Effects of N-enriched sewage sludge on soil enzyme activities

Sewage sludge is increasingly used as an organic amendment to soil, especially to soil containing little organic matter. However, little is known about utility of this organic amendment with N-enriched or adjusted C:N ratios in soil. We studied the effects of adding of different doses (0, 100, 200 and 300 t ha⁻¹) and C:N ratios (3:1, 6:1 and 9:1) of sewage sludge on enzyme activities (β-glucosidase, alkaline phosphatase, arylsulphatase and urease) in a clay loam soil at 25 °C and 60% soil water holding capacity. Nitrogen was added in the form of (NH₄)₂ SO₄ solution to the sludge to reduce the C:N ratio from 9:1 to 6:1 and 3:1. The addition of different doses and C:N ratios of the sludge caused a rapid and significant in the enzymatic activities in soils, this increase was specially noticeable in soil treated with high doses of the sludge. In general, enzymatic activities in sludge-amended soils tended to decrease with the incubation time. All activities reached peak values at 30 days incubation and then gradually decreased up to 90 days of incubation. Sewage sludges also the increased available metal (Cu, Ni, Pb and Zn) contents in the soils. However, the presence of available soil metals due to the addition of the sludge at all doses and C:N ratios did negatively affect all enzymatic activities in the soils. This experiment indicated that all doses and C:N ratios of sewage sludge applied to soil would have harmful effects on enzymatic activity. Some heavy metals found in sewage sludge may negatively influence soil enzyme activities during the decomposition of the sludge.     

Investigation and prediction spatial variability in chemical properties of agricultural soil using geostatistics

Determination of the chemical characteristics of soil for balanced fertilization on large scales is an important factor in achieving a precision agriculture. Laboratory analyses of soil properties are usually expensive and time consuming. Surmounting these problems is possible using geostatistics. Therefore, this research aims at selecting a proper interpolation method using 213 soil samples for alfalfa farmland in Hamadan Province, Iran. Various factors such as pH, EC, , , K, P, Fe, Zn, B and Co were measured. Ordinary kriging and co-kriging were assessed to derive maps of soil physico-chemical properties, using mean absolute error (MAE), mean bias error (MBE), root mean squared error (RMSE) and average kriging standard error (AKSE) as statistical criteria. Variography analysis indicated that the ranges of influence for pH, EC, , , K, P, Zn, Fe, B and Co were 65, 55, 78, 79, 75, 60, 50, 65, 70 and 30 km, respectively, and the measuring error varied between 0.366 and 0.843. The results revealed that, based on precision criteria, co-kriging was the best method for interpolating the chemical properties of soil. Finally, using to the co-kriging for each determined variable, a related zoning map for fertility management of the study area was prepared.     

Effect of tillage and residue management on enzyme activities in soils: III. Phosphatases and arylsulfatase

This study was carried out to investigate the effect of tillage and residue management on activities of phosphatases (acid phosphatase, alkaline phosphatase, phosphodiesterase, and inorganic pyrophosphatase) and arylsulfatase. The land treatments included three tillage systems (no-till, chisel plow, and moldboard plow) in combination with corn residue placements in four replications. The activities of these enzymes in no-till/double mulch were significantly greater than those in the other treatments studied, including no-till/bare, no-till/normal, chisel/normal, chisel/mulch, moldboard/normal, and moldboard/mulch. The effect of mulching on activities of phosphatases was not as significant as on activities of arylsulfatase. The lowest enzyme activities were found in soil samples form no-till/bare and moldboard/normal treatments, with the exception of inorganic pyrophosphatase, which showed the lowest activity in no-till/bare only. Among the same residue placements, no-till and chisel plow showed comparable arylsulfatase activity, whereas the use of moldboard plow resulted in much lower arylsulfatase activity. The activities of phosphatases and arylsulfatase were significantly correlated with organic C in the 40 soil samples studies, with r values ranging from 0.71*** to 0.92***. The activities of alkaline phosphatase, phosphodiesterase, and arylsulfatase were significantly correlated with soil pH, with r values of 0.85***, 0.78***, and 0.77***, respectively, in the 28 surface soil samples studied, but acid phosphatase and inorganic pyrophosphatase activities were not significantly correlated with soil pH. The activities of phosphatases and arylsulfatase decreased markedly with increasing soil depth and this decrease was associated with a decrease in organic C content. The activities of these enzymes were also significantly intercorrelated, with r values ranging from 0.50*** to 0.92***. Received: 4 October 1995     

基于GIS和地统计学的低丘红壤地区三种土壤性质空间变异性研究

以浙江省金华市为例,采用地统计学和GIS相结合的方法,对低丘红壤地区土壤有机质、有效N、有效K3种主要性质的空间变异特性进行研究。研究表明,通过平方根转换后,三者都呈很好的正态分布。有机质的变异函数曲线的理论模型较好地符合球状模型,有效N和有效K则符合指数模型。三者都属于中等空间相关性,同时受到结构性因素和随机性因素的共同影响。通过分析3种土壤性质的各向异性,发现不同的土壤性质有不同的空间分布,同一土壤性质在不同的方向上也有不同的空间变异性。     

基于土壤传递函数的土壤持水特性间接估计及其空间变异性研究

A total of 107 soil samples were taken from the city of Qingdao,Shandong Province,China.Soil water retention data at 2.5,6,10,33,100,300,and 1 500 kPa matric potentials were measured using a pressure membrane apparatus.Multiple linear regression (MLR) was used to develop pedotransfer functions (PTFs) for single point estimation and van Genuchten parameter estimation based on readily measurable soil properties,i.e.,MLR-based point (MLRP) PTF and MLR-based parametric (MLRV) PTF.The double cross-validation method was used to evaluate the accuracy of PTF estimates and the stability of the PTFs developed in this study.The performance of MLRP and MLRV PTFs in estimating water contents at matric potentials of 10,33,and 1 500 kPa was compared with that of two existing PTFs,the Rawls PTF and the Vereecken PTF.In addition,geostatistical analyses were conducted to assess the capabilities of these PTFs in describing the spatial variability of soil water retention characteristics.Results showed that among all PTFs only the Vereecken PTF failed to accurately estimate water retention characteristics.Although the MLRP PTF can be used to predict retention characteristics through traditional statistical analyses,it failed to describe the spatial variability of soil water retention characteristics.Although the MLRV and Rawls PTFs failed to describe the spatial variability of water contents at a matric potential of 10 kPa,they can be used to quantify the spatial variability of water contents at matric potentials of 33 and 1 500 kPa.     

两种取样尺度下土壤重金属空间变异特征研究

通过在两种取样尺度下采集重庆地区土壤样品,测定土壤重金属As、Hg、Cd、Pb、Cr含量,研究不同取样尺度下地统计学方法对土壤重金属空间分析的实用性和空间插值质量。研究结果表明,除小尺度中As、Cd、Cr呈正态分布,小尺度中的Pb、Hg和大尺度中As、Hg、Cd、Pb、Cr均呈偏态分布。各重金属变异系数存在明显空间变异(CV介于23.2%~24.1%),小尺度下空间变异较小,大尺度下空间变异大。在两种取样尺度下,土壤重金属均存在典型的半方差结构,表明采用地统计学方法进行重金属空间变异分析是可行的。在小尺度下,各重金属块金系数介于0.112~0.736之间,表明具有强或中等空间自相关;在大尺度下,块金系数介于0.301~0.570之间,表明具有中等空间自相关。空间插值和交互检验结果表明,As、Cr、Hg、Cd在小尺度下的空间估测结果能准确地反映变量的空间变异,在大尺度下估值有偏差,Pb在两种尺度下的估测结果均有偏差。     

Determination of arylsulphatase and phosphatase enzyme activities in soil using screen-printed electrodes modified with multi-walled carbon nanotubes

Sustainability of agricultural systems has become an important issue all over the world. The activity of enzymes is potentially an important quality bioindicator in soils. The aim of the present study was to develop a simple and convenient assay to determine the activity of arylsulphatase (AS), acid (ACP) and alkaline phosphatase (ALP) in agricultural soil. The activities of these enzymes were detected using a non-electroactive substrate, which produces an electroactive product. To this end, p-aminophenyl phosphate (pAPP) was used as a substrate which is converted to p-aminophenol (pAP) after enzymatic dephosphorylation; and 4-nitrocatechol sulphate (4-NCS) was used as a substrate for AS activity based on its catalytic effect on the hydrolysis of 4-NCS into 4-nitrocatechol (4-NC). The products of both enzymatic reactions were quantified on carbon-based screen-printed electrodes (SPCEs) modified with carbon nanotubes (CNTs), using Osteryoung square-wave voltammetry (OSWV). The determination of the reaction products allowed more sensitive determination of ALP, ACP and AS activities in soil than that obtained with a spectrophotometric method. This assay also diminishes the generation of waste, which is desirable in green analytical chemistry. The optimization of the analytical procedure in terms of the nature of electrode type, applied potential, pH of solution, and precision of measurements is reported.     

分形方法在土壤特性空间变异研究中的应用

土壤特性空间变异研究对土壤制图、精准施肥、农业可持续发展等方面具有重要意义。分形几何学是一种探索复杂性的事物的新科学方法和理论,在研究土壤特性空间变异中将有大有可为。本文主要综述了 2000 年以后分形理论在土壤物理特性、化学特性、水分特征及状态参数的空间变异研究中的应用进展,最后对分形理论在土壤特性空间变异研究中的发展方向进行了展望。     

Preliminary observations on the natural variation in the endogenous rhythm of the desert Isopod Hemilepistus reaumurii

The desert woodlouse Hemilepistus reaumurii lives in monogamous pairs, together with their offspring, in self-dug burrows. Every burrow contains only one family. This animal is active on the surface from the beginning of spring to autumn. It remains in the burrow during the hottest part of the day, to avoid the heat, but is active at the surface during morning and evening. During the winter, low temperature prevents its above ground activity. Freshly collected animals, from the north of Kairouan (Tunisia) were transferred to a controlled environment cabinet in the laboratory and their locomotor activity monitored as individuals or in male/female pairs, in annular chambers equipped with an infrared activity recording system. For the first 7 days of recording, the animals were kept in a light–dark cycle in phase with the natural diel cycle. For the second 7 days, animals were maintained in constant darkness. The temperature was held constant at 18±1 °C. Analysis of preliminary data indicates that both individuals and pairs exhibit an endogenous rhythm of locomotor activity with a circadian periodicity. Activity was mostly confined to the hours of the photophase (1–7 days) or to those of subjective day (8–14 days). The activity pattern showed two main peaks, around dusk and dawn, respectively. This bimodal circadian rhythm persisted for as long as the experiments were run, and was clearer in individual recording than in pair recording. The characteristics and biological significance of the rhythm are discussed.     

Characteristics of organic matter in soil surface horizons derived from calcareous and metamorphic rocks and different vegetation types from the Mediterranean high-mountains in SE Spain

A study was carried out on some basic characteristics of the organic matter in the surface horizons of soils from the two different geological (calcareous and acid metamorphic rocks) and ecological systems under a Mediterranean climate in Southeast Spain. The results show some noticeable differences in soil organic matter composition. This is likely due to typical Mediterranean climate and well adapted vegetation. There is a tendency towards a greater stability for the soil humus formed under slightly alkaline soil in comparison to the slightly acidic environment. The samples taken from the latter environment have a higher content in free organic matter, a lower content in total extractable humin and a greater relative proportion of aliphatic chains and lignin in the humic acids. The results also suggest some differences caused by the type of vegetation (forest and scrubland ecosystems) in the soil humus chemistry, with a more obvious negative effect under reforestations with species of Pinus in an acidic soil environment (a higher content in free organic matter, lesser presence of fungal-derived perylenequinonic pigments in the humic acids, and a higher content in little evolved forms of nitrogen and lignin in the humic acids). In general the organic matter under scrubland and Quercus vegetation is more decomposed and the humus is more evolved than under Pinus vegetation.     

海河低平原盐渍区土壤养分空间变异性研究

应用地统计学方法分析研究海河低平原盐渍涝洼地2700m×2100m尺度土壤6个主要养分属性和全盐量的空间变异结构结果表明,在轮荒、撩荒半自然状态下土壤全N 、速效氮、速效磷、速效钾及有机质等含量的空间变异性存在着良好的半方差结构,而全P 半方差结构尚难理想的确定.半方差曲线图遵从指数和球函数等理论模型,最大相关距离分别在340～1173m,结构方差在基台值中所占比例均较大,达40%以上.     

保护地不同灌溉方法表层土壤pH小尺度的空间变异

基于保护地定位灌溉试验,采用经典统计学和地统计学的方法,以网格取样方式采集不同灌溉方法(沟灌、滴灌、渗灌)表层土壤,研究微尺度下土壤pH值的空间变异特征及空间分布。结果表明:经6年灌溉,沟灌处理pH显著降低,沟灌和滴灌0～5cm土层土壤pH表现为中等空间自相关,而其5～10cm和渗灌0～5cm和5~10cm的土壤pH表现为弱空间相关,水分的供给方式和数量影响土壤pH的空间变异。     

Soil penetrometer resistance spatial variability in a Ferralsol at several soil moisture conditions

The penetrometer resistance (PR) spatial variability in a Ferralsol under different soil moisture conditions was characterized through statistical and geostatistical methods. PR measurements were made in a 10-row, 10-columns, 3-m spacing grid at 20–30 cm depth using a hand-pushing penetrometer. Measurements were made for dry soil conditions (before irrigation) as well as 2 and 24 h after irrigation. The soil bulk density (BD) and the relative topographical altitudes (RT) were measured at the same locations. The PR spatial variability is normally distributed for dry soil conditions and after irrigation-water redistribution. A normal distribution fits also to the BD spatial variability. PR mean and coefficients of variations are lower for wet soil conditions and vary notably according to the soil moisture condition. The PR semivariance values are much higher for dry soil conditions than those found for wet soil conditions. However, the semivariogram of PR before irrigation shows almost a pure nugget effect. Irrigation yields a spatial structure in PR measurements. Despite the differences in the shown spatial structure, the range of the PR semivariograms before and 24 h after irrigation is about 8–10 m, which is very similar to the range of the BD semivariogram. The correlation coefficients between PR and the other measured variables are very small before and after irrigation, which could lead to the conclusion that those variables are not related at all. However, according to the co-dispersion coefficients plotted as a function of the separation lag, the correlation between those variables changes according to the separation distance. Particularly, PR and the RT show correlation 24 h after irrigation only for lags between 5 and 12 m. The results pointed out that PR spatial variability depends on soil moisture condition, soil BD and on several local features as microtopography.     

东北地区旱地土壤全氮空间变异性对幅度拓展的响应

土壤氮素不仅是作物必需的营养元素,还是重要的生态元素。不同幅度上土壤全氮含量空间变异的研究是正确评价土壤质量和精确估算土壤氮库的基础。基于中国东北地区第二次土壤普查的1 041个旱地剖面数据,设定三种类型的幅度,即行政区幅度(县、市、省和大区)、土壤分类幅度(土属、亚类、土类和土纲)和土壤类型(地带性土壤和非地带性土壤)-行政区幅度,研究了该区旱地土壤表层(0～20 cm)和剖面(0～100 cm)全氮含量的变异性及其对幅度拓展的响应。结果表明,三种类型幅度上,表层和剖面的平均土壤全氮含量变异性均随着幅度的拓展而增大。在行政区幅度,旱地面积或行政区面积与平均土壤全氮含量变异系数具有较强的对数关系。在土壤分类幅度上,不同土纲的平均土壤全氮含量的变异随幅度变化的趋势、变幅等均存在差异。在土壤类型—行政区幅度,地带性土壤与非地带性土壤的全氮含量随幅度的变化趋势一致,但变化速率有差别,旱地面积与平均非地带性土壤全氮含量变异系数有较强的对数关系。该结果可为东北地区不同幅度下基于土壤类型聚类的旱地土壤氮库估算、土壤资源调查时采样数目的确定提供理论指导。     

海涂围垦区土壤盐分空间变异模拟的比较研究

以苏北海涂围垦区为例,利用人工神经网络(ANN)、普通克里格(OK)插值和序贯高斯模拟(SGS)对典型地块土壤盐分空间分布进行了模拟、插值与预测,获取了各方法的优化结构与参数,并就各方法对土壤盐分分布特征与空间结构的预测能力进行了比较分析。结果表明:ANN、OK和SGS法均较好地模拟和预测了土壤盐分的空间分布,达到了较高模拟、插值与预测精度;ANN获得的土壤盐分空间分布最为连续,SGS法整体分布相对离散;ANN能较好地预测盐分较低的样点,但ANN对高盐分样点的预测结果不如SGS和OK;SGS预测结果最符合实测值的波动特点,ANN预测结果波动范围最窄,SGS较ANN和OK更能反应数据随机变量的结构性和波动性,在整体上要优于ANN和OK法。该结果为滨海地区盐渍土壤的精准评估与高效改良提供了参考依据。     

Small-scale spatial variability of selected soil biological properties

A strategy for sampling soil from intact monolith lysimeters was established based on measurements of spatial heterogeneity within the lysimeter area. This was part of an ongoing study to determine relationships between soil microbial diversity and nutrient loss by leaching. The sampling protocol had to allow collection of soil on a regular basis (as opposed to destructive sampling) and ensure high spatial independence of subsamples. On each of the two sites (one developed under organic crop management and the other under conventional crop management), ten 15 cm soil cores (sampling points) were taken from three areas (replicates) of 50 cm diameter (lysimeter surface area) and separately analysed for biotic (microbial biomass carbon and nitrogen; arginine deaminase activity) and abiotic (total carbon and nitrogen) soil properties. The data were tested for variability, expressed as coefficient of variance (biotic and abiotic), and spatial heterogeneity using geostatistics (biotic properties). The biotic soil properties showed significant differences among sampling points, whereas the abiotic parameters were useful in differentiating on a larger scale, i.e. between sites. For all soil properties tested, the differences among the replicates were smaller than those between the sites or among points indicating that, in the main experiment, all treatments can be sampled following the same pattern. Geostatistical analysis and fitting of an exponential model showed that a spatial structure exists in the biotic soil properties and that the samples are independent beyond separation distances of 25-30 cm. A revised sampling pattern consisting of 11 samples per lysimeter is described.     

贵州喀斯特人工草地土壤水分空间异质性对放牧强度的响应

采用地统计学方法研究贵州南部人工草地不同放牧强度(零牧、中牧和重牧)下浅层土壤剖面(0—10,10—20,20—30cm)水分的空间异质性及其影响因素。结果表明:喀斯特人工草地土壤水分的平均值与变异系数均呈现出明显的放牧强度变化与剖面变化规律;在不同放牧强度下,0—10cm和10—20cm土壤剖面含水量均表现为NGHGMG,20—30cm土层土壤含水量为NGMGHG,变异系数均呈中等变异(10%CV100%),平均含水量处于中等水平时土壤水分变异性较高;土壤水分的Moran’s I自相关分析表明,不同放牧强度下不同土层草地土壤水分均具有较强的空间自相关性,且空间自相关性主要受放牧影响;土壤水分半方差分析表明,不同放牧强度下不同土层草地土壤水分空间分布特征模型为指数模型、球状模型或高斯模型,表明其均为聚集分布;不同放牧强度C/(C0+C)值在0.500~0.817之间,表明土壤水分表现出中等或很强的空间自相关性;不同放牧强度土壤水分变程在2.77~15.61m范围内变化(零牧,2.53~12.82m;中牧,2.77~15.61m;重牧,14.03~18.79m),说明影响土壤水分的生态过程随放牧强度变化在不同尺度上起作用;Kriging maps直观地反映和验证了草地土壤水分的空间变化规律,与Moran’s I和半方差函数分析的结果相吻合。综合分析发现,在小尺度内,重牧是地势平坦的喀斯特人工草地表层土壤水分空间变异的主要影响因素。     

Characterizing spatial variability of soil properties in alluvial soils of India using geostatistics and geographical information system

Alluvial soils constitute significant portion of cultivated land in India and it contributes towards food grain production predominantly. The objectives of this study were to assess the spatial variability of soil pH, organic carbon (OC), available (mineralizable) nitrogen (N), available phosphorus (P), available potassium (K) and available zinc (Zn) of alluvial floodplain soils of Kadwa block, Katihar district, Bihar, India. A total of 85 soil samples, representative of the plough layer (0–25 cm depth from surface) were randomly collected from the study area. The values of soil pH, OC, N, P, K and Zn varied from4.4 to 8.4, 0.20% to 1.20%, 141 to 474, 2.2 to 68.2, 107 to 903 kg ha^–1 and 0.22 to 1.10 mg kg^–1, respectively. The coefficient of variation value was highest for available P (94.3%) and lowest for soil pH (11.3%). Spherical model was found to be the best fit for N, P and Zn contents, while exponential model was the best fit for OC, and Gaussian model was the best-fit model for pH and K. The nugget/sill ratio indicates that except pH and available K all other soil properties were moderately spatially dependent (25–57%). Soil properties exhibited different distribution pattern. It was observed that the use of geostatistical method could accurately generate the spatial variability maps of soil nutrients in alluvial soils.     

Repeated measurements on permanent plots using local variability sampling for monitoring soil cover

On US military installations, training activities such as vehicle use disturb ground and vegetation cover of landscapes, and increase potential rainfall runoff and soil erosion. In order to sustain training lands, soil erosion is of major concern. Thus there is a need for sampling designs to monitor degradation and recovery of land conditions. Traditionally, permanent plots are used to obtain the change of land conditions. However, the permanent plots often provide less information over time in characterizing the land conditions because of the fixed number and locations of plots. In this paper, we analyzed the sufficiency of a permanent plot sample and developed a method to improve the re-measurements of the permanent plots over time for a monitoring system of soil erosion based on spatial and temporal variability of a random function. We first applied a local variability based sampling method to generate reference samples that have sampling distances varying spatially and temporally to monitor a soil erosion relevant cover factor for an installation, Fort Riley, USA. Then, we compared a permanent sample with the reference samples annually over 13 years to determine additional sampling in the areas with high variability and temporarily suspending measurements of the permanent plots in the areas with low variability. The local variability based sampling provides estimates of local variability of the cover factor and thus is more cost-efficient than random sampling. By comparison with a reference samples, the re-measurements obtained should more accurately characterize the dynamics of the land conditions.