Influences of addition of different krilium in saline-sodic soil on the seed germination and growth of cabbage

China is one of the largest countries with huge amount of saline-sodic soil. How to ameliorate these lands is a hotspot in China. Through measurement of soil salinity, pH value and seed germination and growth status of cabbage seedlings, 17 kinds of krilium were added to experimented soil to evaluate their effects on amelioration of heavy saline-sodic soil. Firstly, among these 17 kinds of krilium, 11 (HPMA, gypsum, HEDP, T225, PAPEMP, MA-AA, ATMP, AA/AMPS, PAA, charcoal and BHMTPMPA) were effective agents and could effectively induce seed germination without any germination phenomena in the control saline-sodic soil. HPMA was the best one in ameliorating saline-sodic soil, which has been manifested by various indices of seed germination. Secondly, addition of gypsum together with other organic agents could strongly increase the ameliorative effectiveness if compared with relatively weak agents, while decrease seed germination if compared with the stronger agent of the 2 mixed agents, showing that the synergetic effect between gypsum and other kinds of tested krilium was not evident. Thirdly, optimum dosages for separate addition of HPMA and gypsum were 42.8 L m^?3 and 25 kg m^?3, while mixed-addition of these 2 agents at the same dosages did not cause plus effect in soil improvement. Finally, field application of HPMA could enhance the growth of cabbage seedlings at the first month, but began to wilt thereafter. Thus, instead of one-time addition, several-time addition of HPMA at the suitable dosage in field practice could strengthen the effectiveness of soil amelioration.     

盐碱地土壤改良剂施用对种子萌发和生长的影响

我国是盐碱地大国,如何改良盐碱地一直是研究热点。选择17种盐碱地改良剂施加于重度盐碱土,以白菜种子萌发指标和改良土壤电导率及pH值为评价指标,筛选出适宜盐碱地改良的土壤改良剂及其比例配比,为盐碱地治理改良提供理论依据。结果表明,（1）与对照盐碱土相比,11种有效改良剂（聚马来酸酐、石膏、羟基乙叉二膦酸、丙烯酸-丙烯酸羟丙酯共聚物、多氨基多醚基甲叉膦酸、聚马来酸酐-丙烯酸共聚物、氨基三甲叉膦酸、丙烯酸-2-丙烯酰胺-2-甲基丙磺酸多元共聚、聚丙烯酸、木炭、双1,6-亚己基三胺五甲叉膦酸）不仅使白菜种子发芽,对降低pH有显著作用,对电导率降低影响不明显;其中聚马来酸酐（HPMA）的改良效果最佳,种子发芽各项指标均较高,具有较强的种子生活力,其发芽率、发芽指数、活力指数的活力指标分别达到72.5%,36.2,1.2;种子发芽率,发芽势和发芽指数与土壤pH值有密切关系（p〈0.05）,但与土壤电导率无关（p〉0.05）,从而说明不同土壤改良剂的效果主要显现在调节pH的功能上。（2）在施加钙源石膏辅助下,9种改良剂（聚马来酸酐,聚丙烯酸,木炭,木醋液,乙二胺四乙酸,732型阳离子交换吸附树脂（H＋型）,柠檬酸,柠檬酸钙,氨三乙酸）改良效果有明显提升,改良剂改良后的盐碱土在种子发芽率、发芽指数、活力指数等指标均有所上升,说明外施钙源有助于其它改良剂效果的发挥。（3）不同浓度梯度筛选中,42.8L/m^3聚马来酸酐、25kg/m^3石膏改良效果最佳,能够有效降低土壤电导率和pH值,改良后盐碱土的种子发芽率、发芽势、发芽指数、活力指数均最接近壤土种子发芽率、发芽指数等各项指标,但二者单独施用改良盐碱土其发芽率高于二者混合施用的发芽率,不存在协同效应,故二者不宜混合施用。同时,野外进行改良应该考虑多次少量施用或增加改良剂浓度的方法来增强改良效果。     

钢渣组分特征及其用于土壤改良的可行性初步研究

通过测定钢渣的化学组成分析得出其组分特征,进一步通过在有降解碱剂HPMA参与的重（轻）度盐碱土壤及钢渣中栽种不同植物种子（玉米、茄子、水稻和长春花）,观察植物的长势,探究钢渣是否可以用于土壤改良。结果发现钢渣的化学成分与土壤基本相同,但部分成分如CaO、Fe₂O₃、MgO、MnO₂等显著高于土壤,而另外一些组分TiO₂、K₂O、Na₂O、P₂O₅在钢渣中未检测出来。对比重（轻）度盐碱土壤,钢渣与HPMA共同作用时,玉米、茄子、水稻和长春花等发芽率及生长速率明显提高;与常用的蛭石、珍珠岩改良剂对比实验中,不同植物存在类似的发芽率和生长速率,说明钢渣可以作为温室土壤结构改良剂;与钢渣产地丰富的树皮土资源配比形成复方改良剂,发现其具有类似花土（泥炭土）的生长速率和发芽率。初步研究表明,钢渣可以用于盐碱地改良,而且对于设施农业的土壤结构改良具有功效,与当地树皮土资源结合,具有形成复方土壤改良剂的潜力。     

The Effect of Chelating Agents on Soil Sodicity

Results of laboratory and field tests suggest that chelating agents could be used to alleviate adverse soil properties caused by excess sodium, such as low permeability. Adding multi-dentate carboxylic acid chelating agents to sodic soil, or to mixtures of soil with sodium-contaminated waste, significantly reduced sodium adsorption ratio (SAR) values. Judging from cation concentrations in saturated paste (sat. paste) filtrates, chelating agents act to ameliorate soil sodicity by releasing Ca and to a lesser extent Mg from undissolved compounds. After adding chelating agents to moist soils that contained free lime, measured weight losses were consistent with CO ₂ evolution due to CaCO ₃ decomposition. The electrical conductivity (EC) of the sat. paste filtrate of materials treated with chelating agents increased less than when equivalent Ca or Mg was supplied in conventional, soluble form. Bigger sat. paste vacuum filtration volumes, improved soil permeability and faster field infiltration rates were observed after treatment with chelating agents. The Ca- and Mg-complexes of agents such as citric and malic acid degrade in moist soil; such agents could perhaps be used in a series of applications to improve ease of cultivation and permeability of cropped land. The agent ethylenediamine tetraacetic acid (EDTA) forms stable complexes, and could therefore be used as a one-time treatment for sodic materials that are to be disposed of by burial, following guidelines for soil SAR and EC.     

The experimental watershed liming study: Comparison of lake and watershed neutralization strategies

The Experimental Watershed Liming Study (EWLS) was initiated to evaluate the application of CaCO₃ to a forested watershed in an effort to mitigate the acidification of surface water. The objective of the EWLS was to assess the response of the Woods Lake watershed to an experimental addition of CaCO₃. During October 1989, 6.89 Mg CaCO₃/ha was applied by helicopter to two subcatchments comprising about 50% (102.5 ha) of the watershed area. The EWLS involved individual investigations of the response of soil and soil water chemistry, forest and wetland vegetation, soil microbial processes, wetland, stream and lake chemistry, and phytoplankton and fish to the CaCO₃ treatment. In addition, the Integrated Lake/Watershed Acidification (ILWAS) model was applied to the site to evaluate model performance and duration of the treatment. The results of these studies are detailed in this volume. The purposes of this introduction and synthesis paper are to: 1) present the overall design of the EWLS, 2) discuss the linkages between the individual studies that comprise the EWLS, and 3) summarize the response of the lakewater chemistry to watershed addition of CaCO₃ and compare these results to previous studies of direct lake addition. An analysis of lake chemistry revealed the watershed treatment resulted in a gradual change in pH, acid neutralizing capacity (ANC) and Ca²⁺ in the water column. This pattern was in contrast to direct lake additions of CaCO₃ which were characterized by abrupt changes following base addition and subsequent rapid reacidification. Over the three-year study period, the supply of ANC to drainage waters was largely derived from dissolution of CaCO₃ in wetlands. Relatively little dissolution of CaCO₃ occurred in freely draining upland soils. The watershed treatment had only minor effects on forest vegetation. The watershed treatment eliminated the episodic acidification of streamwater and the near-shore region of the lake during snowmelt, a phenomenon that occurred during direct lake treatments. Positive ANC water in the near-shore area may improve chemical conditions for fish reproduction, and allow for the development of a viable fish population. The watershed CaCO₃ treatment also decreased the transport of Al from the watershed to the lake, and increased the concentrations of dissolved organic carbon (DOC) and dissolved silica (H₄SiO₄) in stream and lakewater. The watershed treatment appeared to enhance soil nitrification, increasing concentrations of NO₃ ^– in soilwater and surface waters. However, the acidity associated with this NO₃ ^– release was small compared to the increase in ANC due to CaCO₃ addition and did not alter the acid-base status of Woods Lake. Acid neutralizing capacity (ANC) budgets for 12-month periods before and after the watershed treatment showed that the lake shifted from a large source of ANC to a minor source due to retention of SO₄ ^2–, NO₃ ^–, Al and the elevated inputs of Ca²⁺ associated with the watershed CaCO₃ application. In contrast to the direct lake treatments, Ca²⁺ inputs from the watershed application were largely transported from the lake.     

松嫩平原退化草地羊草种子萌发对环境因子的响应

研究了温度(恒温和变温)、水分(含水量2.5%-40.0%)和干旱胁迫、土壤类型(盐碱土和非盐碱土)和盐碱胁迫(NaCl和Na₂CO₃)等环境因子对羊草(Leymus chinensis)种子萌发的影响。恒温下未经打破休眠处理的羊草种子发芽率不足2%, 变温下羊草种子发芽率可达85.3%, 表明温度是影响羊草种子萌发的关键因素之一。羊草种子萌发的适宜土壤含水量为2.5%-15.0%, 随着含水量继续增加, 发芽率呈下降趋势。松嫩平原盐碱化土壤对羊草种子萌发具有显著的抑制作用, 羊草种子在重度盐碱土(pH 10.24)中发芽率仅为6.0%, 而在非盐碱土中发芽率可达61.3%。羊草种子在萌发阶段的耐盐碱能力差, 随着NaCl和Na₂CO₃浓度增加, 发芽率呈显著下降趋势, 且Na₂CO₃的抑制作用更强。松嫩平原盐碱环境下羊草种子萌发受到抑制是该地区羊草草地退化的原因之一。     

A chemical and biological approach towards the definition of calcareous soils

Summary Several agricultural problems are associated with the presence of certain levels of CaCO₃ in soils. The level of CaCO₃ at which the phosphate fixation becomes an apparent agricultural problem, is thought to be an appropriate margine at which the soil can be considered calcareous. Thus, a set of soil mixtures, ranging in CaCO₃ content from 1 to 96% was prepared and used in a column study to determine the level at which the CaCO₃ fraction becomes a dominant factor controlling. P³² movement and distribution.Increasing the percentage of oolitic sand, in the soil mixture, from 1 to 10% caused a sharp drop in P³² movement with soil solution and any increase in CaCO₃ content above 10% did not show any further drop in P³² movement. The amount of P³² removed with the soil solution was generally low compared to that retained in soil columns. Studying the distribution of P³² in soil columns, after five displacements, has indicated that the migration of P³² from the top soil increased by increasing CaCO₃ from 1 and 2 to 6%. The amount of P³² removed was however retained in lower sections. A very sharp decrease in P³² migration from the top soil was observed when CaCO₃ content was raised from 8 to 10%.A similar picture was shown when the CaCO₃ material used was in clay size fraction. However the sharp increase in phosphate retention in top soil sections took place at CaCO₃ content of 8% rather than at 10%. A limit of 8 to 10% CaCO₃ was proposed as an appropriate margine for defining calcareous soils.     

Effect of H2SO4, HCl and Al2(SO4)3 on the yield,chemical composition and Ca uptake from applied Ca45CO3 by dhaincha (Sesbania aculeata Pers.) in a saline alkali soil

Summary Application of CaCO₃ and a lime-solubilizing agent (viz H₂SO₄, HCl, and Al₂(SO₄)₃) to a saline-alkali soil caused a significant increase in the dry matter yield of dhaincha (Sesbania aculeata Pers). The extent of yield enhancement by these amendments was in the decreasing order: HCl, H₂SO₄ and Al₂(SO₄)₃. Calcium content in the plant increased significantly with the application of these amendments and it was in the decreasing order: H₂SO₄, Al₂(SO₄)₃ and HCl. The uptake of Ca from native CaCO₃ was much less than that from the added Ca⁴⁵CO₃. Phosphorus content in the plant increased with the HCl and H₂SO₄ treatments and decreased with the Al₂(SO₄)₃ treatments. Nitrogen and Na contents decreased with the addition of these amendments. re]19730521     

施加改良剂对重度盐碱地土壤盐碱动态及草本植物生长的影响

为了探索内陆重度盐碱地的改良新方法,实验通过聚合有机酸(聚马来酸酐和聚丙烯酸)作为降盐碱剂,采用阻盐碱层、表土成膜剂以及土壤孔隙改善剂相结合的方法,对大庆市典型内陆盐碱土进行了改良实验,并在改良后的土壤及对照样地上种植不同植物--白菜、萝卜、菠菜、豚草和长春花,评价改良效果.结果发现:(1)通过施加降盐碱剂、阻盐碱剂及土壤孔隙剂,土壤的pH值和含盐量均有明显降低,下降幅度分别为pH:0.8～1.2、含盐量:0.2%～0.5%,而且表层改良效果优于深层;(2)在上述改良基础上施用表土成膜剂,使得土壤深层与表层盐碱运动减慢,即表层盐碱更低而深层更高,有利于保持表层适宜作物生长的条件;(3)2种聚合有机物比较来看,聚马来酸酐的改良效果好于聚丙烯酸;(4)从5种植物的生长状况来看,施用上述改良剂后较对照能够明显提高作物成活以及生长,特别是改良早期5种植物均呈现明显的生长趋势,而在后期存在生长力下降的趋势,因此,在大面积改良过程中需要考虑连续多次施加降盐碱剂以增强效果.     

不同秸秆填埋量对盐碱土水盐运移及垂柳反射光谱的影响

在宁夏西北盐化生态脆弱区的典型盐碱化土地,通过随机区组试验,探究在栽植穴填埋秸秆2000(T_1)、7000(T_2)、12000kg/hm~2(T_3)及17000 kg/hm~2(T_4)等作隔盐层对土壤水盐运移及垂柳(Salix babylonica)反射光谱的影响,将地下土壤水盐变化与地上植物生长及生理状况相结合,以期更准确的反映出各处理对盐碱土壤改良效果及地上植被恢复情况。研究结果表明:(1)填埋一定量的秸秆作隔盐垫层可以改变地下土壤水盐的剖面分布特征。T_2、T_3和T_4处理与对照组相比,20—80 cm土层土壤含水量都显著提高,填埋的秸秆层起到了蓄水保墒的作用;都明显降低了0—80 cm土层土壤盐分含量和盐溶质浓度;但这3种处理之间无显著差别。T_1由于填埋秸秆量过少,无显著蓄水控盐效果。(2)通过检测植物叶片反射光谱可以反映出地上植物生长及生理状况的变化。填埋一定量的秸秆作为隔盐垫层有助于改善垂柳的生理状况。T_2的垂柳叶片光合色素含量最高,光合特性及营养状况最好,其他光谱参数结果都显著提高。T_3显著提高叶绿素含量和光合特性,但效果均不如T_2,且营养状况差。T_4处理类胡萝卜素含量与叶片水分含量均处于最高水平,但叶绿素含量、营养状态以及光合特性都显著降低。T_1处理效果最差。(3)在地下填埋秸秆作隔盐层,会通过对地下土壤水盐运移及微域生态系统环境的调节,影响到地上植物生长及生理状况。综合地下水盐分布与地上植物叶片反射光谱的结果,T_2是宁夏引黄灌区盐碱地改良中最适宜的秸秆填埋量。     

Loss of soil and nutrients by surface runoff in two agro-ecosystems within an Andean paramo area

High Andean paramo and cloud forest ecosystems in South America are undergoing transition to agricultural activities such as potato farming and cattle grazing in many areas. There is a lack of data quantifying the contributions of these land uses to soil erosion and nutrients loss. Thus, we assessed soil quality in patches of potato crops and pasture for cattle grazing, and tested soil and nutrient loss from these two land uses in response to heavy rainfall simulation rates (100 mm h⁻¹). Physico-chemical analyses were also carried out in soil and runoff water samples. We found that potato farming had more severe impacts on soil quality, with substantial loss of the silt fraction (low silt levels of 11.9% were found in soil composition) that prevents aggregates formation and increase soil instability. Furthermore, we found that potato farming resulted in much higher soil loss rate (5.67 g h⁻¹) compared to that of pastoral land use (0.61 g h⁻¹). Meanwhile, N and P average losses measured in runoff were 1.22 mg N-NO₃ l⁻¹ plus 0.12 mg P-PO₃ l⁻¹ for the potato crop, and 0.86 mg N-NO₃ l⁻¹ plus 0.09 mg P-PO₃ l⁻¹ for the pastures, respectively. We postulate that more effective and continuous rooting prevents soil disaggregation in pasture relative to cropping, and that continuous and extensive foliage protects the soil from rain-splash erosion. Finally, direct relationships appeared between the two agricultural practices evaluated and the loss of soil and nutrients. Thus, if anthropogenic practices such as those studied herein continue their widespread trend observed in recent years in the region, then two of the most important paramo eco-systemic services, that is, water regulation and high water quality supply, may be impaired with all the consequences this brings for human settlements and their livelihoods located down waters.     

A negative influence of manure on calcareous soils

Summary On a soil rich in CaCO₃ in a semiaride climate in Algeria a hard soil layer, impermeable for plant roots, was formed in a depth of 20–40 cm after farmyard manure application and irrigation. To find the reason soil samples of this field were taken and leaching experiments were carried out in the laboratory, with the result that much more Caions and HCO₃-ions were leached out of the soils with farmyard manure application than from the soils without manure. Probably the high amount of CO₂, being liberated by the organic matter, and the irrigation water dissolved the CaCO₃ in the soil, and the formed Ca- and HCO₃-ions followed the movement of water in the soil. Where the Ca(HCO₃)₂ reached soil layers with a less amount of CO₂, CaCO₃ precipitated and formed the hard soil layer. In order to avoid the formation of such calcareous crusts on irrigated, limy soils in a dry climate it is recommended to fertilize rather often small quantities instead of rarely big quantities of farmyard manure.     

Sentinel-2 Satellite Imagery Application to Monitor Soil Salinity and Calcium Carbonate Contents in Agricultural Fields

The estuary tides affect groundwater dynamics; these areas are susceptible to waterlogging and salinity issues. A study was conducted on two fields with a total area of 60 hectares under a center pivot irrigation system that works with solar energy and belong to a commercial farm located in Northern Sudan. To monitor soil salinity and calcium carbonate in the area and stop future degradation of soil resources, easy, non-intrusive, and practical procedures are required. The objective of this study was to use remote sensing-determined Sentinel-2 satellite imagery using various soil indices to develop prediction models for the estimation of soil electrical conductivity (EC) and soil calcium carbonate (CaCO₃). Geo-referenced soil samples were collected from 72 locations and analyzed in the laboratory for soil EC and CaCO₃. The electrical conductivity of the soil saturation paste extract was represented by average values in soil dataset samples from two fields collected from the topsoil layer (0 to 15 cm) characteristic of the local salinity gradient. The various soil indices, used in this study, were calculated from the Sentinel-2 satellite imagery. The prediction was determined using the root mean square error (RMSE) and cross validation was done using coefficient of determination. The results of regression analysis showed linear relationships with significant correlation between the EC analyzed in laboratory and the salinity index-2 “SI2” (Model-1: R² = 0.59, p = 0.00019 and root mean square error (RMSE = 1.32%) and the bare soil index “BSI” (Model-2: R² = 0.63, p = 0.00012 and RMSE = 6.42%). Model-1 demonstrated the best model for predicting soil EC, and validation R² and RMSE values of 0.48% and 1.32%, respectively. The regression analysis results for soil CaCO₃ determination showed linear relationships with data obtained in laboratory and the bare soil index “BSI” (Model- 3: R² = 0. 45, p = 0.00021 and RMSE = 1.29%) and the bare soil index “BSI” & Normalized difference salinity index “NDSI” (Model-4: R² = 0.53, p = 0.00015 and RMSE = 1.55%). The validation confirmed the Model-3 results for prediction of soil CaCO₃ with R² and RMSE values of 0.478% and 1.29%, respectively. Future soil monitoring programs might consider the use of remote sensing data for assessing soil salinity and CaCO₃ using soil indices results generated from satellite image (i.e., Sentinel-2).     

Forest soil solutions: Acid/base chemistry and response to calcite treatment

Soil solution chemistry was investigated at a forested watershed draining into Woods Lake. N.Y. as part of the Experimental Watershed Liming Study (EWLS). The objective of this study was to assess the response of soil water to watershed treatment of calcite (CaCO₃). This material was applied in an effort to mitigate the effects of acidic atmospheric deposition. Soil solutions draining Oa and Bs horizons in reference subcatchments were characterized by low pH and acid neutralizing capacity (ANC) due to elevated concentrations of SO ₄ ^2– , NO ₃ ^– and organic anions relative to the sum of base cation (C_B Ca²⁺, Mg²⁺, Na⁺, K⁺) concentrations. Seasonal and spatial variation of pH andANC in soil solutions appeared to belargely controlled by variations in the concentrations of dissolved organic acids which, in turn, were regulated by reactions of Al with soil organic matter. Nitrate was positively correlated and SO²⁺ was negatively correlated with Ca²⁺ and Al concentrations in reference soil solutions, indicating that changes in NO ₃ ^– influences spatial and seasonal variations in Ca²⁺ and Al concentrations. On this basis, NO ₃ ^– appears to be important in soil acidification and the dynamics of drainage water acidity. Comparison of our results with historical data for the site showed declines in concentrations of SO ₄ ^2– , which are consistent with decreases in emissions of SO₄, in the eastern U.S. and atmospheric deposition of SO ₄ ^2– , to the Adirondack region. Mineral soil solutions have shown large increases in concentrations of NO ₃ ^– . Declines in concentrations of C_B and increases in concentrations of Al have occurred over the last ten years, suggesting depletion of soil pools of exchangeable basic cations and increased sensitivity to acidic deposition. Calcite (CaCO₃) treatment of 6.89 Mg/ha resulted in a significant increase of Ca²⁺, ANC and pH in both Oa and Bs horizon soil solutions. Soil water response to CaCO₃ addition was most evident during the first year after treatment, apparently due to macropore transport of particulate and dissolved CaCO₃ However, increases in ANC and pH in the mineral soil waters were not sustained and appeared insufficient to result in substantial improvement in surface water quality over the 43 month study period.     

Land use impacts on physical properties of 28 years old reclaimed mine soils in Ohio

Reclamation enhances soil quality by improving physical and chemical properties, which helps in restoration of mine soils. Evaluation of the effects of post-reclamation land uses on physical and chemical properties of mine soils helps to identify suitable land uses for mining companies. The objectives of this study were to evaluate the effects of post-reclamation land uses (e.g., forest, hay and pasture) on selected physical properties of soil in relation to undisturbed forest and agricultural land use. Soil samples were collected from the 0- to 5-, 5- to 15- and 15- to 30-cm depths in order to determine particle size distribution, bulk density, water-stable aggregates, mean-weight diameter and soil moisture retention. Cone index and infiltration rate were determined at soil surface. After 28 years of reclamation, bulk density in the surface layer of all land uses in the reclaimed mine soil (RMS) was similar to that of undisturbed forest (1.1 Mg m⁻³) but lower than that of agricultural soils (1.3 Mg m⁻³). However, soil bulk density at lower depths was not affected. The cone index was higher in the RMS-pasture (2.6 MPa) than the RMS-forest (1.4 MPa) and RMS-hay (1.5 MPa) due to the trampling effect of grazing animals. The water-stable aggregates (>2 mm), of 5–8 mm aggregates, were higher in RMS-forest by 24%, 90%, 66%, and under RMS-hay by 13%, 74%, 43% for the 0- to 5-, 5- to 15-, and 15- to 30-cm depths, respectively, than that under undisturbed forest. The mean-weight diameter (0- to 30-cm) of aggregates under RMS-forest and RMS-hay were higher than that under undisturbed forest by 41% and 27%, respectively. The initial infiltration rates at 5 min in RMS under forest, hay and pasture were less by 20%, 53% and 85%, respectively, than that under undisturbed forest (19.3 cm min⁻¹). The reclamation of mine soils with forest and hay improved surface soil bulk density and cone index, and enhanced water infiltration capacity and water-stable aggregates at the lower depths. Therefore, establishment of forest and hay should be encouraged in the RMS.     

胞外多糖产生菌的筛选鉴定及其促生改土作用

【背景】一些微生物具有较强的产胞外多糖潜力,在改良盐碱土壤、促进作物生长方面潜力巨大。【目的】筛选耐盐碱且产胞外多糖的微生物,为开发具有盐碱土壤改良效果的菌剂提供菌种资源。【方法】从滨海盐碱植物根际土中筛选可在盐碱土壤中增殖、产胞外多糖、解有机磷和钾等能力的微生物菌株,并通过形态、生理生化、基于16S rRNA基因序列和gyrB基因的分子鉴定确定菌株类别,分析该菌株的生长、产胞外多糖特性受盐碱胁迫的影响,考察该菌对盐碱土壤不同粒径团聚体比例的影响,并结合盐碱土壤番茄种植试验考察对植物生长指标和土壤指标的影响。【结果】从727株滨海盐碱土壤菌株中筛选出一株产胞外多糖、具有较强盐碱土壤增殖能力且能解有机磷和钾的芽孢杆菌GBW HF-98,确定该菌为枯草芽孢杆菌沙漠亚种(Bacillus subtilis subsp. inaquosorum)。该菌可耐受pH值达10.0和NaCl浓度达110 g/L,在改善轻和中盐度土壤中不同粒径团聚体比例的效果较为显著。该菌的高剂量浓度T2组,在中度盐碱土壤的番茄种植试验中,与对照相比显著增加了壮苗指数、根干重、全株干重、茎粗和株高等指标,增幅分别为33.8%、59.3%、37.2%、12.3%和15.6% (P<0.05);显著降低pH、全盐含量和土壤容重,降幅分别为8.9%、27.9%和17.9%;显著提升土壤速效磷和速效钾指标,增幅分别为36.0%和17.4% (P<0.05)。【结论】GBW HF-98菌株具有较强的胞外多糖产生能力,在中度盐碱土壤中促进番茄生长和改良土壤的效果显著,可用于盐碱土壤改良菌剂的研制。     

基于土地利用/覆被变化的荒漠绿洲碳储量动态评估

以典型的荒漠绿洲区为研究对象,基于不同时期土地利用/覆被类型图,运用Bookkeeping模型,结合土壤、植被碳密度基础资料及调查数据,评估了近30年临泽绿洲土地利用/覆被变化特征及其对碳储量的影响。结果表明:(1)临泽荒漠绿洲区的土地利用/覆被变化特征主要表现为:居民及建设用地、耕地、林地呈增加趋势,增幅分别为90.2%、75%、46.5%;盐碱地、水体、沙地、荒漠草地则呈减少趋势,减幅分别为73.9%、67.8%、46.2%、5.5%。(2) 30 a耕地面积增加了269.38 km~2,其中耕地开垦面积为372.57 km~2,开垦主要来源于盐碱地、荒漠草地和沙地,分别占耕地开垦面积的24.7%、24.4%和21.05%。耕地转变为其他土地覆被类型的面积为103.19 km~2,转变后的主要去向分别是居民及建设用地、盐碱地和荒漠草地,分别占耕地转变为其他土地覆被类型面积的32.78%、17.8%和15.37%。(3)土地利用/覆被变化导致总碳储量增加5.89×10~5t,其中土壤碳储量增加量为4.02×10~5t,植被碳储量增加量为1.86×10~5t;耕地变化使碳储量增加4.91×10~5t,其中使碳储量增加的转变分别是荒漠草地-耕地、沙地-耕地、盐碱地-耕地、耕地-林地,相反的转变则使碳储量减少。总体来看,临泽荒漠绿洲土地利用/覆被面积和结构均发生了变化,耕地开垦为最主要的土地利用/覆被变化,土地利用/覆被变化导致碳储量总体呈增加趋势,耕地变化是影响碳储量变化的主要因素。     

Sulphur fractionation in calcareous soils and bioavailability to plants

Sulphur fractionation and availability to plants are poorly understood in calcareous soils. Sixty-four calcareous soils containing varying amounts of CaCO₃ were collected from ten provinces in China and their S fractions determined. Organic S was the predominant fraction of S, accounting for on average 77% of the soil total S. The amounts of adsorbed sulphate were found to be negligible. 1 M HCl extracted substantially more sulphate than either 0.01 M CaCl₂ or 0.016 M KH₂PO₄, indicating the existence of water-insoluble but acid-soluble sulphate, probably in the form of sulphate co-precipitated with CaCO₃. The concentrations of water-insoluble sulphate correlated positively with the contents of CaCO₃ and accounted for 0.03–40.3% (mean 11.7%) of soil total S. To test the bioavailability of water-insoluble sulphate, a sulphate-CaCO₃ co-precipitate labelled with ³⁵S was prepared and added to a calcareous soil in a pot experiment with either NH₄⁺ or NO₃^– as the N source. In 29 days, wheat plants took up 10.6% and 3.0% of the ³⁵S added to the soil in the NH₄⁺ and NO₃^– treatments, respectively. At the end of the pot experiment, the decrease of water-insoluble, acid-soluble, sulphate was more apparent in the NH₄⁺ than in the NO₃^– treatment. The results indicate that sulphate co-precipitated with CaCO₃ in calcareous soils may become partly available for plant uptake, depending on rhizosphere pH, if the field precipitate is similar to the laboratory prepared sample studied.     

Soil acidity and nutrient deficiency in central Amazonian heath forest soils

Experiments were carried out to test the effects of liming and nutrient additions on plant growth and soil processes such as C and N mineralisation in three contrasting forest types in central Amazonia: the stunted facies of heath forest (SHF), the tall facies of heath forest (THF) and the surrounding lowland evergreen rain forest (LERF). Calcium-carbonate additions increased soil respiration in the field plots in the SHF; in laboratory incubations, soil respiration was higher in the SHF when soils were fertilised with N, and in THF and LERF after S additions. The addition of N alone or in different combinations generally induced a net immobilisation of soil N. Net nitrification increased during the incubation in SHF and THF soils fertilised with N+P, and in LERF soils fertilised with either N, or P, or CaCO₃. In a field experiment using ingrowth bags, a higher fine root production was observed in all forest types when bags were fertilised with CaCl₂ or CaCO₃, suggesting that Ca may be a limiting nutrient in these soils. Calcium-carbonate addition in a glasshouse bioassay experiment with rice showed an overall positive effect on the survival and growth of the seedlings. In other treatments where soil pH was not raised, the rice showed acute toxicity symptoms, poor root and shoot growth and high mortality. Similar results were yielded in a field experiment, using naturally established seedlings in the field plots in SHF, THF and LERF. It is concluded that the acute H⁺ ion toxicity is a major growth-limiting factor for non-adapted plants in heath forest soils in central Amazonia.     

Nitrogen fertilization raises CO2 efflux from inorganic carbon: A global assessment

Nitrogen (N) fertilization is an indispensable agricultural practice worldwide, serving the survival of half of the global population. Nitrogen transformation (e.g., nitrification) in soil as well as plant N uptake releases protons and increases soil acidification. Neutralizing this acidity in carbonate‐containing soils (7.49 × 10⁹ ha; ca. 54% of the global land surface area) leads to a CO₂ release corresponding to 0.21 kg C per kg of applied N. We here for the first time raise this problem of acidification of carbonate‐containing soils and assess the global CO₂ release from pedogenic and geogenic carbonates in the upper 1 m soil depth. Based on a global N‐fertilization map and the distribution of soils containing CaCO₃, we calculated the CO₂ amount released annually from the acidification of such soils to be 7.48 × 10¹² g C/year. This level of continuous CO₂ release will remain constant at least until soils are fertilized by N. Moreover, we estimated that about 273 × 10¹² g CO₂‐C are released annually in the same process of CaCO₃ neutralization but involving liming of acid soils. These two CO₂ sources correspond to 3% of global CO₂ emissions by fossil fuel combustion or 30% of CO₂ by land‐use changes. Importantly, the duration of CO₂ release after land‐use changes usually lasts only 1–3 decades before a new C equilibrium is reached in soil. In contrast, the CO₂ released by CaCO₃ acidification cannot reach equilibrium, as long as N fertilizer is applied until it becomes completely neutralized. As the CaCO₃ amounts in soils, if present, are nearly unlimited, their complete dissolution and CO₂ release will take centuries or even millennia. This emphasizes the necessity of preventing soil acidification in N‐fertilized soils as an effective strategy to inhibit millennia of CO₂ efflux to the atmosphere. Hence, N fertilization should be strictly calculated based on plant‐demand, and overfertilization should be avoided not only because N is a source of local and regional eutrophication, but also because of the continuous CO₂ release by global acidification.