Long-Term Crop Rotation Effects on Organic Carbon,Nitrogen, and Phosphorus in Haplustoll Soil Fractions

Soil organic matter (SOM) or carbon (SOC) consists of a number of fractions (which can be separated by granulometric wet sieving) having different properties among them. Information on fraction nutrient distribution and long-term crop rotations is lacking for semiarid environments. The objective of this research was to study the agronomic effects on soil OC, N, and P fractions. The humified OC was the largest and least variable fraction of the SOC. Soil under continuous mixed pasture had higher OC contents than under annually tilled treatments. Similarly, soil total nitrogen under the cropped treatments decreased from 1.7 g N kg-¹ in noncultivated soils (reference plots) to 1.0, 0.7 an 0.7 g N kg-¹ under mixed pasture, pasture-crop, and wheat-crop respectively, in the fine soil fraction. The reference plots also showed significantly lower levels of organic phosphorus (P o ) in comparison to the other treatment (from 67.1 w g P o g-¹ to greater than 100 w g P o g-¹ in the fine fraction of the treatments and years). The noncultivated soil showed larger values of P o and inorganic P in the large-size granulometric fraction (0.1-2 mm) than in the soil fine fraction (0-01 mm). However, the rotation treatments had greater concentrations of P in the fine fraction. The P o from the coarse fraction appears to be the most labile and sensitive fraction to tillage and environmental conditions, and may be closely related to P availability.     

Soil Physicochemical Changes Following Buffelgrass Establishment in Mexico

Clearing brush from rangeland and seeding it to buffelgrass (Cenchrus ciliaris L.) is a popular range improvement practice in Mexico, but no data are available on the effects of these practices on soil properties. Twenty-nine study sites were randomly selected across 3 major climatic regions in Mexico: 13 in the northwest, 11 in the northeast, and 5 in the southeast. Soils under buffelgrass stands more than 10 years old and on adjacent virgin rangelands were sampled at 0-10, 10-20, and 20-30 cm depths to quantify sand, silt, clay, organic C, total N, pH, EC, CEC, available P, and exchangeable Ca2+, Mg2+, Na+, and K+.Because soil variables were not significantly (P 0.05) different among depths, only data from the surface horizon received further analysis. Soils in the northwest had higher (P 0.05) sand content and were particularly low in total N (0.08%), Ca2+, and K+, while soils of wetter and warmer southeast Mexico were significantly (P 0.05) higher than the other two regions in measures of soil fertility such as organic C (10 times higher), total N, and CEC (both at least 3 times higher). Long-term buffelgrass establishment had the most effect on soils in the southeast and no significant effect (P0.1) on soils of northeast Mexico. Soil organic C and total N both declined (P 0.025) by about 40% under buffelgrass pastures in the southeast; excgangeable Ca2+ decreased (P=0.027) by 21% in the same region, and Mg2+ declined (P=0.03) by 36% under buffelgrass in the northwest. Soil P did not respond to buffelgrass establishment. The findings of this study suggest that high forage yields following conversion of rangeland to buffelgrass pasture will be less sustainable in subtropical regions with high rainfall (mean of 1070 mm in this study) than in the semiarid zone with inherently poorer soils.     

Straw Management Effects on Organic Matter Mineralization and Salinity in Semiarid Agricultural Soils

The impact of straw incorporation (6 Mg ha -1 year -1 ) into agricultural soils compared with straw removal on organic matter mineralization and salinity was studied. The mineralization coefficient (CO 2 -C evolved/organic C ratio) was obtained to evaluate organic matter mineralization. Soil salinity was measured as means of electrolytic conductivity of saturation paste extract. Both parameters were measured seasonally during two years in two salt-affected soils of the semiarid Central Ebro Valley (northeast Spain), a saline soil and a saline-sodic soil. The electrolytic conductivity (ranging from 2.5 dS m -1 to 24.3 dS m -1 ) and the mineralization coefficient (ranging from 5.9 10 -4 day -1 to 37.9 10 -4 day -1 ) varied widely during seasonal samplings of both soils. The lowest electrolytic conductivity values, coincided with the highest mineralization coefficient values. Straw mulching and burying decreased significantly the average seasonal electrolytic conductivity of both soils: 2.5 times in the saline soil, and 1.9 times in the saline-sodic soil. The EC reduction only increased significantly (P < 0.05) the mineralization coefficient on saline soil (1.6 times). Straw amendment, followed by rainy periods, allowed the soluble salts leaching but did not modify significantly sodium content. A logarithmic regression was found between mineralization coefficient and electrolytic conductivity (r 2 = 0.41), considering both soils. Infiltration, water aggregate stability, and qCO 2 were improved with the straw amendment, but only in saline soil. Soil differences showed the existence of a double effect: an osmotic and a specific ion effect.     

Effects of the invasive shrub,Lantana camara,on soil properties in the Eastern Cape,South Africa

Lantana camara L. is an invasive alien shrub of worldwide significance due to its impacts on biodiversity. It can alter the soil properties of invaded ecosystems and, as a result, affect management outcomes. However, knowledge on the impacts of L. camara on soil properties is scanty, especially in South Africa, despite the pervasive presence of the plant in the country. In this comparative study, the soils underneath L. camara were assessed in order to determine if they had different properties (soil physico‐chemical properties, penetration resistance, infiltration, hydraulic conductivity and water repellency) in comparison to the soils in adjacent natural sites in the Eastern Cape, South Africa. Soil samples were collected from the top soil beneath the canopy of both L. camara‐invaded and adjacent natural sites in five different locations over three summer months. The soils that were collected from underneath L. camara had a significantly higher total C, total P, gravimetric soil moisture (in November and December) and were repellent, compared to the soils in the adjacent natural sites. Soil penetration resistance was significantly higher in the natural sites than in the L. camara‐invaded sites. The soil hydraulic conductivity, soil infiltration rate, soil pH, exchangeable cations and total N showed no significant difference between the invaded and the natural sites. It appears that the soils underneath L. camara have a high total C and total P, soil moisture and are repellent, thus influencing nutrient cycling, potentially making the soil properties underneath it ideal for its own growth. This could contribute to the success of L. camara as an invasive species.     

内蒙古奈曼旗中部地区沙漠化土壤养份动态分析

采用系统取样法在奈曼旗中部沙区草场布置110个监测点,研究沙漠化发展与逆转过程中土壤养分的变化规律。结果表明,在沙漠化发展的初期阶段,土壤养分急剧下降;沙漠化发展到严重阶段时,其养分继续损失并不十分明显。沙漠化逆转过程中土壤养分恢复缓慢,尚不及沙漠化发展过程中土壤养分损失速度的十分之一。     

Distribution of P Forms in Natural and Fertilized Forest Soils of the Central Western Spain: Plant Response to Superphosphate Fertilization

Soil responds dynamically to the addition of phosphates by establishing exchanges among the different reservoirs of P existing in the soil. The aim of this work was to find out the effects of surface applied fertilization with triple superphosphate at two concentrations (50 and 100 kg P ha -1 ) in soils of the Sierra de Gata mountains (Spanish Central System) on forms of soil P, the availability of P for plants, and the impact on above-ground production of the tree cover and grasses. Soil P was deter mined according to Hedley, and P availability was quantified using ion exchange membranes. The effects of P fertilization on P forms were observed mainly in the first 10 cm of the study soils; there were no significant differences at greater depths because of the high P sorption capacity of these soils. With a moderate fertilization of 50 kg P ha -1 only two of the four studied soils showed a significant increase in labile P contents and of P adsorbed by sesquioxides. An intense fertilization (100 kg P ha -1 ) had significant effects on the distribution of soil P, independently of the initial available P of soils. However, fertilization with triple superphosphate did not significantly affect the aerial production of the tree cover (except in the-rst year), whereas it did affect herbaceous production at two sites, possibly because they have a larger root mass near the soil surface.     

Global Assessment of Human-Induced Soil Degradation

Soil is a valuable natural resource that in the short - term is nonrenewable and is difficult to reclaim when degraded. The use of soils on a sustainable basis requires that their capability to withstand the demands upon them is not exceeded. Those people concerned with conservation should be aware of the vital importance of soil for maintaining food supplies for an increasing world population. Increasing demands place a greater strain upon the soil. If the demands become too great, the soil becomes degraded. As soil is the basis of all terrestrial ecosystems, a degraded soil means lower fertility, reduced biodiversity, and human poverty. To provide basic information on soil degradation worldwide, a survey of soil loss through erosion, physical deterioration, and chemical pollution was made. Digital databases are not available to hold information necessary to monitor and combat soil degrada tion at global and national scales. Soil degradation is recognized as a serious and widespread problem, so in September 1987 the International Soil Reference and Information Centre was commissioned to make a survey for a map at a scale of 1:10,000,000 entitled "Global Assessment of Human - Induced Soil Degradation" (GLASOD). Until it was published in 1990, there was no uniformly collected body of information on soil degradation worldwide. The GLASOD survey provides basic data on the world distribution and intensity of erosional, chemical, and physical types of degradation. The original purpose of GLASOD was to provide factual information, to replace sweeping statements about soil and land degradation, and to raise awareness of policy makers and governments for the continuing need for soil conservation. The GLASOD survey also enables comparisons to be drawn between degraded soils of different continents, and the methodology used can be a basis upon which plans for restoration of degraded lands can be based.     

Subsurface Drainage for Rehabilitation of Waterlogged Saline Lands: Example of a Soil in Semiarid Climate

In irrigated agriculture of arid and semiarid regions, soil salinity, coupled with waterlogging, is a serious problem. Provision of subsurface drainage seems to be a prerequisite for optimal crop production. A study was conducted to evaluate the long term (8-year) impact of a subsurface drainage system on soil properties and yields of wheat. The study was located in a severely affected, waterlogged, barren, sandy loamsaline soil (Comborthids). The subsurface drainage system was installed at a 1.75 m depth with three drain spacings (25, 50, and 75 m). The drains facilitated reclamation of the waterlogged saline land which had variations in salt removal with space and time. The removal of salts from the root zone varied initially with distance from the drain and with depth. However, after a few years, the variations were reduced and the land was reclaimed sufficiently to grow most of the crops of the region. Plots provided with a drain spacing of 75 m required more time for complete reclamation compared to plots provided with 25 m drain spacing. Leaching through subsurface drainage increased soil porosity, modulus of rupture, infiltration rate, organic carbon, available nitrogen, phosphorus, potassium, and available water, and decreased bulk density differently in the three drain spacings (20, 50, and 75 m). In the 75 m drain spacing plots, soil salinity (EC e ) and water content remained higher than in the 25 and 50 m drain spacing plots. Soil EC e and water content were less near the drains, were highest in areas midway between the drains, and the effects were more apparent in the summer season. Wheat grain yield decreased with increasing drain spacings in the initial years of reclamation. With the gradual improvement in soil salinity, yields from plots with a 75 m spacing reached those of the narrower drain spacing plots by the fourth year. It was concluded that by installing a subsurface drainage system in a monsoon climate, waterlogged saline soils can be reclaimed by the natural leaching that can take place from rainfall. The optimum yield can be attained with a drain spacing of 75 m, which is 50% more than the design spacing of 50 m. Faster reclamation and more yield were obtained with a 25 m drain spacing and was achieved at a higher cost for the more expensive drainage system.     

The effect of water spreading system on the functionality of rangeland ecosystems

In recent decades, the control of floods is an efficient management practice for the rehabilitation of rangelands in most arid and semiarid areas. To evaluate the benefits, we used the Landscape Function Analysis (LFA) method to assess the function of patches and qualitative capability of a rangeland ecosystem in Gareh Bygone region, Fars province, southwestern Iran. Landscape functionality depends on soil, water and nutrient (collectively called "resources") conservation and use within a given ecosystem. Many landscapes are naturally heterogeneous in terms of resource control and possess patches, where resources tend to accumulate, and inter-patches. Assessing rangeland health and function of landscape patches in response to environment and management can give rise to correct management decisions for qualitative improvement of the ecosystem. Therefore, our study area was divided into two parts, i.e. water spreading and control parts, and sampling was done using LFA method in each part separately. Structural parameters, including the number, length and width of patches, and the mean length of inter-patches, were determined by the method to characterize the functional status of the monitoring sites. For each patch/inter-patch type identified in the transect organization log, we recorded its soil surface properties classified according to the Soil Surface Assessment Method. The density, canopy cover and composition of plants were then assessed. The results showed that the number of ecological patches and their dimensions were significantly increased in the water spreading site. Soil stability and the values of nutrient cycling indices were increased but the infiltration values were decreased in the water spreading site. It could be related to the effect of suspended materials transported by floods to the soils in the study area. The improvement of ecological patches and rangeland ecosystem was achieved where water spreading systems were practiced. Therefore it can be concluded that water spreading as a management plan plays an important role in arid land ecosystem functionality.     

Impacts of livestock grazing on a savanna grassland in Kenya

The dynamics of most rangelands in Kenya remain to be poorly understood.This paper provides baseline information on the response of a semiarid rangeland under different livestock grazing regimes on land inhabited by the Massai people in the east side of Amboseli National Park in Kenya.The data were collected from grasslands designated into four types:(1) grassland from previous Massai settlements that had been abandoned for over twenty years;(2) grassland excluded from livestock grazing for eight years;(3) a dry season grazing area;and (4) a continuous grazing area where grazing occurred throughout all seasons.Collected data included grass species composition,grass height,inter-tuft distance,standing grass biomass and soil characteristics.The results indicated that continuous grazing area in semiarid rangelands exhibited loss of vegetation with negative,long-term effects on grass functional qualities and forage production,whereas grassland that used traditional Maasai grazing methods showed efficiency and desirable effects on the rangelands.The results also showed that abandoned homestead sites,though degraded,were important nutrient reservoirs.     

Variation in soil water content to rainfall under Caragana microphylla shrub in Horqin Sandy Land

In order to investigate the spatio-temporal variability of soil water content to rainfall under Caragana microphylla shrub in Horqin Sandy Land,a plot of 25 m × 25 m,where there were 6 shrub canopies of C. microphylla,was sited for measuring soil water content at two soil layers of 0-20 cm (top layer) and 20-40 cm (lower layer). Soil water content was measured on the 1st,5th,10th and 15th day after a 42 mm rainfall in Naiman of Inner Mongolia. The results showed that soil water contents at both layers under C. microphylla shrub were gradually decreased after the rain. Soil water content at the top layer outside the shrub canopy was higher than that inside the shrub canopy within 5 days,and became similar inside and outside the shrub canopy on the 10th day after the 42 mm rainfall,and it was lower outside than that inside the shrub canopy on the 15th day. The soil water content at lower layer in the area without shrubs was higher than that under shrub canopy all along. All the measured values of soil water content can be fitted to a variogram model. There was significant autocorrelation of the values of soil water content between top layer and lower layer,except for the fourth measured values of soil water content at top layer. The range and spatial dependence of soil water content at top layer were lower than that at lower layer.     

Long-Term Maize,Sorghum, and Millet Monoculture Effects on an Argentina Typic Ustipsamment

Maize, sorghum, and millet monoculture effects on soil properties of a Typic Ustip samment in the semiarid pampa of Argentina were evaluated after 27 years in a plot experiment. A permanent Eragrostis curvula pasture was used as a reference. Millet was the most destructive crop to the soil because it decreased dry aggregate stability by 10%, soil organic matter (OM) by 30%, extractable K by 20%, available P by 44%, inorganic P by 11%, available Fe by 20%, available Zn more than 90%, available Cu by 30%, and available Mn by 26%, and it increased wet aggregate instability by 75%. Grain sorghum was less destructive to the soil than millet because it only decreased OM by 30% and extractable K by 24%. All studied crops decreased the cation exchange capacity of the soil between 20 and 30%, the pH values, and the concentration of soil extractable Mg2+by 38 to 63%. Soil extractable Ca2+ was decreased 30% by the Eragrostis pasture and 40% by maize. The negative effect of millet and grain sorghum on OM was attributed to a low coverage of the soil with plant residues left by these crops as well as the long exposition of the bare soil during temperate and wet periods. Decreases of soil nutrient contents were attributed to plant uptake in all cases, except the Zn concentrations, which were related to variations on soil pH and phosphate concentrations. It was concluded that maize, the most commonly cultivated crop in the region studied, did not affect physical and chemical soil properties to a large extent. Conversely, millet had the most negative effect on physical and chemical properties of the soil.     

Sorghum-cowpea Intercropping: An Effective Technique Against Runoff and Soil Erosion in the Sahel (Saria,Burkina Faso)

In the Central Plateau of Burkina Faso, runoff on bare soil amounts to 40% of annual rainfall and soil losses reach 4 to 8 Mg ha-¹ a-¹, despite slopes of under 3%. Several studies have shown that mulching the soil surface can reduce runoff by over 60%. However, the scarcity of straw and the incompatibility of mulching with mechanical soil preparation have prevented the large-scale adoption of the technique. The study conducted in Saria village where annual rainfall is 800 mm,set out to evaluate the efficacy of sorghum-cowpea intercropping in reducing runoff and erosion. The study design comprised five plots set up so as to recover runoff and transported solids, on a Ferric lixisol with a slope of 0.7%. Three years results showed that sorghum-cowpea intercropping reduces runoff by 20-30% compared to a sorghum monoculture and by 45-55% compared to a cowpea monoculture. Soil loss is also reduced with intercropping by at least a half compared to sorghumand cowpea monoculture. Moreover, it transpired that sorghum-cowpea intercropping is also beneficial in agricultural production terms, since the grain yield of the intercropped plots was double that obtained with sorghumor cowpea monocultures. The better crop production can be an asset for the widespread use of this technique in the country. An evaluation of the advantages of the legume in terms of nitrogen supplies to the cereal (N 2 symbiotic fixation) and of added soil OM will be useful in improving the cost-effectiveness of such a technique.     

黑龙江省耕地土壤养分贫瘠化研究

在Arcgis空间分析功能和SPSS数理统计功能支持下,利用隶属度模型、层次分析法、综合指数模型、障碍度诊断模型、叠加法等方法,分析黑龙江省耕地土壤养分贫瘠化状况与区域生态问题,诊断识别耕地土壤养分障碍因子与最佳量化表征性指标,空间表达土壤养分障碍类型区。结果表明:(1)全省70.58%耕地处于轻度及以上土壤养分贫瘠程度,从西南到东北逐渐减弱,其中重度贫瘠区主要分布在松嫩平原西部,占耕地面积的2.95%,农田生态问题是土壤沙化严重,中度贫瘠区主要分布在松嫩平原中部构造上属于断陷的中央凹陷区、三江平原西北部处于山前平原向平原的过渡带,占耕地面积的41.09%,农田生态共性问题为易积水,其中松嫩平原还存在土壤盐渍化问题,轻度贫瘠区主要分布在松嫩平原东部、东北和东南地区,少量分布在三江平原西部、西北和西南部,占耕地面积的26.54%,农田生态问题是水土流失;(2)有机质和全氮是区域土壤养分贫瘠化的主要障碍因素,累积占比达88.37%;(3)有机质是耕地土壤养分贫瘠化指数及养分因子含量最佳量化表征性指标;(4)区域47.92%的耕地存在中度及以上障碍因子,障碍类型区共计14类,以双因素MC-MN,三因素MC-MN-MP、MC-MN-MK占比最大,累积占比率为39.84%。     

短期N、P添加对荒漠草原土壤非保护性有机碳的影响

以干旱、半干旱地区荒漠草原土壤为研究对象,研究N、P养分添加对荒漠草原0~30 cm土层土壤颗粒有机碳和轻组有机碳含量、分配比例、敏感指数的影响,探讨荒漠草原土壤非保护性有机碳分配比例及其向保护性有机碳的转化速率对N、P添加的响应。研究结果表明:短期N、P添加能促进荒漠草原表层土壤(0~10 cm)土壤颗粒有机碳和轻组有机碳的积累,分别使其增加了50%~70%、15%~31%。短期N、P添加显著增加土壤非保护性有机碳分配比例(25%~52%),而降低了土壤非保护性有机碳向保护性有机碳转化速率常数(24%~42%)。荒漠草原土壤有机碳主要以非保护性有机碳形式储存,短期N、P添加通过影响土壤非保护性有机碳分配比例,使土壤肥力提高,土壤有机碳的活性组分增加,不利于土壤有机碳的稳定。     

Rhizosphere organic phosphorus fractions of Simon poplar and Mongolian pine plantations in a semiarid sandy land of northeastern China

The aim of this study was to investigate the role of rhizosphere organic phosphorus(P) in soil P supply in semiarid forests and the effects of tree species on rihizosphere organic P. We examined organic P fractions in rhizosphere and bulk soils of mono-specific Simon poplar(Populus simonii) and Mongolian pine(Pinus sylvestris var. mongolica) plantations in a semiarid sandy soil of Horqin Sandy Land in Northeast China. Total organic P(TPo) accounted for 76% of total P across the two stands. The concentration of organic P(Po) fractions decreased in the order of Na OH-Po>Res-Po>HCl-Po>Na HCO3-Po in both plantations. The concentration of Na HCO3-Po was 38% and 43% lower in rhizosphere soil than in bulk soil in Simon poplar and Mongolian pine plantations, respectively. In contrast, total P, TPo and Na OH-Po significantly accumulated in rhizosphere soil in Simon poplar plantations, but no change in Mongolian pine plantations. Soil recalcitrant organic P fractions were positively correlated with soil organic carbon. The results suggest that rhizosphere labile organic P was an important source of plant-available P in this semiarid region, but the dynamic of rhizosphere recalcitrant organic P fractions varied with tree species and was correlated to organic carbon dynamics.     

黄土高原森林草原区退耕还林还草土壤保持效应评估

黄土高原地处生态过渡带和环境脆弱区,区内大范围的土壤侵蚀严重影响了当地的生态环境。以黄土高原森林草原区为研究对象,应用修正通用土壤流失方程,根据2000、2005、2010年气象数据及土地利用等数据,从不同坡度、植被覆盖度、土地利用类型评估了黄土高原森林草原区退耕还林还草工程的土壤保持效应。结果表明,(1)随着退耕还林还草工程的实施,林地和草地面积明显增加,分别增加2 219.41 km~2、2 205.27 km~2,研究区植被覆盖度逐渐改善。(2)2000—2010年土壤保持量增加2.41亿t,单位面积土壤保持量由3 033.15 t·km~(-2)·a~(-1)增加至5 114.86 t·km~(-2)·a~(-1),土壤保持效应显著提升。(3)研究区土壤保持效应与植被覆盖度呈正相关关系,在不同土地利用类型中,林地、草地和耕地具有较高的土壤保持效应,单位面积土壤保持量分别为5 405.57、3 598.41、3 078.81 t·km~(-2)·a~(-1)。退耕还林还草工程的实施提升了区域的土壤保持效应,但是,区内东北部由于矿产资源开采导致的植被破坏、地表塌陷以及土壤侵蚀问题亟待解决。     

晋西黄土区核桃-谷子间作系统水肥影响域

为了定量判定晋西黄土区果农间作系统水肥主要竞争区域,以核桃-谷子间作系统为研究对象,对土壤水分和土壤养分进行定位监测,采用移动窗口法定量判定间作系统中土壤水分和土壤养分的影响域。结果显示:当窗口宽度为2时,移动窗口法能有效地判定出土壤水分和土壤养分的影响域。40~100 cm土层,距树行不同距离处的土壤水分和土壤养分含量相异性较小,难以判定影响域;综合0~40 cm、0~100 cm土层的土壤水分状况,土壤水分的影响域范围是距树南侧1.75 m到距树北侧1.25 m,影响宽度为3 m,即主要竞争区域为距树南侧1.75m到距树北侧1.25 m;不同的土壤养分指标影响域的范围不同,综合考虑土壤养分的四个不同指标(有机质、全氮、速效磷和速效钾)及其在0~40 cm、0~100 cm两个土层的分布情况,土壤养分的影响域是距树南侧2.25 m到距树北侧2.25 m,影响宽度为4.5 m,即主要竞争区域为距树南侧2.25 m到距树北侧2.25 m。建议在土壤水分和土壤养分的主要竞争区域,采取改变垄沟、起垄覆膜、选择性施肥等措施,缓解核桃、谷子之间的竞争,提高资源利用效率,增加当地农民经济收入。     

宁南山区土地利用和开发战略探讨

宁南山区地表结构复杂，是典型的温带大陆性半干旱偏旱季风气候。在调查分析土地利用现状特点和存在问题的基础上，提出统一规划，合理布局；增加肥料投入，改良培肥土壤；推广和使用旱作农业丰产技术，发展集流农业和节水灌溉技术；开发区域名优特产，建立绿色食品生产基地；以饲草生产为突破口，加速发展畜牧业经济的区域土地开发战略措施。     

Nematode Population Dynamics under the Canopy of Desert Halophytes

The effects of soil conditions on nematode populations were investigated in a field study at the Avdat Research Farm, Israel. Soil samples from the upper soil layer (0-10 cm) were collected monthly during November 1997 and October 1998, under the canopy of three halophyte shrubs: Zygophyllum dumousum, Hammadetum scopariae and Reaumuria negevensis. Ecological indices such as fungivore to bac terivore ratio (F/B), ratio of fungivores and bacterivores to plant parasites (WI), trophic diversity (TD) and Shannon index (H') were used to assess and compare the response of nematode populations to the soil conditions. The mean numbers of total nematodes during January 1998 April 1998 were less under Z. dumosum than under H. scoparia, and those of total nematodes during April 1998 October 1998 were higher under R. negevensis than under the control soil. Bacterivores under the three shrubs were the most abundant trophic group. Significant differences were found between months and between treatments for total nematodes, bacterivores and plant parasites. The content of K + exhibited a positive correlation with total nematodes, bacterivores, plant parasites and omnivores-predators, and that of Ca 2+ presented a negative correlation with bacterivores. F/B, WI, TD, and H' were effetive in distinguishing differences in nematode populations during the study period.