Assessing soil quality under intensive cultivation and tree orchards in Southern Italy

Concerns about groundwater contamination as well as pesticide residues in food and soil have fuelled vigorous debates about the sustainability of chemical-intensive agriculture. Search has been prompted for agronomic strategies with lower environmental hazards. In this multidisciplinary study we compared the characteristics of soils from 20 agricultural farms selected in five geographical areas of Southern Italy with different soil types. In each farm, fields with management regime classified as high-input (HIMR, intensive cultivation under plastic tunnels) or low-input (LIMR, tree orchards) were selected. Soil samples were analyzed for 31 parameters including physical and chemical properties (bulk density, water holding capacity, texture, pH, limestone, electrical conductivity, organic C to a depth of 0–20 and 20–40 cm, total N, P₂O₅, Ca²⁺, Mg²⁺, K⁺, Na⁺, cation exchange capacity), enzymatic activities (dehydrogenase, arylsulphatase, β-glucosidase, phosphatase and urease) and microbiological features (potential respiration, functional diversity of microbial populations by BIOLOG EcoPlates™, microbial biomass, fungal mycelium, culturable actinomycetes, bacteria and fungi, pseudomonads and bacterial species richness by 16S rDNA-DGGE). Finally, a soil bioassay was performed in order to evaluate the plant growth of a biotest plant (Lactuca sativa) and soil suppressiveness of the Rhizoctonia solani–L. sativa pathosystem.Results showed that many soil properties were influenced by management regime more than by the sampling area. Compared to LIMR, HIMR soils consistently had reduced soil organic C (−24%), enzymatic activities, microbial biomass and fungal mycelium (−40% and −18%, respectively), functional diversity (−18%) and bacterial species richness (−14%). On the contrary, the same soils showed a remarkable increase in the values of the parameters related to the mineral soil fraction (electrical conductivity +370%; P₂O₅ +72%; Na⁺ +86%). Management regime did not affect cation exchange capacity, pH, limestone and soil texture. The lettuce bioassay showed a higher plant growth (+17%) in the LIMR compared to HIMR soils, despite the lower content of mineral nutrients. Suppression of R. solani was not influenced by management regime, but significant differences were recorded among farms. Differences among the assessed soil parameters indicate a trend of soil quality deterioration under the high-input management regime.     

Impact of farm size and topography on plant and insect diversity of managed grasslands in the Alps

Since the second half of the 20th century, the intensification of land-use practices and the associated decline in semi-natural habitats have been the major drivers of farmland biodiversity loss. In many marginal agricultural systems, a structural transformation of farms, from small and traditional to large and intensive, has also been observed. We unravelled the impact of farm size and slope on plant, orthopteran and butterfly diversity in 132 hay meadows in a region of the Italian Alps. We defined three farm size classes representing different levels of intensification and used mixed models to test the influence of farm size along with topographic slope. The diversity of plants, orthopterans and butterflies declined with management intensity at the field scale, which mainly depended on farm size and grassland topography. We found a positive effect of slope and a negative influence of farm size on species richness of the three taxonomic groups. Large farms were strongly associated with higher production of organic fertilizers and higher soil fertility than small traditional farms, irrespective of meadow slope. At the regional scale, we found that large farms managed flatter meadows (slope = 9.0) than small traditional farms (slope = 13.5), contributing to the abandonment of steep species-rich grassland areas. Regional stakeholders should consider targeted conservation schemes to prevent the ongoing substitution of small farms with large intensive farms. A complementary solution could be to target future conservation measures to support farms with low production of organic fertilizers and to reward the maintenance of the current management of steep meadows.     

Legumes Functional Group Promotes Soil Organic Carbon and Nitrogen Storage by Increasing Plant Diversity

Community composition strongly affected the soil C and N storages. However, the influences of community composition on native grassland remain poorly understood. The purpose of this study is to investigate the ability of plant communities including how legumes affect the soil C and N storages in the semi‐arid grassland. Experimental grassland communities were separated by whether or not containing legumes. We measured soil C and N storages and determined above‐ground and below‐ground biomass, litter biomass, plant species richness, and species diversity to understand the mechanisms underlying the changes of soil C and N storages and to determine the relationship of species diversity and productivity. The results showed that legumes increased above‐ground and below‐ground biomass and C and N storages. Soil C and N storages were significantly and positively related to above‐ground and below‐ground biomass, litter biomass, plant species richness, and diversity in the presence of legumes. The presence of legumes increased soil C and N simultaneously but not synchronously, which resulting in a higher C:N ratio. This study indicated that legumes increased soil C and N storages possibly through increasing biomass and soil C and N inputs. The increases are mediated by plant diversity and plant functional complementarity. We suggest that the combination of legumes‐grass species may greatly enhance ecosystem services such as soil C and N storages, productivity, and diversity in semi‐arid grassland. Copyright © 2016 John Wiley & Sons, Ltd.     

Soil microbiological and biochemical properties for assessing the effect of agricultural management practices in Estonian cultivated soils

A set of soil microbiological and biochemical properties was used to assess the influence of agricultural practices such as rotation, usage of pesticides, and fertilizers on the three most widespread soil types (Calcaric Regosols, Calcaric Cambisols and Stagnic Luvisols) in the fields of horticultural farms throughout Estonia. Microbial biomass, dehydrogenase and alkaline phosphatase activity were significantly higher in Calcaric Regosols, whereas measured soil chemical parameters showed practically no difference among soil types. Multivariate exploratory analysis of soil biochemical and microbiological parameters clearly distinguished soils with different management practices when the effect of soil type was taken into account in data analysis. Activity of dehydrogenase, potential nitrification, N-mineralisation, and microbial biomass contributed most strongly to the differentiation of soils from differently managed fields. Soils managed according to organic farming principles were generally characterized by elevated microbiological parameter values, but at the same time the variation of those parameters among soils from these fields was also highest. The application of organic manure positively affected microbial biomass, N-mineralisation, potential nitrification, dehydrogenase and acidic phosphatase activity. Data analysis indicated that the amount of mineral nitrogen fertilizers added over time has a stronger effect on microbial biomass than the amount added in a given year. Legume-based crop rotation increased soil respiration and microbial biomass.     

Landscape history and soil properties affect grassland decline and plant species richness in rural landscapes

Past semi-natural grassland extent is thought to have a major influence on contemporary species richness in rural landscapes. The loss of grasslands over the last 300 years was reconstructed for 12 rural landscapes in Sweden, ranging from open modern agricultural landscapes to more forested landscapes. Old maps and aerial photographs from 1950s and today were used to reconstruct landscape patterns in four time-steps to investigate how present plant species richness relates to past grassland extent and decline in old and new grassland habitats. The relative importance of soil properties on the timing of grassland decline was assessed. Plant species occurrence was recorded in managed and abandoned grassland habitats in each landscape.Past and present grassland distribution was a major factor in determining plant species patterns found in grasslands today. All landscapes had an average of 80% grassland 300 years ago. Since then grassland has declined by 90% across all landscapes. Proportion of clay soils influenced the timing of grassland decline, where grasslands in landscapes dominated by clay soils were conversed to crop-fields more than 100 years ago. Grasslands on coarser soils declined later, primarily to forest. Landscapes with more than 10% semi-natural grassland left today had 50% higher species richness in all grasslands, including both abandoned and new grassland. Time since major grassland decline also seems to have an effect on the landscapes’ species richness. The results show that plant species patterns in grasslands at local scales are determined by broader landscape processes which may have occurred many centuries ago.     

Multivariate evaluation by quality indicators of no-tillage system in Argiudolls of rolling pampa (Argentina)

The purpose of this study was to develop operationally important soil quality indicators to evaluate long-term sustainability, at the farm scale, for no-tillage systems in Argiudolls of rolling pampa (Argentina). The soil was classified as series Arroyo Dulce (Typic Argiudoll), a fertile dark, deep and well-drained soil of the hills. Three situations were considered: pristine soil with grass vegetation, grassland soil (also considered as a reference situation); and 15 years no-tillage soils from four production plots. Physical, physico-chemical, chemical and biochemical indicators were considered. Data were analyzed by principal components analysis (PCA) with canonical discriminant analysis (CDA). The first three components explained 90% of the overall variation. For pristine undisturbed soil, the main variables selected by PCA were particulate C, pH, respiration and total organic C, and in the case of grassland they were C stock (mass of C in the 0–10 cm soil horizon), water-soluble C, and % silt. The no-tillage area was separated in different plots according to the degree of erosion with different depths of the A horizon. Clay content and bulk density were the main variables in the less degraded no tillage plots. Cluster analysis was applied to construct an average linkage distance dendrogram.     

Biochemical analysis of soil organic matter and microbial biomass composition—a pilot study

Biochemical composition of both intracellular (biomass) and extracellular soil organic matter was determined after extraction with 0.5 M K₂SO₄. Extractable carbon, hexoses, pentoses, total reducing sugars, ninhydrin-reactive nitrogen (NRN), proteins and DNA content were colorimetrically determined. The objective of the pilot study was to examine the information potential included in newly measured biochemical characteristics, their environmental variance and the relationships with main soil properties. Correlation analysis and PCA showed independence between biochemical parameters and physico-chemical properties of the soil. Thus, the parameters characterising biochemical composition of the soil biomass and extracellular matter seem to bring new information about the soils beyond the physico-chemical parameters. They also seem to reveal a more detailed view on microbial biomass or extracellular organic matter pool than C_bio or C_ext alone, respectively. The variance, which occurred in biochemical characteristics, also displayed a high discrimination potential between the defined soil categories. Three types of indices were newly proposed: index I (“substrate quantity index”)—the biomass-specific amount of the extracellular organic compounds, index II (“immobilisation ratio”)—the portion of the organic compound immobilised in microbial biomass, and index III (“substrate quality index”)—the extracellular organic compound content related to extracellular organic carbon. The indices displayed a higher potential than both soil biotic and abiotic parameters to discriminate soil characters and soil types.     

阿尔泰山布尔津林区不同草地类型物种多样性特征与生产力的关系

为探讨物种多样性与地上生物量的相关性以及物种多样性的垂直变化特征.以阿尔泰山布尔津林区5种草地类型为研究对象,通过对布尔津林区各草地类型的调查,分析了阿尔泰山布尔津林区各草地类型的物种多样性变化特征.结果 表明:(1)5个草地群落类型地上生物量差异明显,荒漠草原和山地草甸草原较低,山地草原最高,而山地草甸和高寒草甸处于...     

松嫩平原盐碱化人工草地土壤与植被群落空间变异特征研究

松嫩草地由于受太平洋季风气候的影响,具有较好的水热条件,且地势平坦,非常适宜畜牧业的机械化发展。在过去的几十年间,松嫩草地物种丰富度较高,优质的牧草以多年生的羊草为主,且在植被下形成了肥力较高的黑土。然而,松嫩草地独特的地形与高矿化度的地下水,导致了盐渍土与黑土接壤,因此松嫩草地生态环境较为脆弱。此外,由于草地的过度利用,导致了松嫩草地发生退化与盐碱化,进而使得草地生产力降低。较低的草地生产力已成为限制该区域畜牧业发展的主要因素,而草地生产力与土壤水盐动态密切相关。故本研究以松嫩盐碱化人工草地为研究对象,采用经典统计学与地统计学相结合的方法,对松嫩平原西部地区的盐碱化人工草地土壤理化性质以及牧草生物学-生态学性质的空间变异特征进行研究。结果表明,0～15 cm和15 ～30 cm层土壤的pH、电导率（EC）、总碱度（TA）、以及土壤质量含水量（MWC）具有中度或强空间变异。此外,试验区域的生物多样性指数（SWI）、紫花苜蓿的株高（SH）、生物量干重（DM）与盖度（CD）均具有强烈的空间变异特征。回归分析结果表明,试验区域盐碱化人工草地紫花苜蓿产量可用公式Y(DM)=2699.73–276.496 pH（7.17< pH<9.76）预估。本研究结果可为苏打盐渍土的精细化管理与利用提供理论基础与数据支持。     

Plant biomass influences rhizosphere priming effects on soil organic matter decomposition in two differently managed soils

We used a continuous labeling method of naturally ¹³C-depleted CO₂ in a growth chamber to test for rhizosphere effects on soil organic matter (SOM) decomposition. Two C3 plant species, soybean (Glycine max) and sunflower (Helianthus annus), were grown in two previously differently managed soils, an organically farmed soil and a soil from an annual grassland. We maintained a constant atmospheric CO₂ concentration at 400±5 ppm and δ¹³C signature at −24.4‰ by regulating the flow of naturally ¹³C-depleted CO₂ and CO₂-free air into the growth chamber, which allowed us to separate new plant-derived CO₂-C from original soil-derived CO₂-C in soil respiration. Rhizosphere priming effects on SOM decomposition, i.e., differences in soil-derived CO₂-C between planted and non-planted treatments, were significantly different between the two soils, but not between the two plant species. Soil-derived CO₂-C efflux in the organically farmed soil increased up to 61% compared to the no-plant control, while the annual grassland soil showed a negligible increase (up to 5% increase), despite an overall larger efflux of soil-derived CO₂-C and total soil C content. Differences in rhizosphere priming effects on SOM decomposition between the two soils could be largely explained by differences in plant biomass, and in particular leaf biomass, explaining 49% and 74% of the variation in primed soil C among soils and plant species, respectively. Nitrogen uptake rates by soybean and sunflower was relatively high compared to soil C respiration and associated N mineralization, while inorganic N pools were significantly depleted in the organic farm soil by the end of the experiment. Despite relatively large increases in SOM decomposition caused by rhizosphere effects in the organic farm soil, the fast-growing soybean and sunflower plants gained little extra N from the increase in SOM decomposition caused by rhizosphere effects. We conclude that rhizosphere priming effects of annual plants on SOM decomposition are largely driven by plant biomass, especially in soils of high fertility that can sustain high plant productivity.     

The importance of mycological studies for soil quality control

Published and original data obtained in the course of long-term studies of mycobiota of several soil types in regions with different pollution levels and composition of the pollutants (Tver, Moscow, and Samara oblasts; West Siberia; and the Komi Republic) are analyzed. The expediency of using mycological characteristics for soil quality control and estimation of the toxic impact on the environment is discussed. The most pollutant-sensitive mycological characteristics were determined for the following soils: oligotrophic peat gley, eutrophic peat, whitish podzolic, Al-Fe-humus podzol, soddy pale podzolic, soddy-podzolic, and brown forest soils. These are (a) the structure of the fungal biomass, (b) the taxonomic diversity of the fungi, and (c) the percentage of melanized forms of micromycetes. At the same time, the total number of fungi (in colony-forming units) and the indices of the richness of individual species and genera proved to be poorly informative for assessing the ecological status of the soils. Criteria for the choice of mycobiotic parameters suitable for scaling the soil ecological quality are suggested.     

Effect of organic,sustainable, and conventional management strategies in grower fields on soil physical,chemical, and biological factors and the incidence of Southern blight

The objectives of our research were to evaluate the impact of organic, sustainable, and conventional management strategies in grower fields on soil physical, chemical, and biological factors including soil microbial species and functional diversity and their effect on the Basidiomycete plant pathogen Sclerotium rolfsii, causal agent of Southern blight. Soils from 10 field locations including conventional, organic and sustainable farms were sampled and assayed for disease suppressiveness in greenhouse assays, and soil quality indicators. Soils from organic and sustainable farms were more suppressive to Southern blight than soils from conventional farms. Soils from organic farms had improved soil chemical factors and higher levels of extractable C and N, higher microbial biomass carbon and nitrogen, and net mineralizable N. In addition, soil microbial respiration was higher in soils from organic than sustainable or conventional farms, indicating that microbial activity was greater in these soils. Populations of fungi and thermophiles were significantly higher in soils from organic and sustainable than conventional fields. The diversity of bacterial functional communities was also greater in soils from organic farms, while species diversity was similar. Soils from organic and sustainable farms had improved soil health as indicated by a number of soil physical, chemical and biological factors and reduced disease.     

Influence of soil properties on microbial populations, activity and biomass in humid subtropical mountainous ecosystems of India

 Microbial populations, biomass, soil respiration and enzyme activities were determined in slightly acid organic soils of major mountainous humid subtropical terrestrial ecosystems, along a soil fertility gradient, in order to evaluate the influence of soil properties on microbial populations, activity and biomass and to understand the dynamics of the microbial biomass in degraded ecosystems and mature forest. Although the population of fungi was highest in the undisturbed forest (Sacred Grove), soil respiration was lowest in the 7-year-old regrowth and in natural grassland (approximately 373 μg g^–1 h^–1). Dehydrogenase and urease activities were high in "jhum" fallow, and among the forest stands they were highest in the 7-year-old regrowth. Microbial biomass C (MBC) depended mainly on the organic C status of the soil. The MBC values were generally higher in mature forest than in natural grassland, 1-year-old jhum fallow and the 4-year-old alder plantation. The MBC values obtained by the chloroform-fumigation-incubation technique (330–1656 μg g^–1) did not vary significantly from those obtained by the chloroform-fumigation-extraction technique (408–1684 μg g^–1), however, the values correlated positively (P<0.001). The enzyme activities, soil respiration, bacterial and fungal populations and microbial biomass was greatly influenced by several soil properties, particularly the levels of nutrients. The soil nutrient status, microbial populations, soil respiration and dehydrogenase activity were greater in Sacred Grove, while urease activity was greater in grassland. Received: 14 October 1998     

The Role of Legumes in Plant Community Succession of Degraded Grasslands in Northern China

Legume species were more and more commonly introduced to degraded grassland for human‐aided restoration. This study aimed to test whether the natural spread of legume contributes to reversal of grassland degradation through making an extensive grassland vegetation and soil survey in Inner Mongolia of China. The results showed that legume biomass increased along a gradient of soil coarsening that was also a gradient of grassland degradation. The total biomass rather than legume biomass was limited by mean annual precipitation at plot level. The presence of legumes increased species richness in degraded steppe vegetation. Constancy of intermediate and climax species of vegetation succession at sites with legumes was higher than that at sites without legumes, implying that legumes might contribute positively to the reversal of grassland degradation. Our study suggests that naturally distributed legumes could benefit the reversal of grassland degradation through promoting plant community succession rather than total plant biomass. Planting legumes would be an effective measure to accelerate the recovery process of degraded grassland with coarsened soil in regions similar to our study region. Copyright © 2015 John Wiley & Sons, Ltd.     

Nematode community structure as indicator of soil functioning in European grassland soils

This investigation analyses whether soil nematode diversity is correlated with soil functional parameters to serve as bioindicator of soil functioning. The analysis focuses on the interrelations of nematofauna, microflora, and soil nitrogen pools. The sites studied represent six major European grassland types: Northern tundra, atlantic heath, wet grassland, seminatural temperate grassland, East European steppe, and mediterranean garigue. Continental and local climate gradients were combined to a wide and continuous range of microclimate conditions. Nematode richness, as indicated by the number of genera, was highest under temperate conditions and declined towards the climatic extremes. Differences in richness affected all nematode feeding types proportionally. Nematode richness was the only parameter among a range of 15 alternatives tested that exhibited consistent correlations with mass and activity parameters of both nematofauna and microflora in the mineral grassland soils (garigue, wet grassland, seminatural grassland, steppe). In the same soils, the nematode Maturity Index was the best indicator of nitrogen status. We conclude that a high nematode richness can generally be seen as a good indicator of an active nematofauna and microflora in mineral grassland soils, and hence as an indicator of the decomposition function. The prospects of exploiting nematode diversity as an indicator of soil functioning are critically discussed.     

Dynamics of soil organic carbon and nitrogen associated with physically separated fractions in a grassland-cultivation sequence in the Qinghai-Tibetan plateau

This study is aimed at quantifying organic carbon (C) and total nitrogen (N) dynamics associated with physically separated soil fractions in a grassland-cultivation sequence in the Qinghai-Tibetan plateau. Concentrations of organic C and N of soil, free and occluded particulate organic matter (OM), and aggregate- and mineral-associated OM in different land uses are increased in the following order: 50 years cultivation < 12 years cultivation ≤ native grassland. The prolonged cropping of up to 50 years markedly affected the concentrations of free and occluded particulate OM and mineral-associated OM. After wet-sieving, 43% of native grassland soil mass was found in >1−10 mm water-stable aggregates that stored 40% of bulk soil organic C and N; only 16% and 7% of soil mass containing 16% and 7% of bulk soil organic C and N was >1−10 mm water-stable aggregates of soils cultivated for 12 years and 50 years, respectively. This indicated that losses of soil organic C and N following cultivation of native grassland would be largely related to disruption of >1–10 mm size aggregates and exposure of intra-aggregate OM to microbial attack. Organic C and N concentrations of soil aggregates were similar among aggregate size fractions (>0.05−10 mm) within each land use, suggesting that soil aggregation process of these soils did not follow the hierarchy model. The increase of the C-to-N ratio of free and occluded particulate fractions in the cultivated soils compared to the grassland soil indicated a greater loss of N than C.     

Biochemical properties and microbial community structure of five different soils after atrazine addition

Atrazine is one of the most used herbicides worldwide; however, consequences of its long-term agricultural use are still unknown. A laboratory study was performed to examine changes in microbial properties following ethylamino-¹⁵N-atrazine addition, at recommended agronomic dose, to five acidic soils from Galicia (NW Spain) showing different physico-chemical characteristics, as well as atrazine application history. Net N mineralization was observed in all soils, with nitrate being the predominant substance formed. The highest values were detected in soils with low atrazine application history. From 2% to 23% of the atrazine-¹⁵N was found in the soil inorganic-N pool, the highest values being detected after 9 weeks in soils with longer atrazine application history and lower indigenous soil N mineralization. The application of atrazine slightly reduced the amount of soil N mineralized and microbial biomass at short term. Soluble carbohydrates and β-glucosidase and urease activity decreased with incubation time, but were not significantly affected by the single application of atrazine. Microbial community structure changed as consequence of both soil type and incubation time, but no changes in the phospholipid fatty acid (PLFA) pattern were detected due to recent atrazine addition at normal doses. The saturated 17- to 20-carbon fatty acids had higher relative abundance in soils with a longer atrazine history and fungal biomass, as indicated by the PLFA 18:2ω6,9, decreased with the incubation time. The results suggested that the PLFA pattern and soil N dynamics can detect the long-term impact of repeated atrazine application to agricultural soils.     

Effects of cropping systems on soil organic matter in a pair of conventional and biodynamic mixed cropping farms in Canterbury, New Zealand

Effects of cropping systems on soil organic matter (SOM) in a pair of conventional and biodynamic mixed cropping farms were investigated. Soil samples (0–75 and 75–150-mm depths) were analysed for total carbon (TC), total nitrogen (TN), microbial biomass C (BC) and microbial biomass N (BN), and sequentially extracted for labile and stable SOM using cold water, hot water, acid mixtures and alkalis. In the biodynamic farm, TC and TN decreased with increasing period of cropping but the reverse occurred under pastures. These were not shown in soils from the conventional farm, probably due to N fertilizer additions. Under pastures, increases in SOM were attributed to greater biological N₂ fixation and the return of plant residues and excreta from grazing animals. Overall, sensitive SOM quality indicators found for labile SOM were BN, BN:TN and HC:TC, and for stable SOM were HCl/HFC, HCl/HFC:TC, humin C, humin N, humin C:TC and humin N:TN. The BN and BN:TN were better indicators than BC and BC:TC. The humin fraction was strongly related to both labile and stable SOM fractions suggesting that humin contained non-extractable strongly complexed SOM components with mineral matter and also non-extractable plant and microbial residual components. Received: 10 October 1996