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排序方式: 共有193条查询结果,搜索用时 78 毫秒
71.
Rad R Rad L Wang W Cadinanos J Vassiliou G Rice S Campos LS Yusa K Banerjee R Li MA de la Rosa J Strong A Lu D Ellis P Conte N Yang FT Liu P Bradley A 《Science (New York, N.Y.)》2010,330(6007):1104-1107
72.
A study on evapotranspiration from potato fields was conducted in the Lower Gangetic Plains of India. The input data required for the CROPWAT irrigation management model was collected, and evapotranspiration (ET) and irrigation water requirement (IWR) for potato crops were calculated using the model. Firstly, the CROPWAT model was validated by comparing simulated crop evapotranspiration (SET) with actual ET calculated through the field water balance method. Thereafter, SET and IWR for nine locations in the lower Gangetic plains of India were calculated for the period from 1996–1997 to 2008–2009, for the current situation (using 20-year-average weather data of the stations), and for elevated thermal conditions, i.e. considering 2 and 3 °C increases over the current temperature. The future change in IWR for potato up to 2050 was also calculated considering the projected climatic scenario generated by the PRECIS model. The CROPWAT calculated IWR values showed an increasing, though not statistically significant, trend in requirement of irrigation water for potato across the nine locations during the period from 1996–1997 to 2008–2009. At a temperature increase of 2 °C over normal, the mean SET of potato would increase by 0.06 mm per day and the average IWR would be 6.0 mm per season more. If the mean temperature would be 3 °C more than normal, the SET would be 0.16 mm day?1 higher and the IWR 16.6 mm. Also based on the projected climatic scenario generated by the PRECIS model, the future SET up to 2050 showed an increasing trend. The present study indicates increasing demand for irrigation water, which may significantly affect the agricultural scenario in the region. 相似文献
73.
Determination of critical limits of soil nutrients for use in optimizing fertilizer rates for fish ponds in red, lateritic soil zones 总被引:1,自引:0,他引:1
Mesocosms containing lateritic soil from West Bengal, India and de-ionized water were treated with different amounts of nitrogen (N), phosphorus (P), and potassium (K) fertilizers. Concentrations of available N, P, and K in soils and gross primary productivity were measured for the mesocosms. Critical concentrations of the three nutrients were estimated by the graphical method of Cate and Nelson that has been used widely for establishing critical soil nutrient concentrations in fertilization research on terrestrial crop plants. Critical concentrations of the three nutrients were: available N, 200 mg kg−1; available P, 13 mg kg−1; available K, 80 mg kg−1. Ponds sited in red, lateritic soil in West Bengal were treated monthly with 20, 15, and 3 kg ha−1 application−1 of N, P, and K, respectively. There was an increase in gross primary productivity when the critical concentrations of available N, P, and K established in the mesocosm study were attained in the pond soils. Fish production in fertilized ponds is positively correlated with gross primary productivity. Thus, the concept of critical nutrient concentrations in soils could be a valuable tool in pond fertilization research. 相似文献
74.
Use of antibiotics for the control of bacterial diseases in shrimp culture has caused several adverse impacts to the industry. This has resulted in the search for alternative environment friendly approaches to overcome bacterial infections. This study was conducted to investigate the use of beneficial bacteria as an alternative to antibiotics. Ten pathogenic bacterial species isolated from shrimp, Penaeus monodon, and Artemia cysts were tested for susceptibility to indigenous marine Bacillus subtilis AB65, Bacillus pumilus AB58, Bacillus licheniformis AB69 and compared with oxytetracycline, chloramphenicol, gentamicin and bacitracin, which are common antibiotics used in Asian aquaculture. The Bacillus spp. were isolated from the local marine environment for bioremediation use in shrimp hatcheries and were proven to reduce total ammonium nitrogen. The pathogenic bacterial isolates were 90% susceptible to B. subtilis AB65, 70% susceptible to B. pumilus AB58 and B. licheniformis AB69 and 100% susceptible to oxytetracycline, chloramphenicol and gentamicin but only 40% to bacitracin. Two representative isolates of the vibrio group, Vibrio alginolyticus VaM11 and Vibrio parahaemolyticus VpM1, when tested for competitive exclusion by a common broth method using the marine Bacillus spp., showed decreased viable counts from 10(8) to 10(2) cfu mL(-1). The results suggest that the action of the marine bacteria appears to be significant in protecting the host shrimp against pathogenic bacteria. In addition to the alternative use of antibiotics, the selected marine bacteria had additional bioremediation properties of reducing ammonia. 相似文献
75.
Andrew O. Finley Sudipto Banerjee Bruno Basso 《Journal of Agricultural, Biological & Environmental Statistics》2011,16(4):453-474
An objective for applying a Crop Simulation Model (CSM) in precision agriculture is to explain the spatial variability of
crop performance and to help guide decisions related to the site-specific management of crop inputs. CSMs require inputs related
to soil, climate, management, and crop genetic information to simulate crop yield. In practice, however, measuring these inputs
at the desired high spatial resolution is prohibitively expensive. We propose a Bayesian modeling framework that melds a CSM
with sparse data from a yield monitoring system to deliver location specific posterior predicted distributions of yield and
associated unobserved spatially varying CSM parameter inputs. These products facilitate exploration of process-based explanations
for yield variability. The proposed Bayesian melding model consists of a systemic component representing output from the physical
model and a residual spatial process that compensates for the bias in the physical model. The spatially varying inputs to
the systemic component arise from a multivariate Gaussian process, while the residual component is modeled using a univariate
Gaussian process. Due to the large number of observed locations in the motivating dataset, we seek dimension reduction using
low-rank predictive processes to ease the computational burden. The proposed model is illustrated using the Crop Environment
Resources Synthesis (CERES)-Wheat CSM and wheat yield data collected in Foggia, Italy. 相似文献
76.
Kaniska Mallick Bimal K. Bhattacharya V.U.M. Rao D. Raji Reddy Saon Banerjee H. Venkatesh Vyas Pandey Gouranga Kar Joydeep Mukherjee Sarweshwar P. Vyas Alaka S. Gadgil N.K. Patel 《Agricultural and Forest Meteorology》2009,149(10):1646-1665
A simplified evaporative fraction (Λ) based single-source energy balance scheme was tested with moderate resolution (1 km) noontime satellite observations to evaluate clear sky latent heat flux (λE) estimates over diverse agricultural landscapes. This approach uses two-dimensional (2D) scatter between land surface temperature (LST) and albedo to determine Λ. The operational utility of this scheme was demonstrated for estimating regional evapotranspiration and consumptive water use during rabi (November to April) crop growing season to predict pre-harvest wheat yield (error within 15.9% of reported mean) using time series data. The existence of triangular relations between Λ and LAI (leaf area index) or NDVI (normalized difference vegetation index) was found with basal line (hypotenuse) linearly coupled with LAI or NDVI at low level of surface soil wetness. The analysis of diurnal course of in situ Λ proved the validity of constant-Λ hypothesis over pure, uniform, homogeneous crop canopies but showed irregular and wave-like patterns over heterogeneous, mixed crop canopies. The root mean square error (RMSE) of noontime and daytime average λE estimates with respect to in situ λE measurements were also smaller over homogeneous agricultural canopies (41 and 23 W m−2) with correlation coefficients (r) 0.94 and 0.96, respectively, from 135 clear sky datasets as compared to RMSE over heterogeneous ones (59 and 28 W m−2 with r = 0.66 and 0.82, respectively from 22 datasets). The intercomparison with another Λ based approach (LST–NDVI 2D scatter) showed the supremacy of Λ determined from LST–albedo 2D scatter. The efficiency of LST–NDVI scatter was better during the dry down or water limited phases of crop growth only. The uncertainties of λE estimates were attributed to errors in core radiation budget inputs, relative loss of conservativeness of Λ due to canopy heterogeneity, and the inherent limitations of the single-source approach. There is further scope to reduce present λE uncertainties by combining the new findings on Λ (LST–albedo scatter)–NDVI triangular relations, diurnal Λ and two-source radiation budget. 相似文献
77.
78.
79.
Tropical Animal Health and Production - 相似文献
80.
Permanent infertility in ewes exposed to plant oestrogens 总被引:1,自引:0,他引:1
NR ADAMS 《Australian veterinary journal》1990,67(6):197-201
In Australia, more than 1 million ewes have permanently damaged reproductive tracts because they have been grazed on oestrogenic pasture. These effects occur in the absence of classical clinical "clover disease". The lesions result from an "organisational" action of oestrogen, causing a mild sexual transdifferentiation to occur in ewes during adult life, with the main lesion being found in the cervix. Diagnosis of the problem depends primarily on detection of the pathological changes, rather than history or clinical signs. On average, affected flocks have around a 10% increase in non-pregnant ewes, but most farmers can achieve an acceptable lambing rate by increasing their management and feed inputs to produce more twin lambs. Agronomic approaches have been used in the past to combat "clover disease", but further progress with the present problem may depend on the development of animal-based solutions. 相似文献