沈阳市苏家屯区耕层土壤养分空间变异性研究

利用地统计学和地理信息系统相结合的方法。研究了沈阳市苏家屯区耕地土壤(0～20cm)有机质、速效氮、速效磷、速效钾含量的空间变异性特征。结果表明，各变量符合正态分布或经对数转换后符合正态分布，最佳的变异函数理论模型均为球状模型，有机质具有较强的空间相关性(C0与C0+C比值为24．11％)，速效氮、速效磷、速效钾具有中度的空间相关性(C0与C0+C比值分别为29．53％、60．77％、58．82％)，各变量的空间自相关距离分别为26．051、28．293、15．132和23．813km。有机质和速效氮的空间变异主要受结构性因子(如成土因子)的影响，速效磷和速效钾主要受随机性因子(如施肥)的影响，Kriging插值绘制出的养分含量空间分布图显示了养分的空间分布格局，它将有助于进一步监测养分动态，为农业和环境管理提供数字地图支持。  

长期施肥对石灰性土壤磷素肥力的影响Ⅰ．有机质、全磷和速效磷

在陕西关中黄土区连续23年进行了不同施肥、小麦-玉米轮作定位试验。研究了0～100cm土层土壤有机质、全磷、速效磷含量变化．结果表明，长期单施化肥或有机肥与化肥且配施均可增加耕层(0～20cm)土壤有机质含量．长期施用厩肥并配施化肥处理对土壤总磷库及无机磷库、速效磷的贡献大于玉米秸秆处理．长期单施化肥可增加土壤全磷、无机磷和速效磷含量，增加幅度低于厩肥和休闲处理，与秸秆处理对全磷、速效磷含量的影响效应相近．23年的不同施肥处理，与无肥处理相比，其理土壤磷素增量在0～100cm土壤剖面中的分布特点是：全磷增量剖面分布可为3层——耕层(0～20cm)为显著累积层，20～60cm土层为微增一亏损层，60～100cm土层为轻度累积层．速效磷增量剖面分布趋势与全磷增量分布趋势基本相同，仅在60～100cm土层累积较弱．  

云南保山西庄山地流域土地利用方式与土壤肥力关系研究

以云南省保山地区西庄流域为例，研究了自然因素及人为活动对土壤性质的影响。该流域的土壤通常pH较低，缺乏有效磷和交换性阳离子。仅发育于石灰岩的土壤具适宜的pH和交换性阳离子量。海拔对土壤有机碳含量具显著影响。文中详细讨论了海拔、母质和土地利用方式等对土壤肥力及土壤侵蚀的影响。  

甘南亚高山草甸人工草地的演替和质量变化

甘南亚高山草甸不同时间建立的垂穗披碱草（Ｅｌｙｍ ｕｓ ｎｕｔａｎｓ）人工草地植物群落结构和草地质量变化及其原因的研究结果表明： １． 垂穗披碱草人工草地只有在播种后第二年的产量最高，而草地质量指数ＩＧＱ （ｉｎｄｅｘ ｏｆｇｒａｓｓｌａｎｄ ｑｕａｌｉｔｙ）在七年生群落中最低； ２． 垂穗披碱草人工草地群落的种类数量和种多样性随年龄而增加，但其增加的模式各不相同； ３． 人工草地中垂穗披碱草地上部生物量的下降和草地质量指数的下降与土壤中速效磷含量的下降有关，而速效氮的含量对其影响不明显。因此，施磷可延长垂穗披碱草人工草地的使用寿命  

磷高效基因型小麦对缺磷胁迫的根际适应性反应

采用奶箱分隔栽培试验法，进行了磷高效与磷低效小麦基因型根际土壤ＰＨ与有效磷变化的研究，结果表明：小麦根际土壤ＰＨ和有效磷含量皆明显低于外围土壤，表现出明显的根际效应特征；磷高效基因型小麦的根际ＰＨ和有效磷含量明显低于磷低效基因型，ＰＨ变异范围和磷素亏缺区也表现明显较大。为了进一步验证磷高效小麦基因型这的这一根际特征，同时进行了施用水溶性，枸溶性磷肥的试验研究，结果表明，以水溶性磷肥对根际ＰＨ和有效  

Phosphorus Transformations in an Oxisol under contrasting land-use systems: The role of the soil microbial biomass

It is generally assumed that phosphorus (P) availability for plant growth on highly weathered and P-deficient tropical soils may depend more on biologically mediated organic P (P_o) turnover processes than on the release of adsorbed inorganic P (P_i). However, experimental evidence showing the linkages between P_o, microbial activity, P cycling and soil P availability is scarce. To test whether land-use systems with higher soil P_o are characterized by greater soil biological activity and increased P mineralization, we analyzed the partitioning of P among various organic and inorganic P fractions in soils of contrasting agricultural land-use systems and related it to biological soil properties. Isotopic labeling was used to obtain information on the turnover of P held in the microbial biomass. Soil samples were taken from grass–legume pasture (GL), continuous rice (CR) and native savanna (SAV) which served as reference. In agreement with estimated P budgets (+277, +70 and 0 kg P ha^–1 for CR, GL and SAV, respectively), available P estimated using Bray-2 and resin extraction declined in the order CR > GL > SAV. Increases in Bray-2 and resin P_i were greater in CR than GL relative to total soil P increase. Organic P fractions were significantly less affected by P inputs than inorganic fractions, but were a more important sink in GL than CR soils. Extractable microbial P (P_chl) was slightly higher in GL (6.6 mg P kg^–1) than SAV soils (5.4 mg P kg^–1), and significantly lowest in CR (2.6 mg P kg^–1). Two days after labeling the soil with carrier free ³³P, 25, 10 and 2% of the added ³³P were found in P_chl in GL, SAV and CR soils, respectively, suggesting a high and rapid microbial P turnover that was highest in GL soils. Indicators of P mineralization were higher in GL than CR soils, suggesting a greater transformation potential to render P_o available. Legume-based pastures (GL) can be considered as an important land-use option as they stimulate P cycling. However, it remains to be investigated whether crops planted in pasture–crop rotations could benefit from the enhanced P_o cycling in grass–legume soils. Furthermore, there is need to develop and test a direct method to quantify P_o mineralization in these systems.  

Incidence and infectivity of vesicular-arbuscular mycorrhizas in some Saudi soils

Anin situ resin bag technique was used to measure the relative availabilities of N and P along a chronosequence of soils in southern New Mexico, and was compared to two more common indices of nutrient availability. Accumulations of N and P during 10-week intervals over an 18 month period were separable into wet season (September–January) and dry season (February–August) groups, with wet season values significantly greater than dry season values. Only accumulations during the wet season showed significant differences among sites, thus stressing the role of field water regime in interpreting resin accumulation results. Total mineral N (NO₃+NH₄) sorbed by resins was significantly correlated to laboratory N mineralization rates. Although accumulation patterns of N and P were similar to patterns of %N and %P in shrub species growing along the chronosequence, these similarities were not statistically significant. A laboratory experiment demonstrated that bicarbonate-form anion resins are preferable to hydroxyl-form resins, as long as standards are made from solutions extracted by resins to account for variable ion recovery efficiencies.  

Erosion and the Rejuvenation of Weathering-derived Nutrient Supply in an Old Tropical Landscape

Studies of long-term soil and ecosystem development on static geomorphic surfaces show that old soils become depleted in most rock-derived nutrients. As they are depleted, however, static surfaces also are dissected by fluvial erosion. This fluvial erosion leads to colluvial soil transport on the resulting slopes, which in turn can rejuvenate the supply of weathering-derived nutrients to plants. We evaluated the influence of erosion and consequent landscape evolution on nutrient availability along a slope on the Island of Kauai, near the oldest, most nutrient-depleted site on a substrate age gradient across the Hawaiian Islands. Noncrystalline minerals characteristic of younger Hawaiian soils increased from 3% of the soil on the static constructional surface at the top of the slope to 13% on the lower slope, and the fraction of soil phosphorus (P) that was occluded (and hence unavailable) decreased from 80% to 56% at midslope. Foliar nitrogen and P concentrations in Metrosideros polymorpha increased from 0.82% and 0.062% to 1.13% and 0.083% on the constructional surface and lower slope, respectively. The increase in foliar P over a horizontal difference of less than 250 m represents nearly half of the total variation in foliar P observed over 4.1 million years of soil and ecosystem development in Hawaii. The fraction of foliar strontium (Sr) derived from weathering of Hawaiian basalt was determined using ⁸⁷Sr:⁸⁶Sr; it increased from less than 6% on the constructional surface to 13% and 31% on lower slope and alluvial positions. Erosional processes increase both nutrient supply on this slope and the fine-scale biogeochemical diversity of this old tropical landscape; it could contribute to the relatively high level of species diversity observed on Kauai.  

Amelioration of growth reduction of lowland rice caused by a temporary loss of soil-water saturation

Decreases in nutrient availability after loss of soil-water saturation are significant constraints to productivity in lowland rainfed rice soils. The effectiveness of soil amendments like lime and straw in ameliorating these constraints are poorly understood. This pot experiment was conducted in Cambodia to investigate changes in soil chemical properties and nutrient uptake by rice after applying lime or straw to continuously flooded or intermittently flooded soil. In continuously flooded soils, exchangeable Al decreased to below 0.2 cmolc/kg. Liming (pH 6.5–6.8) the continuously flooded soil decreased the levels of acetate extractable Fe and P, plant P uptake and shoot dry matter, but had no effect on either Bray-1 or Olsen extractable P values. By contrast, the addition of straw (3.5 g dry straw/kg soil) increased Bray-1, Olsen, and acetate extractable P, plant P uptake, shoot P, and shoot dry matter. The non-amended soils became strongly acidic after loss of soil water saturation: extractable Al increased to 1.0 cmol_c/kg, a potentially harmful level for rice. By contrast, extractable P decreased markedly under loss of soil water saturation as did plant P uptake, shoot P, and shoot dry matter. With loss of soil water saturation, liming substantially depressed the levels of Al but it did not increase plant P uptake, shoot P, and shoot dry matter. Straw addition not only decreased extractable Al levels to well below 0.6 cmol_c/kg under loss of soil water saturation, but it also increased extractability of soil P, plant P uptake, shoot P, and shoot dry matter. Thus, in rainfed environments, the incorporation of straw may be more effective than liming to pH 6.8 for minimising the negative effects of temporary loss of soil-water saturation on P availability, P uptake, and growth of rice.