Soil Chemical Characteristics Research Articles

The effect of salinity on soil chemical characteristics, enzyme activity and bacterial community composition in rice rhizospheres in Northeastern Thailand

Saline soil is one of the major problems limiting rice productivity in the Northeastern area of Thailand. Thus, the aims of this study were to determine soil physicochemical analysis and soil enzyme activities, and bacterial communities in the rhizosphere of ‘RD 6’ rice grown in salt-affected rice fields. The Ban Thum sample showed the highest electrical conductivity (EC; greater than 6 dS m−1) and total Na, while the EC in other fields were at non- or slightly saline levels. The principal component analysis revealed that soil chemical characteristics and soil enzymes activities explained 73.4% of total variation. Soil enzyme activities including dehydrogenase and fluorescein diacetate (FDA) hydrolysis, and soil characteristics including organic matter (OM) and organic carbon (OC) were significantly negatively correlated to EC. This indicated that these soil properties were adversely impacted by salts. Interestingly, activities of all hydrolytic enzymes were not affected by soil salinity. Bacteria that were able to colonize the rhizosphere soils were Achromobacter cholinophagum, Rhizobium tarimense, and unculturable bacteria. In this regard, study on the relationship of soil chemical characteristics and soil enzyme activities together with bacterial communities provided promising data for assessing rice field soil quality in the future.

Influence of Soil Chemical Features on Aromatic Profile of V. vinifera cv. Corvina Grapes and Wines: A Study-Case in Valpolicella Area (Italy) in a Calcareous and Non-Calcareous Soil

In the Valpolicella area (Verona, Italy) one of the most important Italian wines is being produced: Amarone, predominately made by Vitis vinifera cv. Corvina. This wine is subjected to a specific postharvest process, namely, withering, which aims to increase alcohol content and/or high residual sugars while retaining richness in aromas and organoleptic compounds. In accordance with guidelines and strict Amarone protocol set by the Consorzio of Amarone-Valpolicella, withering must be carried out by setting the grapes in a suitable environment. In our study, the withering process was performed following the traditional methods, i.e., in open-air, natural environmental conditions, as generally performed by winegrowers, leading to a weight loss in grapes of up to 30%. Whilst the effect of different postharvest conditions is clear and studied, it is interesting to know how soil can affect both grapes and wine profile, in terms of aromas, which are of great importance for this crafted wine. For this purpose, for two study years, the influence of two different sites (with regards to the carbonates’ content) on aromas were investigated. Furthermore, microvinifications and the sensory profile of the resulting wines were analysed. Our results clearly indicated that different soils’ characteristics, particularly differences in carbonate content, had an important effect, not only on the aromatic compounds of grapes and wines, but on the sensory profile as well. This information will help winegrowers and winemakers in the process of determining site selection for future vineyards in order to obtain a final optimum Amarone wine, in terms of its aromatic composition—one that is able to respond to the market demand.

Soil Diversity of the Island of Gogland in the Gulf of Finland: History of Land Development and Current Status

One of the most effective nature conservation measures is the creation of territories where human impact is limited, this is called specially protected natural areas. A significant contribution to increasing the area of the Russian Federation covered by protected areas was made by the creation of the State Nature Reserve in the Leningrad Region, known as the “East of the Gulf of Finland”. Initially, the reserve was supposed to include the island of Gogland (but it is now not part of the protected area). The locked status of the island, its remoteness from the coast, and the harsh features of the Gulf of Finland have contributed to the transformation of Gogland into a kind of open-air “museum”. The biological diversity of the island is closely connected with edaphic diversity, as soil is a natural habitat for a huge variety of living organisms. Therefore, the purpose of this work was to assess the edaphic potential of the island of Gogland, a territory that has existed for a long time with an extremely weak anthropogenic impact, in order to assess the ecosystem services of the island as one of the approaches to taking effective measures for nature protection. Data on chemical soil characteristics are discussed, as well as current soil pollution processes of these remote areas by trace elements. Edaphic studies carried out showed that the soil cover of the island of Gogland is characterized by sufficient diversity, the presence of soils at initial stages of development, soils with a fully developed differentiated profile with a pronounced eluvial process—eluvozems and various podzols, as well as the rarest, organogenic soils—bog, and bog-gley soils. The pHH2O of the studied soils on Gogland is characterized by a strongly acidic to weakly acidic reaction. The total pollution indicator of the studied soils is characterized by low values (Zc < 16), whereas the geoaccumulation index (Igeo) showed moderate/heavy pollution by only one element: Pb.

Application of Spent Sun Mushroom Substrate in Substitution of Synthetic Fertilizers at Maize Topdressing

Synthetic fertilization can increase maize yields, but also cause environmental impacts, as well as increasing production costs and food security risks. Sun mushroom (Agaricus subrufescens) is an important Brazilian fungus used to generate large amounts of spent mushroom substrate. This residue can be used for maize fertilization, but little is known about its ideal application rates to reduce maize dependence on synthetic fertilizers. Therefore, this study aimed to evaluate the agronomic performance of a maize crop under different combinations of synthetic fertilizers and two different spent mushroom substrate doses. The experiment was carried out in pots and evaluated maize germinate and biometric parameters, as well as soil and leaf chemical characteristics. The results showed that residue application increased maize germination and Emergence Speed Index. Regarding the maize biometric parameters, height, stem diameter, shoot fresh and dry masses, and leaf area were superior for residue with synthetic fertilization at sowing only at higher doses. Moreover, residue with synthetic fertilization at sowing proved to be more relevant for maize growth according to canonical discriminant analysis. In terms of nutrients, the use of spent mushroom substrate increased significantly leaf P, K, and S levels and mainly K content in the soil, justifying non-application at maize topdressing.

Montmorillonite content is an influential soil parameter of grapevine development and yield in South Uruguay

Soil physical and chemical characteristics play a key role on vine growth and yield. The soils of South Uruguay display high content of montmorillonite or illite. The proportion of these minerals deserves special attention as they influence the soil structure and its hydrological properties. The present study was conducted in a 1.1 ha vineyard of this region (Canelones), characterized by a high heterogeneity of plant vigour. It was aimed to determine and map the physical and chemical properties of the soil and their relations with plant vigour and yield. The cation exchange capacity (CEC) and the clay and organic matter contents were measured in 84 locations within this vineyard to calculate the montmorillonite and illite contents of the soil. In addition, the type and abundance of clays was corroborated by X-ray diffractometry analysis. The CEC and montmorillonite contents were positively correlated with vine vigour, expressed by the Normalized Vegetation Index (NDVI), trunk diameter, pruning weight, leaf area, and with yield. Thus, the within vineyard distribution of the ratio montmorillonite/illite conditioned the heterogeneity of vine growth and yield at the field level. The impact of those minerals on water and mineral supply to the plant is discussed.

Effects of earthworm (Eisenia fetida) and arbuscular mycorrhizal fungi improving plant hormones and antioxidant enzymes under simulated acid rain stress

Acid rain is considered one of the three most serious environmental disasters worldwide, disrupting the normal physiological metabolism of plants and inhibiting their growth. Earthworms alleviate plant stress by regulating soil physical, chemical and biological characteristics, and mycorrhizal fungi can promote plant nutrient absorption and improve plant resistance via symbiosis with plants. We used Illumina high-throughput sequencing to conduct a relevant redundancy analysis (RDA) of soil microbial community structure and plant growth factors, and we constructed a structural equation model (SEM) for maize biomass and a biological index to study the mechanisms by which earthworms and mycorrhizal fungi affect maize stress resistance under simulated acid rain stress. The results showed that earthworms promoted the decomposition of soil organic matter; promoted the growth of the root system; and increased the hormone levels of gibberellin A3 (GA3), abscisic acid (ABA) and indole-3-acetic acid (IAA), ultimately improving the stress resistance of maize. Mycorrhizal fungi increased the relative abundance of plant growth-promoting rhizosphere bacteria, increased the levels of plant hormones and antioxidant enzymes, and improved the stress resistance of maize. Earthworms promoted infection by mycorrhizal fungi, and the interaction between earthworms and mycorrhizal fungi increased the root IAA content and the Shannon index of rhizosphere bacteria and alleviated the simulated acid rain stress of the aboveground part of the maize. This funding is crucial to understanding above- and belowground feedback in plant–soil systems under abiotic stress.

Changes in the Physical, Chemical, and Bacterial Community Characteristics of Soil in Response to Short-Term Combined Organic–Inorganic Fertilizers in a Dry Direct-Seeded Paddy Field

Dry direct-seeded rice cultivation is a simple and labor-saving planting method wherein the combined application of organic and inorganic fertilizers can improve yield. However, the effects of combined fertilizers on soil properties and bacteria in dry direct-seeded rice paddy soil are unclear. Here, four treatments, conventional fertilization (NPK), seaweed bio-organic fertilizer + NPK, Jishiwang bio-organic fertilizer + NPK, and attapulgite organic fertilizer + NPK applied for three consecutive years were tested to explore their effects on soil physical, chemical, and bacterial community characteristics in a dry direct-seeded rice paddy field. The combined fertilizers increased alkaline hydrolysis-nitrogen and available potassium while decreasing the bulk density and pH; in addition, a marked increase in the relative abundance of soil macroaggregates (>5 mm) and clay particles and a decrease in that of sand was observed. Urease and neutral phosphatase activities were the highest with the Jishiwang organic fertilizer + NPK, whereas invertase and catalase activities were the highest with attapulgite organic fertilizer + NPK. All combined fertilizers considerably increased the bacterial richness index (ACE) and Chao index; Jishiwang bio-organic fertilizer + NPK also increased the Simpson index, whereas the seaweed bio-organic fertilizer + NPK reduced it. Proteobacteria and Acidobacteria accounted for 54.25–70.49% of the total bacterial relative abundance. The relative abundance of Verrucomicrobia, Chloroflexi, Firmicutes, and Nitrospirae increased with the combined fertilizers. The correlation network analysis showed predominant antagonistic relationships. A redundancy analysis demonstrated that total nitrogen, soil organic matter, urease, and invertase were the main environmental factors affecting bacterial composition. Combined fertilizers may improve soil physical and chemical properties, fertility, and bacterial richness.

Swine slaughterhouse biowaste: an environmental sustainability assessment of composting, amended soil quality, and phytotoxicity

ABSTRACT In this article, the environmental sustainability of a circular economy concept applied to the management of biowaste was studied. To achieve this goal, the composting performance, compost-amended soil health, and phytotoxicity were assessed in the case of management of solid waste from a small swine slaughterhouse. Microorganisms present in a similar composting process were used as inoculums to improve the efficiency of composting. Addition of the inoculum promoted a faster and more efficient composting process than composting without the inoculum. The physical, chemical, and microbiological characteristics of soil were considered to be improved after compost application. Phytotoxicity tests in soils with and without compost amendment showed that a soil–compost mixture (90:10 and 70:30 mass ratios) was not phytotoxic to the plant species Sorghum saccharatum and Lepidium sativum, and that soil with compost showed higher plant biomass growth than that without compost amendment. The triple bottom line methodology used in this study can help in the assessment of circular economy activity in relation to the environmentally sustainable management of solid waste generated in small swine slaughterhouses.

Effect of Bottom Ash Application on Hot Pepper Growth and Soil Chemical Characteristics

Effect of Bottom Ash Application on Hot Pepper Growth and Soil Chemical Characteristics

Impact of Short-Term Cultivation on Some Selected Properties of Sandy Soil in an Arid Environment

Soil management is recognized to have an impact on soil quality attributes. Depending on the management approach, this impact can either degrade or improve soil quality. There is a severe shortage of information on the impacts of cultivation on sandy soil properties in arid desert regions. Therefore, the objective of this study was to investigate the short-term cultivation effects (5 years) on the properties’ changes of coarse-textured soil in an arid desert region in western Assiut Governorate, Egypt. The current study was conducted on soils sampled at four depth intervals, namely 0–10, 10–20, 20–30, and 30–40 cm, from both cultivated and uncultivated soils, using a systematic sampling grid (10 × 10 m), to investigate the potential impacts of the cultivation process on six soil attributes. Each land use was represented by an area of 0.5 ha (50 × 100 m). A total of 160 composite soil samples (at all depths) were collected from both soils and analyzed for their physical and chemical properties, employing standard laboratory procedures. The data were statistically and geostatistically analyzed to compare the results and map the spatial distributions of the selected soil properties. The results revealed that cultivation had a considerable positive impact on most of the properties of cultivated soil compared to those of uncultivated soil (virgin land). The findings also showed that the available phosphorus levels in cultivated soil were higher than in virgin soil by 16, 9, 8.5, and 6 folds, with increases in organic matter content of 16.8, 12.4, 11.9, and 7.9 times at depths of 0–10, 10–20, 20–30, and 30–40 cm, respectively. Furthermore, compared to virgin soil, cultivated soil exhibited a salinity reduction of −8.9%, −56.4%, −66.3%, and −71.8%, at depths of 0–10, 10–20, 20–30, and 30–40 cm, respectively. Moreover, some other properties of the cultivated soil improved, particularly in the surface soil layers, such as pH reduction, CaCO3 decline, and CEC increase, while the soil texture grade did not change. Therefore, continuous monitoring of the effects of diverse soil management strategies in the short term assists in the understanding of the ongoing changes in soil physical and chemical characteristics, which is critical for maintaining satisfactory soil quality and sustainable soil productivity in arid lands.

Review of the physical and chemical properties of seagrass soils

Seagrasses are a polyphyletic group of angiosperms that colonized marine environments more than 30 million years ago and currently inhabit coastal soft and rocky substrates in all continents except Antarctica. Due to their evolution from terrestrial plants, seagrasses have belowground organs that interact with the substrate, transforming it through chemo-physical processes analogous to terrestrial soil formation. Although seagrass substrates provide valuable ecosystem services including carbon and coastal stabilization, they have been largely regarded as sediments by marine scientists and neglected in soil science research. However, over the last decades, the increasing interest in carbon accumulation by seagrasses has generated multiple data on seagrass soil physical and chemical characteristics. Here, we review clay and silt content (<0.063 mm particle size), redox potential, pH, carbonate content, organic carbon or organic matter contents, dry bulk density, porosity and color of seagrass soils worldwide, summarizing data typically used for soil description, and looking for generalities in soil characteristics across seagrass habitats. The data gathered was biased towards temperate species and high-income countries, while data about color, porosity, redox potential and pH was scarce. Soil characteristics did not show significant differences among seagrass bioregions. Most seagrass substrates showed sandy textures, whereas one of the most sampled genera, Posidonia, was not present in muddy substrates. The soil Corg content was significantly higher in meadows formed by persistent species (mean ± SD; 1.76 ± 2.17 %) than in meadows formed by species with opportunistic and colonizing life-strategies (1.52 ± 2.24 and 0.76 ± 0.95 %, respectively), while mud content was significantly higher in meadows formed by opportunistic and colonizing species (27.87 ± 29.58 and 21.23 ± 21.77 %, respectively) than in those formed by persistent species (11.83 ± 14.45 %). Redox potential was significantly lower in intertidal than in subtidal meadows, although caution is needed when interpreting these differences due to methodological limitations. This review provides an overview of current knowledge on seagrass soil characteristics, while identifying knowledge gaps in seagrass soil science, including geographical, species diversity and soil physico-chemical traits that limit our capacity to characterize and classify seagrass soils worldwide.

Effect of Microbes in Enhancing the Composting Process: A Review

The increase in global population and the resulting economic activity have led to major environmental problems such soil, air, and water pollution. This rise in population growth has resulted in increased use of chemical fertilizers to boost agricultural production resulting in loss of microbiological and physicochemical equilibrium of soil. These factors have led to an increased need for eco-friendly agricultural products that help to enhance the soil's physical, chemical, and microbiological characteristics and, in turn, provide nutrients for plants. Composting has emerged as the preferred method for treatment of organic wastes in order to produce a final, sterilized product that can be used as an organic amendment. Different organic substances are converted into more stable molecules during the aerobic, microorganism-mediated, solid-state fermentation process known as composting. One effective strategy for accelerating the biotransformation of organic materials during the composting process is microbial inoculation. The inclusion of microorganisms could improve the composting process by speeding up the decomposition of organic matter, mineralization, and the activities of microbial enzymes, as well as the quality of the finished products. This review will give a brief idea about the composting process, quality of compost and the most recent strategies for enhancing the composting process mainly with the help of microbes.

Characteristics of Andisols Developed from Andesitic and Basaltic Volcanic Ash in Different Agro-Climatic Zones

This study aimed to identify the characteristics of Andisols under tea plantations affected by different Oldeman’s agro-climatic zones, of different ages, and containing different types of volcanic ash material. For this study, three tea plantation estates were chosen, the Ciater Site (CTR), Sinumbra Site (SNR), and Sedep Site (SDP), having Oldeman’s agro-climatic zones of A, B1, and B2, respectively. Three profiles (CTR-A, CTR-B, and SNR-A) were created from andesitic volcanic ash, and three profiles (SNR-B, SDP-A, and SDP-B) were created from basaltic volcanic ash materials. The CTR-A, SNR-B, and SDP-B profiles were obtained from Holocene parent materials, while the CTR-B, SNR-A, and SDP-A profiles were derived from Pleistocene parent materials. Soil samples were taken from the soil profiles from depths of 0 to 153 cm incrementally, dependent on each soil horizon thickness. The findings of the study reveal that the age of parent materials and the variance in agro-climatic zones result in considerable differences in soil chemical characteristics, such as pH (H2O), base saturation (BS), and organic C, while the qualities of the basaltic and andesitic volcanic ash parent materials were also shown to be unaffected. All Andisol profiles went through cambic weathering processes. Moreover, the key pedogenetic strategies were the production of short-range-order minerals through the leaching of easily dissolved elements and the coprecipitation of SiO2 and Al2O3 gels. Halloysite was formed by the resilication of short-range-order minerals, while gibbsite was formed by desilication. The XRD analysis indicated that amorphous materials predominated with some HIV and kaolinite minerals were also present.

Lactarius and Russula mushroom genera – Similarities/differences in mineral composition within the Russulaceae family

Mineral composition among mushroom species may be similar or significantly different. It is accepted that mushroom species are one of the main determinants of their varying efficiency of accumulating mineral elements. The aim of this study was to establish whether this statement is accurate and what role the mushroom genus may play. For this purpose, fruit bodies of 5 species belonging to the Lactarius genus and 4 species belonging to Russula genus were collected from a forest area as small as compatible with similar chemical soil characteristics. In total, 4 major (Ca, K, Mg, Na) and 33 trace elements (Ag, Al, As, Au, B, Ba, Cd, Ce, Co, Cs, Cu, Fe, Ga, Hf, Hg, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Se, Sn, Sr, Ta, Ti, Tl, U, V, Zn, Zr) were determined. Generally, species belonging to the Lactarius genus contained a higher content of major elements compared to Russula. The obtained results reveal a similarity in the mineral profile of the studied mushrooms within each individual genus. Moreover, within each mushroom genus, a specific species with significantly higher element(s) content was observed, suggesting that both the mushroom species and genera may play an essential role in modulating element accumulation from soil to soil fruit bodies. Due to the fact that collected mushrooms grew in close proximity to trees, we were able to confirm that the presence of Fagus sylvatica might stimulate the accumulation of toxic elements in Lactarius vellereus bodies.

Soil quality in hydromorphic ecosystems decrease with intensification of pre-germinated rice production, even under ecologically based production system

An on-farm assessment of impact of pre-germinated rice intensification on chemical and physical characteristics of subtropical soils was performed in an ecologically based production system in Southern Brazil. Three soil orders (Planosol, Gleysol and Histosol) with different intensity of pre-germinated rice production in the last 11 summer seasons (no-rice – reference areas, under natural vegetation; low – 1 to 4 seasons; medium – 5 to 8 seasons, high – 9 to 11 seasons) were evaluated regarding soil physical and chemical characteristics. In general, even using until 3.5 Mg ha−1 per rice season of organic compost (32% C) in ecologically based rice production, the intensification of pre-germinated rice promoted soil degradation. Histosols were more susceptible to degradation, while Gleysols and Planosols had few soil characteristics influenced by rice cultivation. In comparison to soil under native vegetation, Histosols show losses of 75% of CEC, 33% of porosity, 70% of C and N stocks, 85% and 45% of available P and K, respectively. Our findings show that, even under flooding for half of year, this type of soil, soils under pre-germinated rice production show some degradation in this subtropical ecosystem, even under an ecologically based production system. In these environments, a low intensity of rice production should be performed aiming to avoid soil degradation at high rates. However, aiming to increase the income to farmers, the increase of crop residues input by use of cover crops or pastures in winter may be a feasible management for maintenance soil C and N stocks and nutrient cycling under more intense pre-germinated rice production systems in Southern Brazil.

Soil quality cannot be improved after thirty years of land use change from forest to rangeland

Soil quality can be assessed by measuring its physical, chemical and biological properties. In terrestrial ecosystems, the knowledge of the status of soil quality under different land use/cover can increase our understanding of processes related to soil functioning and help to properly managing ecosystems and increase their services. Conversion of the forest to rangelands is one of the most common forms of land use change having a significant effect on soil quality indicators. Here, we addressed the following objectives: (ii) to study the current status of soil physical, chemical and biological characteristics after more than thirty years of land use change from forest (dominated by Carpinus betulus and Parrotia persica) to rangeland, and (ii) to provide an overview of the spatial distributions of soil properties in forest and rangeland covers using a geostatistical method. For this, two sites (i.e., forest and rangeland) were selected in northern Iran. Within each site, 50 soil samples were collected at 0–10 cm depth along two sampling lines (250 m length) with a total of 100 soil samples for each site. Results showed that following the change of land use from forest to rangeland soil porosity, aggregate stability, pH, electrical conductivity and nutrient (i.e., total N and available P, K, Ca and Mg) contents increased, whereas soil bulk density and C/N ratio decreased. In addition, the population of soil biota (i.e., earthworms, acarina, collembola, nematode, protozoa, bacteria and fungi), microbial and enzyme activities decreased after more than thirty years of land use change from forest to rangeland. Principal component analysis confirmed that forest site had a more fertile soil and a higher biological activity than rangeland cover. Based on heat plots of soil properties, forest ecosystems created hot spots of soil quality indicators in the study area. Based on the geostatistical approach, most of the soil variables in the rangeland site followed a linear model, while in the forest site, most models were exponential and spherical. The fractal dimension values of the soil properties in the forest (1.62–1.99) had larger variations than in the rangeland (1.75–1.99) site. As a general conclusion, soil quality was not improved after more than thirty years of land use change from forest to rangeland, suggesting that degraded forest habitats should be restored by native tree species rather than converted to other land uses.

Black Shade Net Effects on Soil Properties and Cabbage Water Use Efficiency in Humid Coastal Environment

Cabbage is a popular vegetable grown in Kenya for food and income generation. Despite the important role played by the crop within the country, current climate change effects and population pressure pose a need for increasing production through utilization of available resources. A study was therefore conducted to evaluate the effects of black shade net on soil properties and cabbage water use efficiency in humid coastal environment. Black shade nets of 0%, 50% and 70% shading intensity and two cabbage types (Brassica rapa and Brassica oleracea) were evaluated in Randomized complete block design with three replications. 0% represented open field. Data collected included: soil chemical characteristics, soil moisture content, air temperature, fresh head weight, dry matter weight, and water use efficiency. Data obtained were subjected to analysis of variance using general linear model SAS Computer package version 9.1 and means separated using Tukey’s test at 5%. From the findings obtained, the use of black shade net of 70% and 50% shading significantly increased soil moisture content by 5.1% and 2.6% than open field. Maximum air temperature in 70% and 50% shade nets was lower than open field by 4.6⁰C and 1.8⁰C respectively while minimum air temperature under 70% and 50% shade nets was higher than open field by 2.7⁰C and 1.6⁰C respectively. Brassica rapa from 70% shading had 35% more fresh weight per plant than open field while those from 50% had 30%. Brassica oleracea from both 70% and 50% shading had 44% and 29% more fresh weight per plant respectively than those from open field. Although shade nets did not have significant effect on availability of nutrients within soil solution, Brassica rapa under 70% shading recorded 49% higher water use efficiency than open field while, 50% shading recorded 50% more WUE than open field. Brassica oleracea under 70% shading recorded 41% higher water use efficiency than open field, while 50% shading recorded 25% increase than open field. Owing to the fact that shade nets did not have significant effect on available nutrients within the soils but significantly influenced WUE, there is need for further studies to understand the effects of shade nets on cabbage nutrient use efficiency under the same environment.

Long-term excessive application of K2SO4 fertilizer alters bacterial community and functional pathway of tobacco-planting soil.

To improve tobacco leaf quality, excessive K2SO4 fertilizers were applied to soils in major tobacco-planting areas in China. However, the effects of K2SO4 application on soil microbial community and functions are still unclear. An eight-year field experiment with three kinds of K2SO4 amounts (low amount, K2O 82.57 kg hm-2, LK; moderate amount, K2O 165.07 kg hm-2, MK; high amount, K2O 247.58 kg hm-2, HK) was established to assess the effects of K2SO4 application on the chemical and bacterial characteristics of tobacco-planting soil using 16S rRNA gene and metagenomic sequencing approaches. Results showed that HK led to lower pH and higher nitrogen (N), potassium (K), sulfur(S) and organic matter contents of the soil than LK. The bacterial community composition of HK was significantly different from those of MK and LK, while these of MK and LK were similar. Compared to LK, HK increased the relative abundance of predicted copiotrophic groups (e.g. Burkholderiaceae, Rhodospirillaceae families and Ellin6067 genus) and potentially beneficial bacteria (e.g. Gemmatimonadetes phylum and Bacillus genus) associated with pathogens and heavy metal resistance, N fixation, dissolution of phosphorus and K. While some oligotrophic taxa (e.g. Acidobacteria phylum) related to carbon, N metabolism exhibited adverse responses to HK. Metagenomic analysis suggested that the improvement of pathways related to carbohydrate metabolism and genetic information processing by HK might be the self-protection mechanism of microorganisms against environmental stress. Besides, the redundancy analysis and variation partitioning analysis showed that soil pH, available K and S were the primary soil factors in shifting the bacterial community and KEGG pathways. This study provides a clear understanding of the responses of soil microbial communities and potential functions to excessive application of K2SO4 in tobacco-planting soil.

The Coffee Processing Method Had a More Pronounced Effect than Location and Production Systems on the Overall Quality of Kaffa Biosphere Reserve Coffees

A comprehensive examination of the physical and cup quality of Kafa Biosphere Reserve coffees was essential to identify the inherent qualities of the coffees in connection with the area’s soil physical and chemical characteristics. As a result, preliminary coffee quality data was acquired from bean physical and cup quality examination of coffees derived through a three-stage nested design combining districts (Gimbo, Gawata, and Decha), coffee production systems (forest, semiforest, and garden), and coffee processing methods (wet, semiwet, and dry). Representative soil samples were collected according to the sampling structure and analyzed following the standard procedures. Multiple factor analysis and Pearson’s correlation coefficient analysis were applied to the collected data. According to the results of multiple factor analysis, the Gimbo and Decha districts are not significantly different from each other in terms of coffee quality. However, they are substantially different from the Gawata district in terms of coffee quality. Similarly, within each district, there are no clear differences in coffee production systems. However, the production systems of districts varied significantly. The coffee processing method had a pronounced effect on the overall quality and preliminary grade, physical and raw quality variables of coffee. Screen retention (14) was correlated with soil iron, but it was related negatively to boron and sodium contents. A significant and positive relationship was observed between green coffee bean moisture content and soil potassium, calcium, magnesium, boron, sodium, organic carbon, silicon content, and soil pH. A positive and significant relationship between soil molybdenum and the coffee quality variable was observed across the studied districts whereas most soil micronutrients, specifically, zinc, sulfur, and manganese, were significantly and negatively related to the organoleptic qualities of the coffees. Further investigation that includes the effects of elevation is recommended in future studies.

Cultivos de cobertura asociados a quinua (Chenopodium quinoa Willd) en el Altiplano peruano: Reducción de la erosión, mejora de la salud del suelo y rendimiento agrícola

The Peruvian Altiplano presents increasing fertility losses, being susceptible to natural erosion. For many years, conventional agricultural management has generated losses of the topsoil and deterioration of soil properties, impacting in crop yields and deepening the degradation of this vulnerable ecosystem. The aim of this research was to determine the benefits of cover crops against erosion, soil health and quinoa yield. The trial was carried out in Huancarani and Cahualla towns, Mañazo district, Puno; with a randomized complete block design (RCBD) with four treatments: without cover and with clover (Medicago hispida G.), vetch (Vicia villosa) and mulch covers. We evaluated the physical, chemical, and biological characteristics of soil, the biomass of the cover crops and the quinoa yield. The results showed that the treatments with clover, mulch and vetch covers reduced soil erosion by 59.61%, 51.87% and 49.50%, respectively. Likewise, the use of clover and vetch covers increased organic carbon (29.71% and 31.16%), nitrogen (36.94% and 48.65%), and available phosphorus with clover cover (26.11%). Finally, clover cover associated with quinoa increased the yield of quinoa grain by 17% and reduced soil erosion significantly. These results show that cover crops have great potential for restoring soil health and improving yield.