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51.
Abstract. In organic farming systems, fertilizing materials can be used when potassium (K) deficiency is shown, but such systems are dominantly nitrogen (N) limited and this is likely to affect crop utilization of K. The supply of K to grass/clover from a range of mineral and organically based K fertilizers and its interaction with N supply were studied in a greenhouse experiment. Sequential plant cuts were taken for yield and nutrient content determinations in crop and soil. Crop yields were limited by N: where N supply was increased either through the mineralization of N from organic materials (rapemeal, farmyard manure) or inorganic fertilizer, plant yields increased significantly. Grass/clover responded better to additional K where sufficient N was available. However, yield responses to K were generally small, even in the presence of adequate N. Of the different fertilizers, kali and MSL-K increased yields above those of the control by less than 5%, sylvinite, DKSI and farmyard manure by 10–20%, and rapemeal and potassium sulphate by more than 25%. In all treatments, K offtakes in the grass/clover were considerably greater than fertilizer K inputs. The grass/clover showed an increased uptake of Na where insufficient K was available. However, the Mg content of the grass/clover was not adversely affected by K fertilizer application. Organic farmers need to consider the soil K status, the rotational nutrient budget, the supply of all nutrients in fertilizing materials and nutrient interactions to achieve effective K management in organic farming systems. 相似文献
52.
Aldridge BB Fernandez-Suarez M Heller D Ambravaneswaran V Irimia D Toner M Fortune SM 《Science (New York, N.Y.)》2012,335(6064):100-104
Cells use both deterministic and stochastic mechanisms to generate cell-to-cell heterogeneity, which enables the population to better withstand environmental stress. Here we show that, within a clonal population of mycobacteria, there is deterministic heterogeneity in elongation rate that arises because mycobacteria grow in an unusual, unipolar fashion. Division of the asymmetrically growing mother cell gives rise to daughter cells that differ in elongation rate and size. Because the mycobacterial cell division cycle is governed by time, not cell size, rapidly elongating cells do not divide more frequently than slowly elongating cells. The physiologically distinct subpopulations of cells that arise through asymmetric growth and division are differentially susceptible to clinically important classes of antibiotics. 相似文献
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55.
Apparent amino acid availability coefficients and protein digestibility of four animal products [fish meal (FM), meat and bone meal (MBM), poultry by‐product and feather meal] and four plant protein‐rich products [soybean meal (SBM), cottonseed meal‐28, cottonseed meal‐38 and corn gluten meal (CGM)] were determined for Nile tilapia, Oreochromis niloticus. Ingredients were incorporated to a practical reference diet at a 7 : 3 ratio (70% of reference diet and 30% of test ingredient). Chromic oxide was used as external digestibility marker. Among animal products poultry by‐product meal (PBM; 89.7%) and FM (88.6%) presented the highest apparent protein digestibility (APD) while MBM (78.4%) and feather meal (78.5%) presented the lowest APD. Among plant protein‐rich products CGM (91.4%) and SBM (92.4%) presented the highest APD values while cottonseed meal‐28 presented the lowest APD (78.6%). Average apparent amino acid availability of feed ingredients was similar to protein digestibility with 92.3%, 89.6%, 73.4%, 80.7%, 88.9%, 84.4%, 91.2% and 79.7% values for SBM, CGM, cottonseed meal‐28 and 38, FM, MBM, PBM and feather meal respectively. These results indicate that O. niloticus is able to utilize efficiently different feedstuffs. 相似文献
56.
Distribution of nitrogen pools in the soil profile of undisturbed and reseeded grasslands 总被引:8,自引:0,他引:8
A. Bhogal D. V. Murphy S. Fortune M. A. Shepherd D. J. Hatch S. C. Jarvis J. L. Gaunt K. W. T. Goulding 《Biology and Fertility of Soils》2000,30(4):356-362
This study evaluated the effect of cultivation and reseeding on the distribution and fate of soil mineral N (SMN), soluble
organic N (SON) and potentially mineralisable N (PMN) in the soil profile of two long-term grasslands in the UK. Cultivation
and reseeding significantly increased the total soluble N concentration (SMN plus SON) of the soil profile (0–90 cm), with
over 50 mg SON kg–1 observed. By contrast, the PMN pool was unaffected by cultivation and declined with increasing soil depth. The flush in SON
and SMN observed in both soils disappeared within 1 year following cultivation. The fate of SON appeared to be dependent on
soil type, with considerably more movement to deeper layers apparent in the profile of a silty clay loam (30% clay) than in
a clay loam (49% clay). Mineralisation and/or immobilisation of SON in the topsoil probably accounted for the changes observed
in the SON content of the clay loam. SON is an important N pool in grassland soils and cultivation has a significant impact
on its release. Measurements of SON should therefore be included in studies of N cycling in agricultural cropping systems,
so that full account may be taken of its potential as a source or sink of mobile N.
Received: 17 February 1999 相似文献
57.
Polymorphisms of RDH16 and VEGFR1 influence M. trapezius steatosis in Japanese Black carcass
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Takafumi Ishida Kosuke Noda Fortune Ntengwa Jomane Tadaaki Tokunaga 《Animal Science Journal》2017,88(8):1037-1041
The exact cause of steatosis, one of defects in Japanese beef carcasses, has not been elucidated to date, because it is very difficult to diagnose cyclopedically with certain reproducibility due to the bias in the outbreak. Therefore, the objective of this study was to assess the influence of polymorphisms in retinol dehydrogenase 16 (RDH16), myoferlin (MYOF) and vascular endothelial growth factor receptors 1 and 2 (VEGFR1, VEGFR2) on carcass‐graded Musculus trapezius steatosis. For logistic regression analysis, 646 carcasses shipped from 29 farms in Miyazaki, Japan, were used. The GG genotype in RDH16 showed significant odds ratios against AA and AG. In VEGFR1, CT had a significant odds ratio against CC. After evaluating for interaction, highly significant odds ratios were observed in the combinations that included the GG risk genotype in RDH16. It is noteworthy that there was no steatosis in the combination GG (RDH16) and CC (VEGFR1). It may be concluded that there is a possibility that steatosis can be suppressed by the CC genotype in VEGFR1. The current study revealed the influence of genetic polymorphisms on M. trapezius steatosis that had not been reported until now, and may help elucidate the cause of steatosis. 相似文献
58.
NRO Paula G Galeati DIA Teixeira ES Lopes Júnior VJF Freitas D Rondina 《Reproduction in domestic animals》2005,40(2):108-110
For 6 months, 10 adult Saanen crossbred goats were fed undernutrition diet (70% maintenance), and finally five goats were refed for 6 weeks with 150% maintenance. In all animals oestrus was synchronized using 45 mg FGA vaginal sponge for 11 days, 300 IU eCG and 50 microg cloprostenol 48 h prior to sponge removal. From oestrus onset, during a 24-h period, blood samples were collected for oestradiol and NEFA assay. Ovulation was verified by laparoscopy 3 days after sponge removal. Body mass loss was 18.62 +/- 3.03% of initial weight and in refed goats body weight recovery was 90.63 +/- 3.56%. NEFA level was higher in restricted goats (p < 0.05). Fifty per cent of underfed goats (2/4) and all refed goats (4/4) exhibited oestrus and ovulation. Significant relationship (p < 0.05) was found between weight loss and the interval sponge removal-oestrus onset (r = 0.91) or ovulation rate (r = 0.70). Only in the refed group was the ovulation rate related to the oestradiol amount (r = 0.99) (p < 0.05). Collectively results showed that a short period of improved feeding re-established the responsiveness of oestrus synchronization in chronically fasted goats. 相似文献
59.
Mesoscale physical processes and the distribution and composition of ichthyoplankton on the southern Brazilian shelf break 总被引:1,自引:0,他引:1
BÁRBARA CRISTIE FRANCO JOSÉ HENRIQUE MUELBERT MAURICIO MAGALHÃES MATA 《Fisheries Oceanography》2006,15(1):37-43
The southern Brazilian shelf supports the largest fish stocks in the country, and studies on physical–biological processes in the ecology of ichthyoplankton have been recommended to provide a better understanding of the variability of the recruitment of fishing resources. This study is the first to examine the influence of mesoscale physical processes on the distribution of early life stages of fish in this shelf‐break region. Collections of fish eggs and larvae and measurements of temperature and salinity were made at 13 stations along cross‐shelf transects in December 1997. Myctophidae, Bregmacerotidae, Clupeidae, Synodontidae and Engraulidae were the most abundant larvae in the northern region, while Engraulidae and Bregmacerotidae prevailed further south. In situ hydrographic data, NOAA/AVHRR images and merged TOPEX/POSEIDON + ERS‐1/2 satellite altimetry taken during the cruise revealed an anticyclonic eddy dominating the shelf around 31°S. Larval fish abundance was lower at the centre of this feature, suggesting that the eddy advected poorer offshore waters of tropical origin towards the inner shelf‐concentrating the larvae around the eddy. 相似文献
60.
E Reddington A Sapienza B Gurau R Viswanathan S Sarangapani ES Smotkin TE Mallouk 《Science (New York, N.Y.)》1998,280(5370):1735-1737
Combinatorial screening of electrochemical catalysts by current-voltage methods can be unwieldy for large sample sizes. By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified. A fluorescent acid-base indicator was used to image high concentrations of hydrogen ions, which were generated in the electrooxidation of methanol. A 645-member electrode array containing five elements (platinum, ruthenium, osmium, iridium, and rhodium), 80 binary, 280 ternary, and 280 quaternary combinations was screened to identify the most active regions of phase space. Subsequent "zoom" screens pinpointed several very active compositions, some in ternary and quaternary regions that were bounded by rather inactive binaries. The best catalyst, platinum(44)/ruthenium(41)/osmium(10)/iridium(5) (numbers in parentheses are atomic percent), was significantly more active than platinum(50)/ruthenium(50) in a direct methanol fuel cell operating at 60 degreesC, even though the latter catalyst had about twice the surface area of the former. 相似文献