排序方式： 共有13条查询结果，搜索用时 31 毫秒
1.
Summary Loess and grumusol soils with sodicity levels of 2.5, 6.5 and 17–21 percent were spread over with 3, 5 and 10 t/ha of powdered phosphogypsum (PG) and were rained with distilled water (DW). Phosphogypsum at the rate of 5 t/ha increased the final infiltration rate (FIR) of the loess with ESP of 2.5, 6.5 and 21.0, from 3.0, 1.1 and 0.9 mm/h, respectively in the control to 13.4, 8.5 and 8.3 mm/h, respectively.The final infiltration rate of the same soils with the same ESP levels, rained on with saturated gypsum solutions was lower than that obtained by the PG powder treatment. It was suggested that, besides their effect on the electrolyte concentration of the percolating water, PG particles on the soil surface interfere with the continuity of the crust and may act also as a mulch, and thus increase the IR of the soil.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1024-E, 1984 series 相似文献
2.
Summary The effect of soil texture and CaCO3 content on water infiltration rate in crusted soil was studied with the use of a rain simulator. Two types of soils with low exchangeable sodium percentage (ESP < 3.0%) were studied: (i) calcareous soils (5.1–16.3% CaCO3) with a high silt-to-clay ratio (0.82–1.47) from a region with < 400 mm winter rain; and (ii) non-calcareous soils with a low silt-to-clay ratio (0.13–0.35) from a region with > 400 mm winter rain. Soil samples with clay percentages between 3 and 60 were collected in each region. Distilled water (simulating rainfall) and saline water (simulating irrigation water) were sprinkled on the soil. The soils were exposed to rain until steady state infiltration and corresponding crust formation were obtained. For both types of soils and for both types of applied water, soils with 20% clay were found to be the most sensitive to crust formation and have the lowest infiltration rate. With increasing percentage of clay, the soil structure was more stable and the formation of crust was diminished. In soils with lower clay content (< 20%), there was a limited amount of clay to disperse and, as a result, undeveloped crust was formed. Silt and CaCO3 had no effect on the final infiltration rate for either type of applied water, whereas with saline water, increasing the silt content increased the rate of crust formation.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1130-E, 1984 series 相似文献
3.
High levels of soil sodicity, resulting from intensive irrigation with saline-sodic waters, lead to an increased soil susceptibility to seal formation and to severe problems of runoff and soil erosion. The objective of this study was to investigate the efficacy of the addition of small amounts of an anionic polyacrylamide (PAM) to the irrigation water in controlling seal formation, runoff and soil erosion. Two predominantly montmorillonitic soils were studied, a grumusol (Typic Haploxerert) and a loess (Calcic Haploxeralf), having naturally occurring exchangeable sodium percentage (ESP)>12. The soils were exposed to 60 mm of simulated irrigation with commonly used tap water (TW, electrical conductivity=0.8 dS m–1; sodium adsorption ratio (SAR)=2), or saline water (SW, electrical conductivity=5.0 dS m–1; SAR>12). PAM effectiveness in controlling runoff and erosion from the sodic soils was compared with runoff and erosion levels obtained from untreated soils having low ESPs (<4). For both soils and for both water qualities and polymer concentrations in the irrigation water, PAM was efficient in controlling runoff at low ESP levels and inefficient at high ESP levels. At moderate ESP levels, PAM's efficacy in controlling runoff was inconsistent and varied with water quality and polymer concentration. Conversely, in general, soil loss originating from rill erosion, was significantly and effectively reduced in moderate and high ESP soils by addition of PAM to the irrigation water, irrespective of water quality and polymer concentration. PAM was more effective in reducing rill erosion than in reducing runoff in the moderate and high ESP samples, because the energy involved in generating runoff is much higher than that involved in rill erosion. PAM treated surface aggregates were not stable against the distructive forces leading to seal formation and runoff production; but they were stable enough to resist the hydraulic shear exerted by the runoff flow. 相似文献
4.
内蒙古河套灌区有效灌溉及盐碱控制的战略思考 总被引：8，自引：5，他引：8
位于中国干旱地区的河套平原,有着得天独厚的自然条件,在我国农业生产上占有重要的地位。但是这里没有灌溉就没有农业。长期过量灌溉引起了该地区土地的盐碱化。水资源短缺问题受到越来越广泛的关注,该地区引黄河水量将进一步削减,但另一方面随着社会和经济的发展,耕地面积将进一步扩大;农业节水和传统的用水洗盐方式是一对需要解决的矛盾。现代灌溉技术如喷灌、滴灌、微灌等无论是在技术上还是在经济上都很难在这里得到应用,地面灌溉方式在近期内仍将是主要的灌溉方式。合理的灌溉方式和地下水位的有效控制将是解决问题的 相似文献
5.
Interrill erosion depends on soil detachment and sediment transport, which are affected by seal formation and runoff. The objective of this study was to investigate the effect of wetting rate (WR) on runoff and soil erosion in semi-arid Israeli soils varying in clay content and exchangeable sodium percentage (ESP). Six soils, ranging in clay content between 90 and 680 g kg−1 and ESP between 0.9 and 20, were packed in 0.2 m×0.4 m trays, wetted at 3 WRs (2, 8, or 64 mm h−1), and thereafter exposed to 60 mm of distilled water rain in a laboratory rainfall simulator. Under non-sodic conditions (ESP<2), highest runoff and erosion were obtained from loam (220 g kg−1 clay and 350 g kg−1 silt) which was ascribed to its high susceptibility to seal formation, runoff and detachability. Runoff and erosion increased with an increase in ESP and WR. The effect of WR on runoff and erosion was negligible in loamy sand and generally increased with an increase in clay content. In clay soils (>600 g kg−1 clay), WR played a greater role in determining runoff and erosion compared with raindrop impact. A linear type dependence existed between erosion and runoff for soils with ESP<5 or when slow WR was used. For high ESP soils, or when medium or fast WR were used, an exponential type relation described better the dependence of erosion on runoff. It is suggested that for sodic soils or for conditions favoring aggregate slaking, runoff level and its velocity were high enough to initiate rill erosion that supplemented raindrop detachment in markedly increasing erosion. 相似文献
6.
Arnon Dag Zohar Kerem Nir Yogev Issac Zipori Shimon Lavee Eric Ben-David 《Scientia Horticulturae》2011
Harvesting plays a major role in the virgin olive oil production line, being the most expensive single component, but also due to its significant effect on the whole year's produce. Previous studies have focused on the effects of harvest timing on either oil yield or quality. Here we determined the separate and combined effects of harvesting date, fruit maturation, cultivar and fruit load on olive oil quality and quantity. Cultivars typical to the Middle East region were selected: the traditional cv. Souri and the newer cv. Barnea, grown under intensive conditions. The results demonstrate fundamental differences between the two cultivars with respect to harvest strategy. In high-yielding ‘Barnea’, oil accumulation continued throughout the ripening season resulting in increasing yield of oil with time while maintaining high quality. Hence, exploiting the production potential in ‘Barnea’ requires late harvest and advanced fruit maturity. However, in heavily loaded ‘Souri’, oil accumulation was accompanied by early massive shedding of fruits. Furthermore, late harvest and advanced maturation in ‘Souri’ were associated with a sharp increase in free fatty acids combined with a rapid decline in polyphenol content, and in MUFA to PUFA and saturated to unsaturated fatty acid ratios, all resulting in loss of oil quality. Rapid decline in oil yield coupled with deterioration of oil quality call for early harvesting at low maturity index in ‘Souri’. In medium-yielding trees of both cultivars, maturation progressed more rapidly, resulting in earlier harvest to utilize optimal oil potential. 相似文献
7.
ESP值和黏粒含量对土壤表面封闭作用的影响 总被引：2，自引：2，他引：2
降雨导致土壤表面结皮形成封闭是自然现象，它能降低土壤入渗，增加土表径流，导致土壤侵蚀。该文系统地研究了不同性质土壤表面的封闭作用过程，分别确定封闭过程中的物理机械作用和化学作用。试验采用了具有不同土壤交换性钠百分率(ESP)值(2、5、10、20)和黏粒含量(10％、20％、40％、60％)的4种土壤进行降雨模拟试验，通过土壤表面播撒磷石膏(PG)(2000 kg/hm2)和PG与聚丙烯酰胺(PAM)(PG 2000 kg/hm2+PAM 20 kg/hm2)混合物的处理，分别抑制了土壤的化学封闭和物理封闭，论述了ESP值和黏粒含量对土壤化学封闭和物理封闭作用的影响，结果表明：在高ESP值土壤中，化学封闭作用占土壤封闭的主导作用；低ESP值土壤中，土壤的物理封闭作用增大。当黏粒含量较低时，土壤物理封闭作用较低；当黏粒含量较大时，土壤物理封闭作用显著增大。 相似文献
8.
PAM特性对砂土壤入渗及土壤侵蚀的影响 总被引：2，自引：0，他引：2
选择3种分子量(12×106、15×106和18×106Da)和3种水解度(7%、20%和35%)聚丙烯酰胺(PAM),测试PAM特性对土壤入渗和侵蚀的影响。结果表明,3种不同分子量PAM均能明显提高土壤入渗,与对照相比,稳定入渗率分别增加了58.9%、92.2%和83.3%。中分子量和高分子量PAM处理增加入渗效果明显大于低分子量处理,但前两者之间差异不显著。同样不同分子量PAM处理可显著降低土壤侵蚀量,与对照相比,土壤侵蚀量分别降低26.3%、52.6%和26.3%。3种分子量之间比较,中等分子量效果明显好于其他两种分子量。3种水解度PAM提高稳定入渗率分别为对照的1.9倍、2.4倍和2.3倍,20%中等水解度增加初始入渗效果明显高于7%与35%水解度,PAM的水解度对侵蚀量影响不明显。低分子量PAM链长较短,不能在相邻的黏粒之间形成"搭接桥",使黏结作用减弱,而高分子量PAM分子链过长,难穿透进入土壤团聚体之间的空隙,中等分子量的分子链长处于中间尺度,较易穿透土壤空隙,也可形成土壤颗粒之间搭接,产生较好黏结效果。PAM水解度小,电荷密度小,吸附作用弱,但水解度大,电荷密度大,造成分子链之间互斥作用增强,反而导致PAM黏结作用减弱,因而,中等水解度施用效果较好。 相似文献
9.
Dripper Discharge Rates and the Hydraulic Properties of the Soil 总被引：1，自引：0，他引：1
The hydraulic properties of soils areneeded in predicting runoff and erosion,irrigation design and general transportphenomena in the soil. Theoretical toolshave been developed to estimate them frommeasurements of water distribution near apoint source assuming stable homogeneousand isotropic soils. Soil wetting rate andits interaction with soil texture was notconsidered in these analyses even thoughreports indicated that a high wetting ratedisintegrates soil's aggregates and isassociated with deterioration of soilstructure and reduction of the hydraulicconductivity (HC) and infiltration rates(IR) especially in clay soils. Objectiveswere to: (i) show how IR of a soil, wettedfrom a point source, are affected by thedischarge rate of the dripper. (ii)identify the mechanisms responsible forthis reduction and (iii) investigate theeffect of emitter's discharge on theresultant HC of sand,loam and clay. Werelated the reduction of IR under highemitter discharge to the breakdown of soilaggregates by fast wetting anddeterioration of the hydraulic propertiesof soils, (the pedological mechanism,).Results show that relative to the idealstable soil the steady IR decreased withan increase in the discharge rate of thedripper. The resultant saturated HC(Ks) was, erroneously, negative forclay and loamy soils but not for sand.When determining hydraulic properties ofsoils with a point source, low dischargesshould produce better results especiallyin soils with medium to high clay content. 相似文献
10.
不同PAM施用方法对土壤入渗和侵蚀的影响 总被引：12，自引：3，他引：9
施用土壤调理剂PAM可增加入渗率和减少土壤侵蚀,为了研究不同PAM形态与施用方法对施用PAM效果的影响,该文对3种形态的PAM（溶胶态、溶液与干粉状）以及干粉PAM与石膏混合的2种施用方法进行了试验。结果表明,3种不同形态PAM均能够显著增加土壤入渗、减少侵蚀量。与对照相比,喷洒溶胶和溶液PAM可分别提高土壤稳定入渗率1.0～2.5、1.7～2.8倍,直接施用干粉PAM可提高0.25～1.8倍。综合比较干粉PAM的两种施用方法,地表直接撒施干粉比与土壤混合效果略好一些,与石膏联合施用可明显提高干粉PAM增加入渗效果,并且增加幅度随着石膏混合量增加而增加。地表直接撒施干粉PAM,与对照相比减少土壤侵蚀量最大约80%,可达到施用溶胶态与溶液PAM减少侵蚀相同的效果。干粉PAM与表层土壤混合施用将降低PAM减少侵蚀的效果。增加石膏掺入量可以加强干粉PAM增加土壤入渗、减少径流的效果,但会降低减少土壤侵蚀的作用。综合比较3种形态PAM及干粉PAM施用方法对入渗与侵蚀的影响,直接使用干粉PAM不仅具有较好效果,且施用方法简单易行,适合在旱作农业区推广使用。 相似文献