In situ radiometric mapping of soil erosion and field-moist bulk density on cultivated fields

Abstract. Recent developments in in situγ ray spectrometry offer a new approach to measuring the activity of radionuclides such as ¹³⁷Cs and ⁴⁰K in soils, and thus estimating erosion or deposition rates and field moist bulk density (ρ_m). Such estimates would be rapid and involve minimal site disturbance, especially important where archaeological remains are present. This paper presents the results of a pilot investigation of an eroded field in Scotland in which a portable hyper pure germanium (HPGe) detector was used to measure γ ray spectra in situ. The gamma (γ) photon flux observed at the soil surface is a function of the ¹³⁷Cs inventory, its depth distribution characteristics and ρ_m. A coefficient, Q_Cs, derived from the forward scattering of ¹³⁷Cs γ ray photons within the soil profile relative to the ¹³⁷Cs full energy peak (662 keV), was used to correct the in situ calibration for changes in the ¹³⁷Cs vertical distribution in the ploughed field, a function of tillage, soil accumulation and ρ_m. Based on only 8 measurements, the agreement between in situγ ray spectrometry and soil sample measurements of ¹³⁷Cs inventories improved from a non significant r²=0.05 to a significant r²=0.62 (P<0.05). Erosion and deposition rates calculated from the corrected in situ¹³⁷Cs measurements had a similarly good agreement with those calculated from soil cores. Mean soil bulk density was also calculated using a separate coefficient, Q_K, derived from the forward scattering γ photons from ⁴⁰K within the soil relative to the ⁴⁰K full energy peak (1460 keV). Again there was good agreement with soil core measurements (r²=0.64; P<0.05). The precision of the in situ¹³⁷Cs measurement was limited by the precision with which Q_Cs can be estimated, a function of the low ¹³⁷Cs deposition levels associated with the weapons testing fallout and relatively low detector efficiency (35%). In contrast, the precision of the in situ ρ_m determination was only limited by the spatial variability associated with soil sampling.     

Re-defining tillage erosion: quantifying intensity–direction relationships for complex terrain

Abstract. Current tillage erosion models account for the influence of tillage direction in the magnitude of the soil (tillage) transport coefficient. It is argued here that this is counter-intuitive and causes significant problems in modelling tillage erosion in areas of complex terrain. This article examines whether a re-modelling of tillage erosion is possible that separates tillage direction (an interaction with the landform) from the soil transport coefficient (a measure of tillage intensity representing the combination of implement erosivity and soil erodibility). Experimental data for mouldboard ploughing upslope, downslope and cross-slope at Coombe Barton Farm, Devon are examined. Integration of data for all directions into a single relationship, which relates translocation in the direction of tillage to slope in the direction of tillage and translocation perpendicular to tillage to slope perpendicular to tillage, is not possible using previously published methods of analysis. However, when total translocation distance is regressed against the tangent of the slope at 45° to the tillage direction (bisecting the tillage direction and the direction of overturning) it is found that a single relationship can be used to describe tillage in all three directions. Therefore, this relationship is used to determine a single value of the soil transport coefficient ( k _fTa) for constant soil and implement conditions but different tillage directions. This redefinition of tillage is important both for true estimation of tillage erosion severity, the adirectional coefficient being 40% larger than the directional coefficient, and for modelling of tillage erosion in complex terrain. These improvements are vital when tillage erosion simulation is used to direct soil conservation strategies.     

N_(98s)×特青(亚种间杂交稻)抽穗后物质生产及分配特点研究初报

对N×特青示范田中试区与肥料试验田各处理小区稻株分析结果表明:抽穗后,亚种间杂交稻N×特青比常规稻特青干物质生产能力强,灌浆速度快;地上部各器官占植株干重比例,前者叶片比重大于茎,后者茎比重大于叶。亚种间杂交稻对肥料反应敏感,抽穗后,干物质累积,植株高度,每穗总粒数和粒重均随施肥量增加而增加,在高肥区有利于进一步提高产量,但增施氮肥后,灌浆速度明显滞后。     

Impact of pig slurry on soil properties, water salinization, nitrate leaching and crop yield in a four-year experiment in Central Spain

Abstract. The repeated application of pig slurry to agricultural soils may result in an accumulation of salts and a risk of aquifer pollution due to nitrate leaching and salinization. Under Mediterranean conditions, a field experiment on a sandy loam soil (Typic Xerofluvent) was performed with maize (Zea mays) in 1998, 1999 and 2001 to study the effects of applying optimal (P1) and excessive rates (P3) of pig slurry on soil salinization, nitrate leaching and groundwater pollution. The rate of pig slurry was established considering the optimal N rate for maize in this soil (170, 162 and 176 kg N ha^?1 for 1998, 1999 and 2001, respectively). Pig slurry treatments were compared to an optimal N rate supplied as urea (U) and a control treatment without N fertilizer (P0). The composition of the slurries showed great variability between years. Mean NO₃^? leaching losses from 1998 to 2001 were 329, 215, 173 and 78 kg N ha^?1 for P3, P1, U and P0 treatments, respectively. The amount of total dissolved salts (TDS) added to the soil in slurry application between 1998 and 2001 was 2019 kg TDS ha^?1 for the P1 treatment and 6058 kg TDS ha^?1 for the P3 treatment. As a consequence, the electrical conductivity (EC) of the slurry‐treated soils was greater than that of the control soil. The EC correlated significantly with the sodium concentration of the soil solution. Over the entire experimental period, 2653, 2202 and 2110 kg Na ha^?1 entered the aquifer from the P3, P1 and P0 treatments, respectively. The P3 treatment did not significantly increase grain production in 1999 and 2001 compared with that achieved with the optimal N rate treatment (P1). This behaviour shows the importance of establishing application guidelines for pig slurry that will reduce the risk of soil and groundwater pollution.     

高校图书馆电子阅览室管理和服务

本文介绍湖南科技大学图书馆电子阅览室管理现状与管理系统,探讨高校图书馆电子阅览室的软、硬件的管理维护,推行读者柔性管理和开展电子阅览室特色服务的途径。     

我国被征地农民权益保护问题探析

对目前我国的征地问题进行思考,可对有效化解政府与农民冲突以及保护农民权益起到一定的启示作用。     

梅州市五华县石灰岩矿区土壤铅污染现状研究及改良对策

对梅州市五华县几个石灰岩矿区周边土壤中铅含量进行了测定，结果表明，污染土壤的铅含量远远超出了国家土壤环境质量三级标准（对土壤生态环境产生影响的最低浓度值），对生态产生影响。根据内梅罗污染指数评定得出，矿区土壤铅污染达到重污染的程度。提出了减轻铅污染对生态环境危害的控制污染源措施和改良对策。     

变频器电磁谐波污染及抑制措施

变频器高次谐波带来的电磁干扰和污染问题危害较大,本文从变频器工程实际应用出发,从隔离、屏蔽、滤波和接地四个方面全面阐述了抑制和消除干扰的方法。     

立地管理措施对7年生2代杉木林生长的影响

对福建省南平峡阳国有林场29年生1代杉木人工林采伐迹地,采取5种不同立地管理措施营造的第2代杉木人工林7年生时的生长量进行调查分析,结果表明,BL3(收获树干和树皮,加倍采伐剩余物)处理对7年生2代杉木林的生长最为有利,其次为BL2(收获树干和树皮,不炼山)处理、BL1(全树收获)处理和BL0(收获地上所有有机质)处理,而SB(收获树干和树皮,炼山)处理杉木生长最差。炼山处理的7年生杉木蓄积量仅为不炼山处理的85.73%,但不同试验处理之间杉木生长量的差异均未达到显著水平(P<0.05)。     

大庆市畜禽粪便处理与利用状况的分析研究

根据大庆市畜牧业现状,分析了畜牧生产所产生的粪、尿数量及畜禽粪便对大庆市环境产生的压力,并对各区县进行了区划分析。分析了大庆市畜禽粪便处理的主要模式,以及利用程度,提出减少畜禽粪便污染的控制措施。