Average Soil pH Research Articles

Cropland acidification increases risk of yield losses and food insecurity in China

Distinct cropland acidification has been reported in China due to nitrogen (N) fertilizer overuse. However, the impacts on food production and thereby on food security are largely unknown. Yield losses in the period 1980–2050 were therefore assessed by simulating soil pH changes combined with derived pH-yield relationships for wheat, maize and rice. If the N fertilizer input continues to increase at 1% annually, the predicted average soil pH decline is about one unit and relative yield losses are expected to increase from approximately 4%–24% during 2010–2050. If the N fertilizer increase stops in 2020 (N2020), the expected losses are approximately 16% in 2050, which is comparable to a scenario of 100% crop residue return (100%RR). However, if 30% of the N fertilizer is replaced by manure N (30%MR), the losses reduce to near 5% in 2050. Soil acidification was predicted to reverse and expected losses are only 2.5% in 2050 in a combined scenario of N2020, 100%RR and 30%MR. Our results illustrate the potential food insecurity induced by cropland acidification and address the necessity of mitigation.

Soil quality decrease over 13 years of agricultural production

Soils are a key issue in the management of global environmental changes and food supply. The goal of this work was to characterize the soil changes that were promoted by agriculture in Uruguay in the period 2002–2014. We analysed the association between pH, Ca2+, Mg2+, K+, Na+ and soil organic carbon (SOC) and its tendency through the years of soil analysis database 2002–2014 that belong to Experimental Station Alberto Boerger INIA La Estanzuela (Colonia, Uruguay). During the study period, the average soil pH, SOC, and exchangeable base content across the archive sample set were reduced. The exchangeable K+ content decreased by 0.04 mmol kg−1 year−1 with the increase in grain production. The SOC decreased by 0.43 mg (g year)−1 even when most agricultural activity followed a no-tillage system. A reduction of 0.02 units of pH per year also occurred. If these changes continue in the future, agricultural soils will significantly decrease their food production potential, and will not be adequate for sustainable crop production.

The first tropical ‘metal farm’: Some perspectives from field and pot experiments

Agromining is the chain of processes of phytoextraction of economically valuable elements by selected hyperaccumulator plants, and subsequent processing of biomass to produce targeted metals or commercial compounds of high value. Although substantial unrealized opportunities exist for developing economic nickel (Ni) agromining in the tropics, this technology has remained relatively unexplored. This study investigated the soil chemistry of a newly established tropical ‘metal farm’ and elucidated the performance of a prospective ‘metal crop’ species (Phyllanthus rufuschaneyi) to be used in a large-scale tropical Ni agromining program on ultramafic soils in Sabah (Malaysia). We found that a major portion of the site (>90%) had high total Ni concentrations (>2000 μg g−1) in the soil (shallow Eutric Cambisol Magnesic). This study also recorded high phytoavailable soil Ni concentrations in the field site, which is a desired property of soils intended for Ni agromining. Moreover, the average soil pH of the field (pH 6.4) is ideal for maximum Ni uptake in the local candidate species. We recorded low concentrations of Ca, K and P, suggesting the need for a fertilizer regime in the farm. The extraordinary shoot Ni concentrations (>2 wt%), coupled with the high purity of the ‘bio-ore’ derived from Phyllanthus rufuschaneyi, confirm its high potential for economic Ni agromining. The success of our first field trial is critical to provide ‘real-life’ evidence of the value of large-scale tropical ‘metal farming’. Research priorities include the need to intensify the search for candidate species, determine their agronomy, develop mass propagation methods, and to test technologies to process the biomass to recover valuable products.

Effects of biochar amendment on net greenhouse gas emissions and soil fertility in a double rice cropping system: A 4-year field experiment

A 4-year field experiment was conducted to investigate the effects of biochar amendment on the net greenhouse gas emission (NGHGE), greenhouse gas intensity (GHGI), soil fertility and crop yield in a typical double rice cropping system in the central subtropics of China, from April 2012 to April 2016. Three biochar treatments were studied in this experiment, with application rates of 0, 24 and 48 t ha−1 (named CK, LB and HB, respectively) using straw-derived biochar applied once at the beginning of the experiment. In each treatment, the fluxes of methane (CH4), nitrous oxide (N2O) and soil heterotrophic respiration (Rh) were measured using a static chamber/gas chromatography method. Major soil fertility properties were also determined throughout the experimental period. Biochar amendment was found to persistently decrease annual total CH4 emissions by 20 to 51% in the four years, but increased the annual total N2O emissions and Rh by 150 to 190% and 2 to 19% in the first year and the following three years, respectively. On a 4-year average, biochar addition significantly reduced annual NGHGE and GHGI by 156 to 264% and 159 to 278%, respectively (p < 0.05), with much higher reduction in the first year than those in the following three years (916 to 1911% vs 24 to 51%) due to soil carbon sequestration from biochar addition in the first year. The reduction of NGHGE and GHGI was mainly caused by the decrease of CH4 emissions (71 to 74% contribution), and the increase of soil carbon sequestration (25 to 29% contribution) in biochar treatments. Biochar amendment also significantly and persistently increased soil pH, total organic carbon (TOC), total nitrogen (TSN), and total phosphorus (TSP) by 6 to 14%, 33 to 61%, 11 to 15%, and 9 to 12%, respectively (p < 0.05), in the four years. Significant increases (p < 0.05) of microbial biomass carbon and nitrogen contents were found only in the first year after biochar amendment. Soil pH was also increased significantly (p < 0.05) with biochar amendment, but showed a declining trend in the four years. Annual grain yields for the biochar treatments were enhanced by 1 to 13%, with an average of 4 to 7% in the four years, compared to CK (p = 0.07–0.26). Compared to the LB treatment, the HB treatment significantly decreased average NGHGE and GHGI, and significantly increased average soil pH value and TOC content, but there was no significantly difference in average TSN, TSP, and yield between LB and HB treatments (p < 0.05). The gross margin analysis by considering the profit from rice grain, gain for NGHGE, and cost for biochar indicated that the economical profit for the LB treatment might be higher than that for the CK and HB treatments. Our results suggest that addition of biochar at 24 t ha−1 can be regarded as a consistently effective and economic measure for greenhouse gas emission mitigation, and soil fertility improvement, in the double rice cropping system.

Immobilization of lead in shooting range soil using biochar from spent mushroomsubstrateImmobilization of lead in shooting range soil using biochar from spent mushroomsubstrate

Spent mushroom substrate (SMS) was pyrolyzed at 450°C for 2 hours and characterized using elemental analyzer and Boehm titration. Shooting range soil was incubated with 2.5% w/w and 5.0% w/w of SMSB for four weeks and the soil were characterized on the elemental composition, pH, electric conductivity (EC) and cation exchange capacity (CEC). The mobility of Pb in the incubated soil were studied using a modified selective sequential extraction (SSE) scheme. Total Pb in shooting range soil is 29385.5 mg/kg. The texture of shooting range soil is loamy sand with an average soil pH of 4.69, EC value 0.17 mS/mand CEC value 6.0 mEq/100g. After treatment with SMSB, the soil pH and CEC were increased and the concentration of exchangeable Pb decreased. Conclusively, this study found that there is potential in using SMSB for remediating Pb contamination in the shooting range soil.

Effect of different amounts of acid application in fertigation on calcareous soil pH

ABSTRACTThis study was carried out during 3 different periods and in 24 various greenhouses. Average pH values of the irrigation water (7.61, 7.55, 7.29) and average soil pH values before fertigation (7.61, 7.57, 7.55) were measured. Average fertigation pH values were measured to be 6.80, 6.61 and 6.44. Depending on fertigation pH values, average soil pH values decreased at the rate of 0.52, 0.65 and 0.60 compared to those before fertigation. Although average soil pH decreased depending on acid doses used by growers in the greenhouse, this decrease was not sufficient. In conclusion, if growers fertilize with lower fertigation pH doses, availability of plant nutrients can be increased. Additionally, this may lead to less fertilizer use by increasing availability of fertilizers used in fertigation in soils that have calcareous and high pH values. It is clear that further studies should be done with this approach.

Soil Acidification Aggravates the Occurrence of Bacterial Wilt in South China.

Soil acidification is a major problem in modern agricultural systems and is an important factor affecting the soil microbial community and soil health. However, little is known about the effect of soil acidification on soil-borne plant diseases. We performed a 4-year investigation in South China to evaluate the correlation between soil acidification and the occurrence of bacterial wilt. The results showed that the average soil pH in fields infected by bacterial wilt disease was much lower than that in non-disease fields. Moreover, the proportion of infected soils with pH lower than 5.5 was much higher than that of non-infected soils, and this phenomenon became more obvious as the area of bacterial wilt disease increased at soil pH lower than 5.5 from 2011 to 2014. Then, in a field pot experiment, bacterial wilt disease developed more quickly and severely in acidic conditions of pH 4.5, 5.0, and 5.5. These results indicate that soil acidification can cause the outbreak of bacterial wilt disease. Further experiments showed that acidic conditions (pH 4.5–5.5) favored the growth of the pathogen Ralstonia solanacearum but suppressed the growth and antagonistic activity of antagonistic bacteria of Pseudomonas fluorescens and Bacillus cereus. Moreover, acidic conditions of pH 5.5 were conducive to the expression of the virulence genes PopA, PrhA, and SolR but restrained resistance gene expression in tobacco. Finally, application of wood ash and lime as soil pH amendments improved soil pH and reduced the occurrence of bacterial wilt. Together, these findings improve our understanding of the correlation between soil acidification and soil-borne plant diseases and also suggest that regulation of soil acidification is the precondition and foundation of controlling bacterial wilt.

Effect of organic amendments and microbial application on sodic soil properties and growth of an aromatic crop

In this experiment, we studied the effects of microbial inoculation, vermicompost and sludge application on physical, chemical and microbial properties of sodic soil and growth of Ocimum basilicum (holy basil). Sodic soil collected from natural field was amended with two bacterial strains A and C (isolated from the same soil), vermicompost and tannery sludge @ 5tha−1 upto 0–15cm soil depth of field buried cement barrels (125cm height, 49.5cm diameter) in such a way that nine treatments (control sodic soil (T0), vermicompost or VC (T1), VC+strain A (T2), VC+strain C (T3), VC+strain A and C (T4), tannery sludge or TS (T5), TS+strain A (T6), TS+strainC (T7), and TS+strain A and C (T8) were formed. After application of these treatments, soil was incubated for one month at constant moisture. After one month of incubation period, 35 days old seedlings of O. basilicum were planted in barrels. Significant changes in soil properties (physico-chemical, microbial and enzyme activities), due to application of microbes and organic amendments, were observed after one month of incubation (AIS) and at crop harvest (ACH). On an average soil pH, electrical conductivity (EC), exchangeable sodium (Na), soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), soil respiration (SR), microbial quotient (Cmic:Corg), and metabolic quotient (qCO2) were significantly higher in incubated soils than crop harvested soils. Study concludes that use of vermicompost, sludge and microbial inoculants increase soil fertility and enhance yield and oil quality of Ocimum basilicum. Furthermore, incubation for one month before crop plantation was sufficient time for amendments to facilitate changes in sodic soil properties.

Effects of Liming to Near-neutral pH on Vitis vinifera L.

Wine grape vines are sensitive to soil pH and liming. The effects of pre-plant liming at rates sufficient to promote average soil pH levels (1M KCl) of 5.05 (unlimed, treatment L0), 5.64 (L1) and 6.56 (L2) in two wine grape (scion) varieties and four rootstocks five years after planting were investigated over six seasons in a factorial field trial at Stellenbosch. Yields tended to decrease in the sequence: L0 > L1 > L2, and were significantly (P = 0.05) lower in L2 than in L0. Conversely, cane masses increased progressively with lime application rate, with L1 exceeding L0 by 11.0% and L2 exceeding L1 by 13.0%. These increases were significant. Compared to L0, liming decreased the ratio of yield to cane mass by 13.6% in L1 and 28.8% in L2, but increased Ca:Mg ratios in the soil and petioles. Wine quality was significantly better from L0 than L2. Petiole N concentrations were above normal in all treatments. Suppressed yields and wine quality in the limed treatments were attributed to a lime-induced imbalance between vegetative and reproductive growth, possibly exacerbated by increased Ca:Mg ratios and excess nitrogen.

Effects of liming and selected heavy metals on ammonium release in waterlogged agricultural soils

Many farmlands are periodically flooded or ponded by excessive precipitation resulting in changes to soil chemical and biochemical properties. In this study, one set (eight treatments with four replications) of field-moist surface soils (0–15 cm) and their air-dried counterparts obtained from a long-term liming experiment were incubated at 30 °C under waterlogged conditions for 10 days, and the amounts of net NH4+-N released (soluble and exchangeable) were determined after extraction with 4 M KCl. Another set of three surface soils were used to evaluate the effect of six heavy metals on the NH4+-N release under waterlogged conditions. Results showed that increasing the liming rate from 0 to 17,930 kg ha−1 effective calcium carbonate equivalent increased the average soil pH from 4.98 to 7.06, averages of the amounts of NH4+-N released ranged from 1.6 to 5.2 mg N kg−1 field-moist soil, and the corresponding amounts released in air-dried soils ranged from 18.9 to 32.9 mg N kg−1 soil. This increase of the amount NH4+-N released in air-dried soil samples is presumably due to a slaking effect. At 5 mmol kg−1 soil, all six heavy metals inhibited the NH4+-N released. The relative effectiveness of the heavy metals in inhibition of the NH4+-N released varied among the three soils. Lead(II) was the most effective inhibitor of NH4+-N release in Clarion and Harps soils and Cd(II) in Harps soil. Cobalt(II), Cu(II), and Cd(II) were the least effective inhibitors of NH4+-N release in Clarion, Harps, and Okoboji soils, respectively.

Changes of weed infestation under long-term effect of different soil pH levels and amount of phosphorus:potassium

ABSTRACTThe aim of the present study was to investigate changes of weed species density as a result of long-term (1976–2005) exposure to different soil pH levels, and P2O5:K2O amount in soil created by initial and subsequent periodical liming, and fertilization. As a result of liming during the period 1976–2005, average soil pH levels at the start of the sixth crop rotation (2001–2005) ranged from 4.1 (unlimed) to 6.6. And in each pH plot were four sub-plots with a different amount of mobile phosphorus:potassium. In acid soil (pH 4.1), in spring oilseed rape and in spring barley crops, the dominant weed Spergula arvensis density decreased significantly at a pH of 5.1 or higher. With increasing amount of P2O5:K2O in soil, the abundance of S. arvensis in spring rape and spring barley crops was reduced at all soil pH levels. At pH 5.1, Chenopodium album and Tripleurospermum perforatum were prominent. Elytrigia repens tended to decrease with increased alkalinity and nutrient amount in soil. With reduction of soil acidity from pH 4.1 to 6.6, the total weed infestation consistently declined in all crops. A low amount of P2O5:K2O in soil caused the decline in the abundance of S. arvensis, E. repens and increase in C. album and T. perforatum.

Comportamiento del pasto Taiwán (Pennisetum purpureum) fertilizado con efluente de biogas en época de máxima precipitación pluvial

This work was conducted at the Centro Universitario Regional del Litoral Atlántico (CURLA) at 15°47’north latitude and 86°50’ west longitude, 10 km west La Ceiba, Honduras. The ecosystem Is characterized as tropical rain forest having 2700 mm of rainfall per year and an average annual temperature of 27°C with 82% relative humidity. Soils in the region are characterized by having an average soil pH of 4.9, have low levels of available N and P, high levels of Fe and intermediate levels of Mn. A randomized complete block design was employed with 4 replications. Plot size was 2 x 3 m encompassing 3 rows. In each block three rates of biogas effluent were applied at 250,500 and 750 kg N/ha/year. An added check with zero effluent was also included. The grass was cut at the surface of the soil every 56 days and the application of effluent was made in split applications. The results indicate that these treatments increased yield at least 25 % above the check. In the first cuttings there was a tendency to decrease yields although final cuttings demonstrated increased yields. This same response was observed in plant protein, especially in the last cutting where a 48 % increase was obtained. The best treatmentrelative to forage production and protein content was found when 500 kg N/ha/year was applied.

Punjab-Soil Health and Green Revolution: A Quantitative Analysis of Major Soil Parameters

ABSTRACTSoil health in the Indian Punjab has been a debatable issue for the last two decades mainly because of lack of pragmatic scientific inquiry. The currently available literature not only seems in contradiction but also limited relative to investigation of the soil health in the light of sustainability indicators. The current systematic and multifaceted study was designed to provide a deep understanding of the soil health issues in Punjab, the epicenter of “green revolution,” in the light of socioeconomic factors. The results should be applicable to the entire Indo-Gangetic Plain. We used a database of 120 soil samples to measure the current state of soil health in Punjab and pointed out the main socioeconomic factors that affected it. The results were compared and contrasted with the available literature to investigate the temporal changes in soil health between 1980–1981 and 2010–2011. Results revealed average soil pH to be 8.2; electrical conductivity (EC) 0.27 dS/m; organic carbon (OC) 0.49%; available phosphorus (P) content 17 mg/kg soil; and available potassium (K) content 171 mg/kg soil. Besides agro-climatic conditions, the size of landholding and farmer education showed a significant association with soil health. Large landowners had healthier soils than the small and medium holders. Contrary to expectations, graduate farmers had poorer soils than those who were either illiterate or possessed average education. An examination of the temporal changes revealed that Punjab soils had become healthier across time, particularly with respect to OC, P, and K. The pH exhibited a declining trend, whereas EC stayed almost constant between 1980–1981 and 2010–2011. Crop intensity had no negative impacts on soil health; therefore, farmers may grow leguminous crops during April--May as third (Zaid) crop, which will not only improve soil nitrogen supply but also fetch additional earnings.

Characteristics of Soil Chemical Properties in Abandoned Coal Mine Forest Rehabilitation Areas in Boryeong City, Chungcheongnam-do

The objectives of this study were to investigate soil chemical characteristics for forest rehabilitation and suggest management in abandoned coal mine areas in Boryeong City, Chungcheongnam-do. Total study sites were seven sites, and soil properties analyzed were soil pH, total organic carbon (TOC), total-N, C/N ratio, and available P2O5 (A.v. P). Average soil pH (range) was 5.9 (4.5～7.0). Three study sites (Samgwang, Shinsung1, and Shimwon1) showed lower soil pH than standard (pH 5.6~7.3) of Korea Industrial Standards (KS) for abandoned coal mine forest rehabilitation. Average contents of TOC, and total-N were 1.5% (0.1～4.7%), and 0.10% (0.03～0.23%), respectively. Five study sites where the collapsed time was less than 10 years (Wangjashingang, Wonpoong, Samgwang, Shinsung1, and Shinsung2) showed lower TOC level than standard of KS (more than 1.2%). Wangjashingang, Wonpoong, Samgwang, and Shinsung1 showed lower level of total-N than standard of KS (more than 0.09%). C/N ratio of six study sites except Shimwon1 was out of proper range (15:1~30:1). Average A.v. P (range) was 20.7 mg kg-1(4.8～63.1), less than other abandoned coal mine fores rehabilitation areas in Mungyong City, and Hwasun-gun. TOC, total N and A.v. P increased with elapsed time from forest rehabilitation, while other soil properties did not show distinct pattern. Betula platyphylla was planted in Samkwang and Sinsung where soil pH was less than KS standard. Because the growth of Betula platyphylla can be limited in acid soil, it is necessary to neutralize soil pH to proper level with some soil amendment such as lime or shell of oyster. Furthermore, TOC, total-N and A.v. P in early stage of forest rehabilitation showed lower level than proper to vegetation growth. Therefore it needs continuous monitoring of soil characteristics and fertilization for vegetation growth and influx from surrounding forest in early stage of rehabilitation.

Long-Term Trends of Nitrogen and Phosphorus Use and Soil pH Change in Northern Idaho and Eastern Washington

ABSTRACTExtension educates growers about using best management practices (BMPs) for nutrient management. However, it is important to understand grower management trends to prepare the best possible educational programs for growers. Three mail-based grower surveys conducted in 1981, 1996, and 2011 were used to document changing nitrogen (N) and phosphorus (P) fertilizer use and soil pH trends in the >450-mm precipitation zone of northern Idaho and eastern Washington, USA. The information collected in this paper spans a 40-year period. Nitrogen application rates have slightly increased, while P application rates on cereal crops have remained constant over the past 40 years. Average soil pH values have declined significantly over this time period; however, only about half of the surveyed growers were aware of this. This study is valuable because it (1) contains important information provided by growers on fertilization trends for the past 40 years (1971 to 2011), (2) quantifies the awareness of growers about soil pH decline in the region, and (3) provides baseline information, which can be used both in educational programming and to compare with future nutrient management.

English

The present study was carried out in two grass land of Kumrat Dir Kohistan, North Hindukush regions of KPK Pakistan. Locally these two grass land are known as Roshi Dab and Bothore Dab. The area of these two Dabs is about 400 hectare. The elevation of these two Dabs ranges from 7665 feet to 7954 feet while the geographic location of the study site was N 35&deg; 33.249&rsquo; and E 72&deg; 12.258&rsquo;. Stratified random sampling method was used for data collection. 18 soil samples were taken with the depth of 0-15 cm and 16-30 cm. The average soil pH was 5.3. The mean soil bulk density was 1.107 -g/cm3. In present study it was found that the undisturbed range land stored maximum amount of soil carbon (32.69 tons hac-1) as compare to range land near to the agriculture land (29.77 tons hac-1) Similarly the rangeland near to forest land stored 35.62 t ha-1 carbon, also stored more carbon as compare to range land near to agriculture land 29.77 t ha-1. The results of the present study confirmed that conversion of range land into agriculture land reduced the soil carbon in the study area. &nbsp; Key words: Carbon stocks, climate change, soil bulk density, range lands, forestry. &nbsp

인천국제공항 식재기반 구조 및 토양특성 연구

This study aims to suggest adequate soil management through the analysis of physicochemical properties of soil in the planting grounds of Incheon International Airport, which was constructed on a massive land reclamation site. Study areas were 5 sites at the international business complex, the passenger terminal, the airport support complex, the free trade zone, and the access road. Soil profile analysis showed that 9 plots out of the 27 plots were hardpan and heterospere within 80cm from the soil surface. The earth laid on the ground was categorized as gravel based soil(4 plots), dredged soil from the sea bottom and mixed reclamation materials(2 plots), clay with poor permeability(3 plots) and waste construction material(1 plot). Average soil hardness was and soil textures were sandy soil, sandy loam and loamy sand. Average soil pH was 6.7 and average organic matter content was 0.7%. Electrical conductivity was 0.0dS/m and exchangeable cation concentrations were 3.4cmol/kg, 1.5cmol/kg, 0.3cmol/kg and 1.0cmol/kg. Average cation exchange capacity was 11.0cmol/kg. Although average figures in Solum mostly meet the landscape design criteria, properties of each soil layer showed various values sometimes over the limit. Base saturations were 29.9%, 13.3% and 3.7% for lower soil, 33.3%, 17.0% and 2.7% for mid-soil and 32.6%, 12.2% and 1.9% for upper soil. Exchangeable sodium percentages were 16.4% for lower soil, 7.5% for mid-soil and 4.7% upper soil. Sodium adsorption rates were 0.8 for lower soil, 0.3 for mid-soil and 0.2 for upper soil. Factors affecting to the vegetation growth were heterogeneity and poorness of solum, disturbance of dredged soils, high soil hardness including hardpan in the subsurface soil layer and shallow effective soil depth, high soil acidity, imbalance of base contents, low organic matter content and low available phosphate levels in the soil.

Critical appraisal of assumptions in chains of model calculations used to project local climate impacts for adaptation decision support—the case of Baakse Beek

In order to enable anticipation and proactive adaptation, local decision makers increasingly seek detailed foresight about regional and local impacts of climate change. To this end, the Netherlands Models and Data-Centre implemented a pilot chain of sequentially linked models to project local climate impacts on hydrology, agriculture and nature under different national climate scenarios for a small region in the east of the Netherlands named Baakse Beek. The chain of models sequentially linked in that pilot includes a (future) weather generator and models of respectively subsurface hydrogeology, ground water stocks and flows, soil chemistry, vegetation development, crop yield and nature quality. These models typically have mismatching time step sizes and grid cell sizes. The linking of these models unavoidably involves the making of model assumptions that can hardly be validated, such as those needed to bridge the mismatches in spatial and temporal scales. Here we present and apply a method for the systematic critical appraisal of model assumptions that seeks to identify and characterize the weakest assumptions in a model chain. The critical appraisal of assumptions presented in this paper has been carried out ex-post. For the case of the climate impact model chain for Baakse Beek, the three most problematic assumptions were found to be: land use and land management kept constant over time; model linking of (daily) ground water model output to the (yearly) vegetation model around the root zone; and aggregation of daily output of the soil hydrology model into yearly input of a so called ‘mineralization reduction factor’ (calculated from annual average soil pH and daily soil hydrology) in the soil chemistry model. Overall, the method for critical appraisal of model assumptions presented and tested in this paper yields a rich qualitative insight in model uncertainty and model quality. It promotes reflectivity and learning in the modelling community, and leads to well informed recommendations for model improvement.

铅锌矿冶区水稻土氟污染状况及污染源分析

以华南某铅锌矿冶区周边农田为研究对象，利用网格布点法，系统调查研究区域水稻土氟污染状况，开展铅锌矿冶区周边农田土壤氟污染源分析。结果表明，水稻田土壤氟污染严重，73%的采样点土壤氟含量超过800 mg∙kg−1，土壤氟含量平均值高达1118 mg∙kg−1；土壤健康指数平均值为1.36，绝大部分采样区域处于土壤高氟污染区，易诱发地氟病；土壤pH值、铅锌含量与水稻土氟的分布存在相关关系，土壤氟含量与土壤pH值呈正相关，与土壤铅含量呈负相关；萤石矿开采和伴生萤石矿的开采是水稻土氟污染的主要来源。研究结果将为掌握当地土壤氟污染状况、预防地氟病发生、改善水稻田土壤环境提供科学依据。 Fluorine pollution of a certain lead-zinc mining area and pollution sources of surrounding farmlands were investigated using mesh points method. The results showed that the fluorine pollution of the paddy soils was serious, with 73% of sampling areas higher than 800 mg∙kg−1, which would easily lead to endemic fluorosis. Average soil fluorine content was 1118 mg∙kg−1, and the average soil health index of fluorine was 1.36, and average soil pH was 5.40. Soil lead contents were ranged from 43 mg∙kg−1 to 4961 mg∙kg−1, with an average of 517 mg∙kg−1. Soil zinc contents were ranged from 83 mg∙kg−1 to 4620 mg∙kg−1, with an average of 650 mg∙kg−1. Moreover, fluorine contents were significantly positively correlated with pH (P < 0.05), and negatively correlated with lead contents. Fluorite mining, mineral mine mining and smelting may be the main sources of fluorine pollution in paddy soils of the investigated area. Soil parent material, pesticides and chemical fertilizers could cause fluorine contamination in the paddy soils. The research is potential for improving soil environments and the control of endemic fluorosis.

Estimation of time elapsed since the death from identification of morphological and histological time-related changes in dental pulp: An observational study from porcine teeth.

Aim:Putrefaction of the human body with its rate and stages of the various changes occurring in this entire process have been explored widely by the forensic medicine experts to estimate the time elapsed since death. However, experimental data reported in literature pertaining to rates of putrefaction of the dental pulp retrieved from jaws of the dead is scarce. This study makes an attempt to find out the series of various changes which occur during the process of putrefaction of the dental pulp in a coastal environment like that of Southern India. An attempt has also been made to estimate the time elapsed since the death by assessing the duration for which dental pulp remains microscopically intact.Materials and Methods:Three different study setups at different times, followed one by other were created. In each setup, 10 specimens of porcine jaws with teeth were buried in surface soil and 10 specimens in subsurface soil. Dental pulp was retrieved at an interval of every 24 h to see for the various changes. All the environmental parameters including average daily rainfall precipitation, temperature, soil humidity, soil temperature, and soil pH were recorded.Results:A specific series of morphological changes in terms of changes in size, color, consistency, and odor; and a sequence of histological changes were observed from both surface and subsurface samples.Conclusion:Dental pulp buried in a coastal environment goes through a specific series of morphological and histological changes which can be interpreted up to 144 h from burial, after which pulp ceases to exist.