退化草地土壤农化性状与微生物区系研究

通过对三种退化程度不同的草地土壤农化性状与微生物区系进行研究，结果表明，草地退化后，其土壤肥力水平、土壤微生物数量和微生物种类有随退化程度增高而下降的趋势；退化草地存在不同的程度的营养元素比例失调，表现为少氮、缺磷、富钾和高有机质含量，且退化程度接近的草地间，在土壤微生物区系和农化性状有部分类似的特征。     

退化演替对高山草地植被和土壤理化特性影响

[目的]分析3种不同草地退化阶段(轻度退化,中度退化和重度退化)草地植被和土壤理化特性的变化规律,为类似区域退化草地植被恢复提供有效途径。[方法]野外植被调查、土壤取样和室内分析。[结果]草地退化不同阶段草地植物群落组成和物种多样性均有差异,退化对草地土壤理化特性有明显影响。重度退化草地土壤容重显著高于轻度退化草地(p0.05)。轻度和中度退化样地0—10cm土壤空隙度显著高于重度退化草地。重度退化草地的土壤有机质、全碳、全钾、全磷和有效钾均明显小于轻度退化草地(p0.05),但土壤pH值和有效氮含量没有显著变化。[结论]高山草地退化演替对该区土壤物理特性具有显著影响。     

The effect of soil pH manipulation on chemical properties of an agricultural soil from northern Idaho

Abstract

Selected chemical properties of an artificially acidified agricultural soil from northern Idaho were evaluated in a laboratory study. Elemental S and Ca(OH)₂were used to manipulate the soil pH of a Latahco silt loam (fine‐silty, mixed, frigid Argiaquic Xeric Argialboll), which had an initial pH of 5.7. A 100 day incubation period resulted in a soil pH manipulation range of 3.3 to 7.0. Chemical properties evaluated included: N mineralization rate, extractable P, AI, Mn, Ca, Mg and K and CEC. N mineralization rate (assessed by anaerobic incubation) decreased with decreasing soil pH. Nitrification rate also decreased as NH₄ ⁺‐N accumulated under acid soil conditions. Sodium acetate extractable P was positively linearly correlated (R²= 0.87) with soil pH over the entire pH range evaluated. Potassium chloride extractable Al was less than 1.3 mg kg^‐1of soil at pH values higher than 4.4. Consequently, potential Al toxicity problems in these soils are minimal. Extractable Mn increased with decreasing soil pH. Soil CEC, extractable Mg, and extractable K all decreased with increasing soil pH from 3.3 to 7.0. Extractable Ca levels were largely unaffected by changing soil pH. It is likely that the availability of N and P would be the most adversely affected parameters by soil acidification     

中度火干扰对林草地土壤理化特性的短期影响

火干扰作为一种自然扰动现象,对土壤物理、化学、矿化和微生物等土壤性质产生一定影响.在河南具茨山国家级森林公园过火林地和草地,进行土壤样品(0～5和5～10 cm土层)采集,测定表征土壤渗透性和持水能力的指标,研究中度火干扰对不同土层土壤理化特性的短期影响.结果表明:中度火干扰造成草地和林地土壤表层(0 ～5 cm)的土壤密度、含水率和非毛管孔隙度显著下降(P＜0.05),但火烧前后,土壤5～ 10 cm层上述物理特性指标之间没有显著差异(P＞0.05);火烧后草地和林地土壤表层(0～5 cm)有机C和全N显著下降(P＜0.05),而土壤pH、全P和全K显著上升(P＜0.05),相似的现象出现在草地土壤5～10 cm层,火烧前后林地土壤5～ 10 cm层,各化学特性指标没有显著差异(P＞0.05).火烧使草地和林地土壤0～5cm层的土壤初渗率、稳渗率和平均入渗率均显著上升(P＜0.05),而对土壤5 ～10 cm层土壤各渗透特性指标没有显著影响(P＞0.05);火烧使草地和林地土壤0 ～～5 cm层土壤最大持水量和有效持水量均显著下降(P＜0.05),草地和林地最大持水量分别从未过火289.984和390.971t/hm2,下降到258.072和342.386 t/hm2.该研究为开展火烧迹地植被恢复、水土保持和森林经营管理措施的制定,提供科学依据.     

宁夏盐池县草地沙化对植被与土壤特征的影响

通过野外调查和室内分析相结合的方法,研究了盐池县不同沙化程度下草地植被特征和土壤特性的变化,以探讨植被和土壤对沙化的响应机制。结果表明,随着草地沙化程度的加剧,植被组成发生变化,多年生草本植物呈逐渐减少,一年生草本植物呈逐渐增加的趋势;生物多样性指数变化趋势为轻度沙化草地到中度沙化草地增加,自中度沙化草地至极度沙化草地先降低后又增加,中度沙化阶段是草地植物群落特征变化的重要转折时期。随着草地沙化加剧,土壤含水量、有机质、氮含量降低;重度沙化阶段土壤磷、钾含量最高,pH值和可溶性盐无明显变化规律。     

川西北不同沙化程度草地土壤细菌群落特征

研究川西北不同沙化程度草地（未沙化草地、轻度沙化草地、中度沙化草地、重度沙化草地）土壤细菌多样性和群落结构特征,利用Illumina二代高通量测序技术MiSeq对土壤细菌的16 SrRNA V₃—V₄可变区进行测序,研究土壤细菌多样性、物种组成和丰富度,并结合土壤理养分探讨影响细菌群落结构的环境因素,对发挥土壤潜在肥力,了解土壤健康状况,实现该区植被的管理与可持续利用有着重要的意义。结果表明:（1）不同沙化草地土壤养分具有明显差异,依次表现为:随着沙化程度的增加,土壤pH值逐渐增加,而土壤有机碳、全氮、全钾、碱解氮和速效磷逐渐降低;（2）不同沙化程度草地土壤样品中共检测到细菌的32个门,65个纲,169个目,优势菌门为变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、绿弯菌（Chloroflexi）、浮霉菌门（Planctomycetes）,主要的优势菌纲为放线杆菌纲（Actinobacteria）、α-变形菌纲（α-Proteobacteria）、酸杆菌纲（Acidobacteria）、β-变形菌纲（β-Proteobacteria）、浮霉菌纲（Planctomycetacia）,与沙化草地相比,未沙化草地优势菌主要是变形菌门（Proteobacteria）和放线菌门（Actinobacteria）;（3）随着沙化程度的增加,OUT数目、Chao指数、Ace指数、Shannon指数逐渐减小,其中不同沙化草地土壤细菌覆盖率和Simpson指数差异不显著（p > 0.05）;（4）冗余分析和Pearson相关性分析表明,土壤pH值、土壤有机碳（SOC）和全氮（TN）是土壤细菌群落结构和多样性的主要影响因子。     

A preliminary watershed scale soil quality assessment in north central Iowa, USA

Soil quality assessment has been recognized as an important step toward understanding the long-term effects of conservation practices within agricultural watersheds. Our objective was to assess soil quality within the South Fork watershed of the Iowa River using various indicators and assessment approaches. Soil samples were collected during 2003 and 2004 from 29 areas of 32 ha (80 acres) each along two transects traversing the watershed. Soil pH, Mehlich III extractable P, K, Ca and Mg, electrical conductivity (EC), total organic carbon (TOC), and total N (TN) were measured. The Soil Management Assessment Framework (SMAF) was used to compute a soil quality index (SQI), while soil loss, the soil tillage intensity rating (STIR), N-leaching potential, and soil conditioning index (SCI) were determined for each sampling area using the 2003 version of the Revised Soil Loss Equation (RUSLE2). Overall, there were no soil fertility limitations within the watershed based on an average pH of 6.96 and extractable P and K levels of 36 and 162 mg kg⁻¹, respectively. Soil loss, STIR, N-leaching, and SCI averaged 1.13 Mg ha⁻¹, 68, 3, and 0.4, respectively. The SMAF analysis indicated soils within the watershed were functioning at 87% of their full potential. The lowest indicator score was associated with TOC (0.60) because the average value was only 28.4 g kg⁻¹. The SCI and SQI indices were positively correlated although since it used measured data, the SMAF appears to provide more information about the effects of management practices within the watershed. Soils in upper landscape positions had lower TOC and C:N ratios indicating an increased risks for both erosion and for nitrate leaching. Management of soils on hilltops may be the most effective way to minimize N and P losses within the watershed.     

EFFECT OF SOIL WATER AND NUTRIENTS ON PRODUCTIVITY OF KENTUCKY BLUEGRASS SYSTEM IN ACIDIC SOILS

The grasslands of the Appalachian region spread over undulating terrain with high annual precipitation rate which causes a large variation in soil and nutrient factors like water potential (WP), pH, nitrogen (N) and phosphorus (P) levels. There is a need to understand these factors and their interactive effects to design precise agronomic practices for acidic grasslands to maximize production. A pot experiment was conducted with an objective to quantify the effects of WP, pH, N and P rates on herbage accumulation and nutrient recovery of Kentucky bluegrass (Poa pratensis L.) cropping system. Centrally rotatable composite design was applied to study the effects of two levels of WP and five levels each of pH, N, and P fertilizer additions in order to optimize bluegrass herbage mass (yield). WP, pH, and N were significant main effects, as were the interactions WP × pH, WP × N, and pH × N. The yield response function was derived from these four factors. The order of importance for these model parameters based on their effect on herbage accumulation was WP > N > WP × pH > pH >WP × N > pH × N. The optimum levels of WP, soil pH, N, and P rates were predicted for Kentucky bluegrass by using the response surface yield model of this pot study i.e., WP of ?422 kPa to ?166 kPa, 5.5–6.1 soil pH, 50–68 N mg kg^?1, 36–40 P mg kg^?1. Concentration (%) of nutrients like N, P, potassium (K), calcium (Ca), and magnesium (Mg) were determined to study the impact of WP, pH, N, and P factors and their interactions on plant nutrient recovery. Main effects like WP, pH, and N levels had significant influence on N and P concentration in plant tissue. K, Ca, and Mg concentrations in plant tissue were significantly affected by WP, pH and their interaction. The results of this greenhouse study imply the necessity to incorporate the information about the variation of soil and nutrient factors in designing precise agronomic practices to low productive acid reclaimed grasslands with undulating topography and high annual precipitation rate.     

Historical influences on the vegetation and soils of the Martha’s Vineyard, Massachusetts coastal sandplain: Implications for conservation and restoration

Both disturbance history and previous land use influence present-day vegetation and soils. These influences can have important implications for conservation of plant communities if former disturbance and land use change species abundances, increase colonization of nonnative plant species or if they alter soil characteristics in ways that make them less suitable for species of conservation interest. We compared the plant species composition, the proportion of native and nonnative plant species, and soil biogeochemical characteristics across seven dominant land use and vegetation cover types on the outwash sandplain of Martha’s Vineyard that differed in previous soil tillage, dominant overstory vegetation and history of recent prescribed fire. The outwash sandplain supports many native plant species adapted to dry, low nutrient conditions and maintenance of native species is a management concern. There was broad overlap in the plant species composition among pine (Pinus resinosa, P. strobus) plantations on untilled soils, pine plantations on formerly tilled soils, scrub oak (Quercus ilicifolia) shrublands, tree oak (Q. velutina, Q. alba) woodlands, burned tree oak woodlands, and sandplain grasslands. All of these land cover categories contained few nonnative species. In contrast, agricultural grasslands had high richness and cover of nonnative plants. Soil characteristics were also similar among all of the woodland, shrubland and grassland land cover categories, but soils in agricultural grasslands had higher pH, extractable Ca²⁺ and Mg²⁺ in mineral soils and higher rates of net nitrification. The similarity of soils and significant overlap in vegetation across pine plantations, scrub oak shrublands, oak woodlands and sandplain grasslands suggests that the history of land use, current vegetation and soil characteristics do not pose a major barrier to management strategies that would involve conversion among any of these vegetation types. The current presence of high cover of nonnative species and nutrient-enriched soils in agricultural grasslands, however, may pose a barrier to expansion of sandplain grasslands or shrublands on these former agricultural lands if native species are not able to outcompete nonnative species in these anthropogenically-enriched sites.     

东祁连山不同退化草地植物群落特征与土壤养分特性

为探究东祁连山不同退化草地植物群落特征、土壤养分特性及其相关性,以轻度退化草地、中度退化草地和重度退化草地为研究对象,采用野外调查、室内测定和数据统计分析相结合的方法,分析了不同退化草地植被特征、土壤养分特性及其之间的相关性。结果表明:(1)从轻度退化草地-重度退化草地,植物群落特征(地上生物量、高度、密度、频度和总盖度)整体呈现降低趋势,且差异显著(P<0.05),中度退化草地Margalef指数、Shannon指数和Evenness指数最高,Dominance指数最低;(2)研究区植物共有19科38属41种,生态适应性较强的植物主要集中在豆科、禾本科、菊科和蔷薇科,不同退化草地植被型分别为矮生嵩草(K.humilis)+赖草(Leymus secalinus)、矮生嵩草+高山唐松草(Thalictrum alpinum)、矮生嵩草+赖草,其中矮生嵩草是各退化草地的优势种,不同退化草地的功能群以杂类草占优势,其次是禾草类,毒草类所占的比例最少;(3)随草地退化程度加重,土壤速效氮、有效磷、有机碳和含水量呈降低的趋势,而pH整体呈现升高的趋势;(4)不同退化草地土壤因子对植被生长贡献率最高分别为速效氮、有效磷和含水量。综上,随着草地退化程度加重,植物群落结构向单一趋势过渡,土壤养分含量减少,且土壤因子对植物贡献率也相应发生变化。     

盐碱草甸植被退化对土壤硝化作用强度的影响

为了解不同退化阶段盐碱草甸草原土壤硝化作用强度特征及其影响因素,采用空间代替时间的方法,以松嫩平原盐碱草甸草原植被退化过程中4种典型植物群落为对象,以未做处理为参照,设置刈割、施氮和刈割同时施氮3种处理,测定了土壤的硝化作用强度(NI)、pH值、电导率(EC)、含水量(SMC)和有效磷(OP)、硝态氮(NO^-₃-N)、铵态氮(NH+4-N)及全氮(TN)的含量。结果显示:(1)土壤NI与pH值、电导率、含水量、OP和NO^-₃-N呈极显著正相关关系(p<0.01);通过逐步回归分析的方法得出土壤NI的重要影响因子,重要影响因子对土壤NI影响强弱表现为:pH值>有效磷含量>含水量>硝态氮含量,并推断土壤硝态氮含量可作为土壤NI的一个重要表征参数。(2)未作处理时,星星草群落与碱蓬群落土壤硝化作用强度分别为13.4,13.5 mg/(kg·h),显著高于羊草群落和退化羊草群落的5.0,2.5 mg/(kg·h),刈割和施氮处理分别使星星草群落土壤NI提高96.88%,253.77%,混合处理使其提高413.70%,显著高于其他3种植物群落,由此可见,在人为刈割和施氮肥的干预下,星星草群落土壤铵态氮可能更易转变为硝态氮,氮素流失的风险也更大,因此可认为星星草群落处于盐碱草甸退化过程中的关键阶段。     

Long-term cultivation impacts on selected soil properties in the northern Great Plains

Long-term cultivation impacts soil properties. During the early 1920s a study comparing non-cultivated and cultivated soils was done in eastern SD (Beadle, McCook, Minnehaha, and Union Counties), USA. The objectives of the current study were to: (1) determine the long-term (>80 years) impact of cultivation on selected soil properties; and (2) establish baseline soil data that can be used for future comparisons. Sample sites were located in well-drained summit and upper backslope positions. These topographic positions are strongly influenced by erosion processes from tillage, wind, and water. Previous studies at other locations in the region suggest that one might expect a loss of 10–20 cm of soil in >80 years of cultivation at these topographic positions. In the early 1920s the soils were tested for carbon (C) (total, organic, inorganic), total nitrogen (N), total sulfur (S), total calcium (Ca), total phosphorus (P), total potassium (K), and total magnesium (Mg). The 1920s study sites were resampled at 0–15, 15–50, and 50–100 cm depths and analyzed for C (total, organic, inorganic), N (total, nitrate-N), extractable P, extractable K, delta N (¹⁵N/¹⁴N or δ¹⁵N) for total N, delta C (¹³C/¹²C or δ¹³C) for total C, and pH. Long-term cultivation (>80 years) in the northern Great Plains of the United States has caused many significant reductions in surface soil (0–15 cm) extractable P, extractable K, surface pH, total C, organic C, total N, and δ¹⁵N for total N. In addition, the organic C to total N ratio for the 15–50 cm depth of cultivated soils was significantly lower when compared to non-cultivated soils. Cultivation caused significant increases in nitrate-N, delta C, inorganic C, and in the total C to total N and inorganic C to total N ratios (15–100 cm depths). Soil properties varied significantly with increasing soil depth. Soil pH, δ¹³C for total C, inorganic C, total C to total N ratio, and inorganic C to total N ratio increased significantly as soil depth increased. Nitrate-N, extractable P, extractable K, δ¹⁵N for total N, organic C, and total N decreased significantly as soil depth increased. Soil carbon changes at the sample sites are a combined result of differences in the reference surface elevation, carbon mineralization, and redistribution of carbon due to erosion. Changes in soil nutrient levels reflect crop removal, leaching, erosion, and pedogenic processes.     

Comparison of mehlich 3, mehlich 1, ammonium bicarbonate‐DTPA, 1.0M ammonium acetate,and 0.2M ammonium chloride for extraction of calcium,magnesium, phosphorus,and potassium for a wide range of soils

Abstract

Extractants employed for routine soil analysis vary from one laboratory to another. Lack of a universal soil extractant is a serious limitation for interpretation of analytical results from various laboratories on nutritional status of a given soil. This limitation can be overcome by developing functional relationships for concentrations of a given nutrient extractable by various extradants. In this study, extractability of Ca, Mg, P, and K in a wide range of soils (0–15 cm) from citrus groves in Florida representing 21 soil series, with varying cultural operations, were compared using Mehlich 3 (M3), Mehlich 1 (M1), ammonium acetate (NH₄AOc), pH = 7.0 (AA), 0.2M ammonium chloride (NH₄Cl), and ammonium bicarbonate‐DTPA (AB‐DTPA) extractants. Soil pH (0.01M CaCl₂) varied from 3.57 to 7.28. The concentrations of Ca or Mg extractable by M3, M1, AA, and NH₄Cl were strongly correlated with soil pH (r² = 0.381–0.482). Weak but significant correlations were also found between AB‐DTPA extractable Ca or Mg and soil pH (r² = 0.235–0.278). Soil pH relationships with extractable K were rather weak (r² = < 0.131) for M1 and NH₄Cl but non‐significant for M3, AB‐DTPA, and AA. Concentrations of Ca, Mg, and K extractable by M3 were significantly correlated with those by either M1, AA, or NH₄Cl extractants. Mehlich 3‐P was significantly correlated with P extractable by M1 extractant only. Mehlich 3 versus AB‐DTPA relationship was strong for K (r² = 0.964), weaker for Mg and P (r² = 0.180–0.319), and non‐significant for Ca. With the increasing emphasis on possible use of M3 as an universal soil extractant, data from this study support the hypothesis that M3 can be adapted as a suitable extractant for routine soil analysis.     

Soil‐test values after eight years of tillage research on a Norfolk loamy sand

Abstract

Long‐term effects of alternate tillage systems on soil‐test values for Coastal Plain soils were unknown. Therefore, soil pH, organic carbon, and Mehlich I extractable P, K, Ca, and Mg concentrations measured during an eight‐year tillage study on Norfolk loamy sand (fine‐loamy, silicious, thermic, Typic Paleudults) have been summarized. Yields for corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] are also summarized to provide an indication of nutrient removal by the crops. Soil‐test measurements after six years showed no significant differences in Mehlich I extractable nutrient concentrations for the 0‐ to 20‐cm depth between disked (conventional) and nondlsked (conservation) tillage treatments, but for pH, P, Ca, and Mg, the tillage by depth of sampling interaction was significant at P‐0.05. Stratification did not appear to affect crop yield. Soil organic matter concentration in the Ap horizon nearly doubled after eight years of research at this site. This change occurred within both tillage treatments, apparently because high levels of management produced good crop yields, residues were not removed, and even for the disked treatment, surface tillage was not excessive. These results show that long‐term average yields for corn and soybean on Norfolk soil will not be reduced by adopting reduced or conservation tillage practices. They also show that nutrient levels can be maintained at adequate levels for crop production on Coastal Plain soils by using current soil‐test procedures and recommendations for lime and fertilizer application.     

Development of soil microbial communities during tallgrass prairie restoration

Soil microbial communities were examined in a chronosequence of four different land-use treatments at the Konza Prairie Biological Station, Kansas. The time series comprised a conventionally tilled cropland (CTC) developed on former prairie soils, two restored grasslands that were initiated on former agricultural soils in 1998 (RG₉₈) and 1978 (RG₇₈), and an annually burned native tallgrass prairie (BNP), all on similar soil types. In addition, an unburned native tallgrass prairie (UNP) and another grassland restored in 2000 (RG₀₀) on a different soil type were studied to examine the effect of long-term fire exclusion vs. annual burning in native prairie and the influence of soil type on soil microbial communities in restored grasslands. Both 16S rRNA gene clone libraries and phospholipid fatty acid analyses indicated that the structure and composition of bacterial communities in the CTC soil were significantly different from those in prairie soils. Within the time series, soil physicochemical characteristics changed monotonically. However, changes in the microbial communities were not monotonic, and a transitional bacterial community formed during restoration that differed from communities in either the highly disturbed cropland or the undisturbed original prairie. The microbial communities of RG₉₈ and RG₀₀ grasslands were also significantly different even though they were restored at approximately the same time and were managed similarly; a result attributable to the differences in soil type and associated soil chemistry such as pH and Ca. Burning and seasonal effects on soil microbial communities were small. Similarly, changing plot size from 300 m² to 150 m² in area caused small differences in the estimates of microbial community structure. In conclusion, microbial community structure and biochemical properties of soil from the tallgrass prairie were strongly impacted by cultivation, and the microbial community was not fully restored even after 30 years.     

松嫩平原盐碱草地主要植物群落土壤酶活性研究

采用现场采样及室内测试方法,研究了松嫩平原盐碱草地主要植物群落羊草(Leymus chinensis)、芦苇(Phragmites australis)、虎尾草(Chloris virgata)、碱茅(Puccinellia tenuiflora)、碱蓬(Suaeda glauca)以及盐碱荒地上土壤磷酸酶、脲酶和蔗糖酶的酶活性值以及垂直分布规律,并对3种酶活性与各理化因子之间进行了相关分析。结果表明:羊草群落的磷酸酶、脲酶、蔗糖酶活性值均为最高,芦苇、虎尾草群落土壤的酶活性值也较高,碱茅群落的土壤酶活性较低,而碱蓬群落土壤酶活性值最低,接近于盐碱荒地上土壤酶活性值。各植物群落的土壤酶活性垂直分布多表现为随着土壤深度的加深而呈现依次递减的规律,且表层(0～10 cm)土壤酶活性在所有根层总酶活性中所占的比例最大,占根层(0～40 cm)土壤酶活性的50%以上。土壤酶与土壤理化因子相关分析表明,土壤的土壤酶活性大多与EC、pH值显著负相关,对土壤酶活性影响较大;土壤酶活性与土壤养分正相关,脲酶与其相关性较大,蔗糖酶与养分的相关关系不是很明显。     

Phosphorus sorption by four soils receiving long‐term applications of fertilizer

Abstract

A laboratory study was conducted to evaluate P sorption in the Ap horizon of four soil series in the Ultisol order (Benndale Is, Hartsells fsl, Lucedale fsl, and Dewey sicl) receiving the same fertility treatments since 1929. Soil was collected in the spring of 1985 from 4 treatments: i) no‐lime, plus P (total fertilizer P = 1584 kg/ha from 1929 to 1985); ii) no‐K, plus P (total fertilizer P = 1584 kg/ha); iii) low‐P (total fertilizer P = 442 kg/ha); 4) standard treatment (total fertilizer P = 2376 kg/ha). The soils and treatments within a soil varied in pH, total P, Mehlich 1 extractable P, K, Ca and Mg, and KC1 extractable Al. The four soils had large differences in P sorption capacity which increased with increasing clay content. The Dewey (27 % clay) soil had the highest P sorption capacity and the Benndale (4 % clay) soil had the smallest P sorption capacity. Sorption of P within a soil was affected by the rate of added P and past fertility treatment. Treatment differences in P sorption were due primarily to the level of extractable P and soil pH. Within a given soil, P sorption (at a given rate of added P) generally decreased as the level of extractable P increased. Regression analysis of P sorption data for equilibrium P concentrations of 1 to 32 μmol/L showed that the parti‐ tioning between sorbed and solution P (buffer power) had not been changed by 56 years of annual applications of P. The maximum P sorption capacity of the four soils was decreased slightly by P fertilization.     

Relationship of soil phosphorus with uranium in grassland mineral soils in Ireland using soils from a long‐term phosphorus experiment and a National Soil Database

Phosphorus fertilizer contains contaminants that may increase the content in the soil and in plants. The relationship between soil P and soil uranium (U) was investigated to determine potential effects of P‐fertilizer use. This study is based on a long‐term experiment (38 years with 0, 15, and 30 kg fertilizer P ha^–1 y^–1) for beef production on grassland at Teagasc, Johnstown Castle, Wexford, Ireland and also on soils from a National Soil Database (NSD). The NSD soils were taken at fixed locations on a predetermined grid system at the density of one sample every 50 km². Of the 1310 samples in the NSD, the 760 grassland mineral soils were selected for this study. The aim was to determine to what extent P fertilizer increases the content of U in the soil. The results showed that there was a small but significant increase in soil U in the high‐P treatments, which contained high levels of soil P, in the long‐term field experiment. The results from the NSD showed that there was not a significant relationship between extractable (Morgan's) soil test P (STP) and U. It is concluded that the use of chemical P fertilizer at normal rates used in agriculture in Ireland is not a major threat to U content of soil based on the results of this study. There was a significant relationship between total P and STP, in the NSD, with the latter making up approx. 1% of the former. Soil available P increased with soil pH, probably reflecting the use of chemical P fertilizer and lime on agricultural soils.     

不同气候条件对旱地红壤微生物群落代谢特征的长期影响

利用1988年设置的暖温带和中亚热带两种气候条件下的土壤置换试验,采用BIOLOG方法,研究了气候条件对红壤中微生物群落功能的影响。结果表明,长期处于不同的气候条件改变了红壤的pH和养分状况,从而影响红壤微生物群落的代谢特征。与中亚热带气候条件相比,暖温带气候条件下,红壤的pH和全磷含量显著升高,速效钾含量显著下降;红壤微生物群落活性(以AWCD值表示)也显著降低。主成分分析表明,不同气候条件下红壤微生物群落代谢特征显著不同,与暖温带气候相比,中亚热带气候条件下,红壤微生物群落对氨基酸、胺类和酚类化合物等含氮化合物的利用显著增加。相关分析表明,影响不同气候条件下红壤微生物代谢特征的主要因素有:温度和降雨量气候因子,土壤pH、速效钾和全氮含量等土壤因子。     

The effect of soil type on phosphorus sorption capacity and desorption dynamics in Irish grassland soils

Abstract. The phosphorus (P) sorption and desorption dynamics of eleven major agricultural grassland soil types in Ireland were examined using laboratory techniques, so that soils vulnerable to P loss might be identified. Desorption of P from soil using the iron-oxide paper strip test (Pfeo), water extractable P (Pw) and calcium chloride extractable P (Pcacl₂) depended on soil P status in all soils. However, soil types with high organic matter levels (OM), namely peat soils (%OM >30), had lower Pfeo and Pw but higher Pcacl₂ values compared to mineral soils at similar soil test P levels. Phosphorus sorption capacity remaining (PSCr) was measured using a single addition of P to soils and used to calculate total P sorption capacities (PSCt) and degree of P saturation (DPS). Phosphorus sorption capacities correlated negatively with % OM in soils indicating that OM may inhibit P sorption from solution to soil. High organic matter soils exhibited low P sorption capacities and poor P reserves (total P, oxalate extractable P) compared to mineral soils. Low P sorption capacities (PSCt) in peat soils were attributed to OM, which blocked or eliminated sorption sites with organic acids, therefore, P remained in the soil solution phase (Pcacl₂). In this work, peat and high organic matter soils exhibited P sorption and desorption characteristics which suggest that these soils may not be suitable for heavy applications of manure or fertilizer P owing to their low capacities for P sorption and storage.