Measuring Soil Nitrogen Mineralization under Field Conditions

Land application of animal manure is known to alter rates of nitrogen (N) mineralization in soils, but quantitative information concerning intensity and duration of these effects has been difficult to obtain under field conditions. We estimated net effects of manure on N mineralization in soils under field conditions in a completely randomized design, at six field sites, by comparing liquid swine (Sus scrofa) manure treatments to plots receiving no manure. Soil samples were collected immediately after manure application to determine inorganic N concentrations, and those samples were also incubated 28 d in the laboratory to determine amounts of N mineralized from the soil. Analyses and incubation were repeated on a second set of samples collected after various times, depending on the site. Differences in inorganic N concentrations were significant among treatments at all six locations for the first sampling and five of the six locations for the second sampling. In comparison, significant differences in inorganic N concentrations measured after 28 d of laboratory incubation were observed for only two of the six sites for each sampling time. Our results illustrate how to distinguish between the effects manure has on rates of N mineralization in soils and rates at which manure N is mineralized.     

田间非饱和土壤水分运动参数测定

在秦王川灌区利用双环入渗仪在现场进行了积水入渗试验,同时利用γ射线测定土壤水分剖面,进而根据室内外所测定的土壤水分特征曲线,推求了该灌区非饱和土壤水分运动参数,并对室内外所确定的结果进行了对比分析。     

Optimizing Weight Method to Evaluate Nitrogen Release Characters of Polymer-Coated Urea in Paddy Soil under Field Conditions

Polymer-coated urea can improve nitrogen (N) use efficiency of rice. But, the nitrogen release characters from flooded paddy soil are lacking. Traditional weight methods use a vacuum oven to dry. Depending on the coating, some polymer-coated urea still retain water after drying. A new weight method was proposed: washing fertilizer granules in the buried bags with distilled water, and transferring to a plastic bag, then placing it at ?80°C for 2 h, and then transferring to the lyophilizer to dry for 24 h. The method was compared with chemical analyses. This result indicated that the weight method can be used for determining N release characteristics in paddy soil. In the whole growing season, over 75% of N was released. Different amounts of granules in the bag can influence the result. The release rate of 10.0 g in bags was higher than 3.0 g. Surface applied polymer-coated urea has a higher rate than deep application.     

非饱和土壤中氟离子迁移规律实验研究

采用实验室土柱法,在3种pH(4.0,5.5,7.5)淹灌和降雨条件下,研究了非饱和土壤中氟离子的迁移转化。结果表明:不同pH降雨、淹灌条件下,随着淋洗时间的增加,淋滤液中的可溶性氟含量逐渐增大,特别是pH5.5和pH7.5淋滤液中氟的变化规律明显。淹灌条件下淋滤液中氟含量低于降雨条件下淋滤液的氟含量。淋溶前后土壤表层的氟含量变化明显,淋滤后表层土壤表现为淋溶状态。土壤pH值是影响土壤氟存在形态的重要因素之一,对土壤可溶性氟有着重要的影响。     

Improved Estimation of Proportions Using Inverse Binomial Group Testing

Inverse sampling for proportions is useful when there is a need to estimate the prevalence of a disease without delay. This can be combined with group (pooled) testing, in which individuals are pooled together and tested as a group for the disease. Pritchard and Tebbs (in Journal of Agricultural, Biological, and Environmental Statistics 16, 70–87, 2011a) introduced this combination to the statistical literature, and we have addressed some of the key problems raised, for groups of equal size. Most point estimators of the proportion are biased, especially the MLE, but by applying a suitable correction we have developed an estimator which is almost unbiased in the region of interest. We propose two interval estimators which improve on existing methods and have excellent coverage properties. Our recommendation is a score-based method with a correction for skewness, but a good alternative is an exact method with a mid-P correction.     

Measurement of Fertilizer Leaching from the Root Zone Using an Automated Infiltration Soil Water Sampler in an Unsaturated Sandy Field

In sandy fields with vegetable cultivation, fertilizer leaching may occur and it should be well-controlled. The development of a direct soil water sampler is necessary to examine solute transport and fertilizer leaching in the vadose zone, since soil water reflects timely monitoring of data more accurately than groundwater. We developed a Suction-Controlled Flux Sampler to collect infiltration soil water in a sandy soil. In the present study, we monitored fertilizer leaching in an unsaturated sandy field during the rainy season, while evaluating the sampling performance of SCFS for the sampling of infiltration water. SCFS directly collected the infiltration water effectively over a period of several months in the sandy field and recorded the Water-Collecting Efficiency from 92 to 115% under various infiltration conditions during a period of 50 d. WCE was affected by the rainfall intensity as well as by previous rainfall, which enhanced WCE. The results obtained from the use of SCFS and several sensors demonstrated that the amount of leached water remained low as long as irrigation was applied according to the cultivation manual. However, an unexpected heavy rainfall event led to fertilizer leaching. The fertilizer leaching trend was effectively monitored by several sensors inserted into the soils, while detailed analysis of the components was performed after collection by using SCFS. Direct access to infiltration water enabled to examine the infiltration process and detailed variations in the amounts of discharged anions. The sensor-equipped monitoring system together with SCFS is suitable for precise management of fertilizer and irrigation application.     

Assessing Soil Properties Controlling Interrill Erosion: An Empirical Approach under Mediterranean Conditions

Soil erodibility is a complex phenomenon that comprises a number of different soil properties. However, most current (empirical) erodibility indices are based on only a few soil properties. A feasible soil characterization of interrill erosion (IE) prediction at large scale should be based on simple, quick and inexpensive tests to perform. The objective of this work was to identify and assess those soil properties that best reflect soil vulnerability to IE. Twenty‐three agricultural soil samples located in Spain and Italy were studied. Forty‐nine different physical and chemical soil properties that presumably underpin IE were defined. Experiments were carried out in the field (in microplots using simulated rainfall) and in the lab. The most relevant variables were detected using multivariate analysis. Six key variables were finally identified: RUSLE K factor, a granulometric/organic matter content index, exchangeable sodium percentage, shear strength, penetration resistance and permeability of soil seal. The latter is proposed as a useful technique to evaluate soil susceptibility to crusting even when the crust is not present at the time of the field survey. The selected variables represented a wide range of soil properties, and they could also be successfully applied to different soils with different characteristics than those evaluated in our experiments. Copyright © 2017 John Wiley & Sons, Ltd.     

Unsaturated Soil Hydraulic Properties according to Double-Ring Infiltration of Saline Water

Eurasian Soil Science - Inverse modeling is a relatively complex procedure that allows quick estimation of soil hydraulic properties, yielding parameters for both soil water retention and...     

高肥力稻田分次施氮对氮素淋失的影响

通过自行设计的渗漏计研究在控水灌溉条件下稻田不同氮肥处理氮素淋失的动态规律,结果表明:在水稻整个生育期间,渗漏水中铵态氮、硝态氮保持较低的浓度,均小于1mg/L,但对硝态氮而言,仍是氮素淋失的主要类型。从总的趋势来看,渗漏水中氮素浓度随施肥量增加而增加。每次施肥后,不同处理渗漏水中的NO3--N浓度均表现为短期内迅速上升、后期逐渐下降的趋势,其中NH4 -N浓度与NO3--N消长规律相似,但表现出峰值超前的特征。各小区渗漏计中NH4 -N、NO3--N及TN累积渗漏量与施肥量之间存在显著相关性,R2分别达到0.933*,0.984**和0.982**。另外从环境和经济角度考虑,建议在土壤质地粘重、基础肥力较高的水稻土施肥量控制在75～150kg/hm2为宜,控制氮素淋失主要时期为施肥后一周内,特别在基肥施后尤为关键。     

Migration of Sr,Nd and Ce in Unsaturated Chinese Loess under Artificial Sprinkling Conditions: A Field Migration Test

Double concentration peak phenomenon has been observed in nuclide migration tests in unsaturated Chinese loess during the cooperative research between China Institute for Radiation Protection (CIRP) and Japan Energy Atomic Research Institute (JEARI), and was considered conflicting with traditional theory of solute migration. In order to confirm the existence of this phenomenon and better understand its formation mechanism, we conducted a nuclide migration test that lasted 470 days using Sr, Nd and Ce which are analogues of ⁹⁰Sr and actinides, with loess and fine arenaceous quartz, respectively, as tracer carriers. In addition, we examined the efficacy of capillary barrier which is constructed by placing fine-grained soil on a layer of course-grained material, according to its influence on nuclide migration. When using loess as tracer carrier, a fraction of Sr migrated downward from the source layer to form a migration peak, and the residual Sr formed another concentration peak which corresponds to the source layer; while Nd and Ce hardly migrated during the 470 day test with only one concentration peak in the source layer. When using fine arenaceous quartz as tracer carrier, double concentration peak phenomenon occurs for all the nuclides examined, with the peaks distributing, respectively, on the upper and lower sides of the source layer. This phenomenon was suggested to result from the very low water containment ability and nuclide retentivity of the source layer arenaceous quartz. Thus, the so called double concentration peak phenomenon is formed by the source and subsequent migration of part of the source. The obviously reduced migration of Sr when taking fine arenaceous quartz as tracer carrier demonstrated significant influence of the capillary barrier formed by the fine arenaceous quartz layer and overlying loess on nuclide migration. Considering that the fine arenaceous quartz layer is very small (7 mm) in thickness and horizontally placed and the small dimension of the test pit, capillary barrier could be an effective way to protect the underlying waste from leaching.     

非饱和土壤物理特性数据处理软件APPIA的数理基础分析

APPIA是用于非饱和土壤物理特性数据处理的专用软件,可快速分析非饱和土壤持水曲线和导水曲线并给出相关参数.系统分析了APPIA的数理基础,并对不同方法分析的结果进行了比较.结果表明:用APPIA程序可获得较为准确的非饱和土壤物理参数,应广泛推广使用.     

非饱和土壤物理特性数据处理软件APPIA的数理基础分析

ＡＰＰＩＡ是用于非饱和土壤物理特性数据处理的专用软件,可快速分析非饱和土壤持水曲线和导水曲线并给出相关参数。系统分析了ＡＰＰＩＡ的数理基础,并对不同方法分析的结果进行了比较。结果表明：用ＡＰＰＩＡ程序可获得较为准确的非饱和土壤物理参数,应广泛推广使用。     

Estimation of Mineral Weathering Rates under Field Conditions Based on Base Cation Budget and Strontium Isotope Ratios

Base cation (BC) concentrations of rain, throughfall, percolation from leaf litter, and soil solution were periodically measured in two forests: Kannondai (red pine stand on volcanic soil) and Yasato (deciduous stands on granitic soil). Calculation of a BC budget gave the rate of BC release from soils; the BCs originated from mineral weathering and cation exchange. Weathering rates under field conditions were estimated from the Sr isotope ratios (⁸⁷Sr/⁸⁶Sr) of water and soil samples. Isotope ratios decreased in the order rain > throughfall > percolation > soil solution. Clay and silt had extremely high isotope ratios; this suggests that the sandy fraction, whose isotope ratio was smaller than that of the soil solution, was the main contributor to mineral weathering. Estimated BC weathering rates (kmol_c·ha^?1y^?1) were 1.16 for Ca and 0.57 for Mg at Kannondai, and 0.82 for Ca and 0.51 for Mg at Yasato. The unexpected high weathering rate of granitic soil in Yasao was due to the wide coverage of the original parent material by volcanic ash. The contribution of cation exchange derived by subtraction was a little smaller than the weathering rates and was similar to the values estimated from a dynamic model that we developed.     

Establishment of Hybrid Arctic Bramble under Field Conditions

The effect of different factors on plant diameter and yield in hybrid arctic bramble (Rubus arcticus nothosubsp. stellarcticus) was examined in two field experiments with a factorial design. The studied factors included planting time (August, September, May or June), plant type (bare-rooted or potted plants) and ground cover (no ground cover or mulching with a dark plastic film). Development of bare-rooted and potted plants did not differ when transplanted in the autumn and in May. Potted plants developed better than bare-rooted plants when transplanted in June. In one year, plants transplanted in May developed best, while in another, plants transplanted in the autumn developed best. Mulching with a dark plastic film improved plant development. The rate of vegetative development during the first growth season was reflected in the yields in both the first and the second harvest year; the greater the plant diameter after the first growth season, the higher the yield.     

Leaching of Saline Calcareous Soil under Laboratory Conditions

Eurasian Soil Science - Soil salinity is a major problem in Kerman pistachio (Pistacia vera) orchards which caused low pistachio’s productivity in recent years. Farmers excessively use gypsum...     

浙江嘉兴保护地土壤障碍的农化性状指标研究

通过对保护地土壤pH(H2 O及KCl)、NO3-N、电导率、可溶性盐等性状进行调查分析 ,初步摸清了嘉兴市保护地作物产生生理障碍的土壤因子 ,并拟订提出当地保护土壤农化性状的安全指标、临界指标及严重障碍指标 ,为矫治保护地土壤障碍提供技术依据 .     

全国棉花种植面积遥感监测抽样方法设计

棉花是我国重要的经济作物之一，准确、及时地提供棉花的播种面积，对政府部门及时掌握棉花生产情况、制定相关调控政策，对棉花加工企业与棉农预测市场情况有重要意义。由于中巴卫星的应用，对新疆农情的及时遥感监测成为可能，从而使遥感监测可以覆盖全国。但是，考虑到中国东、中、西部县级面积相差很大，必须设计不同的抽样方法。在新疆棉花监测的抽样设计中，采用了标准地形图幅作为分层抽样的抽样单元的方法。在黄淮海、长江中下游棉区采用县为单元的分层抽样的方法，抽样样本用遥感调查的方法获得。设计了满足生产应用的全国作物面积遥感监测抽样运行方法。     

应用137Cs示踪技术估算土壤侵蚀的若干问题探讨

[目的]探讨用~(137)Cs示踪技术估算土壤侵蚀量方法(以下简称"~(137)Cs示踪方法")所存在的几个关键问题,促进该方法的标准化和系统化。[方法]对大量已发表的相关文献进行分析,根据作者的研究经验,归纳出~(137)Cs示踪方法在实践应用中所存在的核心问题。[结果]~(137)Cs示踪方法中关于~(137)Cs在空间是均匀分布的假设存在不合理性,不能直接用于定量估算单钻点取样的土壤侵蚀量。~(137)Cs活度的空间变化存在随机性的成分。敏感度和不确定性分析结果证明~(137)Cs活度的空间随机变化量是~(137)Cs示踪方法不确性的最大来源。[结论]可以用多钻点样本平均值来减少~(137)Cs随机变化量所引起的侵蚀估算误差。以统计学为基础的试验设计和采取独立样本的办法可以消除该误差。虽然~(137)Cs模型已被广泛应用,但由于缺乏长期观测资料诸多模型还处在理论研究阶段,没有得到严格的验证和评判。因为不同模型估算的侵蚀量差别甚大,模型验证和筛选对该方法的成功运用至关重要。     

Temporal Changes in Cadmium, Thallium, and Vanadium Mobility in Soil and Phytoavailability under Field Conditions

A field study was conducted over a 30 mo period to examine movement of Cd, Tl, and V through the profile of a Coastal Plain soil (Typic Kandiudult) and the availability of these trace metals to bush bean (Phaseolus vulgaris L.) plants. The metals were applied to field plots as dissolved salts and mixed into the surface 7.5 cm. The greatest concentration of all three metals was observed in the surface soils, with a steep decrease occurring down to the 7.5 to 15 cm depth. Thallium was the most mobile of the three metals; approximately 15% of the applied Tl and <3% of the applied Cd and V moved below the surface 7.5-cm region during the 30-mo experiment. Extractable concentrations of all three metals in the surface soils decreased significantly (P ≤0.05) during the initial 18 mo after treatment. No further decrease occurred between 18 and 30 mo. The presence of Al- and Fe-oxides and small amounts of clay minerals and organic matter in this highly-weathered, low cation-exchange soil were likely responsible for the retention of the trace metals. Bioavailability, as measured by concentrations and total amounts of metals in root and aboveground tissues of plants, did not change significantly between 18 and 30 mo. These data suggest that bioavailability of Cd, Tl, and V decreased over time as a result of transformation of these elements into unavailable forms and not to leaching. These changes in bioavailability occurred soon after application, becoming negligible after 18 mo.     

花粉源尺寸对水稻花粉扩散的影响

以花粉为介导的基因飘流是水稻转基因逃逸的主要途径之一,因此,掌握花粉扩散规律对于水稻基因飘流研究具有重要意义。本文设计了5m×5m（TR1）、10m×10m（TR2）和15m×15m（TR3）三种花粉源尺寸,通过观测单位面积的有效穗数、每穗的开花颖花数和单个颖花的花粉量以及主风向上的花粉沉降量,计算了花粉源强和有效源强比,就花粉源尺寸对花粉源强、花粉沉降量和有效源强比以及花粉扩散距离的影响进行研究。结果表明：（1）花粉源尺寸不影响单位面积的花粉源强,只改变总源强的大小。TR1、TR2和TR3的总源强比例为1:4:9。（2）花粉源尺寸不改变主风向上花粉沉降量的空间分布特征。在花粉源区,花粉沉降量先迅速增加,达到最大值后缓慢下降;在下风区,花粉沉降量与距离的关系可用负指数形式表达。（3）花粉源尺寸越大,各个距离上的花粉沉降量就越多,花粉扩散距离也相应增加。但是,这种效应会随着花粉源尺寸的增大而逐渐减弱。（4）所有处理的有效源强比为27.9%～33.4%,意味着所有花粉中仅30%左右可以扩散到源区以外可能产生基因飘流。然而,随着花粉源尺寸的增大,有效源强比逐渐减小。（5）风对不同花粉源尺寸处理的影响类似。大风增加了有效源强比和花粉扩散距离,而风向主要影响有效源强比。需要注意的是,风对大尺寸花粉源的影响更显著。