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141.
Mary Nyawira Muchane Bashir Jama Caleb Othieno Robert Okalebo David Odee Joseph Machua Jan Jansa 《Agroforestry Systems》2010,78(2):139-150
A field study was carried out on a six-year-old on-farm field trial during long-rains season (April–August) 2003 to investigate
the effect of improved fallow systems and phosphorus application on arbuscular mycorrhiza fungi (AMF) symbiosis in maize.
The trial comprised of maize rotated with a fast growing leguminous Crotalaria
grahamiana fallow and a non-leguminous Tithonia diversifolia fallow for 3 years followed by continuous maize. The experiment was randomized complete block design with three cropping
(continuous maize, Crotalaria fallow and Tithonia fallow) systems and two phosphorus levels (0 and 50 kg P/ha). AMF colonization in maize roots, maize yield and macro-nutrients
uptake were recorded. Phosphorus applications improved (P < 0.05) early (<8 weeks old maize) AMF colonization, nutrient uptake and maize yield in improved fallow systems. Greater
differences due to phosphorus application were noted in maize in Tithonia fallow than in Crotalaria fallow. Following phosphorus application, a positive relationship existed between early AMF colonization and maize yield
(r = 0.38), and phosphorus and nitrogen uptake (r = 0.40 and r = 0.43, respectively), demonstrating the importance of phosphorus fertilization in enhancing low-input technologies (improved
fallows systems) in phosphorus deficient and acidic soils of western Kenya. 相似文献
142.
In the province of Bolívar in the Andean region 212 farmers, six salesmen and 14 technicians, involved in maize production,
were interviewed. The majority of the farmers interviewed were small-holders; 64% of the farmers had a farm size of less than
4.5 ha. Maize is the most important crop and is often grown in association with beans. Most maize, 96%, is soft maize meant
for human consumption. The cultivars grown are open pollinated ones. One cultivar, ‘Guagal’, was grown extensively. A few others, among which an improved version of Guagal were of some importance. In the production
of maize the farmers consider damage due to insects, wind (lodging), diseases, drought and hail, the low prices for their
surplus maize and the high costs of fertilizers, chemicals, sowing seed and labour as the most important constraints. The
seed for sowing the next crop mainly came from seed kept from the last harvest. Farmers indicated that they select from the
harvested ears the healthy looking larger ones. Kernel type also was a selection criterion. Selection for plant type in the
field was rarely done. Of the farmers 71% stored the maize as kernels while 29% stored the seed kept on the ears. The storage
was predominantly done somewhere in the house in plastic (56%) or cloth bags (14%), in a pile (13%), just on the floor (4%)
or in cans (4%). Some farmers still had seed left from the last sowing and were willing to give a sample for testing. From
32 such samples the quality was assessed by INIAP, the Ecuadorean governmental research and breeding organisation. The samples
were consistently of a low quality. Especially the vigour of the seedlings was poor and most of the seeds were infected or
contaminated by fungi. In the region a few salesmen offer maize seed for sale of cultivar Guagal at prices affordable by the
farmer. Of improved cultivars the prices were higher than most farmers are willing to pay. The technicians considered good
seed quality and good maintenance of the cultivars effective methods in obtaining better yields. Many farmers do not have
access to seed of INIAP and are not familiar with the improved cultivars. 相似文献
143.
Photochemistry of the herbicide 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) (I) was investigated by irradiating at approximately 313 nm. Aqueous phase photoreactions of 0.078–7.800 × 10?5m solutions of I were carried out at different pH values. Quantum yields for the loss of I in buffered solutions were 0.008 (±0.0004), 0.048 (±0.0024), and 0.044 (±0.0022) at pH 2.6, 7.0, and 11.0, respectively. In neutral and basic conditions, I absorbed more strongly at wavelengths > 290 nm, an environmentally significant region. Phototransformation of I was monitored by HPLC and UV-VIS spectrometry. All photoreactions of I gave rise to the generation of two products, 3-bromo-4-hydroxybenzonitrile and 4-hydroxybenzonitrile. The former photoproduct was tentatively identified from its mass spectral data. The photoproducts can be accounted for with a proposed mechanism involving free radicals. 相似文献
144.
145.
Dirk Hermsmeyer Jan Ilsemann Jrg Bachmann Rienk R. van der Ploeg Robert Horton 《植物养料与土壤学杂志》2002,165(3):339-346
A three‐year long lysimeter experiment with a fine‐grained aluminum (Al) recycling by‐product and a mixture of this by‐product and a coal combustion waste was conducted. The wastes were proposed as possible soil substitutes in an engineered surface barrier covering a potash mining residue mount. To evaluate the suitability of the wastes as surface barrier material, their hydrological behavior under field conditions must be known. Lysimeter experiments provide one means to study the hydrological behavior of soils or soil‐like materials. However, it is difficult to estimate the long‐term hydrological behavior from short‐term lysimeter studies. The present study was conducted therefore to derive from short‐term lysimeter observations the long‐term hydrological behavior of the two waste materials. The lysimeter data were used to calibrate the one‐dimensional soil water flow model HYDRUS‐1D. With the calibrated model, hydrological simulations for the site of the residue mount were carried out for a period of 31 yr. Calculated long‐term annual seepage from the lysimeters was 237 mm for the pure Al waste and 186 mm for the mixture, or 39% and 24% of the average annual precipitation (764 mm). The average discharge of the bare mount is 482 mm or 63%. We conclude that a soil cover could considerably reduce the discharge and that the mixture is better suited as surface barrier than the pure Al waste. 相似文献
146.
Ger Boedeltje Alfons J.P. Smolders Jan G.M. Roelofs Jan M. Van Groenendael 《水产资源保护:海洋与淡水生态系统》2001,11(6):453-471
An Erratum has been published for this article in Aquatic Conservation: Marine and Freshwater Ecosystems 12(2), 2002, 251
- 1. In recent decades shallow zones have been constructed along navigation canals in the Netherlands which form a potential new habitat for aquatic macrophytes and helophytes absent from traditional canals.
- 2. The aim of this study was to examine the relationships between the aquatic plant vegetation that becomes established and the physical and chemical characteristics of water and sediment, in order to find the determinants of species composition and the changes therein. Data were collected in 1998 and 1999 from 80 plots in bank zones at varying stages of development since construction along two navigation canals.
- 3. Plots 3–5 years old were partly dominated by rooting submerged macrophytes such as Potamogeton pectinatus, Elodea nuttallii and Potamogeton pusillus; locally non‐rooting species occurred such as Ceratophyllum demersum, Lemna minor and Spirodela polyrhiza. Older plots contained Phragmites australis, locally mixed with free‐floating species. Hydrological isolation from the eutrophic canals was indicated by the presence of Chara vulgaris.
- 4. Characteristics of both water layer and sediment could explain the variation in vegetation composition. Rooting submerged macrophytes predominantly occurred in sites with a thin (<2 cm) layer of sediment with relatively low concentrations of organic matter; moreover, ammonium concentrations in the water layer and sediment pore water were relatively low. Stands of non‐rooting macrophytes and of Phragmites australis were characterized by a relatively thick sediment layer and high ammonium levels in the pore water. Light limitation in turbid water, associated with navigation and eutrophication, may also play a role.
- 5. Although submerged aquatic macrophytes persist for a relatively short time, shallow zones nevertheless function as a habitat for helophyte communities and contribute to a higher aquatic biodiversity than is associated with traditional banks along navigation canals.
147.
Eva VOSLAROVA Petr CHLOUPEK Jan CHLOUPEK Iveta BEDANOVA Vladimira PISTEKOVA Vladimir VECEREK 《Animal Science Journal》2011,82(4):601-606
Effects of different noise levels (70 or 80 dB) that broilers were exposed to during the entire fattening period and also the effect of the timing of the first exposure to intermittent noise in the course of fattening (day 1 vs. day 7) were monitored. After 7 days of exposure to intermittent noise, experimental chickens already showed a significant decrease in live body weight in comparison with the control group. The difference between the group exposed to intermittent noise at 70 dB and the group exposed to 80 dB levels was not statistically significant, although the mean live body weight of broilers in the latter was lower during the entire fattening period. The chickens exposed to intermittent noise from day 1 of age showed lower mean live weight throughout the fattening period compared to chickens exposed to the same level of intermittent noise only from day 7 of age, although at the end of fattening the difference was statistically significant only in chickens exposed to the higher level of intermittent noise (80 dB). 相似文献
148.
A mixture neural methodology for computing rice consumptive water requirements in Fada N’Gourma Region, Eastern Burkina Faso 总被引:1,自引:1,他引:1
Seydou Traore Yu-Min Wang Chun-E. Kan Tienfuan Kerh Jan Mou Leu 《Paddy and Water Environment》2010,8(2):165-173
Crop consumptive water requirement (Crop-ET) is a key variable for developing management plans to optimize the efficiency
of water use for crop production particularly in semiarid zone. In Burkina Faso, the unfavorable climatic conditions characterized
by the low and unevenly distribution of rainfall have pushed water resources management to the forefront of the crop production
issue. Crop-ET is extremely required in rainwater effective management for mitigating the impact of water deficit on the crops.
Basically, Crop-ET determination involves reference evapotranspiration (ETo) and crop coefficient (Kc) which required complete
climatic data and specific site crop information, respectively. ETo estimation with the recommended FAO56 Penman–Monteith
(PM) equation is limited in Burkina Faso due to the numerous meteorological data required which are not always available in
many production sites. In such circumstances, research to compute directly Crop-ET as an alternative to the two-step approach
of calculating ETo and determining site specific Kc, seems desirable. Therefore, this study aims to evaluate the performance
of a mixture principal component analysis neural network (PCANN) model for computing rice Crop-ET directly from temperatures
data in Fada N’Gourma region located in Eastern Burkina Faso, Africa. From the statistical results, rice Crop-ET can be successfully
computed by using PCANN methodology, when only temperatures data are available in this African semiarid environment. Thus,
in poor data situation, Crop-ET direct computation can be rapidly addressed through PCANN model for agricultural water management
in African semiarid regions. 相似文献
149.
Bettschart-Wolfensberger R Dicht S Vullo C Frotzler A Kuemmerle JM Ringer SK 《Veterinary anaesthesia and analgesia》2011,38(3):186-194
ObjectiveTo test if the addition of butorphanol by constant rate infusion (CRI) to medetomidine–isoflurane anaesthesia reduced isoflurane requirements, and influenced cardiopulmonary function and/or recovery characteristics.Study designProspective blinded randomised clinical trial.Animals61 horses undergoing elective surgery.MethodsHorses were sedated with intravenous (IV) medetomidine (7 μg kg?1); anaesthesia was induced with IV ketamine (2.2 mg kg?1) and diazepam (0.02 mg kg?1) and maintained with isoflurane and a CRI of medetomidine (3.5 μg kg?1 hour?1). Group MB (n = 31) received butorphanol CRI (25 μg kg?1 IV bolus then 25 μg kg?1 hour?1); Group M (n = 30) an equal volume of saline. Artificial ventilation maintained end-tidal CO2 in the normal range. Horses received lactated Ringer’s solution 5 mL kg?1 hour?1, dobutamine <1.25 μg kg?1 minute?1 and colloids if required. Inspired and exhaled gases, heart rate and mean arterial blood pressure (MAP) were monitored continuously; pH and arterial blood gases were measured every 30 minutes. Recovery was timed and scored. Data were analyzed using two way repeated measures anova, independent t-tests or Mann–Whitney Rank Sum test (p < 0.05).ResultsThere was no difference between groups with respect to anaesthesia duration, end-tidal isoflurane (MB: mean 1.06 ± SD 0.11, M: 1.05 ± 0.1%), MAP (MB: 88 ± 9, M: 87 ± 7 mmHg), heart rate (MB: 33 ± 6, M: 35 ± 8 beats minute?1), pH, PaO2 (MB: 19.2 ± 6.6, M: 18.2 ± 6.6 kPa) or PaCO2. Recovery times and quality did not differ between groups, but the time to extubation was significantly longer in group MB (26.9 ± 10.9 minutes) than in group M (20.4 ± 9.4 minutes).Conclusion and clinical relevanceButorphanol CRI at the dose used does not decrease isoflurane requirements in horses anaesthetised with medetomidine–isoflurane and has no influence on cardiopulmonary function or recovery. 相似文献
150.