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31.
32.
Sven Gjedde Sommer Erik Steen Jensen Jan Kofoed Schj⊘rring 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(1):21-24
Abstract Absorption of volatilized ammonia after application of slurry onto the soil surface (sand) between rows of a wheat crop was studied in two experiments. The slurry was labelled with 15N-NH4. During seven days the accumulated gaseous N loss from the slurry varied from 6.9 to 11.1 g N m?2. In April ammonia losses from slurry applied beneath a 5 cm high wheat crop were equal to losses from slurry applied to a fallow, but 2.2% of the lost atmospheric ammonia was taken up by the leaves. In May ammonia loss from slurry applied between the rows of a 43 cm high crop was reduced by 6% compared to the loss from fallow, because of a reduced transfer of ammonia from the slurry to the air. Of the emitted ammonia 3.3% was absorbed by the canopy. 相似文献
33.
Dalgaard T Jørgensen U Olesen JE Jensen ES Kristensen ES 《Science (New York, N.Y.)》2006,312(5781):1743-4; author reply 1743-4
34.
Steen Magnussen Lutz Fehrman William J. Platt 《European Journal of Forest Research》2012,131(2):307-320
Density estimators for k-tree distance sampling are sensitive to the amount of extra Poisson variance in distances to the kth tree. To lessen this sensitivity, we propose an adaptive composite estimator (COM). In simulated sampling from 16 test
populations, a three-component composite density estimator (COM)–with weights determined by a multinomial logistic function
of four readily available ancillary variables–was identified as superior in terms of average relative absolute bias. Results
from a different set of nine validation populations–with widely different stem densities and spatial patterns of tree locations—confirmed
that relative root mean squared errors (RRMSE) of COM were, on average, considerably lower than those obtained with the three-component
k-tree density estimators. The RRMSE performance of COM improved with increasing values of k. With k = 6 and sample sizes of 10, 20, and 30, the average relative bias of COM was between −5 and 5% in seven validation populations
but in an open low-density savanna-like population bias reached −12% (1979 data) and 7% (1996 data). For k = 6 and n = 10, the RRMSE of COM was, in six of the nine validation populations, within 3.3 percentage points of the RRMSE for sampling
with fixed-area plots. Jackknife estimates of the precision of COM estimates of density were negatively biased, leading to
under-coverage (7%) of computed 95% confidence intervals. 相似文献
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OBJECTIVE: To determine effects of management, feeding, and treatment on clinical and biochemical variables in cows with displaced abomasum (DA). ANIMALS: 374 cows that received 470 treatments for DA. PROCEDURE: Blood and milk samples were obtained from 139 affected cows for analysis; for all cows, clinical data, management, feeding, and treatments were evaluated. RESULTS: Multiparous cows were more predisposed to DA than primiparous cows were, and Swedish Friesians were more predisposed than Swedish Red and Whites were. Eighty percent of cows had left-sided DA, and 20% had right-sided DA. In > 50% of affected cows, clinical signs appeared just before calving to 2 weeks after calving. Incidence of twin calves and periparturient diseases was significantly higher in affected cows than in the overall Swedish cow population. Content of neutral detergent fiber in the silage was low in herds with DA. Feeding a total mixed ration was a risk factor for DA. Treatment by surgical methods gave a significantly higher recovery rate than nonsurgical methods. CONCLUSIONS AND CLINICAL RELEVANCE: Displaced abomasum is a periparturient nutritional disease. Feeding roughage with low neutral detergent content is a more important causative factor than the amount of concentrates fed at the time of calving. The basic principle for prevention of DA is to maintain good ruminal filling before and at calving. The amount of high-quality roughage fed before and at calving should be kept to a minimum. By changing routines for periparturient feeding, it should be possible to reduce the incidence of DA. 相似文献
38.
N. D. Ananyeva T. S. Demkina W. J. Jones M. L. Cabrera W. C. Steen 《Biology and Fertility of Soils》1999,29(3):291-299
Non-tilled and tilled plots on a spodosol (Corg 0.65–1.70%; pH 4.1–4.5) and a mollisol (Corg 3.02–3.13%, pH 4.9–5.3), located in the European region of Russia, were investigated to determine variances in soil microbial
biomass and microbial community composition. Continuous, long-term management practices, including tillage and treatment with
inorganic fertilizers or manure, were used on the spodosol (39 years) and mollisol (22 years). Total microbial biomass (Cmic), estimated by the substrate-induced respiration (SIR) method, and total fungal hyphae length (membrane filter technique)
were determined seasonally over a 3-year period. Long-term soil management practices (primarily tillage and fertilizer application)
led to decreases in total microbial biomass (80–85% lower in spodosol and 20–55% lower in mollisol), decreases in the contribution
of Cmic to Corg (2.3- to 3.5-fold lower in spodosol and 1.2- to 2.3-fold lower in mollisol), and 50–87% decreases in total fungal hyphae
length compared to non-tilled control plots. The contribution of fungi to total SIR in virgin mollisol and fallow spodosol
plots was approximately 30%. However, the contribution of fungi to SIR was approximately two times greater in tilled spodosol
plots compared to a fallow plot. In contrast, the contribution of fungi to SIR in tilled plots of mollisol was less (1.4–4.7
times) than for a virgin plot. In summary, long-term soil management practices such as tillage and treatment with organic
or inorganic fertilizers are important determinants of soil microbial biomass and the contribution of fungi to total SIR.
Received: 28 April 1998 相似文献
39.
The authors compared the thyroid function of cows with primary ketosis and clinically healthy cows in the same stage of lactation by a method based on the in vitro erythrocyte uptake of L-3,5,3′- triiodothyronine labelled with I131. This method (EU) proved to be affected by, among other factors, the content of total protein in the blood plasma, which was lower in ketotic than in normal cows. This caused difficulties in interpretation of the measured EU, but the authors consider that the experiments indicated an elevated thyroid activity in ketosis. The importance of continued research into the probable relation between thyroid function and ketosis is stressed. 相似文献
40.
Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is a major problem in modern swine industry worldwide. At present 12 serotypes have been recognized (Nielsen 1990). Serotyping has been based upon capsule associated, heat-stabile antigens of polysaccharide (PS) and lipopolysaccharide (LPS) nature. A variety of tests have been used for serotyping including slide agglutination (Mittal et al. 1982), immunodiffusion (Gunnarsson et al. 1978, Nielsen & O’Connor 1984), indirect haemagglutination (Mittal et al. 1983a) and coagglutination (Mittal et al. 1983b). Recent studies report on serotyping of A. pleuropneumoniae strains using monoclonal antibodies in enzyme-linked immunosorbent assays (Lida et al. 1990, Nakai et al. 1990). 相似文献