Combinations of ripping depth and tine spacing for compacted sandy and clayey soils     

M.A. Hamza  W.K. Anderson   《Soil & Tillage Research》2008,99(2):213-220

Soil compaction is one of the major problems facing modern intensive agriculture. To remove soil compaction and restore soil productivity soil must be ripped to loosen it. Ripping is a costly process involving high fuel consumption, as well as depreciation of the implements through wear and tear. This article shows research into some combinations of tine spacing and ripping depth and their consequences for soil properties and grain yields. Three sites were chosen for these experiments on clayey and sandy soils. Treatments were a factorial of three tine spacings (20, 30 and 40 cm) by three ripping depths (15, 30 and 40 cm) together with the control.Commercial gypsum at 2.5 t/ha was applied to all treatments to maintain soil structure after ripping and the treatments were treatments were monitored for two seasons under wheat and barley crops.The highest grain yield in sandy soil was found with the combination of 40 cm ripping depth and 20 cm tine spacing. In clayey soils tine spacings of 20 cm and 30 cm in combination with 40 cm ripping depth, were equally effective for grain yield. The shallowest depth treatment, 15 cm, did not significantly affect grain yields regardless of tine spacing. It seems that the best practical compromise of tine spacing and ripping depth is 30 cm × 30 cm. The highest stored soil water was obtained from the deepest ripping and the widest tine spacing (40 cm × 40 cm) treatments and the lowest was obtained from the shallowest depth and narrowest spacing (15 cm × 20 cm) treatments which was still higher than the control treatment. However, due to soil re-settlement and re-compaction, the soil water storage obtained in the year after ripping to 40 cm depth was in many cases only equal to that obtained from 30 cm ripping depth. Soils ripped at 30 cm or deeper had significantly higher water infiltration rate than soils ripped at 15 cm depth. Soil bulk density, though decreased significantly in all ripping treatments relative to the controlled treatments in the first year, showed no stable pattern of change in the second year. All shallow ripping treatments (15 cm) regardless of tine spacing had similar soil strength and were not significantly different from the control. The other two ripping depths in general were equal, and significantly better than the controls. It is concluded that ripping to 30 or 40 cm depth in combination with 30 or 40 cm tine spacing was most effective for treating compacted soils.  相似文献   

On modeling repeated binary responses and time-dependent missing covariates     

Lan Huang  Ming-Hui Chen  Fang Yu  Paul R. Neal  Gregory J. Anderson 《Journal of Agricultural, Biological & Environmental Statistics》2008,13(3):270-293

We develop a novel modeling strategy for analyzing data with repeated binary responses over time as well as time-dependent missing covariates. We assume that covariates are missing at random (MAR). We use the generalized linear mixed logistic regression model for the repeated binary responses and then propose a joint model for time-dependent missing covariates using information from different sources. A Monte Carlo EM algorithm is developed for computing the maximum likelihood estimates. We propose an extended version of the AIC criterion to identify the important factors that m a y explain the binary responses. A real plant dataset is used to motivate and illustrate the proposed methodology.  相似文献   

Organic matter accumulation in reclaimed soils under spruce,poplar and grass in the Alberta Oil Sands     

Anderson  Jeff  Prescott  Cindy E.  Grayston  Sue J. 《New Forests》2019,50(2):307-322

Fundamental to the success of forest restoration following major disturbances such as mining is development of a functioning soil, including the amount, properties and rates of accumulation of soil organic matter (SOM). SOM enters mineral soil through leaching of dissolved organic matter from the forest floor; macrofaunal processing of above-ground litter and mixing with soil (bioturbation); and direct deposition of root litter and rhizodeposits. Our study focused on how SOM accumulation in reclaimed mineral soils was affected following re-vegetation with three vegetation treatments: deciduous trees (Populus tremuloides Mitchx. and Populus balsamifera L.), spruce trees (Picea glauca (Moench) Voss.) and grasses (Festuca sp., Bromus inermis), compared to the natural boreal forest. Seventeen sites were studied: 4 reclaimed Deciduous, 5 reclaimed Spruce, 4 reclaimed Grass, and 4 Natural forest. Concentrations of soil organic matter in the upper 30 cm of soil were highest at the Deciduous sites and lowest at Natural sites. SOM concentrations in the top 10 cm of soil were elevated relative to 10–30 cm soil at the Deciduous and Grass sites. The elevated SOM in the upper soil at Deciduous and Grass sites was associated with greater macrofauanal activity and higher root biomass at these sites. The higher macrofaunal activity in the surface organic layer and greater amounts of faunal fecal material in the uppermost cm of soil at Deciduous and Grass sites indicate greater enrichment of upper soil by macrofauna at these sites. SOM concentrations were significantly positively related to root abundance at Grass sites (indicating a contribution of roots to SOM), and a similar trend was apparent at the Deciduous sites. The elevated organic matter concentrations in the upper 10 cm of soil at the Deciduous and Grass sites suggest that planting of aspen following reclamation would hasten C sequestration into soil organic matter.

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Analysis of fungal endophytes in Scottish Sitka spruce plantations shows extensive infections,novel host partners and gives insights into origins     

Carly R. Anderson Stewart  Mingkwan Doilom  Joanne E. Taylor 《Forest Pathology》2019,49(1)

This preliminary study identified the fungal endophytes of Sitka spruce (Picea sitchensis) in four Scottish plantations, analysed their recruitment possibilities and community structure across the sites, and identified the possible origins of the endophytes in this non‐native host. Although Sitka spruce is native to north‐western North America, it comprises a huge portion of Scottish forestry and is an economically vital timber tree. Needles from two age classes were collected and cultured for emerging endophyte isolates. Using a combination of morphological features and genetic sequencing of the nuclear ribosomal ITS regions of representative morphological types, 57 morphotypes were recorded which represented at least 15 different species, including a hypothesized sister species to the pathogen of Pseudotsuga menziesii in North America and Europe, Nothophaeocryptopus gaeumannii (previously P. gaeumannii) that was present at all sites tested. Diversity, recruitment, site, needle age and needle part effects are discussed. The phylogeny of Nothophaeocryptopus based on analysis of combined ITS and Tub2 sequence data is given in order to assess the relationship of the unknown endophyte to the Douglas fir pathogen N. gaeumannii.  相似文献   

草原红牛转铁蛋白和后转铁蛋白多态性及其与生产性能相关性研究(英文)   总被引：4，自引：0，他引：4  

张永宏  潘英树  高妍  马倩  刘同欣  秦莹  赵志辉  张嘉保 《农业科学与技术》2008,9(5):109-112

[Objective] The aim of this study was to investigate the correlation between blood protein polymorphism of red steppe and its performance.[Method]Two blood protein polymorphic loci were detected in transferring(Tf)and posttremsferr(Ptf)from thirteen red steppes and eighteen hybrid of limousin and red steppe by polyacrylamide gel electrophoresis.[Result]Tf and Ptf were controlled by three and two alleles respectively.[Conclusion]The variance analysis of blood protein polymorphic loci and its performance indicates that two protein loci have a positive or negative correlation with some traits of red steppe and the improved limousin cattle population.  相似文献   

Hydrogen radicals, nitrogen radicals, and the production of O3 in the upper troposphere     

PO Wennberg  TF Hanisco  L Jaegle  DJ Jacob  EJ Hintsa  EJ Lanzendorf  JG Anderson  R Gao  ER Keim  SG Donnelly  LAD Negro  DW Fahey  SA McKeen  RJ Salawitch  CR Webster  RD May  RL Herman  MH Proffitt  JJ Margitan  EL Atlas  SM Schauffler  F Flocke  CT McElroy  TP Bui 《Science (New York, N.Y.)》1998,279(5347):49-53

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected.  相似文献   

Contaminated Sites and Environmental Cleanup: International Approaches to Prevention,Remediation, and Reuse (G. William Page)     

Anderson  Todd 《Water, air, and soil pollution》1998,108(1-2):223-224

Water, Air, &; Soil Pollution -  相似文献   

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission   总被引：2，自引：0，他引：2  

MH Acu?a  JEP Connerney  P Wasilewski  RP Lin  KA Anderson  CW Carlson  J McFadden  DW Curtis  D Mitchell  H Reme  C Mazelle  JA Sauvaud  C d'Uston  A Cros  JL Medale  SJ Bauer  P Cloutier  M Mayhew  D Winterhalter  NF Ness 《Science (New York, N.Y.)》1998,279(5357):1676-1680

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.  相似文献   

The sensitivity and specificity of two methods for detecting Fasciola infections in cattle.   总被引：2，自引：0，他引：2  

N Anderson  T T Luong  N G Vo  K L Bui  P M Smooker  T W Spithill 《Veterinary parasitology》1999,83(1):15-24

Counts of Fasciola spp. eggs in faeces and measurements of antibody concentration to the excretory/secretory antigens of Fasciola spp. by ELISA were related to the numbers of flukes in the livers of 92 cattle killed in the abattoirs of Hanoi City, Vietnam. In this population, about 22% of the cattle had no flukes, another 22% had between 1 and 10 flukes, 44% between 11 and 100 flukes and 12% had more than 100 flukes in their livers. Of the 14 animals less than 2 years of age, only three were infected. At 2 years of age the mean number of flukes per liver was 10 whereas at 3 years and older, the mean varied between 60 and 80 flukes. Prevalence of infection was 78.3%. No eggs of Fasciola spp. were detected in the faeces of one third of infected cattle and 60% of the counts were less than 100 eggs per gram. The sensitivity of the egg counting method was 66.7% and specificity 100%, overall accuracy was 73.9%. Corresponding values for the ELISA method were 86.1, 70 and 82.6%, respectively. The positive and negative predictive values for the egg counting method were 100 and 45.5% and for the ELISA method were 91.2 and 58.3%, respectively.  相似文献   

Improving estimates of population status and trend with superensemble models          下载免费PDF全文

Sean C Anderson  Andrew B Cooper  Olaf P Jensen  Cóilín Minto  James T Thorson  Jessica C Walsh  Jamie Afflerbach  Mark Dickey‐Collas  Kristin M Kleisner  Catherine Longo  Giacomo Chato Osio  Daniel Ovando  Iago Mosqueira  Andrew A Rosenberg  Elizabeth R Selig 《Fish and Fisheries》2017,18(4):732-741

Fishery managers must often reconcile conflicting estimates of population status and trend. Superensemble models, commonly used in climate and weather forecasting, may provide an effective solution. This approach uses predictions from multiple models as covariates in an additional “superensemble” model fitted to known data. We evaluated the potential for ensemble averages and superensemble models (ensemble methods) to improve estimates of population status and trend for fisheries. We fit four widely applicable data‐limited models that estimate stock biomass relative to equilibrium biomass at maximum sustainable yield (B/B_MSY). We combined these estimates of recent fishery status and trends in B/B_MSY with four ensemble methods: an ensemble average and three superensembles (a linear model, a random forest and a boosted regression tree). We trained our superensembles on 5,760 simulated stocks and tested them with cross‐validation and against a global database of 249 stock assessments. Ensemble methods substantially improved estimates of population status and trend. Random forest and boosted regression trees performed the best at estimating population status: inaccuracy (median absolute proportional error) decreased from 0.42 – 0.56 to 0.32 – 0.33, rank‐order correlation between predicted and true status improved from 0.02 – 0.32 to 0.44 – 0.48 and bias (median proportional error) declined from ?0.22 – 0.31 to ?0.12 – 0.03. We found similar improvements when predicting trend and when applying the simulation‐trained superensembles to catch data for global fish stocks. Superensembles can optimally leverage multiple model predictions; however, they must be tested, formed from a diverse set of accurate models and built on a data set representative of the populations to which they are applied.  相似文献