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61.
N, P and K budgets for crop rotations on nine organic farms in the UK   总被引:2,自引:0,他引:2  
Abstract. Nitrogen (N), phosphorus (P) and potassium (K) budgets were calculated for nine organic farms in the UK. The farms were situated on sandy loams, silty clay loams and silty loams over chalk with stockless farming systems and cattle, pig and poultry enterprises with a significant proportion of arable cropping. A soil surface nutrient budget was calculated for the target rotation on each farm using information about field management and measurements of the soil, crops and manure. Losses of N through leaching and volatilization were calculated independently using the nitcat and manner models. Nutrient budgets for seven of the farm rotations showed an N surplus, six a P surplus and three a K surplus. The ratio of N inputs supplied in the form of biological fixation : manure : atmospheric deposition was approximately 2 : 2 : 1 for stocked systems and 2 : 0 : 1 for stockless systems. Phosphorus surpluses resulted from supplementary P fertilizer (rock phosphate) and additional feed for non-ruminant livestock. The stockless system without P fertilizer resulted in a large P deficit and stocked systems, which relied on recycling manure alone, a small P deficit. Only rotations with large returns of manure or imported feed showed a K surplus or a balanced K budget.  相似文献   
62.
Abstract. This paper compares nitrate leaching losses from organic farms, which depended on legumes for their nitrogen inputs (66 site years) with those from conventional farms using fertilizers under similar cropping and climatic conditions (188 site years). The conventional farms were within Nitrate Sensitive Areas in England, but sites following special practices associated with that scheme were excluded. Nitrate losses during the organic ley phase (including the winter of ploughing out) were similar (45 kg N ha–1) to those from conventional long-term grass receiving fertilizer N inputs of less than 200 kg N ha–1 (44 kg N ha–1) and from the grass phase of conventional ley-arable rotations (50 kg N ha–1). Losses from conventional grass receiving higher N inputs were greater than from organic or less intensive grass. Nitrate losses following arable crops averaged 47 and 58 kg N ha–1 for the organic and conventional systems respectively, with part of the difference being due to the greater proportion of non-cereal break crops in the latter. Thus under similar cropping, losses from organic systems are similar to or slightly smaller than those from conventional farms following best practice.  相似文献   
63.
Abstract. The Phosphorus Indicators Tool provides a catchment-scale estimation of diffuse phosphorus (P) loss from agricultural land to surface waters using the most appropriate indicators of P loss. The Tool provides a framework that may be applied across the UK to estimate P loss, which is sensitive not only to land use and management but also to environmental factors such as climate, soil type and topography. The model complexity incorporated in the P Indicators Tool has been adapted to the level of detail in the available data and the need to reflect the impact of changes in agriculture. Currently, the Tool runs on an annual timestep and at a 1 km2 grid scale.
We demonstrate that the P Indicators Tool works in principle and that its modular structure provides a means of accounting for P loss from one layer to the next, and ultimately to receiving waters. Trial runs of the Tool suggest that modelled P delivery to water approximates measured water quality records. The transparency of the structure of the P Indicators Tool means that identification of poorly performing coefficients is possible, and further refinements of the Tool can be made to ensure it is better calibrated and subsequently validated against empirical data, as it becomes available.  相似文献   
64.
Kerstin  Hansson  DVM  Jens  Häggström  DVM  PhD  Clarence  Kvart  DVM  PhD  Peter  Lord  BVSc  FRCVS 《Veterinary radiology & ultrasound》2002,43(6):568-575
Two-dimensional (2-D) echocardiographic measurement of the left atrium (LA) has the potential to be more accurate than the standard M-mode method, because the LA body can be measured. We evaluated a 2-D method for measuring LA and aorta (AO) in a right parasternal short-axis view and compared it to the M-mode method. An index for LA size (LA/AO) was calculated in 166 cavalier King Charles spaniels, 56 normal and 110 dogs with mitral regurgitation (MR) of varying degrees secondary to chronic valvular disease. In normal dogs, the AO-2-D and LA/AO-2-D did not correlate to body weight (BW) or BW2; whereas, all M-mode values and the LA-2-D were significantly (p < .05) related to both BW parameters. In normal dogs, there was no difference between M-mode and 2-D indices. For all dogs (normal and dogs with MR) there was an 11% bias between the M-mode and 2-D index with the LA/AO-2-D being higher than the LA/AO-M. The association between the mean and the difference of the indices demonstrated a quadratic relationship. Dogs with a mean LA/AO of 2.0-2.5 showed the largest difference between the two indices. Small values for the 2-D coefficients of variation for respiration and stage of diastole were found; 3.4 and 3.1%, respectively. The 2-D index is more sensitive to LA enlargement than the M-mode index.  相似文献   
65.
In Venezuela, 1,012 cattle sera were screened for their ability to precipitate Brucella melitensis 16M smooth-lipopolysaccharide (S-LPS), B melitensis B115 polysaccharide B (poly B), B abortus 1119-3 O-polysaccharide (PS), or B abortus 1119-3 cyclic 1,2 linked beta-D-glucan (beta-glucan) in an agar-gel immunodiffusion assay. These sera were previously classified as being Brucella abortus-infected, S-19-vaccinated, or negative after an assessment of historical records and results of 5 standard serologic tests. Most of the sera (85%) from infected cattle precipitated S-LPS, poly B, and PS. Serologic results for poly B and PS were identical. On the other hand, 13% of the sera from vaccinated cattle precipitated S-LPS, but none of these sera precipitated poly B or PS. It was concluded that purified PS can alternate with poly B as an antigen to differentiate sera of B abortus-infected from B abortus S-19-vaccinated cattle. None of these sera precipitated beta-glucan.  相似文献   
66.
Personalized identification (ID) tags that contain contact information for the dog or cat owner can help assure lost animals are quickly reunited with their owners. The authors have previously reported that while the majority of pet owners stated that ID tags were very important, only a third responded that their pet wears an ID tag. The objective of this study was to evaluate if providing and putting on the pet a free collar and ID tag during an owner's visit to a veterinary hospital or spay/neuter facility increased the likelihood that the pet owners would actually keep the identification on their pet at least 6-8 weeks after they were placed on the pet. A second population of dogs and cats that were adopted from animal control and humane society shelters were also studied to assess retention of a collar and personalized ID tag. Telephone follow-up occurred a mean of 8 weeks after the tag was applied. Retaining and using the tag significantly increased for the veterinary group with 13.8% reporting their pets were currently wearing an ID tag pre-intervention, and 84.3% reporting their pets were currently wearing and ID tag post-intervention. Of the dogs and cats that were adopted, at follow-up 94% of owners reported their pets were currently wearing an ID tag. Approximately 5% of those who participated in the post-intervention survey lost a pet and recovered that pet because of the ID tag. This suggests that ID tagging is an effective method to potentially decrease stray intake into shelters and return pets home. The data also support placing tags and collars directly on pets as a method to retain those ID tags and collars on the animals, thus increasing the likelihood they will be returned home if lost or during a disaster.  相似文献   
67.
The Internet is an increasingly common way for consumers to purchase puppies. Yet very little information is available about the types of puppies sold via the Internet. In addition these sales are not subject to United States Depart of Agriculture (USDA) regulation. The objectives of the study were to describe puppies sold via the Internet, to assess the characteristics that contribute to the cost of a puppy, and to compare puppies sold via the Internet with puppies sold by American Kennel Club (AKC) Parent Club breeders. Over 14 weeks in 2008, Yorkshire Terrier, Shih Tzu, English Bulldog, Boxer, and Labrador Retriever puppies for sale on two large-scale online puppy sales sites were categorized based on their Internet advertisements. Data were collected in three categories: puppy characteristics, health characteristics, and policies (such as spay/neuter requirement, health guarantee, and return policy). After the survey was completed, 25 AKC Parent Club breeders and 25 other breeders who advertised via one of the puppy sales websites were randomly selected and interviewed over the phone. Small breed puppies were most frequently advertised with 35.2% (1228/3485) of advertisements for Yorkshire Terriers and 23.0% (802/3485) for Shih Tzus. Almost one quarter of Internet breeders 768/3474 (22.2%) advertised four or more different dog breeds. Champion bloodlines increased the cost of a puppy of all breeds. AKC Parent Club breeders 21/25 (84%) were more likely to mention breed-specific health screening tests when compared to Internet breeders 7/25 (28%). Consumers should apply the same standards for purchasing from a breeder found through a puppy sales site as they would for purchasing from a local breeder. Breeders who advertise at one of the large-scale puppy sales websites are less knowledgeable about breed-specific health issues compared to an AKC Parent Club breeder. Internet breeders are less likely to perform these screening tests on their breeding dogs and may breed dogs with undesirable heritable health risks.  相似文献   
68.
The effects of brassica green manures on Globodera pallida were assessed in vitro and in soil microcosms. Twelve of 22 brassica accessions significantly inhibited the motility of G. pallida infective juveniles in vitro. Green manures of selected brassicas were then incorporated into soil containing encysted eggs of G. pallida. Their effect on egg viability was estimated by quantifying nematode actin 1 mRNA by RT-qPCR. The leaf glucosinolate profiles of the plants were determined by high-performance liquid chromatography. Three Brassica juncea lines (Nemfix, Fumus, and ISCI99) containing high concentrations of 2-propenyl glucosinolate were the most effective, causing over 95% mortality of encysted eggs of G. pallida in polyethylene-covered soil. The toxic effects of green manures were greater in polyethylene-covered than in open soil. Toxicity in soil correlated with the concentration of isothiocyanate-producing glucosinolate but not total glucosinolate in green manures.  相似文献   
69.
Diploid yeast cells repeatedly polarize and bud from their poles, probably because of highly stable marks of unknown composition. Here, Rax2, a membrane protein, was shown to behave as such a mark. The Rax2 protein itself was inherited immutably at the cell cortex for multiple generations, and Rax2 was shown to have a half-life exceeding several generations. The persistent inheritance of cortical protein markers would provide a means to couple a cell's history to the future development of a precise morphogenetic form.  相似文献   
70.
The secretory matrix of the stylar-transmitting tract of angiosperms has been characterized as a nutrient medium for the growth of pollen tubes, acting to guide tubes to the ovules. When nonliving particles (latex beads) were artificially introduced onto the transmitting tracts of styles of Hemerocallis flava, Raphanus raphanistrum, and Vicia faba, they were translocated to the ovary at rates similar to those of pollen tubes. Direct observations were made on the movement of individual beads along the secretory epidermis in the style and ovary of Vicia faba. The transmitting tract may play an active role in extending tube tips to their destination in the ovary.  相似文献   
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