Biological Indicators Of Soil Quality Research Articles

Chemical and biological indicators of soil quality in organic and conventional farming systems in Central Italy

Abstract In the past decade, there has been increased scientific interest in the so-called organic farming, especially in comparison with conventional agriculture. Many recent studies compare these two fundamentally different systems for soil properties, in different regions of the world. In this study, two adjacent fields in Central Italy, one managed according to organic, and the other according to conventional farming methods, were studied to determine the effects of these two agricultural systems on soil quality indicators at the farm level. Chemical and microbiological properties were chosen as indicators of soil quality and were measured at soil depth intervals of 5–20 and 20–35 cm, after 7 years of organic certified and conventional management methods. The field under organic management showed significantly better soil nutritional and microbiological conditions; with increased level of total nitrogen, nitrate and available phosphorus, and an increased microbial biomass content, and enzymatic activities (acid phosphatase, protease and dehydrogenase). No consistent increase in total organic carbon was observed. Results of the study suggest that, over the period of 7 year, organic management method strongly affects soil quality indicators. Large differences between the two soils were found in terms of microbiological properties, which are sensitive soil indicators of changes occurred under the different farming systems.

Three new species of Hemienchytraeus (Enchytraeidae, Oligochaeta) from Amazonian forest soil

The species diversity of tropical enchytraeids is still largely unexplored, although knowledge of them is a desideratum regarding the potential of species‐related data as biological soil quality indicators. Here we describe three new species of the mainly terrestrial enchytraeid oligochaete genus Hemienchytraeus from a primary rain forest plot at the Brazilian Agroforestry Research Facility close to Manaus, Brazil (EMBRAPA‐CPAA: Empresa Brasileira de Pesquisa Agropecuária, Centro de Pesquisa Agroflorestal na Amazônia Ocidental). Hemienchytraeus siljae, H. patricii, and H. tanjae spp. nov. were discovered in a study of soil fauna and litter decomposition in the framework of a project series that was aimed at developing methods for sustainable land use in Amazonian rain forests (SHIFT ENV 52: Studies on Human Impact on Floodplains and Forests in the Tropics). The specimens were investigated alive and as stained whole mounts. The detailed descriptions cover almost the entire light‐microscopical anatomy of the animals, following results achieved with other enchytraeid genera where it has been demonstrated that taxonomical difficulties in Enchytraeidae can be overcome by more detailed descriptions. The three new species differ among each other in at least 16 different traits. Most notable are: (1) the size difference of chaetae in terminal and preclitellar segments; (2) the branching pattern of the oesophageal appendage; (3) the number and location of secondary pharyngeal gland lobes; (4) the number and location of preclitellar nephridia; and (5) the distribution pattern of clitellar gland cells, especially on the ventral side. About half of the differentiating characters are non‐sexual, which increases the possibility of identifying juvenile specimens to the species level—an important point for ecological studies. Most similar to H. siljae and H. patricii is H. stephensoni and most similar to H. tanjae is H. bifurcatus. The comparison of these species is made difficult by the poor original descriptions of H. bifurcatus and H. stephensoni and by an apparent overestimation of their intraspecific morphological variability in following accounts. Hemienchytraeus tanjae is distinguished from H. bifurcatus in coelomocyte size and texture, in the shape of the brain and in the absence of nephridial terminal vesicles. Furthermore, H. bifurcatus is considered as species inquirenda, due to the lack of important details in the original description and to the loss of type material. A literature‐based distinction of H. siljae and H. patricii from H. stephensoni remains inconclusive; type specimens of H. stephensoni (syntype specimens of the nominal species Enchytraeus cavicola, E. myrmecophilus and E. rangoonensis), however, differ clearly from H. siljae and H. patricii by a ventrally fully developed clitellum and by strongly thickened preclitellar septa, among other characters.

(368) Effect of Four Weed Management Systems on Soil Quality in June-bearing Strawberry Production

Sustainable strawberry production depends on effective weed and soil management. Alternative weed management strategies are needed because few herbicides are registered for use in matted-row strawberry culture. Soil analyses are often measured in terms of chemical and physical properties alone. Measuring biological indicators of soil quality that are sensitive to changes in the environment can enhance these analyses. The experiment compared the effects of four weed management systems on weed growth, soil quality properties, and strawberry yield, growth, and development. Treatments were killed-cover crop mixture of hairy vetch (Viciavillosa) and cereal rye (Secalecereale); compost + corn gluten meal + straw mulch; conventional herbicide; and methyl bromide soil fumigation. Results indicated that there were no differences in percentage of weed cover or number of strawberry runners between the four weed management treatments in the planting year (July or Aug. 2004). The soil quality parameters, infiltration rate, soil bulk density, earthworm number, and total porosity were similar for all treatments. Plots that received the straw mulch treatment had a soil volumetric water content 20% higher and air-filled porosity that was 26% higher than the average of other treatments. Although treatment plots received similar N, leaf nutrient analysis showed that plants receiving the straw mulch + corn gluten meal treatment had a similar amount of total N when compared to the conventional and methyl bromide treatments, but was 21% higher than the killed-cover crop treatment.

Assessing Soil Quality Under Long‐Term Rice‐Based Cropping System

Productivity of the rice‐based cropping system is low, and it continues to decline in India because of worsening soil‐related constraints. Keeping in view the importance of soil quality in rice‐based intensive cropping system, the present investigation was undertaken with the objective of identifying several biological, chemical, and physical indicators of soil quality using data collected from a long‐term experiment being conducted since 1972 on rice‐wheat‐jute cropping system in Indo Gangetic alluvial soils of India. The experiment was laid out in a randomized block design with five treatments, under long‐term fertilizer experiment [i.e., control (no fertilizer and manure); 100% of the recommended dose of nitrogen (100% N); 100% of the recommended dose of N and phosphorus (100% NP); 100% of the recommended dose of N, P, and potassium (100% NPK); and 100% of the recommended dose of N, P, K, and farm yard manure (100% NPK+FYM]. Soil samples were collected after the harvest of rice during the 2002 experiment and were analyzed for physical, chemical, and biological parameters. On the basis of the long‐term yield data, sustainable yield index was calculated. Multivariate statistical techniques were used to determine the smallest set of chemical, physical, and biological indicators that account for at least 95% of the variability in the total data set. The total soil N, available P, dehydrogenase activity, and mean weight diameter of the aggregates were the most important indicators in this case study. A multiple regression was run to evaluate the efficacy of minimum data set (MDS) taking sustainable yield index as goal (r2=0.69). Each MDS was transformed into score. The soil quality index (SQI) was calculated by using weighing factors derived from principal component analysis for each scored MDS variable. The highest SQI was found in 100% NPK+FYM treatment followed by 100% NPK, 100% NP, 100% N, and control treatment, respectively. To compare the soil aggradation or degradation, an undisturbed fallow soil was taken as reference, and it has been observed that 100% NPK+FYM and 100% NPK showed positive change in soil quality that is aggradation of soil quality, but the other three treatments, 100% N, 100% NP, and control, showed negative change of soil quality and indicates degradation of the system.

A microcosm approach to assessing the effects of earthworm inoculation and oat cover cropping on CO 2 fluxes and biological properties in an amended semiarid soil

We designed a microcosm experiment to assess the influence of inoculation with Eisenia foetida earthworms and the establishment of an Avena sativa cover crop on biological (enzyme activities and labile carbon fractions) soil quality indicators in a soil treated with a composted organic residue, and to determine the contribution of these treatments to carbon dioxide emissions from the soil to the atmosphere of the microcosm. The microcosms were incubated for 53 days under 28 °C/18 °C day/night temperatures. The addition of earthworms and the planting of A. sativa increased dehydrogenase activity of compost amended soil by about 44% after 23 days of incubation. The metabolic potential, calculated as the ratio dehydrogenase activity/water soluble C, was higher in the compost amended soil planted with A. sativa. The highest total amount of CO 2–C evolved occurred in the soil treated with composted residue and earthworms (about 40% of the total amount of CO 2 evolved came from earthworm activity). The planting of A. sativa increased the decomposition rate constant of organic matter in the amended soil but decreased the potentially mineralizable C pool. In conclusion, the establishment of an A. sativa cover crop and the addition of E. foetida to a degraded agricultural soil treated with composted residue were effective treatments for improving the biological and biochemical quality and the metabolic potential of the soil.

Long-term tillage system effects under moist cool conditions in Switzerland

How do different soil tillage systems influence soil quality over the years? Under moist cool conditions is it possible in the long term to reduce dramatically soil tillage intensity without experiencing reductions in yield or other problems? In 1987, the Swiss Federal Research Station for Agricultural Economics and Engineering in Tänikon initiated a long-term soil tillage trial to clarify these questions. The trial compared mouldboard plough, chisel, paraplow, shallow tillage and no-tillage systems on a well-drained Orthic Luvisol with 160 g kg −1 clay, 310 g kg −1 silt, and under a climate that has a mean annual precipitation of 1180 mm. The tillage treatment effects were evaluated by measuring several biological, chemical, and physical soil quality indicators. Reduced soil tillage increased earthworm populations, reduced Pseudocercosporella herpotrichoides infection in wheat ( Triticum aestivum) and increased plant colonisation by arbuscular mycorrhizal fungi. Yields for no-tillage and other ploughless cultivation techniques were on par with those obtained by ploughing. An exception was direct-drilled maize ( Zea mays), where no-tillage decreased yield by more than 10% over the course of 14 years. In the first 7 years of the trial, the level of soil organic carbon in all the tillage regimes was approximately 40% lower than natural grassland (initial situation 1987=75 Mg SOC ha −1). The no-tillage method did not differ from the others in respect of bulk density, but it showed an increased preconsolidation stress and hence better trafficability. Under Switzerland’s moist cool climatic conditions, it is possible to reduce soil tillage intensity without substantial reductions in yield, and at the same time improve soil quality.

Changes in physical and biological soil quality indicators in a tropical crop system (Havana, Cuba) in response to different agroecological management practices.

The objective of our study was to assess the response of physical (aggregate stability and bulk density) and biological (enzyme activities and microbial biomass) soil quality indicators to the adoption of agroecological management practices, such as the planting of forage species (forage area) and the rotation of local crops (polycrop area), carried out in a representative tropical pasture on an integrated livestock-crop farm. The pasture system was used as control (pasture area). In all three areas, the values of water-soluble C were higher in the rainy season compared to the dry season. Pasture and forage areas had the highest percentage of stable aggregates in the rainy season, while polycrops developed soils with less stable aggregates. Soil bulk density was lower in the pasture and forage areas than in the polycrop area. In the pasture area, the microbial biomass C values, dehydrogenase, urease, protease-BAA, acid phosphatase, and beta-glucosidase activities were higher than in the forage and polycrop areas, particularly in the dry season. The highest increase in the microbial biomass C in the rainy season, with respect to the dry season, was recorded in the pasture area (about 1.2-fold). In conclusion, the planting of forage species can be considered an effective practice for carrying out sustainable, integrated livestock-crop systems, due to its general maintenance of soil quality, while the adoption of polycrop rotations appears to be less favorable because it decreases soil quality.

Developing weed-suppressive soils through improved soil quality management

Manipulating soil microbial communities using soil and crop management practices is a basic strategy in developing sustainable agricultural systems. Sustainable farming is based, in part, on the efficient management of soil microorganisms to improve soil quality. However, the identification of biological indicators of soil quality that can be used to predict weed suppression in soils has received little attention. We investigated differences in soil microbial activity among various crop and soil management systems to assess: (i) the microbiological characteristics of these soils; (ii) determine whether any relationships existed that might be used in the development of weed suppression. Soil enzyme activity, water-stable aggregates, and the proportions of weed-suppressive bacteria were compared among seven cropping systems and one native-prairie ecosystem in mid-Missouri, USA. Assays of soil enzymes (fluorescein diacetate hydrolase, dehydrogenase, phosphatase) revealed that organic and integrated cropping systems, and the native-prairie ecosystem had the highest levels of soil activity. Weed rhizospheres from these same ecosystems also had greater proportions of bacterial isolates characterized as “growth suppressive” to green foxtail ( Setaria viridis [L.] Beauv.) and field bindweed ( Convolvulus arvensis L.): 15 and 10%, respectively. The proportion of water-stable soil aggregates was the greatest in soils with the highest organic matter and was found to be related to higher enzyme and weed-suppressive activity. Selected biological indicators of soil quality were associated with potential weed-suppressive activity in soil when that soil was managed for high organic matter content under reduced tillage systems. This research study provides further evidence that soil quality and sustainable agricultural practices may be linked to integrated weed management systems for the biological suppression of weeds.

Rangeland Management Impacts on Soil Biological Indicators in Southern Alberta

Quantitative techniques are needed to determine the effects of cultivation and livestock grazing on biological indicators of soils of the Northern Great Plains. Our objective was to determine how various management practices, which were representative of those used since European settlement in the 1880's, affected 3 biological indicators of soil quality. The study was conducted at 3 sites that are representative of the major grassland ecosystems in Canada: a Mixed Prairie site with Stipa comota Trin. R 2) alfalfa (Medicago sativa L. 'Beaver'); 3) continuous spring wheat (Triticum aestivum L. 'Katepwa'): 4) spring wheat and fallow rotation; and 5) abandoned cultivated land. Our hypothesis that mineralizable-N, and phosphatase and dehydrogenase activities would be influenced by cultivation was confirmed by significant changes in these indicators that were detected after only 180 days after treatment establishment. The pool of readily decomposable organic matter was reduced with cultivation and not replenished over the period of the study. The 3 biological indicators were sensitive to not only time following external management changes, but also to seasonal fluctuations. We conclude that soil biological indicators can be used to quantify temporal and botanical changes in diverse ecotypes within the Northern Great Plains. DOI:10.2458/azu_jrm_v53i2_dormaar

Rangeland management impacts on soil biological indicators in southern Alberta

Quantitative techniques are needed to determine the effects of cultivation and livestock grazing on biological indicators of soils of the Northern Great Plains. Our objective was to determine how various management practices, which were representative of those used since European settlement in the 1880's, affected 3 biological indicators of soil quality. The study was conducted at 3 sites that are representative of the major grassland ecosystems in Canada: a Mixed Prairie site with Stipa comota Trin. Rupr. dominant in the Brown (Aridic Haploboroll) Soil Zone, a Mixed Prairie site with S. comata Trin. Rupr. and S. viridula Trin. dominant in the Dark Brown (Typic Haploboroll) Soil Zone, and a Fescue Prairie site with Festuca campestris Rydb. dominant in the Black (Udic Haploboroll) Soil Zone. At each site, 6 treatments representing common production practices were imposed and compared with the native community in a randomized complete block design with 4 replicates and a plot size of 3 x 10 m. The treatments included: 1) monoculture seeding of 2 grass species; 2) alfalfa (Medicago sativa L. 'Beaver'); 3) continuous spring wheat (Triticum aestivum L. 'Katepwa'): 4) spring wheat and fallow rotation; and 5) abandoned cultivated land. Our hypothesis that mineralizable-N, and phosphatase and dehydrogenase activities would be influenced by cultivation was confirmed by significant changes in these indicators that were detected after only 180 days after treatment establishment. The pool of readily decomposable organic matter was reduced with cultivation and not replenished over the period of the study. The 3 biological indicators were sensitive to not only time following external management changes, but also to seasonal fluctuations. We conclude that soil biological indicators can be used to quantify temporal and botanical changes in diverse ecotypes within the Northern Great Plains.

Can lucerne ( Medicago sativa L.) strips improve soil quality in irrigated cotton ( Gossypium hirsutum L.) fields?

The effects of sowing lucerne ( Medicago sativa L.) strips in irrigated cotton ( Gossypium hirsutum L.) fields on soil quality was evaluated in a Vertisol at the Australian Cotton Research Institute (ACRI), and in a Vertisol and an Alfisol at two on-farm sites in New South Wales, Australia, from December 1995 to February 1997. Chemical (pH, EC, CEC, exchangeable sodium percentage, organic C), physical (air-filled porosity, plastic limit, dispersion index, soil strength), and biological (earthworm activity) indicators of soil quality were measured in each site. Overall soil quality in cotton and lucerne strips was evaluated using a `soil health condition report card' format to award a score to each soil quality indicator and summing up the individual scores to give a single value for each crop at any one site. The decision to award a particular score to any one indicator was based on a value range derived from the literature. In comparison with cotton, lucerne strips had higher air-filled porosity and organic C in the sub-soil of both on-farm sites, but had no significant effect at ACRI. However, lucerne did result in higher organic C in the soil surface at ACRI. Soil strength was higher and EC lower within lucerne strips in all three sites. Sowing lucerne strips resulted in higher earthworm activity at ACRI and at one commercial site, with highest numbers of earthworm burrows being observed in the former. We suggest that this has affected liquid flow patterns at ACRI where preferential flow mediated via the earthworm burrows appears to dominate. Overall soil quality was improved by lucerne strips only at ACRI, whereas that in the on-farm sites was not affected.

The role of soil organic matter in maintaining soil quality in continuous cropping systems

Maintenance and improvement of soil quality in continuous cropping systems is critical to sustaining agricultural productivity and environmental quality for future generations. This review focuses on lessons learned from long-term continuous cropping experiments. Soil organic carbon (SOC) is the most often reported attribute from long-term studies and is chosen as the most important indicator of soil quality and agronomic sustainability because of its impact on other physical, chemical and biological indicators of soil quality. Long-term studies have consistently shown the benefit of manures, adequate fertilization, and crop rotation on maintaining agronomic productivity by increasing C inputs into the soil. However, even with crop rotation and manure additions, continuous cropping results in a decline in SOC, although the rate and magnitude of the decline is affected by cropping and tillage system, climate and soil. In the oldest of these studies, the influence of tillage on SOC and dependent soil quality indicators can only be inferred from rotation treatments which included ley rotations (with their reduced frequency of tillage). The impact of tillage per se on SOC and soil quality has only been tested in the ‘long-term’ for about 30 yrs, since the advent of conservation tillage techniques, and only in developed countries in temperate regions. Long-term conservation tillage studies have shown that, within climatic limits: Conservation tillage can sustain or actually increase SOC when coupled with intensive cropping systems; and the need for sound rotation practices in order to maintain agronomic productivity and economic sustainability is more critical in conservation tillage systems than conventional tillage systems. Long-term tillage studies are in their infancy. Preserving and improving these valuable resources is critical to our development of soil management practices for sustaining soil quality in continuous cropping systems.

Crop residue effects on soil quality following 10-years of no-till corn

Numerous biological, chemical, and physical indicators of soil quality have been suggested, but few have been evaluated using data from long-term field studies. Our objective was to evaluate several proposed soil quality indicators to determine effects of removing, doubling, or maintaining crop residues for 10 years in a no-till, continuous corn ( Zea mays L.) production study. Soil aggregate characteristics, penetration resistance, bulk density, volumetric water content, earthworm populations, respiration, microbial biomass, ergosterol concentrations, and several soil-test parameters (pH, P, K, Ca, Mg, Total-N, Total-C, NH 4-N, and NO 3-N) were measured on samples collected from Rozetta and Palsgrove silt loam (fine-silty, mixed, mesic Typic Hapludalfs) soils. Soil aggregates from double residue treatments were more stable in water than those from normal and removal treatments. The double and normal residue treatments had higher total carbon concentrations and higher levels of microbial activity as measured by CO 2 evolution. Ergosterol concentrations where crop residues were removed were 8 to 10 times lower suggesting this biochemical measurement of fungal biomass may be a sensitive soil quality indicator. Earthworm populations where crop residues had been removed for 10 years were significantly lower than in either normal or double residue treatments. Measures of force and energy required to crush soil aggregates were extremely variable and showed significant differences only for aggregate size. Several parameters were used to develop a soil quality index that gave ratings of 0.45, 0.68, or 0.86 for removal, normal, or double residue treatments, respectively. This study demonstrates a framework for soil quality evaluation and shows how crop residue management can affect this rating.