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951.
Methane emissions from flooded rice grown under greenhouse conditions were monitored using a closed chamber technique. The three rice cultivars showed similar diel emission patterns though the amplitudes differed. Variation in emissions (maximum emission rate) from the different cultivars ranged from 0.164–0.241 mg/pot/h at tillering stage, 0.714–2.334 mg/pot/h at heading stage, 0.399–1.393 mg/pot/h at ripening stage. The methane emissions increased in the morning at accelerating rates, reached a maximum in the early afternoon, then decreased rapidly to constant rates during the night. The diel emission pattern was modeled using a Gaussian equation for daytime, and a constant for nocturnal emissions. Applying an Arrhenius equation, more than 90% of the diel variation of methane emissions could be predicted from soil temperature fluctuations. The predictions improved by using a diffusion model based on soil temperature and dissolved methane concentrations in soil solution. Soil temperature and methane concentration in soil solution are the two major factors controlling diel methane emissions. 相似文献
952.
M. J. Mohammad S. Zuraiqi W. Quasmeh I. Papadopoulos 《Nutrient Cycling in Agroecosystems》1999,54(3):243-249
Two field experiments were conducted in the Jordan Valley to evaluate potato response to N fertigation. Nitrogen as ammonium sulphate was supplied through irrigation water (fertigation) at rates of 0, 35, 70 and 105 mg N l-1. Soil N application treatment equivalent to the fertigation treatment of 70 mg N l-1 was included. 15N labelled ammonium sulphate was used to evaluate the N recovery and utilization efficiency. Yield increased by the N rate. The soil N application gave higher yield than the zero N and lower than the fertigated treatments. The increase in yield was due to the increase in the size of the tubers. The specific gravity was the highest with the zero N. The index ratios of potato tubers were similar with all treatments. The N derived from fertilizers by both tubers and shoots, increased with the N rate regardless of the method of application. The soil application treatments had fertilizer utilization as high as the fertigation treatments and produced total tuber yield not significantly different from that obtained by the fertigation treatment with similar rate. This might be attributed to the poor fertilizer distribution in the root zone in the fine textured soil. The low value of the fertilizer utilization of the plant receiving the 15N in the preceding season suggested possibilities of rapid transformation and immobilization by the soil microorganisms. 相似文献
953.
A study was conducted to identity factors contributing to the difficult removal of used motor oil from textile materials by
detergency. Infrared spectroscopy and gel permeation chromatography of used motor oil showed that the oil was a saturated
aliphatic hydrocarbon with molecular weight around 950. X-ray analysis revealed that particulates present in the used motor
oil contained S, Mg, Al, Si, K, Ca, Fe, Ni, Cu, and Zn. Used motor oil was distributed throughout the cotton fibers with similar
concentration of oil in the lumen, secondary wall, and surface crenulation. Higher relative concentrations of used motor oil
were observed in the secondary wall of the fiber than has been reported for human sebum. No oil was found in the interior
of polyester fibers although high concentrations of oil were detected in the interfiber spaces and on the fiber surfaces of
polyester fibers. Dispersant additives of motor oil are though to enhance penetration into the cotton structure and wicking
over the polyester fibers, making the nonpolar used motor oil very difficult to remove by detergency. 相似文献
954.
Tejinder S. Khera Milkha S. Aulakh John W. Doran 《Nutrient Cycling in Agroecosystems》1999,54(3):209-213
The influence of different depths of repacked soil cores on changes in N transformation processes was studied with a subtropical semi-arid soil amended with 100 mg N kg-1 of Sesbania green manure (GM) or fertilizer (NH4)2SO4 for 35 days under flooded and nonflooded conditions. Shallow soil depth enhanced the rate of nitrification, particularly where aeration was impeded in flooded soils. However, the opposite occurred for denitrification as the relative predominance of underlying anoxic zone increased with increase in soil depth. Nitrate produced in the thin oxic surface soil layer and overlying water in flooded soils was subsequently lost via denitrification, more rapidly where carbon was supplied by added GM. Decomposition of GM was rapid and apparent recovery of applied 100 mg GM-N kg-1 soil as mineral N after 35 days in flooded soils was 8, 26, 30 and 38% in 1.25-, 2.5-, 5.0- and 7.5-cm deep soil cores, respectively. Soil ammonium-N declined rapidly after an initial rise during decomposition of GM in soil in the shallow soil depth. In contrast, no such decline in NH
4
+
-N was observed in deep soil cores. In conclusion, the use of shallow soil depths during laboratory incubations can lead to variable results under flooded conditions. To simulate field conditions for obtaining reliable and quantitative information regarding N transformations in soils under flooded conditions, soil depths of 7.5 cm or greater should be used for laboratory incubations and growth chamber studies. 相似文献
955.
Soil fertility enhancing technologies (SFETs) have been promoted in the West African Semi-Arid Tropics (WASAT) for many years with limited success. Using a qualitative approach of focus group discussions, long, open-ended interviews and observations from field visits, this paper explores with farmers their beliefs and rationales behind the adoption or non-adoption of SFETs. Farmers are knowledgeable about, and practise SFETs of rock phosphate application, crop residue and farm yard manure, chemical fertilizer and crop rotation to combat soil fertility decline. Their attitudes to and rationales behind adoption decisions are influenced by the availability and use policies of land and labour resources, food security concerns, perceived profitability, contribution to sustainability and access to information. Some of the factors are beyond farmers' control and require a broad and integrated effort from research, extension and government to promote the use of the SFETs in the region. 相似文献
956.
采用电化学工作站测试了X80管线钢在不同含水率的新洲土壤中的电化学噪声,并对噪声数据进行了谱图和频域分析。结果表明:含水率对X80管线钢在新洲土壤中的腐蚀影响较大,在低含水率(14%)和中间含水率(18%)新洲土壤中,腐蚀以点蚀为主,在高含水率(22%)土壤中以均匀腐蚀为主;随着含水率从14%增加到22%,电化学噪声谱的噪声波动持续的时间缩短;X80管线钢发生均匀腐蚀时,其功率谱密度(PSD)图高频线性段斜率较大,与腐蚀初期相比变化较大,且出现高频白噪声;当X80管线钢发生点蚀时,其PSD图高频线性段斜率较小,与腐蚀初期相比变化不大。 相似文献
957.
采用扫描电镜(SEM)、能谱(EDS)和X射线衍射(XRD)等技术观察和分析了交、直流杂散电流干扰下Q235钢在海南土壤中的腐蚀形貌和腐蚀产物,并对腐蚀过程的电化学参数进行了测量。结果表明:杂散电流腐蚀具有明显的电解腐蚀特征,电流流入金属构件部位成为阴极而受到保护,电流流出金属构件部位成为阳极而受到腐蚀;交、直流杂散电流腐蚀具有集中腐蚀特征,腐蚀产物呈絮状,产物层均有明显裂纹、分层、脱落现象,对基体不具有保护作用;交、直流腐蚀产物组成大致相同,主要为Fe3O4、Fe2O3,伴有少量FeS;杂散电流的存在会加剧Q235钢腐蚀,在同等外加电流下,交流杂散电流腐蚀的危害程度是直流杂散电流腐蚀的15.9%。 相似文献
958.
提高肥料利用率化工部门能做些什么? 总被引:15,自引:0,他引:15
介绍了中国肥料利用率状况、所施肥料的去向及土壤中养分的积累与亏损。据估计,中国自1985~1996年,约有9900万吨N被淋失和逸散,6000万吨P2O5和1400万吨K2O固定于土壤中。如何提高肥料利用率是中国化学肥料工业紧迫的课题,针对不同类型化肥厂提出了生产控制释放肥料、腐植酸螯合尿素、稳定的碳酸氢铵、部分酸化磷矿复合肥料、完全水溶性复合肥料以及熔融钾镁肥的途径,以提高肥料利用率。 相似文献
959.
分析了酸性白土在润滑油白土精制过程中对油品的氧化机理。根据小型试验和工业生产数据,提出了真空脱氧是消除精制过程中油品氧化增色的有效途径。 相似文献