants and able to be used for the vegetation restoration of Pb-polluted soil. Red leaf A. tricolor and green leaf A. tricolor in treatment 1500 mg Pb x kg(-1) had the highest Pb accumulation (53.37 and 45.29 mg Pb per 100 plants, respectively) in their aboveground parts, being able to be chosen as the pioneer plants for the remediation of Pb-polluted soil.

[Effects of nitrogen application and ridge film furrow planting on water use of winter wheat in dry land of south Shanxi].

A 2-year (2008-2010) field experiment was conducted to study the effects of basal dressing nitrogen, topdressing nitrogen, and ridge film furrow planting on the 0-2 m soil moisture status and the grain yield and water use efficiency of winter wheat in rain-fed area of South Shanxi Province. In all treatments, the soil moisture status during winter wheat growth period had the same change trend, being increased steadily from pre-sowing to revival stage and decreased sharply from revival stage to heading stage, and then increased gradually till maturity stage. From revival stage to heading stage, the soil water consumption was the most. Increasing nitrogen basal application rate or topdressing nitrogen increased the soil water consumption, widened the soil moisture active layer, and deepened the relatively stable layer. Topdressing nitrogen increased grain yield significantly; ridge film furrow planting decreased soil water consumption obviously. The water use efficiency under ridge film furrow planting was 23.4% and 39.1% higher than that under conventional planting system in 2009 and 2010 (P < 0.01). The grain yield under ridge film furrow planting plus top-dressing nitrogen was 3643 kg x hm(-2), which was significantly higher than that under single ridge film furrow planting or topdressing nitrogen, displaying a preferable water-fertilizer coupling effect.