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C. M. MUNDIE 《European Journal of Soil Science》1976,27(3):331-336
Two methods have been used for the identification and determination of uronic acids in soils and soil fractions. The uronic acids were released by hydrolysis with sulphuric acid. After partial purification by ion-exchange chromatography they were separated either by further ion-exchange or by gas-liquid chromatography of derivatives. The latter method is preferable for determination of the specific activities of uronic acids in soil tracer work. Both galacturonic and glucuronic acids were detected in the four Scottish soils examined, the galacturonic acid being present in slightly greater amounts in each soil. Mannuronic acid was not detected. The total amount of uronic acids found ranged from about 4 mg to 6 mg/g soil. 相似文献
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马光庭 《广西农业生物科学》1994,(3)
本文介绍从德国哥廷根污水处理厂腐化塔污泥中分离出的两株甲烷细菌,其中一株为甲酸甲烷杆菌(Methanobacteriumformicicum),其细胞杆状,可利用甲酸或H2/CO2作为碳源和能源,另一株为甲烷八叠球菌属(Methanosarcina),其细胞球状,成堆排列,可利用甲醇或H2/CO2作为碳源和能源。 相似文献
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For close to a century, rural development policies and practice have taken the view that farmers are mismanagers of soil and water. This paper reviews the history of farmers being advised, paid and forced to adopt new soil and water conservation measures and practices. Many have done so, and environments and economies have benefited in the short term, but ill-conceived policies and badly designed programmes and projects have undermined these efforts in the name of conservation. Most efforts have been remarkably unsuccessful, often resulting in more erosion. They have undermined the credibility of conservation and wasted huge sums of money. For a new era of soil and water conservation, new initiatives are showing how to make conservation sustainable. Farmers are now considered the potential solution rather than the problem, and so the value of local knowledge and skills is being put at the core of new programmes. This involves a major focus on building farmers' capacity to innovate and develop technologies appropriate to their own conditions. Local organizations are strengthened through participatory processes, this participation being interactive and empowering. Recent evidence is indicating that these new interactions between professionals and farmers are producing considerable productive and sustainable benefits. For widespread impact, enabling policy frameworks are still needed to encourage the spread of more sustainable practices for agriculture. © 1997 John Wiley & Sons, Ltd. 相似文献
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黄土与古土壤中重金属的存在形态及风化成土作用对其影响 总被引:1,自引:0,他引:1
本文采用了七步连续萃取方法,研究了洛川黄土剖面黄土与古土壤中Fe,Cu,Zn,Co和Ni五种重金属的存在形态。结果表明:黄土与古土壤中上述元素主要存在于残余态和晶形,无定形氧化铁的结合态中,而且线性回归分析表明Cu,Zn,Ni与晶形氧化铁之间存在关;cU,cO,Ni与无定形氧化铁之间存在相关;黄土风化为古土壤后,碳酸盐结合态的重金属含量增加是古土壤相对于黄土重金属增加的主要原因。 相似文献
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The ability of clay to move ahead of an ice-liquid interface depends on the rate of freezing, the particle size, the release of dissolved air from the water through its probable effect on local freezing rates, and on the electrolyte and its concentration through their effects on interparticle forces and particle mobility. A freezing-rate of 1 cm per hour did not move flocculated clay in most cases, but moved dispersed clay up to 0.7 cm before being trapped in the ice with released air. Aggregates of clay (0.1 to 1 mm) were produced by freezing. After thawing they swelled and dispersed depending on the electrolyte and its concentration in a similar manner to aggregates formed by drying. 相似文献
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《Journal of plant nutrition》2013,36(2):345-356
Aluminum (Al) toxicity has been identified as one of the most important factors limiting plant growth in acid soil. Besides Al, nitrite (NO2 ?) may also be a significant stress factor in an acid environment. The objective of this study was to examine the effects of Al and NO2 ? stress on the growth and potassium (K+) uptake of roots and their transport toward the shoots of an Al-resistant common wheat (Triticum aestivum L. cv. Jubilejnaja 50) and an Al-sensitive durum wheat (T. durum Desf. cv. GK Betadur) grown in 0.5 mM CaSO4 solution at pH 4.1 or 6.5. Root elongation of durum wheat was inhibited with 30% at 10 μM AlCl3 treatment, while this low Al-concentration did not show a significant effect on root growth of common wheat. In all cases shoot growth was not influenced under low-salt conditions by 10 μ M AlCl3, but exposure to 100 μM KNO2 (alone or in combination with Al) had a definite stimulatory effect on growth. Aluminum was found to stimulate the K+(86Rb) influx in short-term (6 h) experiments, but to inhibit it in long-term (3 days) experiments. This treatment was thought to damage the plasma membrane. When 10 μM 2,4-dinitrophenol was present in the uptake solution the Al-stimulated K+ uptake stopped even in short-term experiments. In the case of nitrite and nitrite + Al treatment combinations, however, a striking inhibition was observed in the K+(86Rb) influx and the K+ concentration of the roots and shoots of both species. 相似文献
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Asha Yahya 《Journal of plant nutrition》2013,36(5):670-683
Net uptake and partitioning of sodium (Na+) and potassium (K+) in plants of two sesame cultivars (Sesamum indicum cv. ‘PB-1’ and cv. ‘UCR’) exposed to 20 mM sodium chloride (NaCl) were studied over a period of 28 days. Both cultivars showed a marked discrimination between K+ and Na+ during uptake. The reduction of K+ in the plants caused by the NaCl treatment was of similar magnitude in the two cvs. The cv. ‘UCR’ showed lower Na+ concentrations in the shoot tissues than ‘PB-1’ and K+/Na+ selectivity ratios were higher in cv. ‘UCR’ than in cv. ‘PB-1’. At the last sampling on day 28 there was a marked decrease of shoot growth in cv. ‘PB-1’ in comparison to the cv. ‘UCR’. Leaves of cv. ‘PB-1’ showed clear toxic symptoms, while those of cv. ‘UCR’ did not. It is concluded that Na+ exclusion from the shoot contributes to salt tolerance of sesame, cv. ‘UCR’. 相似文献
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汤贡珍 《广西农业生物科学》1994,(3)
本文论述喂饲草、秸秆或其他残渣时黄牛、水牛的奶肉役力成绩。作者认为,本生产方式是发展广西养牛的一条有效途径,并介绍了适合广西环境条件栽培的国外优良牧草,如象草、银合欢等的特性及饲草价值。 相似文献
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水土保持工程标准化,是实现综合治理,保证各项治理措施质量,提高治理水平,发挥经济效益的重要手段。陕西省水土保持工程标准化技术委员会成立以来,先后制定出两大类13个技术标准,通过贯彻执行,取得了较为显著的经济效益。本文就如何开展此项工作进行了全面总结。 相似文献
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The relationship between root age and root physiology is poorly understood, despite its importance for nutrient absorption. In peaches, roots are white when they first appear and then become brown with age, which corresponds to a number of physiological changes. We related root browning to nitrogen (N) absorption and respiration in order to provide a better understanding of how color changes as typically observed using minirhizotrons relate to changes in root physiology. The experiment was conducted on peach seedlings (Prunus persica cv. ‘Guardian’) grown in 30-L pots in a greenhouse. Brown roots showed lower respiration rates than white roots. White roots showed a higher 15N uptake than brown roots and higher concentration of N, potassium (K), magnesium (Mg), manganese (Mn), iron (Fe) and copper (Cu), no significant differences were observed regarding calcium (Ca), and zinc (Zn) concentration. 相似文献
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水稻对有机、无机态肥料氮和土壤氮的吸收利用探讨 总被引:2,自引:0,他引:2
为了研究我国有机、无机肥配合施用的供肥特点,培土效果和增产作用,我们从1978年春以来,以15N示踪法进行有机、无机态肥料氮转化问题研究,在江苏四种代表性士壤上,即太湖地区黄泥土(代号A),丘陵地区板浆白土(代号B),苏北里下河地区鸭屎土(代号C),淮北地区花碱土(代号D)上进行。以15N标记的怪麻和硫酸按分别作有机和无机态氮源,全部作基肥,供试作物为水稻南粳34号,盆淋试验重复三次,另在板浆白土上增加重复次数,以分期测定土壤、植株中氮素动态。详细的试验材料及方法已另文登载[1]。试验中的不同肥料处理列于表1。 相似文献
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Hongen Liu Chengxiao Hu Xiaoming Hu Zhaojun Nie Xuecheng Sun Qiling Tan 《Journal of plant nutrition》2013,36(12):1751-1760
A hydroponic trial was conducted to assess interaction of molybdenum (Mo) and phosphorus (P) on uptake and translocation of P and Mo by Brassica napus. Molybdenum was applied at four rates (0, 0.01, 0.1 and 1 mg L?1) and P at three rates (1, 30, and 90 mg L?1) in nutrient solution. The results indicated that P increased shoot growth and 0.01 mg L?1 Mo improved the growth of shoots and roots. Molybdenum increased shoot P uptake and root P concentration and uptake when higher P was provided, and had a stimulating effect on P translocation from shoots to roots. P increased shoot Mo concentration and uptake, decreased those in roots, and enhanced Mo transport from roots to shoots. These results implied that both Mo and P had beneficial effects on Mo and P absorption and translocation and co-application of them were necessary to promote growth and utilization of Mo and P for Brassica napus. 相似文献
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不同灌溉策略下冬小麦根系的分布与水分养分的空间有效性 总被引:25,自引:1,他引:25
通过田间试验研究了少量多次和少次多量的灌溉方式下冬小麦根系的分布与水分养分的空间有效性。结果表明 :少量多次的灌溉方式降低了冬小麦返青后表层根系的生长 ,减少了拔节后该层根系的衰退。在少次多量的灌溉方式下返青期不灌水促进了表层根系的生长 ,然而拔节后该层根系衰退较多 ,但中层 ( 3 0~ 60cm)根系生长高于少量多次的灌溉方式。不同灌溉策略下根系分布的差异并不影响冬小麦对土壤水分和养分的吸收 ,由于播前土体内蓄水不足 ,三种灌溉方式下 0~ 90cm土壤可用水在收获后均消耗殆尽。灌溉促进了表层硝态氮的吸收和向下迁移 ,但两种灌溉方式下硝态氮在土体内的迁移均未超出 60cm土体 ,仍在根层之内。而不同的灌溉方式对冬小麦全生育期内土体速效磷钾的分布没有影响。扬花前两种灌溉方式下冬小麦的生长发育和养分的吸收并无差异 ,扬花后少次多量的灌溉方式由于水分供应不足 ,影响了灌浆 ,降低了千粒重 ,进而影响了产量 ,同时土壤水分缺乏也减少了该时期养分的吸收。而在少量多次的灌溉方式下 ,扬花后灌水不仅可以促进冬小麦灌浆 ,提高千粒重 ,而且增加了对养分的吸收。 相似文献
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中国土壤肥料工作的成就与任务 总被引:7,自引:0,他引:7
中国农业取得了举世瞩目的成就。在农业发展中,土壤肥料科学的进步、技术成果转化为现实生产力,以及土壤肥力的培养与提高、土壤资源的合理开发与利用、植物营养与施肥,起着不容忽视的作用。本文侧重从土壤肥料科学技术推广领域这个侧面加以阐述。文章分两大部分:第一部分中国土壤肥料工作的现状和成就,回顾土壤肥料工作,涉及到土壤肥料基础工作和科学技术推广的方方面面;第二部分土壤肥料工作的任务,展望土壤肥料工作,探讨“八五”期间乃至本世纪末土壤肥料科技推广工作的重点任务和措施。 相似文献
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红黄壤的轻矿物和重矿物 总被引:2,自引:0,他引:2
本文研究了玄武岩发育的红壤,花岗岩发育的红壤和山地黄壤中的轻、重矿物。轻矿物的主要成份是石英和长石,石英/长石的比率是玄武岩发育的红壤>花岗岩发育的红壤>花岗岩发育的山地黄壤。重矿物的主要成份是各种含铁矿物及铁氧化物裹着的石英粒,此外还有少量的角闪石、锆石、云母和电气石等。锆石与土壤的风化强度变化有密切关系,作为土壤风化演变过程的指示矿物是很合适的。 相似文献