排序方式： 共有29条查询结果，搜索用时 52 毫秒
1.
J. G. Wesseling C. R. Stoof C. J. Ritsema K. Oostindie & L. W. Dekker 《Soil Use and Management》2009,25(3):274-283
To gain more insight into the hydrological behaviour of coarse-textured soils, the physical properties of artificially created soil mixtures with different texture were determined. The mixtures were prepared according to the specifications of the United States Golf Association (USGA) for constructing putting greens. In addition, the effect of 10 vol.% organic matter addition was studied. The soil moisture retention and hydraulic conductivity relationships of the different mixtures were determined and their hydrological behaviour was studied using the numerical model SoWaM. Both texture and organic matter addition substantially affected the hydraulic properties. Hydraulic conductivity significantly increased with increasing coarseness while moisture retention decreased. On the other hand, organic matter addition reduced saturated hydraulic conductivity by a factor of 10 to 100 and distinctly increased moisture retention capacity. The amounts of total available water were increased by the addition of organic matter between 144% (slightly coarse texture) and 434% (very coarse texture). Results indicate that the mixtures can contain only 2–16% plant available water and therefore need frequent irrigation to maintain plant growth. Addition of organic matter seems a good solution to reduce the irrigation water requirements but it increases the risk of ponding or runoff because of large reductions in the saturated hydraulic conductivity sometimes to below the rate of 3.6 m/day recommended by the USGA. 相似文献
2.
Piovano M Chamy MC Garbarino JA Tita B Vitalone A Di Fabio A Nicoletti M 《Fitoterapia》2003,74(5):497-500
The crude methanolic root extract of Myoschilos oblongum exhibited a significant cytotoxic activity against PZ-HPV-7 human prostate cells. Furthermore, two esters of docosanol were isolated from the CH(2)Cl(2) extract. 相似文献
3.
African hot spot volcanism: small-scale convection in the upper mantle beneath cratons 总被引：2，自引：0，他引：2
Numerical models demonstrate that small-scale convection develops in the upper mantle beneath the transition of thick cratonic lithosphere and thin oceanic lithosphere. These models explain the location and geochemical characteristics of intraplate volcanos on the African and South American plates. They also explain the presence of relatively high seismic shear wave velocities (cold downwellings) in the mantle transition zone beneath the western margin of African cratons and the eastern margin of South American cratons. Small-scale, edge-driven convection is an alternative to plumes for explaining intraplate African and South American hot spot volcanism, and small-scale convection is consistent with mantle downwellings beneath the African and South American lithosphere. 相似文献
4.
Wetting front instability resulting in fingered flow has been found in both wettable and nonwettable soils. Understanding how and when this phenomenon occurs under field conditions is greatly limited. Laboratory research has resulted in a number of expressions for finger diameter. In this paper we test the applicability of one of these equations for three different soils in the Netherlands where detailed soil sampling of moisture content was done earlier. In addition, information needed for finger prediction, such as the main wetting and drying loops of the soil moisture characteristic curves and the unsaturated and saturated soil conductivities, were measured in the laboratory. Results show that predicted finger diameters for the two sandy soils agreed well with the observed moisture patterns, while for the loess soil the wetting front was flat as predicted. The finger diameters in dry soil were based on the main wetting loop and in the wet soils were dependent on the main drying loop. 相似文献
5.
对在pH6.5时含不同浓度锰、锌、铁和铅的培养液中,预处理3天的Pistia stratiotes 叶片,进行了O_2的吸收与释放及其叶绿素a,b含量的测定。结果表明:4种金属离子抑制O_2的释放而促进叶片对O_2的吸收。锌预处理可以提高叶绿素a,b的含量,而铅使叶绿素含量减少。用铁和锰处理时,可使叶绿素a积累而叶绿素b减少。上述结果意味着金属离子防碍叶绿素的形成及光合电子的转移。 相似文献
6.
Isaurinda Baptista Brian Irvine Luuk Fleskens Violette Geissen Coen Ritsema 《Land Degradation \u0026amp; Development》2016,27(7):1679-1690
Field trials have demonstrated the potential of soil conservation technologies but have also shown significant spatial–temporal yield variability. This study considers the Pan‐European Soil Erosion Risk Assessment – Desertification Mitigation Cost‐Effectiveness modelling approach to capture a greater range of climatic conditions to assess the potential effect of an improved agricultural management practice emerged from field trials as a promising strategy for enhancing food security and reducing soil and land degradation. The model considers the biophysical and socio‐economic benefits of the improved soil conservation technique (T3) – residue mulch combined with pigeon pea hedges and an organic amendment, against a local baseline practice (T0). The historic rainfall statistics and 50‐year rainfall realizations provide a unique time series of rainfall and an envelope of the potential crop yield. Envelopes of potential biomass production help express the agricultural risk associated with climate variability and the potential of the conservation measures to absorb the risk, highlighting the uncertainty of a given crop yield being achieved in any particular year. T3 elevates yield under both sub‐humid and semi‐arid climates with greater security for sub‐humid areas even though risk of crop failure still exists. The technology offered good potential to increase yields by 20% in 42% of the dryland area in Santiago Island and reduce erosion by 8·6 Mg ha−1, but in terms of cost‐effectiveness, it might be prohibitively expensive for farmers lacking inputs. The findings can enable the assessment of policy options at larger scale or influence adoption of improved conservation measures under the climatic variability of the Cabo Verde drylands and resilience to future climate change. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
Visualization techniques are helpful in finding spatial relationships of parameters which are otherwise difficult to detect. In this study, visualization techniques were used to examine the basis of moisture distribution patterns in a clay soil and a water repellent sandy soil. In the clay soil, spatial distributions of moisture contents and macropore networks were investigated with computed tomography (CT) images. The macropore networks were determined from CT images from a dry soil core, and the moisture content patterns from CT images after which KI enriched water was applied. Soil moisture and bulk density were investigated and measured in a water repellent sandy soil by intensive sampling of an area 1.2 m long and 0.6 m wide. The measured parameters were visualized in three dimensions using IRIS Explorer on a SGI-Indigo and a SGI-Onyx computer. The 3D computer representations showed that there exists a strong correlation between the moisture content distribution and the geometrical structure of the macropore network for a clay soil. Moisture contents higher than 30% were mostly found inside the upper part of the macropore network and lateral branches of the macropore network were significant drier than the downwards directed branches. The visualizations of the water repellent sandy soil revealed several 10 to 20 cm wide “fingers” starting around 10 cm depth at locations with the highest bulk densities. 相似文献
8.
Fernando Teixeira Tatenda Lemann Carla Ferreira Matjaž Glavan Tóth Zoltán Tamás Hermann Jerzy Lipiec Magdalena Frąc Endla Reintam Minggang Xu Hongzhu Fan Coen Ritsema 《Soil Use and Management》2023,39(1):474-484
This study investigates 11 agricultural management practices (AMPs) and their effects on seven visual soil quality indicators and soil aggregate stability. The survey carried out across eight pedoclimatic zones in Europe and China was based on visual soil assessments (New Zealand VSA method) performed on soils subject to different soil management practices and nearby similar soils, under similar farming features, without the distinctive soil management practice (control). Fisher's exact test was used to test if the management treatment was independent of the score of each visual soil quality indicator and to test if the management treatment produced a higher frequency of the score ‘good’. The results showed a statistically significant (α < .05) higher frequency of the score ‘good’ for ‘soil structure and consistency’ and/or ‘soil porosity’ for six AMPs. For no-till AMP, the null hypothesis can also be rejected for ‘susceptibility to erosion’ and ‘soil stability’ and for ‘mulching + permanent soil cover’ AMP, for the ‘presence of tillage pan’ and ‘soil colour’. The hypothesis that the management treatment was independent of the score of each indicator was rejected for ‘soil structure and consistency’ of three AMPs, for ‘soil porosity’ of three AMPs, for ‘soil colour’ of one AMP and for the ‘presence of tillage pan’ of one AMP. This study demonstrates that farming systems sharing a common influential soil management practice at different locations and with different soil types significantly affect the score of some visual soil quality indicators. 相似文献
9.
Innocent Nzeyimana Alfred E. Hartemink Coen Ritsema Jean Jacques M. Mbonigaba Violette Geissen 《Soil Use and Management》2020,36(1):58-70
Different combinations of organic mulch were applied in smallholder coffee farming systems to assess their effects on soil nutrient contents and coffee yield at three sites in different agro-ecological zones in Rwanda. Mulching systems consisted of Cymbopogon spp. (T1), Panicum spp. (T2), Cymbopogon spp. and Panicum spp. (T3), Eucalyptus spp. and Cymbopogon spp. (T4), mixed residues (T5) and un-mulched coffee used as control (T6). Mulch had significant and specific effects at each site (p < 0.001). T3 reduced soil pH value and exchangeable acidity at Kibirizi, while at Karongi and Ruli, these effects were observed with T4 and T5. T4 and T5 significantly increased the content of soil carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). The amount of nutrients released was regulated by the amount and type of mulch applied, the agro-ecological conditions and the soil properties at each site. The increased soil nutrient levels led to improved soil fertility conditions and increased coffee yields. The coffee yields were significantly increased with T1 at Karongi (p < 0.05) by up to 1.9 t ha−1. T2 and T3 had significantly higher yields at Kibirizi. Yields at Kibirizi were 48% lower compared to yields at Karongi; at this site, T1, T2, T3, T4 and T5 increased yields by 57%, 26%, 31%, 20% and 28%, respectively, when compared to the no mulching treatment (T6). However, coffee yields over 1.9 t ha−1 can only be obtained with additional applications of inorganic fertilizer at different rates depending on the agro-ecological zone and soil type. 相似文献
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