Alteration of the structural attributes of a compact clay loam soil by growth of a perennial grass crop

Soil aggregate stability, organic matter content, pH, bulk density, strength, and macropore attributes were assessed in order to evaluate the influence of grass root growth in a field sward. The amount of grass grown was varied by varying the quantity of applied nitrogen fertilizer: following one year with a uniform application rate, nitrogen fertilizer was applied over the subsequent three years to a compact soil at zero (N0), moderate (N1) and high (N2) rates. Differences in herbage production were evident in the three years of the contrasting nitrogen treatments. An index of soil aggregate stability increased in response to the increased grass growth promoted by heavier applications of nitrogen, but both bulk density and vane shear strength were unchanged. Binary images of the soil solid and pore space showed that for each treatment the largest volume of macropores occurred close to the surface, particularly in N0 where there was more pore space than in either N1 or N2. Analysis of the pore structure attributes of the binary images revealed further differences between treatments, in particular, at 40–80 mm depth, the soil in treatment N0 had fewer and smaller pores, and greater distance between pores, than the soil in the N1 and N2 treatments. The larger macropore volume in N1 and N2 constituted a major portion of the air-filled porosity when the soil was relatively wet. It was concluded that the root growth in the intensively cropped grassland was conducive to maintenance of a relatively stable and porous soil structure. An attendant increase in soil acidity close to the soil surface was a disadvantage of the larger nitrogen inputs.     

松嫩草甸3种主要植物群落土壤脲酶的初步研究

 松嫩草甸羊草（Leymus chinensis）群落、碱茅（Puccinellia tenuiflora）群落和虎尾草（Chloris virgata）群落土壤脲酶活性的季节动态呈单峰曲线变化,在土体中随土层的加深,其活性逐渐递减。各群落0～10 cm土层中的土壤脲酶活性与月平均降雨量呈幂函数关系,与土壤温度呈指数函数关系。土壤脲酶活性受多种土壤理化因子的共同影响,对于羊草群落,各因子的影响程度依次为：pH值>有机质>速效氮>C/N>容重>全氮>速效磷;碱茅群落为：有机质>C/N>全氮>容重>速效磷>速效氮>pH值;虎尾草群落为：全氮>有机质>速效氮>pH值>C/N>速效磷>容重。对该地区土壤肥力影响因子的主成分分析表明：有机质、全氮、速效氮、C/N和土壤容重对土壤肥力的贡献率占主导地位,土壤脲酶活性所占的比重较小,它不能完全反映土壤肥力状况。     

Litter quality effects of beech and hornbeam on undergrowth species diversity in Luxembourg forests on limestone and decalcified marl

Question: Do beech and hornbeam differ in undergrowth species diversity, and could these differences be explained by mass of the organic layer, pH or soil moisture? Could species richness under beech and hornbeam be explained by differences in N dynamics? Location: Ancient forests dominated by beech and hornbeam in Luxembourg, on decalcified and lime‐rich parent material. Methods: Species composition and soil characteristics, i.e. mass of the organic layer, pH, moisture content, bulk density and air‐filled pore space, were determined under beech and hornbeam on decalcified marl and limestone, and analysed with cluster analysis, correspondence analysis and ANOVA, with tree species and parent material as independent factors. Net N mineralization, nitrification and N in soil and microbial biomass were determined in a laboratory incubation experiment over a pH gradient, and correlated with species richness. Results: Species richness was lower under beech than under hornbeam on both decalcified marl and on limestone. Mass of the organic layer was higher under beech in all cases, but pH and soil moisture only differed between tree species on decalcified marl. Species richness increased with soil N, microbial N and nitrification in the mineral topsoil, but was not correlated with net N mineralization, and was negatively correlated with nitrification in the organic layer and with efficiency of N mineralization per unit microbe. Conclusion: Litter quality affected species richness on both limestone and decalcified marl via the organic layer, but only on decalcified marl in terms of pH or soil moisture. Species richness did not seem to be stimulated by high overall net N mineralization or high nitrate availability in the organic layer, but only by high nitrate in the mineral topsoil.     

有机类肥料对土壤养分含量的影响

绿色、可持续是我国发展现代农业的必然要求,肥料投入是关键之一。基于有机肥培肥土壤、生态友好的优势,发展和推广有机肥已经成为我国农业生产的一项基本国策。我国有机肥来源广泛、种类繁多,农业生产条件千差万别。本文分析了我国有机肥产品种类及标准现状、理化性质差异、碳氮矿化特性差异及影响因素,评述了施用有机肥对提高耕地基础地力的作用。因来源、制作工艺不同,不同有机肥的有机碳组分含量、全氮和活性氮含量、碳氮比等基本性质差异明显,这四者是影响有机肥碳氮矿化率、碳氮矿化量、碱解氮释放量等碳氮供应特性的主要内在因素;加之土壤环境等外界因素的影响,不同有机肥表现出不同的养分供应特性。总体上,有机肥一方面对提高土壤有机质含量,尤其是活性有机质含量和碳库管理指数效果明显,另一方面可增加土壤氮磷钾养分容量,减少作物生长消耗带来的土壤养分亏损,促进土壤质量良性发展。今后,应加强有机肥在耕地培肥中的应用,并加强有机肥肥效理论的基础研究和安全高效有机肥新产品的开发,促进有机肥资源的高效循环利用,使其成为重要的农业资源。     

Xiphinema americanum as Affected by Soil Organic Matter and Porosity

The effects of four soil types, soil porosity, particle size, and organic matter were tested on survival and migration of Xiphinema americanum. Survival and migration were significantly greater in silt loam than in clay loam and silty clay soils. Nematode numbers were significantly greater in softs planted with soybeans than in fallow softs. Nematode survival was greatest at the higher of two pore space levels in four softs. Migration of X. americanum through soft particle size fractions of 75-150, 150-250, 250-500, 500-700, and 700-1,000 μ was significantly greater in the middle three fractions, with the least occurring in the smallest fraction. Additions of muck to silt loam and loamy sand soils resulted in reductions in survival and migration of the nematode. The fulvic acid fraction of muck, extracted with sodium hydroxide, had a deleterious effect on nematode activity. I conclude that soils with small amounts of air-filled pore space, extremes in pore size, or high organic matter content are deleterious to the migration and survival of X. americanum, and that a naturally occurring toxin affecting this species may be present in native soft organic matter.     

土壤肥力对板栗枝干病害的影响

通过对土壤肥力与板栗枝干病害关系的研究表明,在土壤物理因素中,土壤类型以粘土、石砾土的栗园发病较重,壤土、沙壤土、黄棕壤的栗园发病较轻;土壤容重与感病指数呈正相关;土层厚度与感病指数呈负相关。在土壤化学因素中,有机质、速效磷与病情呈负相关;pH值、全氮和钾含量与病情关系不显著,并通过对土壤肥力因素与病情关系的逐步回归分析,筛选出土层厚度、土壤容重、粘性土、有机质和速效磷5个因素对病情贡献较大。以此建立了病情预测的回归模型,根据这一模型,可以预测研究范围内的任一给定条件下病害可能发生的水平,该研究将为今后的板栗生产和管理提供指导。     

南亚热带不同植被下丘陵赤红壤结构特征比较研究

比较研究了南亚热带几种植被下丘陵赤红壤结构特征．结果表明,丘陵赤红壤的结构随着植被的演退而退化．表现在表土砂化,即砂粒含量相对增加,粘粒含量相对减少;土壤结构稳定性下降,主要体现在较大粒径水稳性团聚体减少;土壤孔隙性变差,主要体现在容重增加和较大孔径的孔隙减少．自然赤红壤容重增加、较大孔隙减少更为明显;耕型赤红壤结构稳定性下降,表土砂化更为突出．研究结果揭示,由植被演退引起的土壤有机质减少,是丘陵赤红壤结构退化的主要内在因素．     

Soil quality and barley growth as influenced by the land application of two compost types

Agricultural use of organic residues offers an attractive method for their safe disposal and a valuable source of organic amendments and nutrients. A field experiment was conducted to investigate the influences of 0, 25, 50 and 100 t/ha spent mushroom compost (SMC), forced aeration compost (FAC) and inorganic fertilizer on soil properties and yield of barley (Hordeum vulgare). The considered soil properties (0-15 cm), after a growing season, included pH, EC, available P, Kjeldahl N, available cations, DTPA extractable elements, soil OC content, and bulk density and grain yield was also determined. Application of organic materials increased organic status of the soil and nutrient content. The effectiveness of the two composts on improving the productivity of the soil varied. SMC produced strongest correlations between soil nutrient levels and plant yield. Neither compost raised soil copper and zinc to levels that were of concern and high application rates decreased iron content.     

Prediction of nitrogen responses of corn by soil nitrogen mineralization indicators

Soil nitrogen mineralization potential (N min) has to be spatially quantified to enable farmers to vary N fertilizer rates, optimize crop yields, and minimize N transfer from soils to the environment. The study objectives were to assess the spatial variability in soil N min potential based on clay and organic matter (OM) contents and the impact of grouping soils using these criteria on corn grain (Zea mays L.) yield, N uptake response curves to N fertilizer, and soil residual N. Four indicators were used: OM content and three equations involving OM and clay content. The study was conducted on a 15-ha field near Montreal, Quebec, Canada. In the spring 2000, soil samples (n = 150) were collected on a 30- x 30-m grid and six rates of N fertilizer (0 to 250 kg N ha(-1)) were applied. Kriged maps of particle size showed areas of clay, clay loam, and fine sandy loam soils. The N min indicators were spatially structured but soil nitrate (NO3-) was not. The N fertilizer rate to reach maximum grain yield (N max), as estimated by a quadratic model, varied among textural classes and Nmin indicators, and ranged from 159 to 250 kg N ha(-1). The proportion of variability (R2) and the standard error of the estimate (SE) varied among textural groups and N min indicators. The R2 ranged from 0.53 to 0.91 and the SE from 0.13 to 1.62. Corn grain N uptake was significantly affected by N fertilizer and the pattern of response differed with soil texture. For the 50 kg N ha(-1) rate, the apparent N min potential (ANM) was significantly larger in the clay loam (122 kg ha(-1)) than in the fine sandy loam (80 kg ha(-1)) or clay (64 kg ha(-1)) soils. The fall soil residual N was not affected by N fertlizer inputs. Textural classes can be used to predict N max. The N min indicators may also assist the variable rate N fertilizer inputs for corn production.     

Physical Quality Indicators and Mechanical Behavior of Agricultural Soils of Argentina

Mollisols of Santa Fe have different tilth and load support capacity. Despite the importance of these attributes to achieve a sustainable crop production, few information is available. The objectives of this study are i) to assess soil physical indicators related to plant growth and to soil mechanical behavior; and ii) to establish relationships to estimate the impact of soil loading on the soil quality to plant growth. The study was carried out on Argiudolls and Hapludolls of Santa Fe. Soil samples were collected to determine texture, organic matter content, bulk density, water retention curve, soil resistance to penetration, least limiting water range, critical bulk density for plant growth, compression index, pre-consolidation pressure and soil compressibility. Water retention curve and soil resistance to penetration were linearly and significantly related to clay and organic matter (R² = 0.91 and R² = 0.84). The pedotransfer functions of water retention curve and soil resistance to penetration allowed the estimation of the least limiting water range and critical bulk density for plant growth. A significant nonlinear relationship was found between critical bulk density for plant growth and clay content (R² = 0.98). Compression index was significantly related to bulk density, water content, organic matter and clay plus silt content (R² = 0.77). Pre-consolidation pressure was significantly related to organic matter, clay and water content (R² = 0.77). Soil compressibility was significantly related to initial soil bulk density, clay and water content. A nonlinear and significantly pedotransfer function (R² = 0.88) was developed to predict the maximum acceptable pressure to be applied during tillage operations by introducing critical bulk density for plant growth in the compression model. The developed pedotransfer function provides a useful tool to link the mechanical behavior and tilth of the soils studied.     

不同母岩发育土壤的可氧化态有机碳

采用KMnO4氧化法测定了8种不同母岩发育形成的土壤的可氧化态有机碳含量,结果表明,发育母岩不同,土壤可氧化态有机碳含量显著不同。通过对土壤养分、土壤颗粒组成、容重与可氧化态有机碳含量的相关性分析表明,土壤可氧化态有机碳与土壤的速效磷、全氮、速效钾、砂粒、粉粒的含量存在着极显著负相关关系;与土壤容重存在着极显著的正相关关系;与土壤的有机质、碱解氮、粗砂、细砂、粘粒、pH值、石砾含量无相关关系。     

有机无机肥配施对旱地冬小麦产量和硝态氮残留淋失的影响

针对渭北旱塬氮肥施用不合理的问题,通过不同氮肥用量(0、75、150、225、300 kg N·hm^-2)与有机肥(30 t·hm^-2)配施,明确渭北旱塬麦田配施有机肥条件下合理的氮肥用量以及配施有机肥的减氮增产作用和对硝态氮残留淋失的影响.结果表明: 与单施化肥处理相比,有机无机肥配施可以在减少27.1%的氮肥用量情况下,提高14.7%的小麦籽粒产量,其中,施氮量150 kg·hm^-2配施有机肥处理的产量最高;有机无机肥配施可以促进小麦籽粒氮素吸收,氮肥利用率提高20.2%,尤其当氮肥用量为150 kg·hm^-2时,氮肥利用率达到最高值(42.0%);配施有机肥还能减少氮肥当季残留量和小麦生育期硝态氮向深层土壤淋溶,降低夏闲期淋失层硝态氮的淋失比例,当施氮量低于115 kg·hm^-2时,配施有机肥可以降低夏闲期硝态氮淋失量.基于本研究,推荐渭北旱塬在配施有机肥30 t·hm^-2的基础上,氮肥用量150 kg·hm^-2左右可实现小麦高产,提高氮肥利用率,防止氮肥过量残留.     

Increase in pH stimulates mineralization of ‘native’ organic carbon and nitrogen in naturally salt-affected sandy soils

Large amounts of terrestrial organic C and N reserves lie in salt-affected environments, and their dynamics are not well understood. This study was conducted to investigate how the contents and dynamics of ‘native’ organic C and N in sandy soils under different plant species found in a salt-affected ecosystem were related to salinity and pH. Increasing soil pH was associated with significant decreases in total soil organic C and C/N ratio; particulate (0.05–2 mm) organic C, N and C/N; and the C/N ratio in mineral-associated (<0.05 mm) fraction. In addition, mineral-associated organic C and N significantly increased with an increase in clay content of sandy soils. During 90-day incubation, total CO₂-C production per unit of soil organic C was dependent on pH [CO₂-C production (g kg⁻¹ organic C) = 22.5 pH – 119, R ² = 0.79]. Similarly, increased pH was associated with increased release of mineral N from soils during 10-day incubation. Soil microbial biomass C and N were also positively related to pH. Metabolic quotient increased with an increase in soil pH, suggesting that increasing alkalinity in the salt-affected soil favoured the survival of a bacterial-dominated microbial community with low assimilation efficiency of organic C. As a result, increased CO₂-C and mineral N were produced in alkaline saline soils (pH up to 10.0). This pH-stimulated mineralization of organic C and N mainly occurred in particulate but not in mineral-associated organic matter fractions. Our findings imply that, in addition to decreased plant productivity and the litter input, pH-stimulated mineralization of organic matter would also be responsible for a decreased amount of organic matter in alkaline salt-affected sandy soils.     

长期施肥对土壤微生物量及土壤酶活性的影响

 该文以北京国家褐潮土土壤肥力与肥料效益长期监测基地的长期肥料定位试验为平台,研究了长期不同施肥制度对土壤的生物学特性及其土壤酶的影响。主要研究结果：长期撂荒土壤(15年)的有机质和全氮(TN)的含量、微生物量碳(SMB-C)和氮(SMB-N)、土壤的蔗糖酶、磷酸酶和脲酶活性以及SMB-C/SOC(土壤有机碳)和SMB-N/TN比值都高于种植作物的农田土壤;而其代谢商和容重值低于农田土壤。长期施肥的农田(NPK、NPKM 、NPKS和NPKF),其土壤养分含量、微生物量碳和氮以及土壤蔗糖酶、磷酸酶和脲酶活性均高于不施肥的农田(CK);而小麦(Triticum aestivum)-玉米(Zea mays)→小麦-大豆(Glycine max)复种轮作(NPKF)的农田又高于长期复种连作(NPK)的农田;在施肥处理中(NPK、NPKM、NPKS和NPKF),长期化肥与有机肥配合施用的处理(NPKM )的土壤上述指标高于其它施肥处理(NPK、NPKS和NPKF),但其土壤的代谢商、pH值和容重值较低。     

陕北水蚀风蚀交错区两种生物结皮对土壤理化性质的影响

以黄土高原陕北水蚀风蚀交错区六道沟小流域为例,研究了该区以苔藓为主要成分的沙土和黄土两种生物结皮对土壤理化性质的影响。结果显示:(1)两种生物结皮均能显著增加土壤饱和含水量和田间持水量,降低容重和饱和导水率,其中沙土生物结皮还可明显粘化0～25cm土壤质地;(2)两种生物结皮均能不同程度的增加土壤全量养分、速效养分以及有机质含量,降低pH值,但其影响多数集中在表层或结皮层;(3)土壤化学性质中,全氮、速效磷和有机质受生物结皮影响程度较大,而全氮、速效钾和有机质受生物结皮影响土层较深;(4)沙土生物结皮对土壤理化性质的影响程度大于黄土生物结皮。两种类型生物结皮对所研究土壤理化性质的影响总体有利于该区生态环境的改善,且沙土生物结皮较黄土生物结皮具有更为重要的生态功能。     

三江平原典型小叶章湿地土壤氮素净矿化与硝化作用

2004年6月—2005年7月,利用PVC顶盖原位培育法研究了三江平原典型草甸小叶章湿地和沼泽化草甸小叶章湿地土壤(0~15cm)无机氮库、净矿化/硝化速率动态、影响因素及年净矿化/硝化量.结果表明:两种湿地土壤的无机氮均呈明显的动态变化特征,其NH4 -N、NO3-N含量均表现为典型草甸小叶章湿地>沼泽化草甸小叶章湿地.两种湿地土壤的净矿化/硝化速率均呈明显的波动变化,生物固持作用、反硝化作用以及雨季较多降水是导致净矿化/硝化速率出现负值的主要原因.温度、降水、土壤有机质含量、C/N和pH是引起二者土壤无机氮库、净矿化/硝化速率存在明显差异的重要原因.典型草甸小叶章湿地的年净矿化量(19.41kg·hm-2)、年净硝化量(4.27kg·hm-2)以及净硝化量占净矿化量的百分比(22.00%)明显高于沼泽化草甸小叶章湿地(5.51kg·hm-2、0.28kg·hm-2和5.08%),说明前者的氮有效性以及维持可利用氮的能力明显高于后者.     

Anthropogenic N deposition increases soil organic matter accumulation without altering its biochemical composition

Accumulating evidence indicates that future rates of atmospheric N deposition have the potential to increase soil C storage by reducing the decay of plant litter and soil organic matter (SOM). Although the microbial mechanism underlying this response is not well understood, a decline in decay could alter the amount, as well as biochemical composition of SOM. Here, we used size‐density fractionation and solid‐state ¹³C‐NMR spectroscopy to explore the extent to which declines in microbial decay in a long‐term (ca. 20 yrs.) N deposition experiment have altered the biochemical composition of forest floor, bulk mineral soil, as well as free and occluded particulate organic matter. Significant amounts of organic matter have accumulated in occluded particulate organic matter (~20%; oPOM); however, experimental N deposition had not altered the abundance of carboxyl, aryl, alkyl, or O/N‐alkyl C in forest floor, bulk mineral soil, or any soil fraction. These observations suggest that biochemically equivalent organic matter has accumulated in oPOM at a greater rate under experimental N deposition, relative to the ambient treatment. Although we do not understand the process by which experimental N deposition has fostered the occlusion of organic matter by mineral soil particles, our results highlight the importance of interactions among the products of microbial decay and the chemical and physical properties of silt and clay particles that occlude organic matter from microbial attack. Because oPOM can reside in soils for decades to centuries, organic matter accumulating under future rates of anthropogenic N deposition could remain in soil for long periods of time. If temperate forest soils in the Northern Hemisphere respond like those in our experiment, then unabated deposition of anthropogenic N from the atmosphere has the potential to foster greater soil C storage, especially in fine‐texture forest soils.     

Nitrogen mineralization and its controlling factors in various kinds of temperate humid-zone soils

The N mineralization capacity of 41 temperate humid-zone soils of NW Spain was measured by aerobic incubation for 15 days at 28°C and 75% of field capacity. The main soil factors affecting organic N dynamics were identified by principal components analysis. Ammonification predominated over nitrification in almost all soils. The mean net N mineralization rate was 1.63% of the organic N content, and varied according to soil parent materials as follows: soils on basic and ultrabasic rocks < soils over acid metamorphic rocks < soils developed over sediments < soils over acid igneous rocks < soils on limestone. The N mineralization capacity was lower in natural soils than in cropped soils or pastures. The accumulation of organic matter (C and N) seems to be due to poor mineralization which was caused, in decreasing order of importance, by high exchangeable H-ion levels, high Al and Fe gel contents and, to a lesser extent (though more markedly in cropped soils), by silty clay texture and exchangeable Al ions.     

蚂蚁筑巢对西双版纳热带森林土壤碳矿化动态的影响

蚂蚁作为生态系统工程师,能够通过筑巢定居活动增加有机物的输入、改变理化环境及刺激微生物活动,进而影响土壤有机碳矿化动态.本研究以西双版纳高檐蒲桃热带森林群落为研究对象,比较了蚁巢地与非巢地土壤有机碳矿化速率的动态特征,分析蚂蚁筑巢引起的土壤理化性质改变对土壤碳矿化速率的影响.结果表明: 蚂蚁筑巢显著影响土壤有机碳的矿化,相较于非巢地,蚁巢地平均土壤有机碳矿化速率提高19.2%;巢地与非巢地土壤有机碳矿化速率均表现为6月>9月>3月>12月;蚁巢地土壤有机碳矿化速率最大值出现在10～15 cm土层,而非巢地土壤有机碳矿化速率0～5 cm土层最高;蚂蚁筑巢对土壤理化性质产生了显著影响,相较于非蚁巢地,蚁巢地土壤温度、水分、有机碳、微生物生物量碳、全氮、水解氮、硝态氮和铵态氮平均增加幅度分别为7.6%、5.4%、9.9%、14.8%、13.4%、9.9%、24.1%、6.6%和19.4%,而土壤容重和pH平均降幅分别为1.4%和2.5%.相关性分析及主成分分析表明,土壤有机碳和土壤微生物量碳是影响土壤有机碳矿化速率的主控因子,土壤全氮、水解氮、铵态氮、硝态氮、温度和土壤含水率对土壤有机碳矿化的贡献次之.蚂蚁筑巢主要显著改变有机碳矿化的底物组分(土壤有机碳和土壤微生物生物量碳),进而调控西双版纳热带森林土壤有机碳矿化速率的时空动态.     

草原土壤有机碳含量的控制因素

基于374个高寒草原和温带草原土壤样品的测试结果,运用多元逐步回归分析模型定量评估了土壤环境因子对土壤有机碳(SOC)含量的影响.结果表明:高寒草原土壤有机碳含量(20.18 kg C/m2)高于温带草原(9.23 kg C/m2).土壤理化生物学因子对高寒草原和温带草原SOC含量(10 cm)变化的贡献分别是87.84％和75.00％.其中,土壤总氮含量和根系对高寒草原SOC含量变化的贡献均大于对温带草原SOC含量变化的相应贡献.土壤水分是温带草原SOC含量变化的主要限制性因素,其对SOC含量变化的贡献达33.27％.高寒草原土壤C/N比显著高于温带草原土壤的相应值,揭示了青藏高原高寒草原较高的SOC含量是由于较低的土壤微生物活性所导致.