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1.
W. Wolters Nadi Selim Ghobrial H. M. Van Leeuwen M. G. Bos 《Irrigation and Drainage Systems》1989,3(2):103-123
A study of the water balances of The Fayoum irrigated lands and Lake Qarun was made to investigate the management of the irrigation
system and the efficiency of irrigation water use. The two water balances are strongly interrelated. The drainage flow to
Lake Qarun and the water level of the Lake are in delicate balance. A rise in Lake level causes the inundation of adjacent
land. Management of The Fayoum water balance assumes control over irrigation water flows, but this control has technical and
organizational limitations.
Also discussed is the influence of irrigation practices in The Fayoum on the water balance (e.g., the autumn flushing of fields
and farmers' preference for not irrigating at night in winter).
Notwithstanding a high overall efficiency, irrigation efficiency during the winter is low. The reasons for this are given,
together with the constraints against improving system management.
Improved uniformity of the division and application of irrigation water will enable a better technical control of flows and
will result in better water management in The Fayoum.
Abbreviations: FID — Fayoum Irrigation Department, 1 feddan (fe) — 0.4 ha, 1 mcm — 1 million cubic metres: an average annual flow of 3.17
m3/s gives 100 mcm, m3/fe.year — supplied volume (m3) per surface area (fe) per year: 1000 m3/fe.year equals 240 mm/year, MSL — Mean Sea Level 相似文献
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G. C. M. van Leeuwen J. G. N. Wander J. Lamers J. P. Meffert P. H. J. F. van den Boogert R. P. Baayen 《EPPO Bulletin》2005,35(1):25-31
Fields infested with Synchytrium endobioticum can be descheduled when the soil is found free from sporangia of S. endobioticum . For direct examination, EPPO Standard PM 3/59 describes a soil extraction technique based on the use of a sieve shaker with six sieves. We compared recovery of sporangia between this (modified) method and an extraction method employed by the Dutch Plant Protection Service (PPS method). Recovery was determined using an inoculum dilution series: 125, 25, 5, 1, 0.2 or 0.04 sporangia per g soil. Extraction reagents used were chloroform and calcium chloride in the method described by EPPO, calcium chloride and zinc sulphate in the PPS method. At 125 sporangia per g soil, the mean density determined for the modified EPPO method was 228 sporangia per g soil when chloroform was used. Using calcium chloride, recovery percentage was higher for the modified EPPO method than for the PPS method (286, 136%, n.s. P < 0.05). The advantage of the modified EPPO method was the larger soil volume to be processed; its disadvantages were use of complex equipment and noxious reagents (chloroform). Both extraction methods showed high variation in recovery between samples, making accurate estimation of sporangial densities in soil awkward. 相似文献
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T Kassai L Fésüs W M Hendrikx C Takáts E Fok P Redl E Takács P R Nilsson M A van Leeuwen J Jansen 《Veterinary parasitology》1990,37(1):61-77
Responses to a single or repeated infection with 7000 infective larvae of Haemonchus contortus were studied in an experiment using a total of 106 3-month-old lambs with AA, AB or BB haemoglobin (Hb) genotypes. Results were assessed by faecal egg counts, adult worm counts, haematocrit values, haemoglobin concentrations, total serum protein and serum antibody IgG1 and IgA ELISA titres. None of these parameters showed a strong relationship to the Hb type. The prevalence of low responder (greater than 500 worms) and of high responder (less than 50 worms) animals in groups AA, AB and BB Hb types was 3.8 and 34.6, 20.6 and 35.2, 28.1 and 43.7%, respectively, suggesting that the responsiveness to nematode infection is under the control of gene(s) not closely linked with those determining the Hb genotype. Worm counts of a primary infection are more subject to variation than those of a secondary infection. There is a strong relationship between adult worm counts and faecal egg counts taken close to the time of slaughter. In living animals low and high responder discrimination can be based on individual faecal egg counts around 50 days after a secondary infection. Haematocrit values proved to be of little value in the low and high responder selection. In this regard neither Hb concentration nor total serum protein values are of practical significance. In 3-month-old lambs primary infection induced partial immunity which could prevent the establishment of a part of the secondary infection, irrespective of the presence or absence of the primary worm population. The development of immunity was not associated with an increase of serum IgG1 and IgA antibody levels. Specific antibody production was not influenced by Hb types. Mean antibody levels of low responder lambs showed no difference from those of high responders. Thus, serum IgG1 and IgA levels are of no predictive value in identifying lambs which are genetically resistant to Haemonchus infection. 相似文献
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Gerry Van Leeuwen Senior Consultant 《国际木业》2003,33(11):3
尽管在过去10年里日本集成材的进口取得惊人增长,然而值得注意的是日本本国的结构集成材的生产甚至增长更快. 相似文献
8.
Clement C.R. Weber J.C. van Leeuwen J. Astorga Domian C. Cole D.M. Arévalo Lopez L.A. Argüello H. 《Agroforestry Systems》2004,61(1-3):195-206
Agroforestry Systems - Peach palm (Bactris gasipaes) was domesticated as a fruit crop by the first Amazonians in traditional Neotropical agroforestry systems, but research and development... 相似文献
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The influence of pre-treatment and post-treatment illumination upon the herbicidal effect produced in Phaseolus vulgaris L. cv. Berna by simeton, diuron, diquat and ioxynil was examined. The increased effect noted at lower pre-treatment and higher post-treatment levels of illumination was correlated with increased inhibition of net photosynthesis. This increased effect was ascribed to enhanced photo-oxidation. 相似文献