Two pot experiments were conducted, one to evaluate the levels of tolerance of fifteen cowpea [Vigna unguiculata (L.) Walp] lines to aluminum (Al) application, and the second to determine the effect of phosphorus (P) addition on the performance of Al‐tolerant lines (IT 91K‐93–10, IT 93K‐2046–1, and IT 90K‐2 77–2) and Al‐sensitive lines (IT 86D‐719, IT 90K‐284–2, and IT 89KD‐349) in an Alfisol with Al amendment. Fourteen of the fifteen lines tested showed decreased root biomass (between 19 to 81% reduction) with Al addition, but this effect was significant for eight of them. Fewer lines showed decreased shoot biomass and grain yield with Al application. Despite little change in nodule number following Al application, there was a significant decrease in nodule weight (between 24 and 53% reduction) for nearly all lines. Phosphorus fertilization increased shoot and root biomass, grain yield, nodule number, and weight, and nitrogen (N) and P content of nearly all lines. Al‐tolerant lines showed higher response in shoot and root biomass and nodulation to P fertilization than Al‐sensitive lines, with the highest response from IT 90K‐277–2. Increase in shoot dry weight as a result of P fertilization was from 64 to 107% for Al‐tolerant lines and from 44 to 48% for the Al‐sensitive lines, and increase in root dry weight was from 46 to 86% for the Al‐tolerant lines and from 7 to 42% for the Al‐sensitive lines. Results of these trials indicated that lines IT 91K‐93–10, IT 93K‐2046–1, and IT 90K‐277–2 have potential for good performance in soil with Al toxicity problems, and that cowpea lines with inherent genetic tolerance to Al will give higher response to P fertilization when grown in soil with Al toxicity problems. 相似文献
Rape (Brassica napus L.) seedling pot experiments were performed with a red soil treated with goethite which had boron (B) either adsorbed (ad-B-goethite) or occluded (oc-B-goethite). Soil acidity, different forms of manganese in the soils and different elements content of the rape seedlings were determined. It was found that the addition of boron-containing goethite to the soils resulted in increased rape growth, elevated soil pH and decreased exchangeable acidity. Compared with the control, boron-containing goethite elevated the content of exchangeable manganese (Mn) (EXC-Mn), organic matter bound Mn (OM-Mn), reducible oxide Mn (RO-Mn) and residual Mn (RES-Mn) which were difficult to use for plant. Low labile organic matter was significantly correlated with easily reducible oxide Mn (ERO-Mn) (P < 0.01) and RO-Mn (P < 0.05). Middle organic matter and soil pH was significantly (P < 0.05) correlated with RES-Mn. Stepwise regression was used to select the combination of variables that best estimates shoot and root dry weight of rape seedling. Among them, soil pH, EXC-Mn, OM-Mn, RO-Mn and RES-Mn significantly influenced the dry weight of rape seedlings. The addition of boron-containing goethite improved the uptake of iron (Fe), calcium (Ca), magnesium (Mg), and copper (Cu) element and decreased the uptake of Mn and zinc (Zn) element in rape seedling. The results suggested that boron-containing goethite could provide a better soil acidity environment for plant growth; it was also an important agent increasing a part of manganese difficult to use for plant and reducing the activity of soil manganese, which was beneficial to altering rape seedling growth. 相似文献
Friction velocity (u*) and aerodynamic roughness (zo) at the soil–plant–atmosphere interface affect wind erosion, but no attempts have been made to quantify these parameters as affected by tillage systems within the Columbia Plateau region of the Pacific Northwest United States. Wind velocity profiles above adjacent field plots (>2 ha), with plots subject to conventional or undercutter tillage during the summer fallow phase of a winter wheat–summer fallow rotation, were measured over 50 high wind events (wind velocities in excess of 6.4 m s−1 at a height of 3 m) during 2005 and 2006 near Lind, Washington to determine u* and zo of tillage treatments. Wheat stubble plots were subject to either conventional (disks) or undercutter (wide V-shaped blades) tillage in spring and then periodically rodweeded prior to sowing winter wheat in late summer. Prior to sowing, u* for conventional and undercutter tillage respectively averaged 0.36 and 0.46 m s−1 in 2005 and 0.38 and 0.40 m s−1 in 2006 while zo for conventional and undercutter tillage respectively averaged 2 and 7 mm in 2005 and 2 and 4 mm in 2006. The aerodynamically rougher surface of undercutter tillage was predicted to suppress vertical dust flux; this was collaborated with observations in the field where undercutter tillage reduced dust flux as compared with conventional disk tillage. Undercutter tillage, therefore, appears to be an effective management practice to roughen the surface and thereby suppress dust emissions from agricultural land subject to summer fallow within the Columbia Plateau. 相似文献
Submerged plants make an important contribution to nitrogen cycling in lakes including in the rhizosphere microenvironment through microbial activities. The main objective of this study was to investigate the abundance of functional genes for nitrogen cycling and the ecological relationship between these genes in the rhizosphere sediment of a freshwater lake in summer.
Materials and methods
Sediment from the rhizosphere of four submerged macrophytes (Ceratophyllum demersum, Hydrilla verticillata, Potamogeton maackianus, and Vallisneria spiralis) was sampled in Lake Liangzi, China, in summer. The anammox bacteria community structure and abundance of five functional genes for nitrogen cycling, ammonia monooxygenase (amoA) of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), anammox 16S rRNA, and nitrite reductase genes (nirK and nirS) in the sampled sediment, were determined.
Results and discussion
A total of 100 anammox gene sequences were grouped into eight operational taxonomic units (OTUs) and genus Ca. Kuenenia was the dominant species in Lake Liangzi in summer. Quantitative polymerase chain reaction (qPCR) revealed that gene copies of AOA amoA (2.42?×?106 copies g?1) were more than one order of magnitude higher than those of AOB amoA (1.98?×?105 copies g?1). The nirS gene (4.13?×?108 copies g?1) was more abundant than the nirK gene (7.28?×?107 copies g?1). There was no significant difference in the abundance of the AOB amoA gene among the rhizosphere of the four macrophytes. Redundancy analysis (RDA) showed a positive correlation between the abundance of the anammox 16S rRNA gene, AOA amoA and AOB amoA, which suggested two of these microbes may have provided a substrate for anammox bacteria in summer.
Conclusions
The diversity of anammox in the rhizosphere of submerged macrophytes of the freshwater lake in summer was very low, but the plant species could affect the abundance of most nitrogen circulating bacteria, especially for anammox bacteria. Anammox 16S rRNA gene was positively correlated with four other functional genes, indicating that all four genes had significant effects on anammox bacteria.
The objective of the experiment was to investigate the effect of Chinese herb additive on production performance and blood biochemical indices in transition dairy cows.Thirty six Holstein dairy cows were randomly assigned to three treatments,supplemented with 0,150 and 300 g/d Chinese herb additive,respectively.Experimental duration was 7 weeks and the first week was the preliminary period.After delivery,feed,blood and milk samples were collected once a week for the measurement of dry matter intake,blood biochemical indexes and milk components.The results showed that cows fed 150 and 300 g/d Chinese herb additive tended to increase milk production (5.1% and 10.6% respectively) compared to control group,but the difference was not significant (P<0.05).Meanwhile,the somatic cell count in milk significantly decreased (P<0.05),which decreased by 62.7% and 76.6%,respectively.Feeding Chinese herb additive had no significant effect on dry matter intake and other milk composition (P>0.05).Compared to control group,cows received Chinese herb additive significantly decreased the content of serum NEFA (P<0.05),which decreased by 29.0% and 35.1%,respectively.There was no significant difference on other indexes in serum (P>0.05).The results showed that dietary supplementation with 300 g/d Chinese herb additive had a good effect for transition dairy cows,which could significantly reduce the somatic cell count in milk and the content of NEFA in blood,and would improve the health status of dairy cows,and the postpartum production performance of dairy cows. 相似文献