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981.
运用人工模拟降雨和径流小区试验方法,研究了宁夏西吉县黄家二岔小流域的土壤渗透性能。结果表明,影响土壤渗透性能的主要因子是土地利用方式、地面坡度、土壤含水率、土壤总孔隙度和雨强。据此,提出了充分利用干旱地区有限降水资源的建议。 相似文献
982.
A review of tree fodder production and utilization within smallholder agroforestry systems in Kenya 总被引:1,自引:1,他引:0
R. T. Paterson G. M. Karanja O. Z. Nyaata I. W. Kariuki R. L. Roothaert 《Agroforestry Systems》1998,41(2):181-199
Although the biological advantages in terms of animal production and improved soil fertility of the use of herbaceous legumes
have been well demonstrated in Kenya and elsewhere, adoption by small-scale farmers has often been disappointing. This has
led to increased research into the use of both indigenous and exotic fodder trees. In common with conventional pasture legumes,
tree fodders contain high levels of crude protein and minerals and many show high levels of digestibility. They are readily
accepted by livestock and presumably because of their deep-root systems, they continue to produce well into the dry season.
Antinutritive factors can be a problem, however, and polyphenolics, toxic amino acids, cyanogenic glycosides and alkaloids
are found in many tree species. There are abundant niches on small farms where fodder trees can be grown without affecting
crop production. Although detailed management recommendations are lacking, guidelines exist with regard to appropriate cutting
heights and harvesting frequencies. In the Embu region, it has been estimated that three kg of fresh fodder of Calliandra
calothyrsus has the same effect on milk production as one kg of commercial dairy meal. Up to about 500 trees (250 m of hedgerow)
will produce enough fodder to supplement one dairy cow for a complete lactation. The tree fodder can either replace the concentrate
without loss of yield, or it can complement it to produce more milk. It is being enthusiastically adopted by small-scale farmers,
many of whom are starting to produce their own seed. Other tree species are now being studied in order to avoid over-reliance
on a single fodder species.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
983.
984.
林用门式起重机的设计,其工作类型可根据资源、林相、到材方式和产量等因素确定。而现有正在使用的林用门式起重机的实际使用情况.会给设计者提供某些参考数据。本文对伊春林区所用的门式起重机进行了调查统计分析,得出了该林区每台门式起重机的载荷利用率、平均载荷利用率,希望能对确定合理的林用门式起重机工作类型,提供参考数据。 相似文献
985.
城市木材工业是城市林业的组成部分。在发展城市林业的木材工业生产时,要遵守森林资源的综合利用与环境保护相协调,要特森林资源节约放在首位。因此,在发展城市木材工业生产过程中,推行减量化、回收利用、再循环、重组合、代用品、重现性、重整修、再生产等一系列措施,使城市木材工业稳步地可持续发展。 相似文献
986.
中国玉米主要种质杂种优势群的划分及其改良利用 总被引:40,自引:7,他引:33
根据配合力,杂种优势,系谱关系,生理和遗传特点及形态特征等,结合育种实践,将我国玉米种质分改良Reid,Lancaster(Mo17和自330两个亚群)四平头,旅大红骨和其它(外杂选,综合品种选Suwan和低纬度种质4个亚群)5个杂种优势群9个亚群,提出了若干改良利用意见,并对种质基础狭窄,杂优群划分与利用,种质改良等问题进行了讨论。 相似文献
987.
Peng Shini 《保鲜与加工》1998,(5):66-71
This article analyses the hydraulic reliability of gas -transport network under high andmedium pressure in detail, To increase the hydraulic reliability, it is available to improve the send outpressure in permissible condition. 相似文献
988.
989.
Yu Li Jie Wang Yongsheng Cao Weidong Gao Jiahe Fang Xizhi Lou 《Genetic Resources and Crop Evolution》1998,45(2):181-186
The use of crop genetic resources in improvement programmes should be the ultimate objective of all undertakings in the field of germplasm resources. The present situation and future direction of the use of crop germplasm in China was assessed from responses to a questionnaire distributed to 165 plant breeders and curators nationwide. The general opinions for the limiting factors of germplasm utilization were also evaluated. Responses from the questionnaire indicated that the use of germplasm in breeding programmes is much more important than the direct use of germplasm in crop production as cultivars released. Among different types of crop genetic resources, released varieties and breeding lines contribute more to crop breeding. Wild relatives and genetic stocks, however, are expected to play a greater role in the future. Landraces will remain important in improvement. Limited useful germplasm available to breeders is the basic reason for the insufficient use of germplasm in crop breeding at present. The complex reasons which affect the availability of useful germplasm involve the research level, links between breeder and curator and others. To counter these, we propose some suggestions and measures which can be implemented in the near future. 相似文献
990.