排序方式： 共有11条查询结果，搜索用时 15 毫秒
1.
本文不采用缝隙管的假定,提出毛管水头线的多段折线模型;在此基础上,定义了降比r和压比G,根据r的大小,讨论了均匀坡毛管压力水头的分布;讨论了总水头损失计算方法;导出诸水力特征量的计算公式。 相似文献
2.
花岗岩坡地土壤侵蚀强度分级参考指标探讨 总被引：5，自引：0，他引：5
根据实测资料建立了花岗岩坡地土壤侵蚀强度模型,并对土壤侵蚀强度分级标准进行了讨论,认为2OOt/km2为土壤允许侵蚀量较合适。在此基础上建立了土壤侵蚀强度分级参考指标系统。该指标是以侵蚀量为基础的,且各指标在野外获取容易,所以该土壤侵蚀强度分级参考指标可以在条件相似的广大南方花岗岩地区推广试用。 相似文献
3.
In Chongqing,the South Hot Spring,Small Hot Spring,and West Hot Spring,do not flow automatically;the flux of North Hot Spring and East Hot Spring Have fallen.The geothermal water did not flow through the geothermal water hole of East Hot Spring.However,the exploitation of "city of hot spring" is plan after 5 year.The paper discusses the hydro-geological conditions,the dynamic hot springs and correlativity among hot springs,analyzes the replenishment conditions and capacity of store water,and the correlativity among the exploitation points of "city of hot spring".It shows that the exploitation of "city of hot spring" is feasible.But in order to exploit "city of hot spring" sustain-ably,the whole yield of "city of hot spring" along with should be planned the every hot spring yield in a geothermal water system of anticline. 相似文献
4.
本文研究了田间管网优化设计中支、毛管允许压力偏差水头分配的问题。在平地上布置微灌系统时,得出了支、毛管的最优分配比不是一个定值,而是随支管上毛管的根数和支、毛管长度的变化而变化,改进了美国J·凯勒和D·喀麦林提出的只给一个固定常数的方法,对节约管网投资有一定的实际意义。 相似文献
5.
河北低平原潮土氮磷钾平衡状况及评价研究 总被引：5，自引：0，他引：5
对河北低平原潮土氮磷钾养分平衡状况进行了分析和评价。研究结果表明：该地区养分收支情况为氮磷有盈余，而钾处于亏损状态。各养分的平衡系数分别为氮1．07－1．41，磷1．14－1．70，钾0．72－0．96。氮磷钾养分的实际盈亏率都在允许的范围内。氮的盈余率为4．75％，比允许值47．6％低；磷的盈余率为13．7％，比允许值1．6％高；钾的亏缺率为28．1％，比允许值41．3％低。总的来说，在该试验条件下，氮磷钾养分的盈余情况比较合理。 相似文献
6.
Hussein Fawzy Abouziena Mohamed Saber Essam Hoballah Soad El-Ashry Alaa Mohamed Zaghloul 《农业科学与技术》2013,(12):1010-1016
A field experiment was carried out at Abu-Rawash sewage farm to appraise the effect of certain novel remediative amendments on the quality of oil as well as the vegetative parameters and yield criteria of canola plant used as hyperaccumulator for the remediation of sewaged soils. The treatments included fallow soil （irrigated without growing canola）, soil cultivated with canola （Brassica napus L.） and inoculated with arbuscular mycorrhiza （AM）, soil inoculation with Thiobacillus sp. （a mixture of Thiobacillus ferrooxidans and Thiobacillus thiooxidant）, soil treated with a mixture of 250 mg bentonite plus 250 mg rock phosphate/kg soil and inoculated with phosphate dissolving bacteria （PDB）, and soil treated with all the aforementioned remediative amendments. Results indicated that the vegetative parameters and yield criteria of canola plant did not exhibit any serious adverse impact under all treatments applied. The concentrations of Zn and Cu in canola oil extracted from plants grown in soil inoculated with AM and/or Thiobacillus sp. far exceeded the safe permissible levels. On the other hand, the content of both PTEs in the oil extracted from canola plants grown in soil treated with either probentonite or with mixture of all remediative amendments followed the permissible safe levels. 相似文献
7.
The maximum permissible ground pressure of agricultural vehicles to permit satisfactory crop production on heavy loamy Chernozem soil was estimated from six criteria: (1) changes in soil water-physical properties; (2) crumbling characteristics; (3) depth of compaction; (4) rut depth; (5) soil strength potential; (6) self-loosening characteristics. Using these criteria it was possible to obtain reliable data for the maximum permissible ground pressure which was found to be correlated with the soil water content at the time of tillage.
At a water content equal to or somewhat lower than the water content at optimal soil crumbling (0.16–0.24 kg kg−1), the permissible ground pressure was found to be within the range 80–120 kPa. At soil water contents slightly above the optimum soil crumbling (0.26–0.28 kg kg−1), the permissible ground pressure was within the range 30–60 kPa. 相似文献
8.
红壤坡地不同生态模式水土流失规律的研究 总被引：30，自引：14，他引：30
在 8～ 15°的红壤坡地上 ,对水土流失作了 14年的定位观察。结果表明 :水土流失与土壤坡度和植被覆盖度密切相关。红壤坡地一经开发利用 ,径流量就成倍地减少 ;而侵蚀量在开始的头 2年成倍增加 ,第 3年后趋于稳定。土壤侵蚀量与坡度呈极显著的对数正相关 ,坡度每增加 1°,土壤侵蚀量递增约 12 0 t/ (km2·a) ;土壤侵蚀量与植被覆盖度呈显著的负指数相关 ,当植被覆盖度 >6 0 %时 ,土壤侵蚀量在 2 0 0 t/ (km2 · a)以下 ;土壤侵蚀量与耕种方式密切相关 ,等高耕种的侵蚀量仅为顺坡耕种的 1/ 6。应用土壤肥力平衡观点 ,提出了 Q2 红色粘土母质发育的红壤侵蚀允许指标为 <30 0 t/ (km2· a) ,为红壤坡地水土流失的防治和农业可持续发展提供了理论依据 相似文献
9.
High concentrations of antimony(Sb) in soils and vegetables can cause potential health risk. However, the effect of Sb on the growth and response of crops are not well known and to date, there is still no Sb limit standard for Allitic Udic Ferrisols in China. In this study, a greenhouse experiment was carried out to investigate the effect of antimony(Sb) on biomass, physiological performances,and macro- and micronutrient element concentrations of green Chinese cabbage(Brassica chinensis L.), as well as enzyme activities,in Allitic Udic Ferrisols from Hunan Province, China. Antimony was supplied at rates of 0(control), 2, 5, 10, 20, and 50 mg kg-1and thus with the background value of 1.0 mg kg-1, the Sb concentrations in the treated soil samples were 1, 3, 6, 11 21, and 51 mg kg-1, respectively. The results showed the leaf biomass and ascorbic acid content of cabbage significantly(P < 0.05) decreased by 30.6% and 48.3%, respectively, and soil urease and dehydrogenase activities also significantly(P < 0.05) decreased by 33.6%and 32.5%, respectively, when soil Sb concentration was 21 mg kg-1as compared with the control. The uptake of essential nutrient elements such as Mg, Cu, and Zn by cabbage was obviously affected, while the leaf soluble sugar content slightly changed when the soil Sb concentration exceeded 21 mg kg-1. Based on cabbage physiological responses and soil enzyme activities, the permissible concentration of 21 mg kg-1for Sb in Allitic Udic Ferrisols should be recommended. 相似文献
10.
《Communications in Soil Science and Plant Analysis》2012,43(7-8):959-973
Abstract The weekly nitrogen (N), phosphorus (P), and potassium (K) release from 17 polymer‐coated controlled‐release fertilizer (CRF) formulations of Nutricote, Apex Gold, Osmocote, and a 9‐month Macrocote were measured at 30.6±0.8°C and 40.0±1.5°C. Five grams of each CRF were placed at a depth of 50 mm in 280x50 mm acid washed then rinsed silica sand columns which were leached with deionized water three times each week until nutrient recovery ceased. The volume of leachate was recorded each week and subsampled for ammonium‐N, nitrate‐N, phosphate‐P, and K analyses. Each CRF treatment was replicated three times at each temperature. Nutrient release profiles were determined. Longevities, measured as weeks to 90% nutrient recovery, were considerably shorter than the nominated release periods for all formulations. Within each CRF product group, the longevity of 9 and 12 month formulations were similar with Apex Gold 12–14 month high nitrate having the longest (38 weeks for N at 30°C) and Osmocote 8–9 month the shortest (23 weeks for N at 30°C). There were consistent trends in the nutrient release periods across all CRFs with P>K>N and with differences of around 10% in duration between nutrients. The P:N release ratio exceeded 0.10 for most CRFs during the early release period indicating an adequate P supply for most plant species. The mean reduction in longevity for Nutricote, Apex Gold, and Osmocote formulations for an increase in incubation temperature from 30°C to 40°C was 19–21 % for N, 13–14% for P, and 14–15% for K. All CRFs released nutrients unevenly with the highest rate occurring during the early part of the release period. This pattern was accentuated at 40°C and by the shorter term release formulations. The nutrient release rates of all CRFs declined steadily after their maxima. 相似文献