Hydrolytic enzyme activities in agricultural and forest soils. Some implications for their use as indicators of soil quality

Although a great deal of information exists about the effect of land use on soil enzyme activities, much of this is contradictory and brings into question the suitability of soil enzyme activities as indicators of how land use affects soil quality. The purpose of this study was to investigate the effect of land use on different soil biochemical properties, especially hydrolytic enzyme activities, with the aim of providing knowledge about the problems related to the use of enzymes as indicators of soil quality. The data presented derive from various studies in which a large number of soils under different types of forest or agricultural management were analysed by the same methods. All of the soil samples were characterized in terms of their main physical and chemical properties, the activity of several hydrolases, microbial biomass C and soil basal respiration. The results indicate that soil use causes a large reduction in organic matter content and that the effect on enzyme activity varies depending on the type of land use or management and the type of enzyme. Furthermore, the enzyme activities per carbon unit (specific activities) in soils affected by land use are almost always higher than in maximum quality soils (climax soils under oak vegetation or oak soils), and land use also generates greater increases in the specific activity as the C content decreases. The mechanism responsible for these increases probably involves loss of the most labile organic matter. Enzyme enrichment is not always produced to the same degree, as it varies as a function of the enzyme and the type of land use under consideration. It is concluded that the complexity of the behaviour of the soil enzymes raises doubts about the use of enzyme activities as indicators of soil degradation brought about by land use.     

抚仙湖流域典型农田土壤质量状况及烟草种植障碍因素

以云南抚仙湖北岸澄江市约1 130 hm²农田土壤为研究对象,通过调查分析土壤物理、化学性质,评价了研究区土壤质量状况,并进一步利用空间分析、相关分析与主成分分析对研究区烟草种植的主要土壤障碍因子进行了分析。结果表明:研究区土壤整体偏黏(平均黏粒含量496.7 g/kg)、偏碱(pH均值7.45)、有机质含量较高(均值28.55 g/kg)、大中微量营养元素有效态含量也整体偏高(水解性氮均值119.10 mg/kg、有效磷均值68.85 mg/kg、速效钾均值208.44 mg/kg、有效锰均值28.14 mg/kg),但各土壤性质在空间上变异较大。土壤基础地力、人为施肥管理、质地、酸碱性、有效锰是影响该地区土壤肥力的主要障碍因素,这些因素可通过有机质、速效钾、黏粒、pH、有效锰等指标进行评价,并指导烟草种植的土壤管理。烟草种植过程中应根据土壤性质、烟草养分需求,结合土壤养分空间变异采取相应的土壤改良措施。     

Soil fertility affected by land use history,relief position,and parent material under a tropical climate in NW-Vietnam

In Vietnam as much as half of the total land area is already degraded by soil erosion and nutrient depletion. In particular, degradation due to deforestation is increasingly affecting mountainous areas in north-western Vietnam. The necessity to safeguard the farmers' livelihoods requires sustainable resource management, which firstly requires a qualitative and quantitative evaluation of resources. The objectives of the present study were to (1) identify the dominant soil types and their vulnerability using elicitation of local soil knowledge, (2) characterise the physical and chemical properties of the soils and (3) link them to the relief position and land use in order to (4) initiate sustainable soil use based on recommendations deduced from objectives (1) to (3). These objectives were achieved also by the elicitation of local knowledge. The final aim of the study was to initiate sustainable soil use based on recommendations for sustainable land use scenarios. The Chieng Khoi commune in Son La province of northern Vietnam was chosen as representative for other erosion-prone Southeast Asian sloping areas. In a participatory approach, combining local and scientific knowledge, sixteen sites were selected, representative for distinct relief positions, parent material (sand stone and silt stone), land use history, and erosion hazard. Chemical (e.g. content of organic matter, nitrogen, cation exchange capacity, base saturation, and plant available phosphorous) and physical properties (e.g. air capacity, plant available water) were used to estimate soil fertility. The predominant reference soil groups in the study area are Alisols and Luvisols, with a high diversity in respect to soil fertility. These soils are locally named ‘red soil’ and ‘black soil’, respectively. Although the main physical processes are erosion and selective sedimentation, farmers tend to underestimate their impact and causes, whereas soil quality was well-evaluated. Soils with high fertility were found on less eroded upper parts of hills and at sites, where agricultural use started only recently. Once degraded by cultivation practices, soils derived from sandstone did not recover even after more than 50 years of fallow. As a result of unsustainable land use, soils on middle and lower slopes are often affected by severe soil erosion, whereas foot slope soils suffer from accumulation of eroded infertile subsoil material as well as stagnic conditions. This study showed that unsustainable land use at upslope landscape positions has a severe impact on downslope areas. The elicitation of local knowledge facilitated the identification of such hot spots, allowing the implementation of spatially targeted conservation measures.     

Landscape and land use effects on soil resources in a Himalayan watershed

Sustainable land management decisions at all scales require solid, science-based information. Soil quality assessment can provide this regarding soil physical, chemical, and biological characteristics and the ability to provide ecosystem and societal services. Our objective was to make a regional assessment of soils in the Garhwal Himalayas to determine their ability to perform various functions and respond to external influences. Five functional categories were assessed using 13 soil parameters focused on ecological sustainability. Human land use effects on soils were referenced to natural woodlands at each landscape position. Within upper-slope regions, flora and fauna habitat, moisture retention, organic matter and nutrient cycling, air and water infiltration and resistance to erosion were decreased 35, 27, 24, 24, and 9%, respectively. At mid-slope positions the order and magnitude of decrease were organic matter and nutrient cycling, flora and fauna habitat, and moisture retention (26, 22, and 16%, respectively). Changes within the valley were lowest, averaging − 3% for flora and fauna habitat and − 13% for organic matter and nutrient cycling. We conclude that the minimum data set (MDS) used provided a representative assessment of soil quality and could serve as a basis for assessment in similar tropical watersheds.     

连作植烟土壤酚酸类物质变化特征及其与主要环境因子的Mantel Test分析

为明确酚酸类物质在连作植烟土壤中的变化特征,探讨土壤主要环境因子对酚酸类物质的影响,以不同连作年限（4 a,6 a,8 a,14 a和16 a）植烟土壤为对象,研究了不同连作年限植烟土壤酚酸类物质、理化性状、酶活性和细菌多样性的变化特征,并利用Mantel Test分析了酚酸类物质与土壤主要环境因子的相关性。结果表明,随连作年限增加,土壤酚酸类物质和速效钾含量升高,pH、有机质含量、细菌菌群丰度和多样性降低,水解性氮和有效磷含量呈先降低后升高趋势,酶活性呈先升高后降低趋势。Mantel Test分析表明,土壤酚酸类物质含量与理化性状、酶活性和细菌丰度显著相关,且与理化性状相关性最高;不同酚酸类物质含量与土壤主要环境因子相关性存在差异,其中,对羟基苯甲酸和阔马酸与植烟土壤理化性状、酶活性以及细菌丰度的相关性最高。因此,在本试验条件下,连作植烟土壤酚酸类物质具有明显积累特征,植烟土壤环境恶化;酚酸类物质积累受理化性状、酶活性和细菌多样性影响,且理化性状影响最大;不同酚酸类物质受主要土壤环境因子的影响存在差异,其中对羟基苯甲酸和阔马酸积累所受影响最大。     

Assessing and Managing Soil Quality for Urban Agriculture in a Degraded Vacant Lot Soil

Following the decline of industrial manufacturing, many US cities have experienced severe population reductions that have resulted in large areas of vacant land. Urban agriculture has emerged as a desirable land use for these spaces, but degraded soils are common. Therefore, we measured soil and plant responses to amendments and management in urban lots where vacant houses had recently been demolished in Youngstown, OH, USA. Soil degradation was observed following demolition activities in the form of compaction (bulk density of 1·5–1·8 Mg m⁻³) and low soil microbial biomass C (21 mg C kg⁻¹ soil). Our split‐plot experiment measured the effects of organic matter (OM) amendments produced from yard wastes and the use of raised beds on soil properties and vegetable crop yields. Two years after their application, OM amendments resulted in significant improvement to a number of soil physical, chemical, and biological properties. Vegetable crop yields were improved by OM amendments in 2011 and by both OM amendments and the use of raised beds in 2012. A soil quality index, developed using factor analysis and the Soil Management Assessment Framework, produced values ranging from 0·60 to 0·85, which are comparable to those reported for rural agricultural soils. All results indicate that urban agriculture can be productive in vacant urban land and that amendments produced from urban yard wastes can improve soil quality at previously degraded sites and increase crop yields for urban agriculture. Copyright © 2015 John Wiley & Sons, Ltd.     

Characterization of Degraded Soils in the Humid Ethiopian Highlands

Hardpan is a major cause of land degradation that affects agricultural productivity in developing countries. However, relatively, little is known about the interaction of land degradation and hardpans. The objective of this study was, therefore, to investigate soil degradation and the formation of hardpans in crop/livestock‐mixed rainfed agriculture systems and to assess how changes in soil properties are related to the conversion of land from forest to agriculture. Two watersheds (Anjeni and Debre Mewi) were selected in the humid Ethiopian highlands. For both watersheds, 0–45 cm soil penetration resistance (SPR, n  = 180) and soil physical properties (particle size, soil organic matter, pH, base ions, cation exchange capacity, silica content, bulk density and moisture content) were determined at 15 cm depth increments for three land uses: cultivated, pasture and forest. SPR of agricultural fields was significantly greater than that of forest lands. Dense layers with a critical SPR threshold of ≥2000 kPa were observed in the cultivated and pasture lands starting at a depth of 15–30 cm but did not occur in the undisturbed forest land. Compared with the original forest soils, agricultural fields were lower in organic matter, cation exchange capacity, and exchangeable base cations; more acidic; had a higher bulk density and more fine particles (clay and silt); and contained less soluble silica. Overall, our findings suggest that soil physical and chemical properties in agricultural lands are deteriorated, causing disintegration of soil aggregates, resulting in greater sediment concentration in infiltration water that clogged up macro‐pores, thereby disconnecting deep flow paths found in original forest soils. Copyright © 2016 John Wiley & Sons, Ltd.     

Impacts of land use/cover change on soil properties in the Mediterranean region of northwestern Jordan

This study was carried out to evaluate the effects of deforestation on physical and chemical properties of soils under native forest in the Mediterranean region of northwestern Jordan. Land use/cover maps of 1953, 1978 and 2002 were interpreted and analysed within GIS to quantify the shift from forest to rainfed cultivation. Six sites were sampled in a non‐changed forest and in cultivated fields, three for each. Different soil properties of texture, bulk density, organic matter, total nitrogen, pH, cation exchange capacity (CEC), phosphorous and potassium were analysed. Results showed that many forests were changed into cultivated lands at a rate more than the reforestation. Subsequently, adverse effects on the studied physical and chemical properties were observed. The most affected properties were particle size distribution, bulk density of surface soil and subsoil. Organic matter and CEC decreased in cultivated soil as compared to the forest soil. Cultivated soils were found to exhibit a significantly lower status in physical and chemical soil properties as compared to forest soils. This general decline in the soil physical and chemical properties, in turn, contributed to soil erosion, reduction of soil fertility and land degradation. There is an urgent need to improve soil quality by developing sustainable land use practices to reduce the rate of soil degradation and to ensure long‐term sustainability of the farming system in the study area and in similar biophysical settings. Copyright © 2008 John Wiley & Sons, Ltd.     

典型喀斯特地区石漠化演变过程对土壤质量性状的影响

在一个较小的时空尺度上对典型喀斯特地区石漠化过程中的土壤质量演变特征及其退化过程进行了探讨。结果表明：由于植被破坏和耕地的开垦发生土壤颗粒粗化，向石漠化景观发展，土体结构破坏，容重增加0．12～0．60g／cm^3，总孔隙度降低12．0％～39．8％，持水性能变劣，养分也随之下降；〈0．05mm的粘粉粒流失，表层土壤有机质和全氮含量下降33．4％～84．6％和43．3％～85．2％。土壤质量的演变，既有系统本身的自然属性决定的内在原因，更重要的是人为的外部干扰体系的驱动；演变的过程既有渐变型，又有跃变型。     

Watershed-scale assessment of soil quality in the loess hills of southwest Iowa

Soil quality is a concept that integrates soil biological, chemical and physical factors into a framework for soil resource evaluation. Conventional tillage practices can result in a loss of soil organic matter and decreased soil quality. The potential for soil quality degradation with tillage may vary depending upon landscape position and the spatial distribution of critical soil properties. Information on how to accurately integrate soil spatial information across fields, landscapes and watersheds is lacking in the literature. The primary objective of this study was to evaluate the long-term effect of conventional and ridge-tillage on soil quality in three small watersheds at the Deep Loess Research Station near the town of Treynor in southwest Iowa. Soil types included Monona silt loams in summit positions, Ida or Dow silt loams in backslope positions, and Napier or Kennebec silt loams in footslope positions. We removed surface soil cores from transects placed along topographic gradients in each watershed and quantified total soil organic C (SOC), total soil N (TN), particulate organic matter C (POM-C) and N (POM-N), microbial biomass C (MB-C), N mineralization potential (PMIN-N), nitrate N, extractable P and K, pH, water-stable macroaggregates (WSA), and bulk density (BD). We used terrain analysis methods to group the data into landform element classes to evaluate the effect of topographic position on soil quality. Results indicate that soil quality is higher under long-term ridge-tillage compared with conventional tillage. Soil quality differences were consistently documented among the three watersheds by: (1) quantification of soil indicator variables, (2) calculation of soil quality index values, and (3) comparison of indicator variable and index results with independent assessments of soil function endpoints (i.e. sediment loss, water partitioning at the soil surface, and crop yield). Soil quality differences under ridge-till were found specifically for the backslope and shoulder landform elements, suggesting that soil quality increases on these landform elements are responsible for higher watershed-scale soil quality in the ridge-tilled watershed.     

贵州中部岩溶丘陵区不同土地利用和管理方式对土壤肥力的影响

本文研究了黔中岩溶丘陵区几种不同士地利用和管理方式下土壤物理、化学和生物学性状的特征。结果表明,农林(林草)复合利用模式在土壤粒级组成、孔隙分布、持水性能、有机质和N、P养分、酶活性等方面表现出较好的肥力性状特征,有机无机肥配施、精细管理的灌溉农田次之,而粗放管理的旱坡耕地,土壤肥力性状严重恶化,逐步向石漠化景观演变。不同土地利用方式和管理措施显著影响土地肥力变化的程度和方向,调整土地利用结构,实行基本农田精细管理、陡坡耕地退耕还林(革)是保护土地资源,实现区域生态重建和农业可持续发展的根本途径。     

黄河三角洲盐碱地不同利用方式土壤理化性质

为了缓解土壤盐碱性,保证土壤可持续利用,研究了黄河三角洲典型土地利用类型撂荒地、棉田、苜蓿地和梨园土壤理化性质.结果表明:棉田土壤容重较高,而孔隙度和毛管孔隙度低,由于棉田灌水压盐措施,抬高了地下水位,土壤返盐严重.苜蓿地由于管理粗放,对土壤扰动少,容重较低,孔隙度和毛管孔隙度较高,盐碱度较低;每年对苜蓿的采收显著降低了苜蓿地土壤有机质和养分含量,而豆科固氮菌的存在,使表层速效氮含量较高.梨园位于黄河三角洲土壤质地较好的区域,且有机肥料施用一定程度上缓解了土壤板结,盐碱度较低.撂荒地表层土壤理化指标均显著优于棉田,在退化土壤恢复中具有较好的效果.     

城郊结合区蔬菜种植地土壤性质特征

Human activity and urbanization result in urban-rural environmental gradients.Undersanding effect of the gradients on soil properties is necessary for management of the soils around urban areas.In this study,soil quality of some vegetable fields was characterized along an urban-rural gradient in shaoxing County,Zhejiang Province.Fifteen soilphysical and chemical properties were evaluated by using principal component analysis.Results showed that there was a great variation in the soil quality along the gradient.From rural to urban zones,soil organic matter,water-stable aggregates,cation exchangeable capacity(CEC),total N and P,and available K increased,whereas soil pH value decreased.In addition,Pb,Cu,Ni,Co,Zn and Cr in the soils tended to be accumulated toward the urban zone.Sequential chemical extraction showed that mobility of all the heavy metals in the soils tended toincrease from the rural to the urban zones.The variation of soil properties accounted for by the first principal component was significantly explained bythe difference in application rates of municipal wastes.     

The impact of land‐cover change on soil properties in northern Ghana

Effects of changes in land‐cover on soil quality parameters in an area in northern Ghana were studied. Land‐cover changes were derived from maps of the study area for 1984, 1992 and 1999. There were no significant differences between properties of soils under natural vegetation and soils put under cultivation from 1992, but permanently cultivated soils (1984–1999) showed significantly lower physical and chemical soil properties. Soils recently opened up since 1992 for cultivation in the last seven years (i.e. 1992–1999) were found to manifest significantly higher contents of organic C, N, Ca, Mg and ECEC than those under permanent cultivation, suggesting that continuous cropping is responsible for deterioration in soil quality. Minimum organic C contents necessary to meet critical levels of selected soil quality parameters were estimated. The organic C content of recently cultivated soils would need to be increased by about 7 t ha⁻ to replenish soil nutrient capital. This calls for a strategy to synchronize organic matter management with inorganic fertilizer application. Further research is also needed to develop farming systems that conserve organic matter and also improve the quality of organic matter in the study area. Copyright © 2004 John Wiley & Sons, Ltd.     

湘西典型植烟土壤酸碱缓冲特性及影响因素

为探明山地植烟土壤酸碱缓冲特性,采集了湘西山区烤烟典型生产区的28个土壤样本,采用酸碱滴定法和灰色关联法分析了湘西山地植烟土壤酸碱缓冲特性以及土壤缓冲容量与各影响因素之间的量化关系。结果表明：湘西山地植烟土壤酸碱缓冲量为11.35~43.29 mmol·kg^-1,平均为17.26 mmol·kg^-1,黄棕壤的酸碱缓冲量（11.35~43.29 mmol·kg^-1）显著高于黄壤（11.79~20.70 mmol·kg^-1）。有78.57%的样本对酸碱敏感,黄壤土是否对酸敏感由有机质含量决定,黄棕壤土是否对酸敏感与pH和有机质含量密切相关。对于同一土壤类型,有机质和黏粒含量与酸碱缓冲容量显著正相关;对于黄棕壤,酸碱缓冲容量还与pH和阳离子交换量呈显著正相关,与交换性酸和交换性铝呈显著负相关。主要土壤类型之间缓冲性能存在较大差异,黄壤土酸碱缓冲性能主要受土壤有机质、阳离子交换量和黏粒含量的影响;黄棕壤土酸碱缓冲性能主要受pH、阳离子交换量和有机质的影响。在生产中应采用合理施用化肥、增施有机肥、调节土壤酸性等措施提高植烟土壤酸碱缓冲性能,为优质烟叶生产创造良好的生态环境。     

Impacts of historical land use changes on erosion and agricultural soil properties in the Kali Basin at Lake Balaton, Hungary

Historical land use changes may have significant impact on erosion and agricultural soil properties, including soil degradation by acidification, nutrient leaching and organic matter depletion. The Kali Basin study area, a small catchment of high landscape value located in a national park at Lake Balaton, Hungary, with its historical agricultural records, together with the available unique historical land use data for the last 200 years, provides an opportunity to study and model impacts of historical land use changes on erosion and agricultural soil properties. Comparison of long-term land uses with present soil degradation indicator parameters showed that permanent arable land use has led to degradation of both the physical and chemical properties of soils in the Kali Basin. Application of the SEDEM/WATEM distributed erosion and sediment transport model showed that, despite the low overall sediment export from the catchment, land use changes introduced by property ownership and agricultural changes have decreased average soil erosion in the catchment but increased relative sediment export to Lake Balaton. This is due to changes in the land cover pattern that allow more sediment transported to the river system. The overall conclusion of this study is that besides the size and area proportion of land use types, land use pattern seems to be equally important in soil erosion and degradation processes, thus land use pattern is a key factor for landscape planning and development in the Kali Basin. A relationship between the sociological and agro-ecological reasons for the recorded land use changes is also shown in this study.     

亚热带低丘区退化红壤肥力质量恢复性能的研究

试验和分析结果表明 ,退化红壤主要肥力因素的恢复与农用物质的投入和土壤本身理化性质均存在明显的关系。随着物质投入量的增加 ,土壤肥力质量的恢复也逐渐加快。在自然条件下 ,土壤肥力因素的恢复主要与土壤本身属性有关 ,在肥力恢复过程中 ,土壤有机质的增加量与土壤本身有机质含量呈抛物线关系 ,约当土壤有机质含量在 2 0 g/ kg时 ,增幅最大 ;在一定的含氮范围内 ,土壤氮素的增加与土壤全氮含量呈正相关 ;而速效钾的增加量与土壤本身速效钾含量呈反相关。土壤水稳定性团聚体的恢复与土壤粘粒含量及有机质含量呈正相关。试验结果表明 ,在合理的管理条件下 ,红壤肥力质量可以逐渐得到改善     

Quantitative und qualitative Veränderungen im A-Horizont von Sandböden nach Umwandlung von Dauergrünland in Ackerland

Quantitative and qualitative changes in soil properties of A- horizons of sandy soils caused by conversion of grassland to arable land Changes in physical soil properties and in soil organic matter of the A-horizons due to the conversion of permanent grassland to arable land are quantified and described as a function of time for sandy soils. The study was carried out in an area northeast of Hannover. A decrease of about 100 t/ha C_org (- 57%), 5 – 6 t/ha N_org (- 58%) and 1 t/ha S_t (- 58%) was measured for a period of 2 – 4 years after grassland conversion. Thereby the quality of the soil organic matter remains unchanged (no changes of the C/N ratio and of the distribution of N_org in 5 N-fractions). However, an increase of soil bulk density from 1.0 to 1.3 g/cm³ and a decrease of total pore volume from 0.59 to 0.47 were observed. The fast mineralization of soil organic matter in the A-horizon following the conversion of grassland soils results in a temporary heavily increased nitrate input into the groundwater. Furthermore mineralization and leaching of nitrate and sulfate induces an acidification push in the soil by a proton release in the order of 350 keq/ha during a 2 – 4 years period. However, this proton production is compensated quantitatively by several applications of lime or marl by farmers and by the buffering of bases cations released from mineralized soil organic matter.     

Incidence of soil surface crust types in semi-arid Niger

Soil water availability is most essential in the Sahelian agriculture but is hampered by several factors. Surface crusts or crust-like surfaces, which are characteristic of most Sahelian soils, have been shown to decrease water infiltrability and increase runoff. Their type and structure are influenced by soil texture, vegetation cover, erosion and deposition effects of wind and water. A soil and terrain survey in semi-arid SW-Niger was carried out to explain the patterns of soil surface crusts and the deterioration of the land. The soil surface crusts were shown to depend also on specific terrain factors including land use type and intensity, and terrain type and position. Chemical and physical soil factors such as organic carbon, soil colour and texture occurring with specific crusts indicate soil degradation, especially in sloping terrain, which increases runoff and soil erosion. For sandy soils, surface tillage is required to break up the crusts. Higher surface organic matter is recommended to enhance water infiltration in soils.     

Quantification and Remediation of Soil Chemical Degradation in Tropical Australia,China and Thailand

Soil and land degradation in the tropics can be identified and described in terms of physical, chemical,and biological changes from its pristine state brought about by natural and anthropogenic influences. Acharacteristic of these ecosystems is their capacity to recycle nutrients through soil organic matter (SOM).Following disturbance through changed land management, SOM is rapidly mineralized and there is a cor-responding decline in fertility and the variable charge component of the cation exchange capacity. As theseecosystems are strongly dependent on SOM for their functionality, changed land use can have irreversible im-pacts on the productivity of these systems. The paper focuses on quantifying chemical degradation throughprinting. Using values taken from the fingerprint of an undisturbed soil, an index of chemical degradationimprove poor quality soils in their natural condition are discussed, such as the addition of natural clays andsilicated materials. Results are present to show the effect of each of the aforementioned strategies on surfacecharge characteristics and associated increases in plant productivity.