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1.
不同质地土壤上烤烟氮素积累、分配及利用率的研究 总被引：7，自引：0，他引：7
【目的】土壤质地能概括反映土壤内在的肥力特征,对土壤养分供应具有调控作用,是影响农田中土壤氮素供应和氮肥利用的重要因素。本试验通过在皖南烟区3种质地(壤土、黏壤、砂壤)土壤上施用等量氮肥来研究其对烤烟不同生育期的氮素吸收、积累及利用特征的影响,旨在为烟田土壤改良及烤烟合理施肥提供理论依据。【方法】在皖南烟区现代农业科技园的典型壤土、黏壤和砂壤土上分别建立田间试验,采用15N田间微区试验和室内分析相结合的研究方法,在烤烟的团棵期(移栽后38 d)、现蕾期(移栽后53 d)、平顶期(移栽后64d)和成熟期(移栽后103 d),采集长势一致的烟株样品,测定烟株各部位的生物量,并采用凯氏定氮法检测其全氮含量,采用ZHTO2型同位素质谱仪测定其15N丰度。【结果】皖南烟区壤土和黏壤土上烤烟总氮和肥料氮积累均随生育期呈单峰变化,在烤烟平顶期达最大,总氮积累量分别为4.25 g/plant和3.96 g/plant,肥料氮积累量分别为2.34 g/plant和2.54 g/plant,而砂壤土上烤烟到成熟期其总氮和肥料氮的积累量达到最大,分别是5.64 g/plant和2.73 g/plant,均显著高于同时期的壤土和黏壤;壤土、黏壤和砂壤土上烤烟均以叶部肥料氮占总氮比例及氮素分配率较高,茎部次之,根部最低;不同质地土壤上烤烟氮肥利用率与肥料氮的积累动态具有一致的变化趋势,其中壤土和黏壤在平顶期最大,分别为34.5%和40.7%,之后壤土利用率缓慢下降,黏壤下降幅度较大,而砂壤土上烤烟氮肥利用率在生育期内呈上升趋势,至成熟期最大,为43.7%。【结论】不同质地土壤上烟株对氮素的吸收利用顺序为砂壤壤土黏壤,黏壤土在烤烟生育期内供氮能力较弱,应合理调控土壤氮的矿化及增加肥料氮的供应;砂壤土氮肥利用率较高,应严格控制氮肥的施用量。 相似文献
2.
不同土壤质地和含水率对炭基肥料氮素矿化的影响 总被引：1，自引：2，他引：1
为了探究土壤特性对炭基肥料氮素矿化的影响,采用室内培养和大田小区试验,分析了炭基肥在不同土壤质地(砂质壤土、粉砂质壤土、黏土)及含水率(80%、60%、40%田间最大持水量)条件下,氮素矿化动态变化特征。结果表明:在室内培养条件下,对于不同土壤质地,炭基肥在砂质壤土条件下矿化势最高,其次为黏土,最低的为粉砂质壤土;对于不同田间持水量,在粉砂质壤土条件下,炭基肥矿化势最高的为80%田间最大持水量(80%SMC),其次为60%SMC,最低的是40%SMC;在砂质壤土和黏土条件下,炭基肥的矿化势均表现为60%SMC>80%SMC>40%SMC。培养状态下粉砂质壤土、砂质壤土、黏土条件下最大氮素有效性分别是34.12%、56.31%、41.14%,而在大田条件下,炭基肥单季氮素最大矿化率在粉砂质壤土、砂质壤土、黏土3种土壤质地下分别是50.61%、32.27%、34.29%。 相似文献
3.
《Communications in Soil Science and Plant Analysis》2012,43(21):2778-2793
This research aimed to determine the optimum nitrogen fertilization rate on three soils for producing biomass sweet sorghum (Sorghum bicolor cultivar M81E) and corn (Zea mays cultivar P33N58) grain yield and to compare their responses. The research was conducted in Missouri in rotations with soybean, cotton, and corn. Seven rates of nitrogen (N) were applied. Sweet sorghum dry biomass varied between 11 and 27.5 Mg ha?1) depending on year, soil type, and N rate. Nitrogen fertilization on the silt and sandy loam soils had no effect (P > 0.05) on sweet sorghum yield grown after cotton and soybean. However, yield increased in the clay soil. Corn grain yielded from 1.3 to 12.9 Mg ha?1, and 179 to 224 kg N ha?1 was required for maximum yield. Increasing biomass yield required N application on clay but not on silt loam and sandy loam in rotations with soybean or cotton. 相似文献
4.
Maize growth responses to deep tillage, straw mulching and farmyard manure in coarse textured soils of N.W. India 总被引：1，自引：0，他引：1
Abstract. The effects of deep tillage, straw mulching and farmyard manure on maize growth in loamy sand and sandy loam soils were studied in experiments lasting three years. Treatments included all combinations of conventional tillage (10 cm deep) and deep tillage (35–40 cm deep), two farmyard manure rates (0 and 15 t/ha) and two mulch rates (0 and 6 t/ha), replicated three times in a randomixed block design.
Deep tillage decreased soil strength and caused deeper and denser rooting. Mulching decreased maximum soil temperature and kept the surface layers wetter resulting in better root growth. Farmyard manure also improved root growth, and the crop then extracted soil water more efficiently. All three treatments increased grain yield in the loamy sand, but in the sandy loam only tillage and farmyard manure increased yields significantly. Deep tillage and straw mulch effects varied with soil type and amount of rainfall in the growing season. In the loamy sand the mean responses to deep tillage and mulching were largest in a dry year. A tillage-mulch interaction was significant in the loamy sand. 相似文献
Deep tillage decreased soil strength and caused deeper and denser rooting. Mulching decreased maximum soil temperature and kept the surface layers wetter resulting in better root growth. Farmyard manure also improved root growth, and the crop then extracted soil water more efficiently. All three treatments increased grain yield in the loamy sand, but in the sandy loam only tillage and farmyard manure increased yields significantly. Deep tillage and straw mulch effects varied with soil type and amount of rainfall in the growing season. In the loamy sand the mean responses to deep tillage and mulching were largest in a dry year. A tillage-mulch interaction was significant in the loamy sand. 相似文献
6.
Crop yield and SOC responses to biochar application were dependent on soil texture and crop type in southern Quebec,Canada 
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下载免费PDF全文 Rachel G. M. Backer Timothy D. Schwinghamer Joann K. Whalen Philippe Seguin Donald L. Smith 《植物养料与土壤学杂志》2016,179(3):399-408
Changes to soil nutrient availability and increases for crop yield and soil organic C (SOC) concentration on biochar‐amended soil under temperate climate conditions have only been reported in a few publications. The objective of this work was to determine if biochar application rates up to 20 Mg ha?1 affect nutrient availability in soil, SOC stocks and yield of corn (Zea mays L.), soybean (Glycine max L.), and switchgrass (Panicum virgatum L.) on two coarse‐textured soils (loamy sand, sandy clay loam) in S Quebec, Canada. Data were collected from field experiments for a 3‐y period following application of pine wood biochar at rates of 0, 10, and 20 Mg ha?1. For corn plots, at harvest 3 y after biochar application, 20 Mg biochar ha?1 resulted in 41.2% lower soil NH on the loamy sand; the same effect was not present on the sandy clay loam soil. On the loamy sand, 20 Mg biochar ha?1 increased corn yields by 14.2% compared to the control 3 y after application; the same effect was not present on the sandy clay loam soil. Biochar did not alter yield or nutrient availability in soil on soybean or switchgrass plots on either soil type. After 3 y, SOC concentration was 83 and 258% greater after 10 and 20 Mg ha?1 biochar applications, respectively, than the control in sandy clay loam soil under switchgrass production. The same effect was not present on the sandy clay loam soil. A 67% higher SOC concentration was noted with biochar application at 20 Mg ha?1 to sandy clay loam soil under corn. 相似文献
7.
毛管埋深和层状质地对番茄滴灌水氮利用效率的影响 总被引：7，自引：3，他引：4
为了确定不同质地土壤中地下滴灌的适宜毛管埋深,通过两年日光温室滴灌施肥灌溉试验,研究了毛管埋深、土壤层状质地和施氮量对番茄产量、品质及水分利用效率（WUE）、氮肥表观利用率（AFUE）和氮肥偏生产力（PFP）的影响。研究结果表明,均质壤土中,毛管埋深、施氮量及其交互作用对番茄产量和WUE影响不显著,地下滴灌番茄Vc含量比地表滴灌低;番茄AFUE随毛管埋深增加而降低,施氮量由150 kg/hm2增加到225 kg/hm2时,番茄PFP显著降低。对均质壤土,建议毛管埋深15 cm、施氮量150 kg/hm2,以获得较高的PFP。土壤的层状质地结构明显降低番茄的产量、WUE和PFP,与均质壤土处理相比,上砂下壤和砂土夹层处理WUE分别低32%和11%,产量和PFP分别低33%和12%,从提高水氮利用效率的角度出发,建议在上粗下细（上砂下壤）的层状土壤中慎重使用地下滴灌。 相似文献
8.
不同土质工程堆积体径流产沙差异 总被引：13，自引：3，他引：10
依据野外调查结果概化堆积体下垫面,采用室内人工模拟降雨方法,研究不同雨强(1.0、1.5、2.0、2.5 mm/min)条件下4种砾石质量分数(0、10%、20%、30%)的壤土、黏土及砂土工程堆积体径流产沙特征差异。结果表明:1)砂土堆积体坡面产流开始所需时间较壤土及黏土堆积体长。3种土壤质地工程堆积体含砾石的平均流速较纯土体(砾石质量分数为0)小,大小表现为黏土壤土砂土。砂土堆积体平均径流率较壤土和黏土分别减少20.7%和18.8%;2)砂土堆积体平均侵蚀速率分别是壤土和黏土的3.0和2.3倍。3种土壤质地工程堆积体的平均侵蚀速率随雨强增大递增,但随砾石质量分数递增呈显著线性递减(P0.05);3)砂土堆积体平均侵蚀量分别是壤土和黏土的4.5和3.4倍。3种土壤质地工程堆积体的侵蚀量与径流量和雨强均显著相关。研究成果可为建立生产建设项目工程堆积体水土流失量测算模型提供数据基础和理论依据。 相似文献
9.
《Communications in Soil Science and Plant Analysis》2012,43(22):2935-2946
The concern for groundwater pollution by agrichemicals through solute movement within the soil is widespread. Zeolite is a type of soil amendment that is utilized to improve physical properties of soil and ameliorate polluted soil. The high negative charge of the zeolite and its open space structure allows adsorption and access of heavy metals and other cations and anions. The objectives of this research were (i) to determine the effects of different application rates of zeolite (0, 2, 4, and 8 g kg?1) on the immobile water content and mass exchange coefficient in a loam soil and then (ii) to determine the effects of optimum application rate of zeolite on the immobile water content and mass exchange coefficient of sandy loam and clay loam soils in saturated conditions by a mobile and immobile (MIM) model. In a disturbed soil column, a method was proposed for determination of MIM model parameters, that is, immobile water content (θim), mass exchange coefficient (α), and hydrodynamic dispersion coefficient (Dh). Breakthrough curves were obtained for different soil textures with different zeolite applications in three replicates, by miscible displacement of chloride (Cl?1) in disturbed soil column. Cl?1 breakthrough curves were evaluated in terms of the MIM model. The results showed that the pore water velocity calculated based on the total soil volumetric water content (θim+ θm) and real pore water velocity calculated based on the mobile water content (θm) increased in the loam soil with an increase in zeolite application rate, so that, between these different rates of zeolite application, the maximum value of pore water velocity and real pore water velocity occurred at zeolite application rates of 8.6 and 11.5 g kg?1, which are indicated as the optimum application rates. However, the comparison between different soils showed that the zeolite application rate of 8 g kg?1 could increase pore water velocity of sandy loam and loam soils by 31% more than that of clay loam soil. The immobile water content and mass exchange coefficient of loam soil were correlated with the zeolite application rate and reduced with an increase in the rate of applied zeolite. In a comparison between different soils at zeolite application rate of 8 g kg?1, the immobile water contents of the zeolite-treated soil decreased by 57%, 60%, and 39% on sandy loam, loam, and clay loam soils, respectively, compared with the untreated soil. Furthermore, zeolite application could reduce mass exchange coefficient by 9%, 43%, and 21% on sandy loam, loam, and clay loam soils, respectively. A positive linear relationship was found between θim and α. Zeolite application increased real pore water velocity of sandy loam soil by 39% and 46% compared with loam and clay loam soils, respectively. In other studies there was a decrease in ammonium and nitrate leaching due to the zeolite application, and therefore, an increase in real pore water velocity due to zeolite application in sandy loam soil, as compared with the loam and clay loam soils, may not show more rapid movement of solute and agrichemicals to the groundwater. 相似文献
10.
Ingrid K. Thomsen 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):166-170
Abstract Four rates of straw (0, 4, 8 and 12 t ha?1 yr?1) were incorporated in a field experiment with continuous spring barley. The experiment was conducted on a sandy soil (5.5% clay) and a sandy loam soil (11.2% clay). After eight years, the straw incorporation was combined with catch-crop growing with and without winter application of animal slurry and also spring fertilization with mineral fertilizer (0, 50, 100 or 125 kg N ha?1 yr?1). The combined experiment was conducted for three lyears on the sandy soil and for four years on the sandy loam soil. The effects on barley dry matter yield and N uptake are presented together with the long-term effects of the straw incorporations on crop growth and soil C and N. Grain yield on the sandy loam was unaffected by straw incorporation. On the sandy soil the highest straw application rates reduced grain yield in the unfertilized barley. When the barley received mineral fertilizer at recommended levels (100 kg N ha?1 yr?1), grain yield on this soil was also unaffected by the high straw rates. Including a catch crop had a positive effect on the grain yield of barley on both soils. The total N uptake in grain and straw generally increased with straw application up to 8 t ha?1 yr?1. With the highest straw application rate (12 t ha?1 yr?1), the total N uptake decreased but still exceeded N uptake in barley grown with straw removal. The barley accumulated higher amounts of N when a catch crop was included. The total N uptake in the barley was significantly higher after animal slurry application. The extra N uptake, however, was much lower than the amounts of N applied with the slurry. Incorporation of straw had only a small influence on N uptake after slurry application. The straw, therefore, was not able to store the applied N during winter. In the two four-year periods before the combined experiment, grain yield on the sandy loam was generally negatively affected by straw incorporations. In the second period, N uptake began to show a positive effect of the straw. On the sandy soil, grain yield and N uptake during the whole period were generally positively affected by the straw incorporations except for the highest straw rate (12 t ha?1 yr?1). The sandy loam soil showed higher increases in C and N content after the repeated straw incorporations and catch-crop growing than the sandy soil. When application of animal slurry was combined with the catch crop, no further increases in soil C and N were found relative to soil where a catch crop was grown without slurry application. Large amounts of the N applied with the slurry may therefore have been lost by denitrification or nitrate leaching. 相似文献
11.
容重对土壤水分入渗能力影响模拟试验 总被引：59，自引：21，他引：38
通过人工改变土壤颗粒级配,配制典型砂壤、中壤、黏壤,并设置不同容重水平,用土柱积水入渗模拟了土壤容重对其入渗能力的影响,为土壤改良和促进天然降水转化利用提供理论依据。结果表明,容重对土壤入渗能力有较大影响。试验土壤入渗能力随容重增大递减,3种典型土壤稳定入渗速率与容重均呈对数负相关,砂壤120 min累积入渗量与容重呈幂函数负相关,中壤、黏壤则呈线性负相关。考斯加科夫入渗模型中,表征初始入渗速率的参数随容重增大递减,表征入渗能力衰减速度的参数则随容重增大递增,说明土壤初始入渗能力随容重增大递减,入渗能力衰减速度随容重增大递增。 相似文献
12.
H. C. F. Riley M. A. Bleken S. Abrahamsen A. K. Bergjord A. K. Bakken 《Soil & Tillage Research》2005,80(1-2):79-93
Tillage trials were established on a poorly drained silty loam overlying silty clay loam and on a freely drained sandy loam overlying medium sand, in 1988 and 1989, respectively. Autumn and spring ploughing and two ploughless systems were compared for 12–13 years, with three replications at each site. The ploughless treatments comprised deep versus shallow spring harrowing until 1999, and thereafter autumn plus spring harrowing versus spring harrowing only. In 6 years, treatments with and without fungal spraying of the cereal crops were included. In other years, fungicides were not used. Perennial weeds were controlled by herbicides as necessary, on nine occasions up until 2001. Average spring barley (Hordeum vulgare L.) and spring oat (Avena sativa L.) yields were similar with spring ploughing as with autumn ploughing at both sites. In treatments without ploughing, average yields on the silty loam over clay were 93% of those obtained with ploughing, and on the sandy loam over sand they were 81%. Smaller and non-significant yield differences were found between spring harrowing versus deep spring harrowing, and between autumn plus spring harrowing versus spring harrowing only. Fungal spraying increased yields markedly at both sites (25%), but there was no significant interaction between this treatment and tillage system. Oat was compared with barley in 2 years, with oat performing better under ploughless tillage. At both sites increases in penetrometer resistance occurred in the topsoil of unploughed treatments. These were considered particularly limiting on the sandy loam. On the silty loam there was an increase in surface horizon porosity in the absence of ploughing, which was associated with an increase in topsoil organic matter content. On this soil there was also a tendency toward lower penetrometer resistance at >30 cm depth on autumn plus spring harrowed soil than on ploughed soil, indicating that the plough pan may have diminished. This was supported by observations of greater earthworm activity on unploughed soil. Soil chemical analyses revealed that mineral N and plant-available P and K accumulated in the upper horizon under ploughless tillage. The percentage yields obtained in individual years with autumn as opposed to spring ploughing, were positively correlated with air temperature during 0–4 weeks after planting on the silty loam, and with precipitation during 0–12 weeks after planting on the sandy loam. In the case of yields obtained with spring harrowing only, relative to spring ploughing, positive correlations were found with 0–4 week temperature on both soil types, suggesting that low early season temperatures may limit yields under ploughless tillage. 相似文献
13.
不同质地小麦根际土壤有机碳、氮含量及特性研究 总被引：3，自引：0，他引：3
测定了两种不同质地土壤小麦根际土及非根际土中不同形态有机碳、氮的含量及特性。结果表明,粘壤土及砂质壤土两种不同质地土壤小麦根际土中有机碳、可溶性有机碳(WEOC),土壤全氮、可溶性有机氮(WEON)、游离氨基酸及硝态氮和铵态氮均显著高于非根际土;根际土及非根际土中WEON的含量均高于硝态氮及铵态氮含量,其在根-土界面氮素转化中的作用值得关注。不同质地土壤相比,粘壤土中各指标的含量均显著高于砂质壤土。根际土有机碳矿化累积量及矿化率均高于非根际土;培养期间粘壤土释放的CO2量明显低于沙质壤土,这可能与粘壤土粘粒含量高,对土壤有机碳的保护作用有关。 相似文献
14.
土壤质地和灌水器材料对负压灌溉出水流量及土壤水运移的影响 总被引：7，自引：5，他引：7
负压灌溉法是一种新近提出的节水灌溉技术，灌溉时供水水头为“负值”，即灌溉水源高程低于灌水器高程。不同材料灌水器和土壤质地是影响灌溉系统出水流量及土壤水运移的重要因素。该文研究了在高程差H为-0.5 m情况下两种灌水器及两种质地土壤对两者的影响。结果表明：灌水器相同时，累计入渗量、水平和垂直最大湿润距离随时间呈幂函数关系变化；在历时相同时黏壤土较砂壤土大；湿润体近似为六分之一的竖直椭球体，但黏壤土水平与垂直最大湿润距离之比大于砂壤土。土壤质地相同时，纤维灌水器较陶土灌水器出水流量高。试验结果进一步证明了负压灌溉的可行性，并为确定负压灌溉系统应用范围及规划设计过程中灌水器选择提供了依据。 相似文献
15.
This paper reviews some research studies on tillage methods influencing soil and moisture conservation in the eastern African countries of Kenya, Tanzania, Malawi and Ethiopia during the past four decades. Most of these studies were conducted in marginal rainfall (semi arid) areas and on shallow soils of various textures (sandy clay loam, sandy clay, clay and loam). The studies were meant to establish the effects of tillage and residue management practices on physico-chemical soil properties (i.e. structure, bulk density, soil moisture and organic matter contents), runoff and infiltration.
This review emphasizes the importance of appropriate tillage and residue management methods (contour bunds and terraces, minimum tillage, tied ridging, mulching and conventional tillage) in providing soil conditions favourable for soil moisture conservation and subsequent crop performance and yield on smallholder farms. 相似文献
16.
Soil tilth has been defined in terms of a ‘Physical Index’ based on the product of the ratings of eight physical properties — soil depth, bulk density, available water storage capacity, cumulative infiltration or apparent hydraulic conductivity, aggregation or organic matter, non-capillary pore space, water table depth and slope. The Physical Index and a tillage guide were used to identify the tillage requirements of different soils varying in texture from loamy sand to clay in the semi-arid tropics. The physical index was 0.389 for a loamy sand, 0.518 for a black clay loam and 0.540 for a red sandy loam soil and the cumulative rating indices in summer and winter seasons were 45 and 44 for loamy sand, 52 and 51 for red sandy loam and 54 and 52 for black clay loam soils, respectively. The compaction of the loamy sand by eight passes of a 490 kg tractor-driven roller (0.75 m diameter and 1.00 m length) increased the physical index to 0.658 and chiselling of the red sandy loam and black clay loam increased the physical indices to 0.686 and 0.729, respectively. The grain yields of rainfed pearl millet and guar and irrigated pearl millet, wheat and barley increased significantly over the control (no compaction) yields by compaction.
The chiselling of the soils varying in texture from loamy sand to clay at 50 to 120-cm intervals up to 30–40 cm depth, depending upon the row spacing of seedlines and depth of the high mechanical impedance layer, increased the grain yields of rainfed and irrigated maize on alluvial loamy sand, rainfed maize on alluvial sandy loam and red sandy loam, rainfed sorghum on red sandy loam and black clay loam, irrigated sorghum on black clay loam and rainfed black gram on red sandy loam, pod yield of rainfed groundnut, tuber yield of irrigated tapioca and fresh fruit yield of rainfed tomato on red sandy loam and sugarcane yield on black clay soil, significantly over the yields of no-chiselling systems of tillage such as disc harrow and country plough. 相似文献
17.
Influence of soil strength on root growth: experiments and analysis using a critical-state model 总被引：3，自引：0，他引：3
Roots grow thicker in compacted soil, even though it requires greater force for a large object to penetrate soil than it does for a small one. We examined the advantage of thickening in terms of the stresses around a root penetrating with constant shape, rather than the stresses around an expanding cylinder or sphere, as has been studied previously. We combined experiments and simulations of the stresses around roots growing in compacted soils. We measured the diameter of pea roots growing in sandy loam and clay loam at four different densities, and the critical‐state properties of the soils. At a penetration resistance of about 1 MPa the diameter of the roots in the sandy loam was about 40% greater than that at 0.7 MPa, and at 2 MPa it was about 60% greater. In the clay loam, there was less thickening – about 10% greater at 1 MPa and about 20% greater at 1.5 MPa. The maximum axial stresses were predicted using a critical‐state finite‐element model to be at the very tip of the root cap. When there was friction between the root and the soil, shear stresses were predicted with smaller values at the tip than just behind the tip. When the interface between the soil and the root was assumed to be frictionless, there were by definition no shear stresses. In the frictionless case the advantage of root thickening on relieving peak stress at the root tip was diminished. The axial and shear stresses were predicted to be smaller in the clay loam than in the sandy loam and may explain why the roots did not thicken in this soil although its resistance to penetration was similar. Our results suggest that the local values of axial and shear stresses experienced by the root near its tip may be as important in constraining root growth as the total penetration resistance. 相似文献
18.
ABSTRACT Long-term irrigation with untreated industrial sewage effluents causes accumulation of high concentrations of chromium (Cr) and other heavy metals in soil and subsequently in crop plants (especially leafy vegetables), which can be phytotoxic to plants and/or a health hazard to animals and humans. Greenhouse experiments were conducted to determine the effects of Cr application on the growth of spinach (Spinacia oleracia L.) and to develop critical toxic ranges of Cr in plants and in soil. The study involved growing of spinach variety ‘Punjab Green’ in a greenhouse on silty clay loam and sandy soils equilibrated with different levels of applied Cr (0, 1.25, 2.5, 5, 10, 20, 40, 80, 160, and 320 mg Cr kg? 1 soil). Plants were harvested at: three growth stages 45, 60, and 90 days after sowing (DAS). Critical toxic ranges were estimated by regressing and plotting data on ammoniumbicarbonate-diethylenetriaminepenta-acetic acid (AB-DTPA) extractable Cr in soil or Cr concentration in plants versus dry-matter yield (DMY) of spinach at the three growth stages. Toxic ranges, i.e., slightly toxic (80%–90%), moderately toxic (70%–80%), and extremely toxic (< 70%) in terms of DMY relative to the attainable maximum DMY, were established for both soils and for plants at all three growth stages. There was no germination of spinach with applied Cr at 320 mg Cr kg? 1 rate in silty clay loam soil and at 40 mg Cr kg? 1 rate in sandy soil due to Cr toxicity. Roots accumulated more Cr in comparison with shoots. Chromium concentrations of 0.47–1.93 mg Cr kg? 1 soil in silty clay loam soil, 0.13–0.94 mg Cr kg? 1 soil in sandy soil, 1.08–5.40 mg Cr kg? 1 plant DM in silty clay loam soil and 0.54–11.7 mg Cr kg? 1 plant DM in sandy soil were found to be toxic. The critical toxicity ranges of Cr thus established in this study could help in demarcating Cr toxicity in soils and in plants such as spinach and other leafy vegetables due to irrigation of soils with untreated sewage water contaminated with chromium. 相似文献
19.
《Soil & Tillage Research》1988,12(1):65-79
The effects of zero, minimum and conventional tillage on soil physical properties and on the growth and yield of mungbean (Vigna radiata L.) grown after lowland rice (Oryza sativa L.) were studied in field experiments conducted during the 1984 and 1985 dry seasons (DS) at two Philippine sites (clay loam, Vertic Tropaquept, with shallow water table and sandy loam, Aeric Tropaquept, with deep water table). Effects on maize (Zea mays L.) were studied only in 1984 on clay loam soil.All parameter measurements were not significantly different with minimum and conventional tillage. Tillage, averaged over minimum and conventional and in both seasons, significantly lowered bulk density (10%) and increased aeration porosity (120%) of the 0–0.10 m clay loam soil layer. In sandy loam soil in 1985, it decreased bulk density by 7% and increased aeration porosity by 61%. Tillage only slightly affected the matric suction, strength and temperature of both soils.Maize seedling emergence was 15% higher with zero tillage than with minimum and conventional tillage. Tillage, however, did not affect mungbean emergence. It significantly increased maize plant height (42%) and root length (61%) as compared with no tillage. In mungbean, tillage increased plant height (18%) and root length (60%), as averaged over both sites and seasons. In clay loam soil, tillage increased grain yield of maize by 242%. On the same field, tillage increased mungbean grain yield by 78% in 1984 and 20% in 1985. In sandy loam, tillage produced 38% more mungbean grains than without tillage. 相似文献
20.
Summary Soil texture affects pore space, and bacterial and protozoan populations in soil. In the present study we tested the hypothesis that bacteria are more protected from protozoan predation in fine-textured soils than in coarse-textured soils because they have a larger volume of protected pore space available to them. The experiment consisted of three sterilized Orthic Black Chernozemic soils (silty clay, clay loam, and sandy loam) inoculated with bacteria, two treatments (with and without protozoa), and five sampling dates. The soils were amended with glucose and mineral N on day 0. On day 4 bacterial numbers in all three soils were approximately 3×109 g–1 soil. The greatest reduction in bacteria due to protozoan grazing occurred between day 4 and day 7. Compared to the treatment without protozoa, bacteria in the treatment with protozoa were reduced by 68, 50, and 75% in the silty clay, clay loam, and sandy loam, respectively. On day 4, 2 days after the protozoan inoculation, all protozoa were active. The numbers were 10330, 4760, and 15 380 g–1 soil for the silty clay, clay loam, and sandy loam, respectively. Between day 4 and day 7, the period of greatest bacterial decline, total protozoa increased greatly to 150480, 96160, and 192100 g–1 soil for the three soils, respectively. Most protozoa encysted by day 7. In all soils the addition of protozoa significantly increased CO2–C evolution per g soil relative to the treatment without protozoa. Our results support the hypothesis that bacteria are more protected from protozoan predation in fine-textured soils than in coarse-textured soils. 相似文献