Effect of Different Agricultural Farming Practices on Microbial Biomass and Enzyme Activities of Celery Growing Field Soil

Soil quality is directly affected by alterations in its microbiological, biological, biochemical, physical, and chemical aspects. The microbiological activities of soil can affect soil fertility and plant growth because it can speed up the cycling of nutrients, enzymes, and hormones that are needed by plants for proper growth and development. The use of different agricultural management practices can influence microbial biomass and enzyme activities by altering soil microclimate, soil microorganism habitat, and nutrient cycling. Based on this, the present work planned to evaluate the impact of conventional, low-input, and organic farming systems in a vegetable field growing celery on microbial biomass and different soil enzyme activities. The present study showed a comparison of the effect of different practices on biological soil quality indicators during two sampling times, i.e., one month after colonization and one month before harvesting. It was observed that the soil microbial biomass in the organic farming system was significantly higher than that found in conventional and low-input practices. Under an organic farming system, the soil microbial biomass in December was significantly higher than that in October. The soil microbial biomass carbon in the 0–20 cm soil layer showed higher variation compared to that in the 20–40 cm layer for all the three of the farming management practices that were used in the study. Additionally, the soil total carbon and total organic carbon were recorded as being higher in the December samples than they were in the October samples. Under all the three of the management practices that were applied, the soil catalase activity was higher in the October samples than it was in the December soil samples that were collected the from 20–40 cm soil layer compared to those that were taken from the 0–20 cm layer. The application of organic fertilizer (chicken and cowmanure compost) resulted inincreases in the soil urease and in the protease activity. The protease activity of the soil samples that were extracted from the 0–20 cm and 20–40 cm soil layers in October was higher in the samples that were taken from farms using conventional practices than it was in the samples that were taken from farms using organic and low-input practices, while the samples that were collected during December from both of the soil layers showed higher protease activity when organic methods had been used. No significant variation in the soil urease activity was observed between the two soil layer samples. Urease activity was the highest when organic management practices were being used, followed by the low-input and the conventional modes. For the conventional and low-input practices, the soil urease activity showed an obvious trend of change that was related to thetime of sampling, i.e., activity in December was significantly higher than activity in October. The novelty of this study was to determine the microbial biomass carbon and enzymatic activity in a six-field crop rotation (tomato, cucumber, celery, fennel, cauliflower, and eggplant) using three management practices: low-input, conventional, and organic systems. The present study showed that the long-term application of organic fertilizers plays a large role in maintaining excellent microbial and enzyme activitythat result in improved soil quality.

Recent Efforts in the Discovery of Urease Inhibitor Identifications

: Urease is an attractive drug target for designing anti-infective agents against pathogens such as Helicobacter pylori, Proteus mirabilis, and Ureaplasma urealyticum. In the past century, hundreds of medicinal chemists focused their efforts on explorations of urease inhibitors. Despite the FDA’s approval of acetohydroxamic acid as a urease inhibitor for the treatment of struvite nephrolithiasis and the widespread use of N-(n-butyl)thiophosphoric triamide as a soil urease inhibitor as nitrogen fertilizer synergists in agriculture, urease inhibitors with high potency and safety are urgently needed. Exploration of novel urease inhibitors has therefore become a hot research topic recently. Herein, inhibitors identified worldwide from 2016 to 2021 have been reviewed. They structurally belong to more than 20 classes of compounds such as urea/thioure analogues, hydroxamic acids, sulfonamides, metal complexes, and triazoles. Some inhibitors showed excellent potency with IC50 values lower than 10 nM, having 10000-fold higher potency than the positive control thiourea.

Soil urease inhibition by various plant extracts

Urea is the most popular and widely used nitrogenous fertilizer. High soil urease activity rapidly hydrolyses applied urea to ammonia which contributes to soil nitrogen (N) losses and reduces N use efficiency of crop plants. The ammonia losses can be minimized by the inhibition of soil urease activity which has been explored using various potential chemical inhibitors. However, the soil urease activity inhibition potential of plant extracts is rarely explored to date. In the present study, extracts of 35 plant materials were taken and evaluated against jack bean urease. Eleven extracts, showing >50% jack bean urease inhibition, were selected and further investigated in 13 soils collected from various districts of Punjab, Pakistan. Interestingly, except Capsicum annum, Melia azedarach, Citrus reticulata and Quercus infectoria, the plant extracts showed urease inhibition activities in soils, the extent of which was lower as compared to that observed in jack bean urease though. Maximum urea hydrolysis inhibition (70%) was noted with Vachellia nilotica which was 40% more than that of hydroquinone (50%) followed by that of Eucalyptus camaldulensis (24%). The extracts of V. nilotica and E. camaldulensis were coated on urea and applied to soil in the next step. At 21st day, 239% and 116% more urea-N was recovered from soil treated with V. nilotica and E. camaldulensis extracts coated urea, respectively, as compared to uncoated urea. Conclusively, these results indicated that the coating of V. nilotica and E. camaldulensis extracts on urea prills prolonged urea persistence in soil owing to minimum urea hydrolysis, probably, the extracts of V. nilotica and E. camaldulensis showed their urease inhibition potential. The results of this study provide a base line for the identification of new soil urease inhibitor compounds from plant materials in future.

Effects of sulfuric, nitric, and mixed acid rain on the decomposition of fine root litter in Southern China

Background China has been increasingly subject to significant acid rain, which has negative impacts on forest ecosystems. Recently, the concentrations of NO3− in acid rain have increased in conjunction with the rapid rise of nitrogen deposition, which makes it difficult to precisely quantify the impacts of acid rain on forest ecosystems. Methods For this study, mesocosm experiments employed a random block design, comprised of ten treatments involving 120 discrete plots (0.6 m × 2.0 m). The decomposition of fine roots and dynamics of nutrient loss were evaluated under the stress of three acid rain analogues (e.g., sulfuric (SO42−/NO3− 5:1), nitric (1:5), and mixed (1:1)). Furthermore, the influences of soil properties (e.g., soil pH, soil total carbon, nitrogen, C/N ratio, available phosphorus, available potassium, and enzyme activity) on the decomposition of fine roots were analyzed. Results The soil pH and decomposition rate of fine root litter decreased when exposed to simulated acid rain with lower pH levels and higher NO3− concentrations. The activities of soil enzymes were significantly reduced when subjected to acid rain with higher acidity. The activities of soil urease were more sensitive to the effects of the SO42−/NO3− (S/N) ratio of acid rain than other soil enzyme activities over four decomposition time periods. Furthermore, the acid rain pH significantly influenced the total carbon (TC) of fine roots during decomposition. However, the S/N ratio of acid rain had significant impacts on the total nitrogen (TN). In addition, the pH and S/N ratio of the acid rain had greater impacts on the metal elements (K, Ca, and Al) of fine roots than did TC, TN, and total phosphorus. Structural equation modeling results revealed that the acid rain pH had a stronger indirect impact (0.757) on the decomposition rate of fine roots (via altered soil pH and enzyme activities) than direct effects. However, the indirect effects of the acid rain S/N ratio (0.265) on the fine root decomposition rate through changes in soil urease activities and the content of litter elements were lower than the pH of acid rain. Conclusions Our results suggested that the acid rain S/N ratio exacerbates the inhibitory effects of acid rain pH on the decomposition of fine root litter.

Effect of passivator DHJ-C on the growth and cadmium accumulation of Brassica napus in Cd-contaminated soil

The farmland polluted by cadmium is increasing drastically, which seriously threatened agricultural production and food safety. Nowadays, efficient and convenient way to solve the problem is urgently needed. In this experiment, a particular compound passivator DHJ-C was applied for soil remediation by pot experiment and the effect on both soil and plant was evaluated. The DHJ-C reduced the toxicity of Cd on soil enzyme activity and growth inhibition on Brassica napus. The soil urease and sucrase activity were significantly increased. The dry weight of mature oilseed rape increased by 14.6–36.0% and the yield of seeds increased by 14.1–52% per plant, which suggested that the passivator effectively reduced the detrimental effects on rape. Similarly, the results of physiology and biochemistry also indicated that DHJ-C can distinctly alleviate the inhibitory effect of Cd on plant growth. Such as the MDA content in plant was reduced by 52.1% in 10 mg/kg Cd treatment. Compared with control, Cd accumulation in seedling stage and mature period was significantly reduced as the concentration of Cd in aboveground part even decreased by 18.4 and 32.0% respectively. Overall, DHJ-C hold sufficient ability to be applied as an excellent passivator to reduce Cd toxicity in contaminated soil and significantly increase the yield of rapeseed.

Allelopathic effects of ginsenoside on soil sickness, soil enzymes, soil disease index and plant growth of Ginseng

Soil sickness of ginseng (Panax ginseng C. A. Mey.) has become a major limiting factor in ginseng cultivation. We found that Total Ginsenoside in Ginseng Root (TSPG) significantly decreased the activities of soil urease, acid phosphatase and laccase. Its high concentration of TSPG (10.00 mg L-1) significantly reduced the activity of soil sucrose. Besides, the TSPG can inhibited the growth of ginseng and increased the incidence of disease. Therefore, allelopathic effects of TSPG may be one of the main causes of Soil Sickness in ginseng.

Variations in Soil Urease and Dehydrogenase Activities as Determined by Diuron, Pyrithiobac Sodium and Quizalofop Ethyl Applied to Cotton Cultivated in Red and Black Soils

Activities of soil enzymes viz., urease and dehydrogenase were studied in two field experiments conducted in red and black soils at Professor Jayashankar Telangana State Agricultural University, Rajendranagar during kharif, 2018. Different doses of diuron in combination with postemergence tank-mix application of pyrithiobac sodium + quizalofop ethyl were tested. Soil urease activity showed an increasing trend and it increased from the day of PE herbicide application to flowering. Highest urease activity was noticed at flowering stage and then after the activity decreased upto harvest. In diuron treatments, the urease activity decreased substantially upto 5 DAHS, which later increased at flowering. Significant differences were observed in urease activity among all the treatments from the day of PE application to the day of postemergence spray in both red and black soils. No significant difference was observed in urease activity due to application of postemergence herbicide in both red and black soils. No significant difference was observed due to the application of pre and postemergence herbicides on the activity of dehydrogenase in both red and black soils but the activity of dehydrogenase increased from the day of PE herbicide application to flowering, exhibited highest activity at flowering stage and there after the activity decreased at harvest in both red and black soils.

Searching for the Correlation Between the Activity of Urease and the Content of Nickel in the Soil Samples: The Role of Metal Speciation

The purpose of this study was to verify the correlation between the activity of urease and the content of nickel in soil of temperate climate in relation to the land management. Moreover, the metal speciation was taken into account in order to search for the above-mentioned correlation. Arable lands, forested lands, and wastelands were analyzed. The basic soil parameters were determined such as pH, clay fraction content, and organic matter content. The speciation of nickel was studied by using BCR (Bureau Communitaire de Reference) sequential extraction procedure and flame atomic absorption spectrometry, while the urease activity was determined spectrophotometrically. The pseudo-total content of Ni in every sample was below 30 mg kg−1 of dry soil. The dominant form of nickel in the soil samples was the residual form. Although the urease activity varied slightly between the samples, the differences turned out to be statistically insignificant. However, the highly positive correlations between the urease activity, organic matter content, and the pseudo-total content of Ni were found and discussed. Moreover, the positive correlations between the urease activity and two geochemical forms of nickel, namely, active and residual form, were confirmed. The results of performed experiments prove that the method of land management does not significantly affect either the topsoil urease activity or the nickel distribution in the case of the extensive agriculture and forestry. However, the existence of at least two forms of the active soil urease was proposed. The first one―contained in the soil solution or loosely adsorbed on the soil particulates and the second one―strongly adsorbed onto the clay minerals. Also the complex role of the organic matter in protecting urease from external factors was presented. Finally, it was postulated that the nickel content in soil may be the indicator of the soil urease activity.