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131.
张永涛 《干旱区资源与环境》1995,9(2):115-122
本文分析了PRED综合研究的特点及应用系统动力学模型于盐池半荒漠风沙区进行综合研究的可能性,并且利用系统动力学专用语言DYNAMO进行建模,并对仿真结果进行分析,其结果证明利用系统动力学模型进行PRED研究是行之有效的方法。 相似文献
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135.
M. Angeles Achon Marion Pinner Vicente Medina George P. Lomonossoff 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(7):697-705
Two isolates of maize dwarf mosaic virus (MDMV-Sp and MDMV-Spl) obtained from maize in the northeast of Spain were studied. Both isolates induced similar reactions on 6 sorghum cultivars, johnsongrass and oat (cv. Clintland), with the exception of MDMV-Sp which produced a different reaction on one sorghum cultivar. Thirty-three grass species were tested as possible hosts (16 previously untested) and 18 were found to be susceptible. Among those, eight were previously unidentified hosts for MDMV:Aegilops ovata, A. ventricosa, Avena barbata, Bromus alopecurus, B. diandrus, B. fasciculatus, Echinaria capitata andLolium rigidum. Both isolates were transmitted from maize to maize nonpersistently byRhopalosiphum maidis, R. padi, Schizaphis graminum andSitobium avenae. The virus was not seed-transmitted in Mo17 and B73 maize inbred lines. Pinwheels, scrolls and short curved laminated aggregates were observed in the cytoplasm of maize cells infected by MDMV-Sp or MDMV-Sp1. In addition, laminated aggregates were observed in cells infected by MDMV-Sp1. 相似文献
136.
调整农林牧结构是干旱、半干旱地区农业走出低谷、摆脱困境的战略措施。本文通过对实验区资源评价、农业生产的历史考察和现状辨识。明确了农业发展的优势和主要问题,运用线性规划模型确立了多目标兼顾的农林牧优化结构。 相似文献
137.
畜以猪为主,肉以猪肉为主是渭北旱塬畜牧业资源及生产配置的基本格局,这种格局既不利于区位资源优势的充分发挥形成畜产优势,促进畜牧业发展;也不利于食物结构的改善和消费水平提高。为此本文从渭北畜牧业资源配置、生产配置现状问题出发,运用模糊数学、系统工程等原理,通过定性定量分析,提出了该区畜牧业资源及生产配置的战略思想。 相似文献
138.
G. Vannier 《Biology and Fertility of Soils》1987,3(1-2):39-44
Summary The author recalls that the late Professor Mercury S. Ghilarov, from the Institute of Animal Morphology and Ecology in Moscow, was a great pioneer in soil zoology and a far-sighted scientist in the evolution of terrestrial faunas. Professor Ghilarov agreed that during their evolution insects passed through the soil as a transitional medium from aquatic to terrestrial habitats. His theory, which is based on morphological and physiological observations, fits the thermodynamics of soil water the author describes when considering all porous bodies (porosphere), such as soil and other media, permitting a slow and gradual transition from an aquatic towards a xeric aerial system. In conclusion, a general concept of water accessibility for soil animals is formulated.Dedicated to the late Prof. Dr. M.S. Ghilarov 相似文献
139.
Hygienic and ecological risks connected with utilization of animal manures and biosolids in agriculture 总被引:2,自引:0,他引:2
In recent years the fate of human and animal pathogen microorganisms as a potential pollutant of the environment has been paid increased attention. Substantial quantities of these compounds and their metabolites are excreted, flushed down the drain, discarded as waste, or left over in animal feedlots. After passing to the sewer, several of these compounds are not adequately eliminated by the methods that are currently used in sewage treatment. Substantial quantities of biosolids and livestock manure end up on agricultural land. Effective sanitation of the environment, particularly of some of its special parts, which can be a source of spreading of diseases, plays an important role in prevention of infectious diseases. In this respect special attention should be paid to the disinfection of infected farm animal excrements. Sanitation of excrements should, on the one hand, ensure effective inhibition of infectious agents and, on the other hand, comply with the requirement of preserving the composition of the manure so it can be used in agricultural production. 相似文献
140.
A study was undertaken to evaluate the effects of incorporating high (HMS) and low (LMS) maturity maize silages into diets based on low (LGS) and high (HGS) feed value grass silages offered to beef cattle. Seventy-two continental cross-bred steers were used in a 14-week continuous design, randomised block experiment. The six treatments were arranged as a 2 × 3 factorial design incorporating the LGS and HGS offered as the sole forage, along with each of the two grass silages offered in a 60:40 ratio (DM basis) with the HMS and LMS. All diets were supplemented with 3 kg/head/day concentrates. Total daily DM and metabolisable energy intakes were higher (P < 0.001) for diets based on HGS compared to those based on LGS. Intakes were similar (P > 0.05) between diets containing LMS and HMS, both of which were higher (P < 0.001) than diets containing grass silage as the sole forage. Highest DM intakes were recorded with a mixture of HGS and HMS (P < 0.05 or greater). Cattle offered diets containing HGS had higher live-weight gain (P < 0.05), final live weight, carcass gain and carcass weight (P < 0.001) than those offered diets containing LGS. Feed conversion efficiency, assessed on a carcass gain basis, was poorer (P < 0.05) with diets containing LGS compared with those containing HGS, though differences between diets containing either LMS or HMS and GS as the sole forage were not significant (P > 0.05). 相似文献