Soil enzymatic activity under coffee cultivation with different water regimes associated to liming and intercropped brachiaria

ABSTRACT: This research evaluated the effects of coffee cultivation with two different water regimes associated or not with liming and the presence/absence of brachiaria as intercrop on the activities of the soil enzymes β-glucosidase, arylsulfatase and acid phosphatase. The study was carried out at the experimental farm of Embrapa Cerrados, using the cultivar IAC 144 (Coffea arabica L.), under a clayey dystrophic Cerrado Oxisol. Two water regimes (WR) were considered, WR1 with irrigation shifts throughout the year and WR3 with controlled water stress, for about 70 days, in the dry season. In each water regime, effects of lime application (with/without) and the presence/absence of brachiaria cultivated between the lines of coffee plants were evaluated. The activities of the enzymes β-glucosidase, arylsulfatase and acid phosphatase were evaluated during the rainy and dry seasons. Liming and intercropped brachiaria positively affected the activities of the three enzymes assessed in this study at varying degrees, depending on season and/or the WR. Our findings evidenced that intercropped brachiaria in coffee rows was the factor that most positively impacted soil enzymes activities.

The effect of the use of a soil improver based on waste brown coal on the enzymatic activity of soil in the cultivation of Paulownia hybrids (Paulownia Siebold & Zuccarini, 1835)

The effect of the use of a soil improver based on waste brown coal on the enzymatic activity of soil in the cultivation of Paulownia hybrids (Paulownia Siebold & Zuccarini, 1835). An important element in controlling the condition of the soil and the plants grown on it are tests of the enzymatic activity of the soil matrix. One of the greatest advantages of using enzyme tests is the ability to make an assessment that also includes other non-measurable factors that affect soil health and condition. The diagnosed changes in soil enzymatic activity are the best parameter for determining the biochemical processes taking place there. This article describes the enzymatic activity of lessive soils on which the Paulownia hybrid variety is cultivated and a soil improver based on waste brown coal is used

Biostimulant Effects of Micro Carbon Technology (MCT®)-Based Fertilizers on Soil and Capsicum annuum Culture in Growth Chamber and Field

Due to the environmental issues that conventional fertilization is causing, biostimulants are proposed as environmentally friendly alternative for crop nutrition in agriculture. The aim of this study was to determine the effects of new Micro Carbon Technology (MCT®) fertilizers with biostimulant activity based on humic acids biologically digested from leonardite on pepper plant growth in three different soils with different textures. The assays were performed under controlled conditions in a growth chamber and in commercial greenhouses in Spain. The effects on soil were analyzed after the addition of the fertilizers by microbial respiration and enzymatic activities (hydrolase, dehydrogenase and urease). For the plant assays, biometric parameters (fresh weight and fruit hardness) and foliar analysis (chlorophyll indices and nutrients) were evaluated. Under controlled conditions, the use of these biostimulants resulted in a greater soil microbial activity in a 24 h interval with increased soil enzymatic activity. In plants, a positive correlation was found between fertilizers with biostimulant activity and Dualex indices of leaves and content of macronutrients Ca and Mg. In commercial greenhouses, the fertilizers with biostimulant activity strongly depended on the soil texture. In conclusion, these products have real potential to replace conventional fertilizers in commercial production fields.

Optimization of Growing Medium and Preservation Methods for Plant Beneficial Bacteria, and Formulating a Microbial Biopreparation for Raspberry Naturalization

The current study focuses on the optimization of bacterial growing medium composition, including the carbon and nitrogen source in different concentrations, the pH value of the medium and the temperature. Optimization was performed for four environmental bacterial isolates belonging to the genera Arthrobacter, Pseudomonas and Rhodococcus, which were previously obtained from wild raspberries. These bacteria proved to be potent antagonists against certain fungal and fungal-like plant pathogens. Furthermore, three preservation methods and three sample preparation techniques were evaluated. In addition, a prebiotic supplementary blend based on previous research was tested. The research included a pot experiment to estimate the influence of bacterial cultures on the growth of plant shoots and roots, on the soil enzymatic activity and the content of macronutrients, minerals and nitrogen in the soil depending on the naturalization strategy. The best carbon and nitrogen source were chosen. The addition of a supplementary blend resulted in the increased growth of two bacterial isolates. Bacterial inoculum applied to the roots and watering resulted in increased shoot mass in objects infected with plant pathogens, although in plants without the pathogen infection, bacterial inoculum resulted in the decreased mass of plants. Naturalization strategy should be matched to the pathogens present at plantations.

Silicon substances for restoration of oil-contaminated areas

Numerous investigations demonstrate that active forms of silicon (Si) enhance the plant tolerance against abiotic stresses by several mechanisms, including increasing the antioxidant activities and minimizing oxidative damage. Soil contamination with oil and oil products relates to abiotic stress that detrimentally affects soil microbial population and plant growth. Considering the crucial role of microorganisms and plants in bioremediation of oil-polluted areas, Si substances can be beneficial to acceleration of soil reclamation. In greenhouse experiment, wheat was grown in Grey Forest Soil contaminated with used motor oil. The effect of fumed silica and monosilicic acid on soil enzymatic activity and plant growth was studied. Both Si substances provided increasing the plant biomass and the activities of catalase and dehydrogenase. As regards the plant growth, the effect of Si was more pronounced in polluted soil, while the enzyme activity was higher affected in unpolluted soil. The activities of catalase and dehydrogenase were closely correlated to the water-soluble Si in soil (R=0.91-0.92). Silicon substances with high content of, plant-and microorganism-available Si might be promising for involvement in bioremediation technology for oil-contaminated soil.

Impact of Subsurface Application of Compound Mineral Fertilizer on Soil Enzymatic Activity under Reduced Tillage

Soil biochemical properties shaping soil fertility and agro-ecosystem productivity depend on the reduced tillage system and the dose and method of application of fertilizer; therefore, the research hypothesis put forward proposes that under reduced tillage system conditions, the subsurface application of a multi-component mineral fertilizer would increase soil enzymatic activity, thus favourably influencing the biodiversity of the soil environment. The objective of the three-year study was to evaluate the impact of subsurface application of varying mineral fertilizer rates on soil enzymatic activity under reduced tillage system conditions in soybean, winter wheat and maize rotations. The field experiment was set up as a split-plot design in four replicates. The first experimental factor included two methods of mineral fertilization application: fertilizer broadcast over the soil surface (S); fertilizer applied deep (subsurface placed) using a specially designed cultivator (Sub-S). The other factor was the rates of the mineral fertilizer (NPKS): 85 kg∙ha−1 (F85) and 170 kg∙ha−1 (F170). The method of application and rate of mineral fertilizer did not have a significant effect on the organic carbon and total nitrogen content in the soil of the plots with all rotational crops. Subsurface application of fertilizer significantly increased available phosphorus content in soil under soybean and winter wheat crops; however, it significantly decreased soil pHKCl values within sites with all crops in the rotation compared to surface application. At the same time, deep application of mineral fertilizer significantly stimulated dehydrogenase activity in the soil under the winter wheat crops and acid phosphatase activity in the soil under all rotation crops. The higher level of mineral fertilization contributed to reduction of soil pHKCl under winter wheat and maize, and promoted an increase in the soil P content. Additionally, significant increases of dehydrogenases and urease activity in the soil under winter wheat and maize crops, alkaline phosphatase activity in the soil under all the studied crops, and acid phosphatase activity in the soil under the soybean crops were found, compared to mineral fertilizer in the amount of 85 kg NPKS∙ha−1. The results of the present study have demonstrated a positive effect of subsurface application of compound mineral fertilizer on the soil biochemical parameters in reduced tillage. This may be a recommendation for the subsurface use of multicomponent mineral fertilizers in sustainable agriculture. However, a full objective characterization of the soil environment processes induced by in-depth application of mineral fertilizer in reduced tillage requires long-term monitoring.

Effect of Charcoal on the Properties, Enzyme Activities and Microbial Diversity of Temperate Pine Forest Soils

Relict charcoal hearths (RCHs) increases soil fertility in forest ecosystems. However, the effects of RCHs on the activity and abundance of soil microorganisms remain unknown. In this paper, we analysed the impact of relict charcoal production on the soil enzymatic activity and composition of soil bacterial and fungal communities in Scots pine forests of the Manowo Forest District in northern Poland. Moreover, we determined the effect of relict charcoal production on the soil properties. Our research was conducted by comparing the physical, chemical, enzymatic and microbiological properties of charcoal-enriched and charcoal-free soils. Significant differences in physical properties were found between these two soil types in terms of their structure and water holding capacity. As expected, horizons enriched with charcoal were characterised by a significantly higher organic carbon content (4.7% on average compared to 2.2% in control horizons), and also by a considerably higher content of available phosphorus (an average of 64.07 mg·kg−1 compared to 36.21 mg·kg−1 in the control). Similarly, RCH horizons displayed a higher pH and higher contents of Ca and Na cations. These results indicated that RCH soils provided more favourable conditions for the soil microbiome, as reflected by the higher enzymatic activity and diversity of the microorganisms. Moreover, bacterial and fungal communities in RCH soils were more diverse and had greater species/genera richness, especially in the case of fungi. Members of the genus Rhodoplanes dominated the bacterial community at both RCH and non-RCH sites, followed by Streptomyces, Burkholderia, Skermanella, Tsukamurella and Candidatus Solibacter. Both culture- and next generation sequencing (NGS)-based analyses showed that soil fungal communities were dominated by Ascomycota, with Penicillium as the most abundant genus. Our results showed that hearth soils may represent a significant C pool in the forest ecosystem. This study supports the strategy of safeguarding such charcoal-enriched soils as precious C reservoirs and ecologically important biodiversity hotspots. Moreover, the application of charcoal may effectively increase the microbial diversity of forest soils, especially during the reforestation or re-cultivation of disturbed habitats.

Agricultural management and cultivation period alter soil enzymatic activity and bacterial diversity in litchi (Litchi chinensis Sonn.) orchards

Background Agricultural management and temporal change including climate conditions and soil properties can result in the alteration of soil enzymatic activity and bacterial community, respectively. Therefore, different agricultural practices have been used globally to explore the soil quality. In this study, the temporal variations in soil property, enzymatic activity, and bacterial community at three successive trimester sampling intervals were performed in the soil samples of litchi orchards that were maintained under conventional and sustainable agricultural practices. Results Agricultural management found to significantly influence arylsulfatase, β-glucosidase, and urease activities across time as observed by repeated-measures analysis of variance. Shannon and Simpson diversity indices, and the relative abundance of predominant Acidobacteria and Proteobacteria were significantly influenced by temporal change but not agricultural management. This suggested that soil enzymatic activity was more susceptible to the interaction of temporal change and agricultural management than that of the bacterial community. Multiple regression analysis identified total nitrogen, EC, and phosphorus as the significant predictors of acid phosphatase, arylsulfatase, and β-glucosidase for explaining 29.5–39% of the variation. Moreover, the soil pH and EC were selected for the SOBS, Chao, ACE, and Shannon index to describe 33.8%, 79% of the variation, but no significant predictor was observed in the dominant bacterial phyla. Additionally, the temporal change involved in the soil properties had a greater effect on bacterial richness and diversity, and enzymatic activity than that of the dominant phyla of bacteria. Conclusions A long-term sustainable agriculture in litchi orchards would also decrease soil pH and phosphorus, resulting in low β-glucosidase and urease activity, bacterial richness, and diversity. Nevertheless, application of chemical fertilizer could facilitate the soil acidification and lead to adverse effects on soil quality. The relationship between bacterial structure and biologically-driven ecological processes can be explored by the cross-over analysis of enzymatic activity, soil properties and bacterial composition.