Higher Soil pH Research Articles

The role of stress factors in severity of Cytospora plurivora in greenhouse and field plantings of 13 peach (Prunus persica) cultivars.

Understanding the host-pathogen-environmental interactions in a pathosystem is essential for management of diseases and diminished crop yields. Abiotic stressors such as cold damage, water deficit, and high pH soils can be major limiting factors to tree fruit production. Along with decreased yields, these abiotic factors can have direct implications for disease severity within orchards. Cytospora plurivora is a ubiquitous fungal canker pathogen in western Colorado, USA and is a major focus in integrated pest management strategies. This research evaluated the influence of biotic and abiotic stress factors on peach tree health. Thirteen peach cultivars were placed under abiotic stress and inoculated with C. plurivora in greenhouse and field conditions. Under deficit irrigation, C. plurivora infections were significantly larger and more severe in both the greenhouse and field trials when compared with those under the full-irrigation controls. In controlled greenhouse conditions, a positive correlation between lesion size and water potential was evident, but no trend of cultivar tolerance was observed. Furthermore, increase in irrigation water pH, through additions of sodium carbonate and bicarbonate, in the greenhouse trials resulted in decreased leaf water potentials and increased pathogen necrotic tissue volumes (mm3). In field trials, there was no positive relationship between lesion size and water potential; trees with the most negative water potentials had the smallest lesions sizes that did not correspond to cultivar, suggesting that other abiotic or biotic factors may be shielding water stressed trees from increased pathogen aggression. This research highlights the importance of proper irrigation and soil pH management as tools for the management of Cytospora canker in peach orchards.

Linkages between Soil Acidity, Soil Plant Nutrients and Land Use on Ferralsols in Central Uganda

A study to examine the linkages between soil acidity, soil plant nutrients and land use on Ferralsols was carried out on smallholder farms in Central Uganda. The objective of the study was to assess the effect of soil pH on soil plant nutrient availability under the current land use. The study was carried out in Mpigi, Masaka, Wakiso, Mukono and Mubende districts representing Central Uganda. Soil samples were randomly collected from Coffee, Banana, soybean, common bean, maize and virgin fields in the five districts and the pH and plant nutrient analyzed accordingly. The analysis of variance (ANOVA) showed significant difference (p<0.01) on soil nitrogen, Calcium (p< 0.05) and Magnesium (p< 0.05). When treatment was assessed, the study showed significant difference (p< 0.01) on potassium. Besides, the study also showed high concentrations of Manganese (Mn) and Iron (Fe) in addition to very high sand and low silt and clay contents. The current land use for coffee production in Masaka district recorded the lowest soil pH (4.4) followed by annual fields (pH 4.60) in Mpigi. The highest soil pH (5.7) was recorded in banana fields in Mubende. The study also recorded very low to low N, P and K. Generally, the study observed rapid soil fertility decline in smallholder farms in the region.

Soil phosphorous is the primary factor determining species-specific plant growth depending on soil acidity in island ecosystems with severe erosion

Disturbances caused by invasive ungulates alter soil environments markedly and can prevent ecosystem recovery even after eradication of the ungulates. On oceanic islands, overgrazing and trampling by feral goats has caused vegetation degradation and soil erosion, which can alter soil chemistry. To understand the effects of the changes on plant performance, we conducted a laboratory experiment to assess herbaceous species growth under various soil conditions with phosphorous, nutrients, and acidity. Subsoil was collected from Nakodo-jima in the northwest Pacific. Six herbaceous species dominating the island were grown in soils with three levels of added CaCO3 and P2O5 and two levels of added KNO3. After 4 weeks of growth, the total dry plant weight was significantly lower with no added P2O5, regardless of the addition of KNO3. Three species weighed more under P2O5 and KNO3 addition in high-pH soil, whereas the remaining three weighed less. Our results indicated that herbaceous species growth is limited primarily by phosphorous availability; the limitation is dependent on soil pH, and the trend of dependency differs among species. This implies that ecosystems with extreme disturbances cannot recover without improving the soil chemistry.

Crack Growth Behavior and Mechanism of X90 Steel in High pH Soil Environment under Different Applied Potentials

Crack Growth Behavior and Mechanism of X90 Steel in High pH Soil Environment under Different Applied Potentials

Response of Diverse Peanut Cultivars to Nano and Conventional Calcium Forms under Alkaline Sandy Soil.

Calcium is one of the most limiting factors for the growth and reproduction of peanut, which ultimately affects pod and seed yields. A two-year field experiment was carried out to assess the impact of five calcium applications, including nano-calcium and conventional forms, on growth, leaf nutrient content, yield traits, and quality parameters of three diverse peanut cultivars (Ismailia-1, Giza-5, and Giza-6). The applied calcium applications were calcium sulfate, which is recommended for commercial peanut cultivation and commonly referred to as gypsum (coded as Ca-1), calcium nitrate (Ca-2), nano-calcium nitrate (Ca-3), 50% calcium nitrate + 50% nano-calcium (Ca-4), and 50% calcium sulfate + 50% nano-calcium (Ca-5). Calcium sulfate (gypsum, Ca-1) was soil-supplied during the seedbed preparation as recommended, while the other calcium applications (Ca-2, Ca-3, Ca-4, and Ca-5) were exogenously sprayed three times at 30, 45, and 60 days after sowing. The soil of the experimental site was alkaline, with a high pH of 8.6. The results revealed significant differences among cultivars, calcium applications, and their interactions. The soil-supplied gypsum Ca-1 displayed lower agronomic performance on all recorded growth, leaf nutrient content, yield traits, and quality parameters. On the other hand, the foliar-supplied calcium, particularly Ca-4 and Ca-5, displayed superior effects compared to the other simple calcium forms. Ca-4 and Ca-5 produced significantly higher seed yield (3.58 and 3.38 t/ha) than the simple recommended form (Ca-1, 2.34 t/ha). This could be due to the difficulty of calcium uptake from soil-supplied calcium under high soil pH compared to the exogenously sprayed nano-calcium form. Moreover, the superior performance of Ca-4 and Ca-5 could be caused by the mixture of fertilizers from the synergistic effect of calcium and nitrate or sulfate. Furthermore, the effect of nitrate was applied in nano form in the Ca4 and Ca-5 treatments, which contributed to improving nutrient uptake efficiency and plant growth compared to the other treatments. The peanut cultivar Giza-6 showed superiority for most measured traits over the other two cultivars. The interaction effect between the assessed cultivars and calcium applications was significant for various traits. The cultivar Giza-6 showed a significant advantage for most measured traits with the mixture of 50% calcium nitrate + 50% nano-calcium (Ca-4). Conclusively, the results pointed out the advantage of the exogenously sprayed nano-calcium form combined with calcium nitrate or calcium sulfate for promoting growth, leaf nutrient content, yield, and quality traits of peanut, particularly with high-yielding cultivars under sandy soil with high pH.

Effects of soil pH and organic carbon content on in vitro Cr bioaccessibility in Ultisol, Alfisol, and Inceptisol

Hexavalent chromium (Cr(VI)) is a toxic heavy metal and its mobility and bioaccessibility in soils are influenced by soil properties. In this study, the soil pH and organic carbon contents of Ultisol, Alfisol, and Inceptisol were adjusted before they were polluted with 230 mg kg−1 Cr(VI). Alkaline digestion, sequential extraction, and an in vitro experiment were conducted to study the valence state, species, and bioaccessibility of Cr in the soils. The results showed that a high soil pH was not favorable for reduction of Cr(VI); therefore the Cr(VI) and exchangeable Cr contents were positively related to soil pH. Soil organic carbon promoted the reduction of Cr(VI). Almost all Cr(VI) was reduced to Cr(III) when the soil organic carbon content reached 10 g kg−1. Chromium bioaccessibility in simulated gastric and intestinal phase solutions was influenced by Cr(VI) and Cr(III) adsorption/desorption, dissolution/precipitation, and redox reactions. Chromium bioaccessibility differences between the gastric and intestinal phases were associated with the Cr(VI)/Cr(III) ratio. Acidic conditions and a high organic carbon content promoted the conversion of Cr(VI) to Cr(III). When soil pH was increased from 4.01 to 5.85, Cr(VI) in Alfisol without the addition of humic acid increased from 96.38 to 174.78 mg kg−1, the exchangeable Cr proportion increased from 9.7% to 22.6%, and Cr bioaccessibility increased from 41.29% to 49.14% in the gastric phase and from 41.32% to 48.24% in the intestinal phase. When the organic carbon content increased from 3.95 to 9.28 g kg−1 in Alfisol, Cr(VI) content decreased from 167.66 to 20.52 mg kg−1, which led to a decrease in Cr bioaccessibility from 49.15% to 13.8% in the gastric phase and from 45.85% to 7.67% in the intestinal phase. Therefore, acidic conditions and increasing soil organic carbon levels can reduce the health risk posed by Cr in soils.

Is Australia weird? A cross-continental comparison of biological, geological and climatological features

Australia’s distinctive biogeography means that it is sometimes considered an ecologically unique continent with biological and abiotic features that are not comparable to those observed in the rest of the world. This leaves some researchers unclear as to whether findings from Australia apply to systems elsewhere (or vice-versa), which has consequences for the development of ecological theory and the application of ecological management principles. We analyzed 594,612 observations spanning 85 variables describing global climate, soil, geochemistry, plants, animals, and ecosystem function to test if Australia is broadly different to the other continents and compare how different each continent is from the global mean. We found significant differences between Australian and global means for none of 15 climate variables, only seven of 25 geochemistry variables, three of 16 soil variables, five of 12 plant trait variables, four of 11 animal variables, and one of five ecosystem function variables. Seven of these differences remained significant when we adjusted for multiple hypothesis testing: high soil pH, high soil concentrations of sodium and strontium, a high proportion of nitrogen-fixing plants, low plant leaf nitrogen concentration, low annual production rate to birth in mammals, and low marine productivity. Our analyses reveal numerous similarities between Australia and Africa and highlight dissimilarities between continents in the northern vs. southern hemispheres. Australia ranked the most distinctive continent for 26 variables, more often than Europe (15 variables), Africa (13 variables), Asia (12 variables each), South America (11 variables) or North America (8 variables). Australia was distinctive in a range of soil conditions and plant traits, and a few bird and mammal traits, tending to sit at a more extreme end of variation for some variables related to resource availability. However, combined analyses revealed that, overall, Australia is not significantly more different to the global mean than Africa, South America, or Europe. In conclusion, while Australia does have some unique and distinctive features, this is also true for each of the other continents, and the data do not support the idea that Australia is an overall outlier in its biotic or abiotic characteristics.

Characterizing atrazine, mesosulfuron‐methyl, and topramezone bioavailability in North Carolina soils using greenhouse bioassays

AbstractHerbicide carryover injury to rotational crops can vary in severity depending on the influence of soil properties on herbicide bioavailability. Greenhouse bioassays were conducted with soybean, radish, and canola to evaluate differences in the bioavailability of three herbicides with carryover risk, atrazine, mesosulfuron‐methyl, and topramezone. Bioassays were conducted in three varying regional soil types with nine herbicide treatment rates including a control. Plant visual injury was evaluated weekly, and aboveground dry biomass was weighed after harvest of soybean 28 days after emergence (DAE) and radish and canola 21 DAE. A log‐logistic dose–response regression model was used to quantify herbicide‐effective concentrations for 30% (EC30), 50% (EC50), and 80% (EC80) visual injury and aboveground dry biomass reduction in each soil type. Relative herbicide‐soil bioavailability was determined through comparisons of herbicide‐effective concentrations among soil types. Pearson correlation revealed that atrazine, mesosulfuron‐methyl, and topramezone EC30 for all species were positively correlated to soil organic matter (OM) content (r = 0.56, 0.48, and 0.40, respectively) and cation exchange capacity (CEC) (r = 0.43, 0.41, and 0.45). Topramezone EC80 for soybean and radish was positively correlated to soil clay content (r = 0.51) and silt content (r = 0.51) and negatively correlated to sand content (r = −0.51) and pH (r = −0.52). Decreased atrazine, mesosulfuron‐methyl, and topramezone bioavailability in soil with high OM and CEC, decreased topramezone bioavailability in coarse‐textured soil and at high soil pH, and differential herbicide sensitivity of crop species can inform grower decisions on herbicide selections and rotational crop plans.

A large-scale assessment on spatial variability of potato yield and soil chemical properties in northern China

Understanding the spatial variability of potato yield and soil chemical properties is critical for designing management strategies and ensuring potato sustainable production. However, there has been no detailed investigation on a large-scale variation in yields and soil nutrients in potato production areas of China. In this study, 938 soil samples and potato production information were collected from the main potato-producing areas in northern China. The results showed that potato yields and selected soil properties varied considerably, with coefficients of variation ranging between 12.2% and 110.8%. Potato yield, pH, soil organic matter (SOM), total nitrogen (TN), available potassium (AK), and electrical conductivity (EC) showed strong spatial correlations, while mineral nitrogen (MN) and available phosphorus (AP) had moderate spatial correlations based on semi-variograms analysis. The spatial distribution of yields indicated that 83.3% of potato yields ranged from 20 to 60 t ha−1. The SOM, TN, AP, and AK showed similar spatial distribution trends with high concentrations in the northeast, while pH showed the opposite trend. EC was found to be highly variable with high values in the west. The high soil pH and low SOM were the most important constraints limiting potato productivity, and the high MN implied excessive nitrogen fertilizer application. The soil quality index (SQI) was calculated using selected soil properties, and a significant correlation between SQI and potato yield was observed. The spatial distribution of SQI showed that 42.2% of the study area was of low soil quality (SQI less than 0.6). A relatively low SQI indicated that there was great potential for increasing potato productivity in northern China. After dividing soil samples into rainfed and irrigated, the effect of soil nutrients on potato yield was found to become weaker at irrigated sites, where there was no correlation between SQI and yield, suggesting that the role of soil moisture overshadowed the role of nutrients. The spatial variability of soil chemical properties provided essential information for developing rational nutrient management strategies and regional planning to achieve sustainable potato production in China.

Role of Soil pH, Lipases and Catalase Activities in the Degradation of Spent Engine Oil and Crude Oil Pollution on Agricultural Soil

The activities of soil pH, lipases and catalase is prominent to oil degradation in the soil and their concentration gives useful information on soil’s the microbial activities. Six lots research site were polluted with spent engine oil and bonny light crude oil as follows A1 = 60cm3 farmland + 2dm3 of spent engine oil; A2 = 60cm3 farmland + 4dm3 of spent engine oil; A3 = 60cm3 farmland + 6dm3 of spent engine oil; B1 = 60cm3 farmland + 2dm3 of spent engine oil; B2 = 60cm3 farmland + 4dm3 of spent engine oil; B3 = 60cm3 farmland + 6dm3 of spent engine oil. Soil samples were collected at specified periods and analyzed for soil pH, catalase and lipase activity. Highest soil pH for topsoil (4.950 ± 0.025) was observed in weeks 2 A2, while at 15cm depth, the highest soil pH (4.390 ± 0.033) was observed in weeks 6 A3. At 30 cm depth, the highest soil pH was 5.385 ± 0.062 for weeks 6 B3. Lipase activity for topsoil was highest in weeks 8 A3 with a value of 3.460 ± 0.038 Unitsml-1. At 15cm depth, highest lipases activity was also observed in weeks 8 A3 with a value of 5.751 ± 0.037 Unitsml-1, while that of 30cm depth was observed in week 7 A2, with a value of 5.050 ± 0.047 Unitsml-1. Highest catalase activity for topsoil was observed in weeks 6 A3 with a value of 0.594 ± 0.047 X102µgml-1, while 15cm depth was 0.534 ± 0.012 X10-2 µgml-1 for week 2 B2 and 30cm depth was 0.472 ± 0.060 X10-2 µgml-1 for weeks 1 A1. The sensitivity of these soil enzymes to petroleum hydrocarbon pollution as observed in this study makes them early sensitive bioindicators of soil quality and soil health.

High Soil pH and Plastic-Shed Lead to Iron Deficiency and Chlorosis of Citrus in Coastal Saline–Alkali Lands: A Field Study in Xiangshan County

Citrus are one of the most important fruit crops in the world, and the citrus hybrid cv. Beni-Madonna (BM) is widely cultivated in Xiangshan County in China because of its profitability. However, due to the lack of technical guidance and management, nutritional unbalances of trees occur frequently and are a major constraint for fruit quality and yield. In this study, the soil and fruit nutritional status of 62 citrus orchards in three diverse landforms (mountain, flat, and coastal saline–alkali land) located in Xiangshan County has been investigated. Higher pH, calcium, and magnesium content but lower soil organic matter, nitrogen, iron, and boron content were observed in orchards of the coastal saline–alkali land compared with the mountain and flat lands. Compared to Citrus x unshiu, another major hybrid citrus cultivar in Xiangshan county, the Fe deficiency in fruits of BM in coastal saline–alkali lands was more severe, leading to chlorosis symptoms. In addition, long-term cultivation under plastic housing increased soil salinization and affected the absorption of Fe and other nutrients by BM. In conclusion, organic fertilizers, acidic fertilizers, and micronutrient fertilizers should be applied in citrus orchards located in coastal saline–alkali lands. Especially, BM orchards should be supplemented with iron fertilizer and not rely excessively on protection with plastic films.

Acidification of previously limed upland pastures – An overlooked flood risk factor?

In low-lying land, the impact of agriculture on flooding has focussed on soil compaction, whilst in the uplands there has been more interest in the influence of afforestation. The potential effect of acidification of previously limed upland grassland soils on this risk has been overlooked. The marginal economics of upland farms has led to inadequate lime application on these grasslands. In Wales, UK, agronomic improvement of upland acid grasslands with liming was widespread in the last century. The extent and topographical distribution of this land use in Wales was estimated and these characteristics were mapped in four catchments studied in more detail. Then 41 sites on improved pastures within the catchments were sampled, where lime had not been applied for periods of between two and 30 years; unimproved acid pastures adjacent to five of these sites were also sampled. Soil pH, organic matter, infiltration rates and earthworm populations were recorded. Grasslands at risk of acidification without maintenance liming were estimated to cover almost 20 % of upland Wales. The majority of these grasslands were located on steeper slopes (gradients >7o) where any reduction in infiltration would promote surface runoff and limit rainwater retention. The extent of these pastures varied markedly between the four study catchments. There was a 6-fold reduction in infiltration rates between high and low pH soils, and this trend was correlated with reductions in anecic earthworm abundance. The vertical burrows of these earthworms are important for infiltration and no such earthworms were present in the most acidic soils. Recently limed soils had infiltration rates similar to those of unimproved acid pastures. Soil acidification has the potential to exacerbate flood risk but further research is needed to assess the extent of any impact. Modelling of catchment specific flood risk should include the extent of upland soil acidification as an additional land use factor.

Variation of Physico-Chemical Properties among Different Soil Orders under Different Land Use Systems of the Majha Region in North-Western India

The impact of different soil orders and land use systems on the distribution of physico-chemical properties is the most critical matter to address in order to maintain sustainable agricultural production. Hence, the present investigation was carried out to study the variation in the physico-chemical characteristics of soil in diverse land use systems (LUSs), i.e., agriculture, horticulture, and forestry, under major soil orders (entisol, inceptisol, and alfisol) in the Majha region of Punjab. A total of 225 depth-wise (at 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm and 80–100 cm) soil samples were collected from three land-use systems under different soil orders. The mean values of the physico-chemical properties ranged from 6.80–7.50, 7.64–8.34 and 6.94–7.87 for pH; 0.13–0.42, 0.19–0.54 and 0.19–0.46 dS m−1 for EC; 0.14–0.99, 0.21–0.69 and 0.15–0.72% for OC; 0.75–2.07, 1.07–3.32 and 0.93–2.29% for CaCO3; 7.77–41.84, 10.56–40.23 and 7.24–39.51 kg ha−1 for P; and 98.37–334.68, 94.51–230.18 and 93.01–367.39 kg ha−1 for K under different land uses in soil orders entisols, inceptisols and alfisols, respectively. Soil parameters including pH, CaCO3, and phosphorus (P) distribution differed significantly among soil orders; however, soil EC, organic carbon (OC) and available potassium (K) did not. The inceptisols under the agricultural land use system (ALUS) had the highest soil pH, EC, and CaCO3 values. The highest soil OC content was found in entisols under forest land use systems (FLUS), followed by horticultural land use systems (HLUS). The highest values of soil-available phosphorous (P) were found in FLUS under inceptisols, while the highest amounts of soil-available potassium (K) were found in entisols and alfisols under ALUS and FLUS, respectively. Thus, the distribution of physico-chemical properties under different LUSs in each soil order is highly variable and does not follow any particular trend. In general, soil properties such as OC, P, and K content decreased with an increase in soil depth, while pH and CaCO3 values increased with depth in all land uses and soil orders. There was a positive correlation between soil OC and EC, as well as available P and K in the soils investigated. The available P and K are negatively correlated with soil pH and CaCO3 content in the soil. The principal component analysis (PCA) revealed that soil pH and OC were the most variable soil parameters, which influence the availability of other physico-chemical properties under different soil orders and land use systems. Therefore, it is suggested that the land use systems play an important role in the distribution of physico-chemical properties of soil in different soil orders. The results of the study will help students, researchers, and agricultural management staff in managing different land uses for maintaining soil fertility and productivity in alluvial soils of North-western India.

Coupling soil washing with chelator and cathodic reduction treatment for a multi-metal contaminated soil: Effect of pH controlling

Contamination of soil with heavy metals has become a significant environmental issue worldwide. In previous studies, a technology that couped EDTA-washing and cathodic reduction technology was developed to further remove heavy metals from soil contaminated with electroplating waste compared with single soil washing technology. Although the method showed a synergistic effect in previous studies, the effect of soil suspension alkalization and the mechanism behind it remain unclear. High soil pH will have an impact on target metal removal, energy consumption and further utilization of soil. In this experimental research, we investigated the efficacy of pH control on coupling soil washing and cathodic reduction to remove multiple heavy metals from soil under various current densities. To alleviate the OH− ions generated by the cathode and improve the reduction efficiency of metals, an automatic pH controller was used, resulting in a significant increase in the removal rate of target metals. The experimental results show that controlling the pH of soil suspension can increase the total removal rate of target metals by 3-6 times. Additionally, the removal efficiency of residual Pb in the soil is increased by about 30%. In terms of ecological risk, pH control could reduce the solubility and mobility of metals by 50%, and the ecological risk was greatly reduced, especially for Zn, from about 90 mg/kg to 50 mg/kg. Further research is needed to explore the mechanism of the synergistic effect and improve the efficiency of this technology for the subsequent development of coupling EDTA-washing and cathodic reduction.

Nitrogen control of transpiration in grapevine.

Transpiration per unit of leaf area is the end-product of the root-to-leaf water transport within the plant, and it is regulated by a series of morpho-physiological resistances and hierarchical signals. The rate of water transpired sustains a series of processes such as nutrient absorption and leaf evaporative cooling, with stomata being the end-valves that maintain the optimal water loss under specific degrees of evaporative demand and soil moisture conditions. Previous work provided evidence of a partial modulation of water flux following nitrogen availability linking high nitrate availability with tight stomatal control of transpiration in several species. In this work, we tested the hypothesis that stomatal control of transpiration, among others signals, is partially modulated by soil nitrate ( ) availability in grapevine, with reduced availability (alkaline soil pH, reduced fertilization, and distancing source) associated with decreased water-use efficiency and higher transpiration. We observed a general trend when was limiting with plants increasing either stomatal conductance or root-shoot ratio in four independent experiments with strong associations between leaf water status, stomatal behavior, root aquaporins expression, and xylem sap pH. Carbon and oxygen isotopic signatures confirm the proximal measurements, suggesting the robustness of the signal that persists over weeks and under different gradients of availability and leaf nitrogen content. Nighttime stomatal conductance was unaffected by manipulation treatments, while application of high vapor pressure deficit conditions nullifies the differences between treatments. Genotypic variation for transpiration increase under limited availability was observed between rootstocks indicating that breeding (e.g., for high soil pH tolerance) unintentionally selected for enhanced mass flow nutrient acquisition under restrictive or nutrient-buffered conditions. We provide evidence of a series of specific traits modulated by availability and suggest that fertilization is a potential candidate for optimizing grapevine water-use efficiency and root exploration under the climate-change scenario.

Analysis of growth resistance mechanisms and causes in tea plants (Camellia sinensis) in high-pH regions of Northern China.

In tea plantations with high-pH (pH > 6.5) in Northern China, tea plants are prone to yellowing disease, albinism, and reductions in components that contribute to plant quality, which affect the scale and rate of tea plantation development in Northern China. To investigate the potential causes of these issues, Camellia sinensis cv. Pingyang Tezao and Camellia sinensis cv. Ruixue were planted in Shouguang city (a high-pH area, soil pH > 6.5) and Rizhao city (a normal-pH area, soil pH is 4.5-5.5), respectively; differences in growth morphology, pigment content, cell structure, quality-determining components, and element content of the two varieties in the two areas were analyzed. The results showed that tea leaves planted in Shouguang had varying degrees of yellowing disease and albinism; the pigment content in both varieties was significantly lower when planted in Shouguang compared with Rizhao. The cell structure was severely damaged and the main quality-determining components were decreased. Nitrogen (N), phosphorus (P), potassium (K), zinc (Zn), copper (Cu) and manganese (Mn) contents in the leaves of the two tea plant varieties were significantly lower when planted in Shouguang compared with those in Rizhao; the levels of these elements in Shouguang soil were significantly higher than in Rizhao soil. Calcium (Ca) contents in Shouguang soil was 9.90 times higher than that of Rizhao soil. We conclude that the soil in high-pH areas hindered tea plant uptake of N, Zn, Cu, and Mn, which had a detrimental effect on chloroplasts and reductions in chlorophyll synthesis, contributing to yellowing disease and albinism. In addition, excessive calcium (Ca) in Shouguang soil was also an important contributor to these negative effects. High-pH soil hindered tea plant uptake of P and K, resulting in reductions in tea polyphenols, amino acids, and other major quality components.

Clean application of pistachio residues-based vermicompost with γ-aminobutyric acid can alleviate the negative effects of high soil pH on P uptake in saffron (Crocus sativus L.)

In semiarid areas dominated by calcareous soils, a large portion of available P may be deformed into insoluble structures due to the chemical activity of carbonate compounds. This phenomenon, known as P deficiency stress, is considered one of the most important limiting factors for saffron (Crocus sativus L.) production. To avoid P limitation, the application of clean and practical techniques has been emphasized to improve saffron adaptability grown in P-deficient calcareous soils. Hence, field experiments were conducted based on a factorial randomized complete block design with three replicates during 2017–2018 and 2018–2019 (farm 1) and repeated during 2018–2019 and 2019–2020 growing seasons (farm 2). Four levels of γ-aminobutyric acid (GABA) (0, 0.5, 1, and 2 mg L−1) and soil amendments (control, pistachio residues-based vermicompost (VP: 10 t ha−1; 50% in each growing season), sulfur (S: 100 kg ha−1; 50% in each growing season), and VP +S) were considered as experimental factors. From the results, application of VP, S, and VP+S decreased soil pH and increased Olsen-P, microbial biomass, and microbial respiration. Furthermore, the increase was observed for flower number, proline content and corm growth. Following GABA foliar application, flower number, proline content and P availability improved. Compared to control treatment, P concentration in large-sized daughter corms increased by 23.6, 16.8%, and 30.8%, following VP, S, and VP +S, respectively. Among the treatments, the highest P acquisition efficiency (39.2%) were recorded by applying VP +S along with 2 mg L−1. Overall, the results recommend the co-application of VP with GABA foliar spray to improve saffron production grown in calcareous soils of semiarid regions.

Partial Substitution of Urea with Biochar Induced Improvements in Soil Enzymes Activity, Ammonia-Nitrite Oxidizers, and Nitrogen Uptake in the Double-Cropping Rice System.

Biochar is an important soil amendment that can enhance the biological properties of soil, as well as nitrogen (N) uptake and utilization in N-fertilized crops. However, few studies have characterized the effects of urea and biochar application on soil biochemical traits and its effect on paddy rice. Therefore, a field trial was conducted in the early and late seasons of 2020 in a randomized complete block design with two N levels (135 and 180 kg ha-1) and four levels of biochar (0, 10, 20, and 30 t ha-1). The treatment combinations were as follows: 135 kg N ha-1 + 0 t B ha-1 (T1), 135 kg N ha-1 + 10 t B ha-1 (T2), 135 kg N ha-1 + 20 t B ha-1 (T3), 135 kg N ha-1 + 30 t B ha-1 (T4), 180 kg N ha-1 + 0 t B ha-1 (T5), 180 kg N ha-1 + 10 t B ha-1 (T6), 180 kg N ha-1 + 20 t B ha-1 (T7) and 180 kg N ha-1 + 30 t B ha-1 (T8). The results showed that soil amended with biochar had higher soil pH, soil organic carbon content, total nitrogen content, and mineral nitrogen (NH4+-N and NO3--N) than soil that had not been amended with biochar. In both seasons, the 20 t ha-1 and 30 t ha-1 biochar treatments had the highest an average concentrations of NO3--N (10.54 mg kg-1 and 10.25 mg kg-1, respectively). In comparison to soil that had not been treated with biochar, the average activity of the enzymes urease, polyphenol oxidase, dehydrogenase, and chitinase was, respectively, 25.28%, 14.13%, 67.76%, and 22.26% greater; however, the activity of the enzyme catalase was 15.06% lower in both seasons. Application of biochar considerably increased the abundance of ammonia-oxidizing bacteria (AOB), which was 48% greater on average in biochar-amended soil than in unamended soil. However, there were no significant variations in the abundances of ammonia-oxidizing archaea (AOA) or nitrite-oxidizing bacteria (NOB) across treatments. In comparison to soil that had not been treated with biochar, the average N content was 24.46%, 20.47%, and 19.08% higher in the stem, leaves, and panicles, respectively. In general, adding biochar at a rate of 20 to 30 t ha-1 with low-dose urea (135 kg N ha-1) is a beneficial technique for improving the nutrient balance and biological processes of soil, as well as the N uptake and grain yield of rice plants.

Plant material decomposition and bacterial and fungal communities in serpentine and karst soils of Japanese cool-temperate forests

ABSTRACT We aimed to reveal the plant material decomposition rate and abundance of bacteria and fungi in serpentine and karst sites of cool-temperate forests. Given the relatively higher soil pH, we hypothesized a higher decomposition rate of cellulose, lower decomposition rate of lignin-containing plant materials, and lower fungi-to-bacteria ratio in serpentine and karst sites than in neighboring non-serpentine/non-karst sites. This study was conducted on serpentine and mudstone sites in deciduous oak forests on Mount Oe and karst and sandstone sites on Mount Ibuki, Japan. We performed a decomposition experiment over 5 months using three chemically distinct materials: cellulose filter, lignin-containing coffee filter, and green tea leaves. These common materials enabled us to compare the in-situ utilization of different carbon substrates by microbial communities between sites. The abundance of bacteria and fungi and their ratio in topsoils and materials that decomposed for 1 month were assessed using quantitative PCR. In contrast to our hypothesis, the decomposition rate was higher in the mudstone site for cellulose and did not differ for the coffee filter compared to the serpentine site. Green teas with higher lignin content than coffee filters decomposed slower at the serpentine site only during the early period of decomposition. The serpentine site showed higher fungi-to-bacteria ratios in the decomposed materials and soil. The karst site also showed different decomposition patterns than our prediction, presenting no clear difference in the cellulose filter compared to the sandstone site. In the karst site, coffee filters decomposed faster at the early period; however, green teas decomposed slower as we expected, especially at the later period of decomposition. The karst site had a lower fungi-to-bacteria ratio in the topsoil, but similar fungi-to-bacteria ratios in the decomposed materials compared with the sandstone site. Our results suggest that the decomposition patterns in the serpentine and karst soils are not simply predicted based on soil pH and other distinct characteristics (e.g., soil moisture content and heavy metal concentration) would more strongly contribute to decomposition and microbial community composition in the study mountains.

Decoupling of cellulose decomposition and glucose mineralization in volcanic forest soils

ABSTRACT Decomposition of organic matters in volcanic soils (ando soils) is generally slowed by sorption onto short-range-order minerals, while decomposition of non-charged substrates such as cellulose and glucose is hypothesized to be promoted by high microbial biomass and nitrogen availability, irrespective of short-range-order minerals. To analyze factors regulating decomposition activities of cellulose and glucose, we measured the decomposition rates of cellulose filter papers and the mineralization rates of 14C-labeled glucose in five volcanic soils in Japan. Glucose mineralization activities increased with increasing microbial biomass C and N, while cellulose decomposition activities (standardized with cumulative temperature) were not related to microbial biomass C or N. Cellulose decomposition activities increased with increasing ratio of soil available N relative to microbial biomass N (microbial N availability), while they decreased with decreasing soil pH and with increasing fungal activities. Soils with relatively high soil pH and microbial N availability exhibit the relatively high potentials of cellulose decomposition. Because cellulose decomposition, rather than glucose mineralization, is a rate-limiting step, soil pH and microbial N availability, rather than microbial biomass, could primarily regulate decomposition rates of cellulose and glucose in volcanic soils.