Mehlich 3 Research Articles

LOSS OF EXTRACTION CAPACITY OF MEHLICH-1 AND MONOCALCIUM PHOSPHATE AS A VARIABLE OF REMAINING P AND ITS RELATIONSHIP TO CRITICAL LEVELS OF SOIL PHOSPHORUS AND SULFUR

The Mehlich-1 (M-1) extractant and Monocalcium Phosphate in acetic acid (MCPa) have mechanisms for extraction of available P and S in acidity and in ligand exchange, whether of the sulfate of the extractant by the phosphate of the soil, or of the phosphate of the extractant by the sulfate of the soil. In clayey soils, with greater P adsorption capacity, or lower remaining P (Rem-P) value, which corresponds to soils with greater Phosphate Buffer Capacity (PBC), more buffered for acidity, the initially low pH of the extractants increases over their time of contact with the soil in the direction of the pH of the soil; and the sulfate of the M-1 or the phosphate of the MCPa is adsorbed by adsorption sites occupied by these anions or not. This situation makes the extractant lose its extraction capacity, a phenomenon known as loss of extraction capacity or consumption of the extractant, the object of this study. Twenty soil samples were chosen so as to cover the range of Rem-P (0 to 60 mg L-1). Rem-P was used as a measure of the PBC. The P and S contents available from the soil samples through M-1 and MCPa, and the contents of other nutrients and of organic matter were determined. For determination of loss of extraction capacity, after the rest period, the pH and the P and S contents were measured in both the extracts-soils. Although significant, the loss of extraction capacity of the acidity of the M-1 and MCPa extractants with reduction in the Rem-P value did not have a very expressive effect. A “linear plateau” model was observed for the M-1 for discontinuous loss of extraction capacity of the P content in accordance with reduction in the concentration of the Rem-P or increase in the PBC, suggesting that a discontinuous model should also be adopted for interpretation of available P of soils with different Rem-P values. In contrast, a continuous linear response was observed between the P variables in the extract-soil and Rem-P for the MCPa extractor, which shows increasing loss of extraction capacity of this extractor with an increase in the PBC of the soil, indicating the validity of the linear relationship between the available S of the soil and the PBC, estimated by Rem-P, as currently adopted.

QUANTIDADE DE FÓSFORO EXTRAÍDO PELAS SOLUÇÕES DE MEHLICH-1 E MEHLICH-3 EM RAZÃO DE DIFERENTES VELOCIDADES DE AGITAÇÃO, TEMPOS DE CONTATO E TEMPERATURAS

A extração de fósforo do solo pode ser comprometida pelas condições em que a análise é realizada e isso pode explicar a variabilidade nos resultados encontrados. O objetivo deste trabalho foi verificar a influência de desvios na velocidade de agitação, no tempo de contato e na temperatura sobre a extração do P pelos extratores Mehlich-1 (M-1) e Mehlich-3 (M-3) em amostras de solo. O estudo foi conduzido por meio de três experimentos executados com 11 amostras de solo provenientes da camada arável de Latossolo, Neossolo, Argissolo, Cambissolo, Planossolo, que são representativas das regiões geomorfológicas do Planalto e da Depressão Central do Estado do Rio Grande do Sul. Para todos os experimentos, adotou-se o delineamento experimental inteiramente casualizado em esquema fatorial 2 × 5 × 11, sendo dois extratores, cinco velocidades, temperaturas ou tempos de contato solo/solução e 11 tipos de solo, com quatro repetições. No primeiro experimento, a mistura solo:solução foi agitada em 80, 100, 120, 140 e 160 oscilações por min (opm). No segundo, após a agitação por 5 min, a mistura solo:solução foi deixada em repouso por períodos de tempo de oito, 12, 16, 20 e 24 h para retirada dos extratos. No terceiro, a temperatura de execução de todo o protocolo de análises foi mantida constante em 15, 20, 25, 30 e 35 °C. O aumento na velocidade de agitação de 120 até 160 opm aumentou a quantidade de P extraído pelos extratores. O aumento no tempo de contato antes da extração da alíquota elevou as quantidades de P extraído pelo M-1 e diminuiu para o M-3. Variações na temperatura não influenciaram significativamente o extrator M-1, mas o M-3 foi mais sensível a variações. Uma padronização na velocidade de agitação, no tempo de repouso e uma climatização dos laboratórios tornam-se necessárias para diminuir a interferência causada sobre as quantidades de P extraído pelos métodos M-1 e M-3 em amostras de solo.

Transfer of cadmium and barium from soil to crops grown in tropical soils

Phytotoxicity and transfer of potentially toxic elements, such as cadmium (Cd) or barium (Ba), depend on the availability of these elements in soils and on the plant species exposed to them. With this study, we aimed to evaluate the effect of Cd and Ba application rates on yields of pea (Pisum sativum L.), sorghum (Sorghum bicolor L.), soybean (Glycine max L.), and maize (Zea mays L.) grown under greenhouse conditions in an Oxisol and an Entisol with contrasting physical and chemical properties, and to correlate the amount taken up by plants with extractants commonly used in routine soil analysis, along with transfer coefficients (Bioconcentration Factor and Transfer Factor) in different parts of the plants. Plants were harvested at flowering stage and measured for yield and Cd or Ba concentrations in leaves, stems, and roots. The amount of Cd accumulated in the plants was satisfactorily evaluated by both DTPA and Mehlich-3 (M-3). Mehlich-3 did not relate to Ba accumulated in plants, suggesting it should not be used to predict Ba availability. The transfer coefficients were specific to soils and plants and are therefore not recommended for direct use in risk assessment models without taking soil properties and group of plants into account.

Extraction of Soil Nutrients Using Mehlich-3 Reagent for Acid-Mineral Soils of Florida

Soil testing is a multistep process starting with the collection of a sample that adequately represents the area or field to be tested. Due to wide-ranging soil conditions across Florida and the United States, multiple soil test methods exist. During the 1970s, Florida along with several other southeastern US states adopted Mehlich-1 (M1) as the official extractant for acidic soils. The UF/IFAS Plant Nutrient Oversight Committee approved the change from M1 to M3 in 2010. Based on observations of the interpretations, the technical committee revised the M3 interpretation in March 2014. The new interpretations have been correlated with the M1 interpretations, as closely and realistically as possible, so the actual nutrient recommendations are not changed. This 7-page fact sheet was written by Rao Mylavarapu, Tom Obreza, Kelly Morgan, George Hochmuth, Vimala Nair, and Alan Wright, and published by the UF Department of Soil and Water Science, May 2014.
 SL407/SS620: Extraction of Soil Nutrients Using Mehlich-3 Reagent for Acid-Mineral Soils of Florida (ufl.edu)

The immobilization of heavy metals in soil by bioaugmentation of a UV-mutant Bacillus subtilis 38 assisted by NovoGro biostimulation and changes of soil microbial community

Bacillus subtilis 38 (B38) is a mutant species of Bacillus subtilis acquired by UV irradiation with high cadmium tolerance. This study revealed that B38 was a good biosorbent for the adsorption of multiple heavy metals (cadmium, chromium, mercury, and lead). Simultaneous application of B38 and NovoGro (SNB) exhibited a synergetic effect on the immobilization of heavy metals in soil. The heavy metal concentrations in the edible part of the tested plants (lettuce, radish, and soybean) under SNB treatment decreased by 55.4–97.9% compared to the control. Three single extraction methods, diethylenetriaminepentaacetic acid (DTPA), Mehlich 3 (M3), and the first step of the Community Bureau of Reference method (BCR1), showed good predictive capacities for metal bioavailability to leafy, rhizome, and leguminous plant, respectively. The polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) profiles revealed that NovoGro could enhance the proliferation of both exotic B38 and native microbes. Finally, the technology was checked in the field, the reduction in heavy metal concentrations in the edible part of radish was in the range between 30.8% and 96.0% after bioremediation by SNB treatment. This study provides a practical strategy for the remediation of farmland contaminated by multiple heavy metals.

Phosphorus-related properties in the profiles of three Italian soils after long-term mineral and manure applications

The long-term evolution (44 years) of phosphorus (P) in 1-m profile of three reconstructed soils (0–80cm=sandy, SDY; clay, CLY; and peaty, PTY; 80–100cm=native layers) typical of the Po Valley (northern Italy) has been studied in a factorial experiment with farmyard manure and mineral fertilizer. Calcium, magnesium, aluminium, and iron concentrations were determined as total (CaT, MgT) and pseuto-total (AlPT and FePT) amounts and as extractable forms by Mehlich-3 (M3) and ammonium oxalate (Ox) extracting solutions. The P distributions in total P (TP), organic P (Porg), H2SO4 P (PH2SO4), and the more mobile NH4F P (PNH4F) and NaOH P (PNaOH) were also measured.As expected soil type always influenced P sorption related soil properties. CaM3/CaT ratios indicated the presence of easily dissolved/released Ca in PTY while Al and Fe dominated in CLY and PTY soils as crystalline and poorly crystalline oxides forms. Treatments affected the pseudo-total Al and Fe with higher contents in manure than mineral, whereas mineral induced higher oxalate/total ratios of both Fe and Al than manure and untreated. Treatment affected the P content with a pattern strongly influenced by soil type and depth. Despite the comparable P balance between mineral and manure, P forms were generally higher in amended plots than mineral fertilized. Manure increased PH2SO4 down to 50cm in CLY and down to 80cm in SDY and PTY. High values of PNaOH were also induced by manure throughout the 0-80cm of SDY.The occurrence of leaching process has been indicated by the general change in some P sorption related properties and P forms found in the native layers. In particular, both stable (i.e. TP) and labile forms (i.e. PNaOH) increased following 44yr of fertilization. The phenomenon occurred not only in the overfertilized SDY but also in CLY and PTY where the P balance was negative. Long-term factors influencing the mobility of P within the soil profile are due not only to excessive P inputs, but also the forms of P fertilizer applied.

Assessing the depletion of soil P following sequential extractions with Mehlich-3 and Olsen solutions

We analyzed in soils with contrasting cultivation histories the depletion of P following sequential extractions with soil testing solutions. Soil samples were collected in three experiments in eastern Canada (L’Acadie, Lévis, and Normandin) and P was sequentially extracted 16 times, once daily, using Mehlich-3 (M3) or Olsen (Ol) solution. The cumulative amount of P extracted was 252 mg PM3 kg−1 and 77 mg kg−1 POl for L’Acadie, 212 mg PM3 kg−1 and 66 mg POl kg−1 for Lévis, and 424 mg PM3 kg−1 and 83 mg POl kg−1 for Normandin. The depletion of P was described by a logarithmic function (Y = a ln (N) + b) for PM3, and a power function (Y = αNβ) for POl. The inorganic P pool decreased in the three soils. The organic P pool did not decrease possibly because soil testing solutions did not directly extract P from this pool. This study demonstrated that laboratory soil testing analysis using M3 or Ol solution principally target P from the inorganic pool, suggesting that P fertilizer recommendations to mineral soils relying on these methods do not account for the potential of the organic P pool to contribute to soil P availability.

Availability of phosphorus for maize in crop-livestock integration system

The objectives of this study were to assess the concentrations of available phosphorus (P) extracted using the Mehlich-1 (M1), ion exchange resin (IER) and modified Morgan (MM) methods after 36 months of experimentation with the application of phosphates in a crop-livestock integration system (CLIS). Moreover, this study aimed to assess which extraction method provides the best correlation of P concentrations with the maize crop attributes. The treatments consisted of applying annual doses of P2O5 on the soil surface of the total area during the sowing of winter forage crops in the form of triple superphosphate (TSP), rock phosphate (RP) or magnesium thermophosphate (MTP). After 36 months of experimentation, soil samples were collected from the 0-5, 5-10, 10-15 and 15-20 cm layers to assess the concentrations of available P. The dry matter yield (DMY), the grain yield (GY), the accumulation of phosphorus in the dry matter (P-DM) and the export of phosphorus (P-Ex) were quantified in maize. The IER method extracted greater amounts of available P, followed by the M1 and MM extractions. The treatments that included the application of TSP and either the M1 or IER extractions had similar efficacies when correlated with the DMY, GY, P-DM and P-Ex attributes of maize. The P extracted by the IER was most correlated with P-DM and P-Ex for the water-insoluble P sources (RP and MTP). The MM solution was ineffective at predicting the availability of P for maize grown in a soil with that had received varying doses and sources of P applications in a CLIS.

What questions can be answered by chemical analysis of recent and paleosols from the Bell Beaker barrow (2500–2200 BC), Central Moravia, Czech Republic?

Mehlich 3 (M3) is the universal extraction procedure used for the analysis of plant available concentrations of many elements in agricultural and forest soils. We used this method for archaeological soils. As a huge amount of M3 background data exists, it can be used for a wide spectrum of soils and enables extraction of many elements. Using M3 together with multivariate statistics, we demonstrated the range of questions that can be answered by analysing soils from a prehistoric barrow. In soil samples collected from different barrow layers and contemporary oak wood and arable soil controls, we determined pH, organic C and total N contents and M3 concentrations of P, K, Ca, Mg, Zn, Cu, Cd and Pb. We used standardized Principal Component Analysis (PCA) to analyze the data.The dark layer beneath the barrow represented the Chernozem soil present on the site before the construction of the barrow. Natural concentrations of elements in this paleosol indicate that the area was not used for settlement, metallurgy or pottery production activities before establishment of the barrow. Chernozems were probably more widespread in the lowland regions of Central Europe in the Late Neolithic than they are today. The fertility of the paleo-Chernozem was similar to contemporary arable soil. Soil horizons characteristic of Albeluvisols and the gradual increase in soil pH and Ca concentrations with depth indicated the natural character of the barrow layers. In oak wood, Albeluvisols develop over a period longer than a century, as indicated by missing characteristic horizons in the grave pit excavated a century ago. Recent wood and arable soils were more contaminated by Pb and Cd than the paleosol, indicating modern Pb and Cd deposition.M3 extraction can be used as an international standard method for analysis of archaeological soils. Analysis of soil properties enables many questions to be answered, and therefore it should be an integral part of any archaeological research effort.

Effects of nickel and nitrogen soil fertilization on lettuce growth and urease activity

Nickel is a micronutrient involved in nitrogen metabolism and a constituent of the urease molecule. Plant growth and urease activity were evaluated in lettuce (Lactuca sativa L.) grown in soil-filled pots in a 2 x 8 factorial design with two nitrogen (N) sources and eight Ni rates, with five replications. Nitrogen was applied at 200 mg dm-3 (half the dose incorporated into the soil at seedling transplanting and half top-dressed later) using the sources NH4NO3 (AN) and CO(NH2)2 (Ur). The Ni treatments (0, 2, 4, 8, 12, 16, 24 and 32 mg dm-3) were applied as NiCl2. The shoot dry-matter yield, leaf urease activity, Ni levels in the lettuce leaves and Ni levels extracted from soil with Mehlich-3 (M-3) and DTPA were determined. In the plants supplied with AN, the shoot dry-matter yield was higher than in those supplied with Ur. There was no difference in shoot dry matter in response to soil-applied Ni. The leaf urease activity increased with Ni application, regardless of the N source. The extractions with M-3 and DTPA were efficient to evaluate Ni availability for lettuce in the Red-Yellow Latosol.

Phosphorus and potassium fertilization in no till southern Brazilian soils

Phosphorus (P) and potassium (K) levels in southern Brazilian (Rio Grande do Sul, RS) soils are largely below the critical concentrations more than four decades after implementation of the officially recommended system. This study aims to evaluate the increase in P and K levels in 0-10 and 0-20 cm deep samples from no-till soils using the Mehlich-1 (M1) and Mehlich-3 (M3) extractants as well as resin methods and to estimate the amount of P2O5 and K2O fertilizers necessary to increase the P and K soil levels by 1 mg·kg-1. The study was conducted in fields cultivated using a no-till system (direct planting) to grow soybeans, wheat, maize, pasture, and cover crops and fertilized with P2O5 and K2O. Soil samples were collected from the 0-10 and 0-20 cm soil layers and analyzed by the M1, M3, and resin methods. The results demonstrated that the P and K levels increased in the 0-10 and 0-20 cm layers. However, the amount of these levels increased depending on the source of phosphate fertilization and on the P and K extraction methods used. The amount of P2O5 fertilization needed to raise the P level by 1 mg·kg-1 was greater in the 0-20 cm layer than in the 0-10 cm layer, and the amount of K2O fertilization needed to raise the K level by 1 mg·kg-1 was higher in the 0-10 cm layer than in the 0-20 cm layer.

A Comparison of Screening Tests for Soil Pb

Soil has been identified as a significant source of lead (Pb) exposure for both children and adults. Therefore, identifying possibly contaminated soils by soil testing is important to protect public health. Soil Pb test results are usually reported as total Pb (mg kg(-1)), carried out using a concentrated nitric acid digestion procedure by hot plate (EPA method 3050) or microwave (EPA method 3051) followed by inductively coupled plasma atomic emission spectrometry to determine total Pb in the digest. However, this procedure is both time-consuming and expensive, sometimes costing homeowners and gardeners over $50 per sample. To make soil Pb testing more economically accessible to homeowners and gardeners, several university soil-testing laboratories offer less expensive screening tests designed to estimate total soil Pb. The first objective of this study was to compare three commonly used screening tests, modified Morgan (MM), Mehlich 3 (M3), and 1 M nitric acid (HNO(3)), to the standard total Pb testing method (EPA method 3051) to find which extractant is the most reliable predictor of total Pb. The second objective was to investigate the effect that different degrees of soil grinding have on the total Pb test and the extracted Pb concentration measured from the 1 M HNO(3) test. Results indicate that the strongest predictor of total Pb is 1 M HNO(3), followed by M3, and MM, and that thorough grinding is necessary if using less than five grams of soil in a Pb test, in order to adequately homogenize Pb-contaminated samples and achieve acceptable testing reproducibility.

Evaluation of Extractants for Boron under the Influence of Organic Matter and Applied Boron in Rhizosphere and Nonrhizosphere Soils Growing Rape (Brassica campestris L.)

Field experiments during 2006–07 and 2007–08 were conducted in an Aeric Endoaquept to evaluate extractants suitable for boron (B) under the influence of organic matter and B in both rhizosphere (R) and nonrhizosphere (NR) soils with rape (Brassica campestris L.) as a test crop. The results reveal that the average B content in Mehlich 3 (MH-3) B was greatest (0.791 mg kg−1) in NR soil, while that of the same in R soil was greatest (0.785 mg kg−1) with Mannitol–calcium chloride (CaCl2) (MCC) followed by hot -CaCl2 (HCC, 0.750 mg kg−1) in the treatment T4 where NPK (80:40:40), B at 0.5 kg ha−1, and farmyard manure (FYM) at 5 t ha−1 were applied together. Based on linear regressions and correlations between different extractants and yield responses, the MH-3 extractant gave the greatest value of co-efficient of determination (R2 = 0.36**, r = 0.598**) and has proved to be a superior extracting solution for B in NR in an Aeric Endoaquept. The results further suggested that the extractability of B with these three extractants did not have any control over rhizosphere soil zone.

Evaluation of Mehlich 3 as a Universal Nutrient Extractant for Australian Sugarcane Soils

This study evaluated the suitability of the Mehlic h3 universal extractant as a part of a multielement test to assess the nutrient status of Australian sugarcane soils. Soil samples from BSES Soil Exchange Programs, representing all major soil types and geographic sugarcane-growing regions, were analyzed using existing BSES, acid-based extraction methods for calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), copper (Cu), zinc (Zn), iron (Fe), manganese (Mn), and phosphorus (P) and the ASPAC 10B3 method for sulfur (S). These were compared with the Mehlich 3 procedure. Mehlich 3 results for Ca, Mg, Na, S, and Mn correlated highly with the BSES procedures (R2 = 0.95, 0.98, 0.99, 0.91, and 0.91, respectively). Satisfactory correlations were also obtained with 0.1 M HCl–extracted Zn, Cu, and Fe (R2 = 0.89, 0.85, and 0.85, respectively) and with the BSES sulfuric acid (H2SO4)–extracted P (R2 = 0.81). The poorest correlation (R2 = 0.79) was observed for K. In conclusion, the Mehlich 3 procedure is suitable as a diagnostic tool to assess the basic nutrient status of Australian sugarcane soils.

Phosphorus Determination after Mehlich 3 Extraction and Anion Exchange Resin in an Agricultural Soil of Northwestern Spain

Differences in soil phosphorus (P) contents measured by various techniques may have implications for agronomic and environmental testing. Reduced-tillage systems combined with surface manure application increase the potential risk of nutrient losses by surface runoff. A field trial was conducted to evaluate the effect of livestock slurry on nutrient accumulation at the surface layer of an acidic soil rich in organic matter with excess P levels and loamy texture. Two reduced-tillage systems, no tillage (NT) and minimum tillage (MT), and four different fertilizer treatments were assessed. The amounts of P extracted by anion-exchange resin (AER) and by Mehlich 3 (M3) were compared; in addition, differences between two determination methods of P contents extracted by Mehlich 3, namely molybdic acid colorimetric standard procedure (M3-COL) and inductively coupled plasma–mass spectroscopy (M3-ICP), were evaluated. Ninety-six soil samples were taken from the 0- to 5-cm surface layer in three successive dates after increasing manure addition. Colorimetric Mehlich 3 P ranged from 49 to 431 mg dm–3. The ranks of mean extractable soil P concentrations were AER < M3-COL < M3-ICP. The linear correlation coefficient between M3-COL and M3-ICP was highly significant (R2 = 0.89; P < 0.01), but a two-straight-lines model or a quadratic relationship were more adequate for describing the dependence between the two determination procedures after M3 extraction. Relative and absolute differences between M3-COL and M3-ICP showed a tendency to increase as organic carbon content increased. Phosphorus content extracted by AER and M3-COL or M3-ICP reported a significant but much less predictable relationship with R2 values of 0.27 and 0.21 (n = 96), respectively. The P in the surface layer accumulated more under NT than under MT.

Anthropogenic effects on the physical and chemical properties of subtropical coastal urban soils

AbstractWe investigated the effects of various anthropogenic factors on urban soil properties in subtropical, coastal Tampa, FL, USA. Specifically, we explored the influence of (i) urbanization as measured by land use, land cover, population density and years since urban development and (ii) socioeconomic conditions as reflected in household income and property values on bulk density (BD) and several key soil chemical properties. Results indicate that Tampa’s urban soils were affected to varying degrees by these factors with chemical properties being more variable than BD. Across land uses significant differences were found for Mehlich‐1 (M1) extractable P, Ca and Na. A similar trend was observed for land‐cover classes, although significant differences were also found for pH and M1‐Cu. Soil properties had no statistically significant relationship with population density. However, time since urbanization did with M1‐P and Na varying significantly across age categories. For our socioeconomic analyses, M1‐K and Mg levels differed significantly by household income while pH, P, Ca and Na values differed significantly by property value. Overall, our findings indicate that despite their inherent heterogeneity, there are identifiable patterns among subtropical coastal urban soil properties. We suggest that a more thorough understanding of these patterns and their drivers is an essential first step towards developing soil management strategies aimed at maintaining environmental quality and ecosystem services in subtropical cities.

Soil Phosphorus Available for Crops and Grasses Extracted with Three Soil-Test Methods in Southern Brazilian Soils Amended with Phosphate Rock

The Mehlich 1 (M1) soil-test method has been used for soil phosphorus (P) extraction in southern Brazil. The objective of this work was to compare M1, Mehlich 3 (M3), and ionic exchange resin (resin) soil-test methods to evaluate the soil P available for crops and grasses in soils amended with phosphate rock (PR). Oxisol and Alfisol received triple superphosphate (TS) and PR. The M1 solution extracted greater P amounts in soils amended with PR compared with the M3 solution and resin methods. Lesser P amounts were extracted with the M3 solution. Crops yields were better associated with the P amounts extracted with M3 and resin methods in soils amended with PR. The results showed that M1 overestimates soil P availability to plants in soils amended with PR; the M3 solution best estimated the soil P available for crops and grasses in soils amended with PR.

Nutrient Source and Tillage Impact on Corn Grain Yield and Soil Properties

Large amounts of animal manure, particularly poultry litter and dairy manure, are generated in southeastern United States, where corn (Zea mays L.) is also extensively grown. Characterizations of management practices and long-term manure and soil nutrient dynamics are critical. This study examined corn grain yield and soil nutrient status under three nutrient sources (two rates of each) as follows: inorganic fertilizer, poultry litter, and dairy manure compared with a nontreated control under two tillage practices (no-till and incorporated). Treatments were replicated four times in a split-plot design from 2004 to 2007. Soil samples were taken annually in the spring before treatment application to evaluate the status of the residual nutrients in soil. Significant differences in corn grain yield between the two tillage practices (main effect) were observed in all 4 years. The high rate of poultry litter application produced similar grain yield as inorganic fertilizer. However, results from dairy manure were not as consistent as poultry litter. After 4 years of poultry litter application, Mehlich-3 (M-3) phosphorus (P) increased from an initial 31.4 to 63.0 mg kg−1 for the 4.5 Mg ha−1 year−1 rate and to 178 mg kg−1 for the 13.5 Mg ha−1 year−1 rate. More specifically, 5.2 kg ha−1 year−1 of P applied as poultry litter increased soil M-3 P by 1 mg kg−1 after 4 years of application. Results indicated that poultry litter is a primary fertilizer at the rate of 13.5 Mg ha−1 applied in four consecutive years on a silt loam soil-produced corn grain yields similar to inorganic fertilizer under both no-till and incorporated systems and did not result in residual soil test P, Cu, and zinc levels considered to be harmful to surface water or cropping systems.

Trace Metals and Polycyclic Aromatic Hydrocarbons in an Urbanized Area of Florida

Contamination of soils by a variety of pollutants in urbanized and rapidly urbanizing regions is an ongoing problem in the world. Our objective in this study was to determine the contamination levels of trace metals and polycyclic aromatic hydrocarbons (PAHs) in urban residential soils. Surface (0–15 cm) samples of soils were collected and analyzed from an urbanized region of Florida (Pinellas County: 725 km2, population: 921,482), for basic soil properties, trace metals, and PAHs. The pH of urban residential soils was between 5.4 and 8.0, the electrical conductivity ranged from 18 to 1170 μS cm−1 with an average value of 233 μS cm−1, and total organic carbon of soils varied widely from 1 to 88 g kg−1. Among the major elements determined in soils, contents of Mehlich 1 (M1) Ca were highest at 2330 mg kg−1 followed by M1–Mg (136 mg kg−1) and M1–Al (135 mg kg−1). Among the trace metals in soils, mean M1–Zn values were highest (18.6 mg kg−1) followed by M1–Fe (10 mg kg−1) and M1–Mn (8.6 mg kg−1). The contents of total PAHs (sum of the individual 14 PAHs) in urban residential soils varied from 83 to 2371 μg kg−1, with a mean value of 731 μg kg−1. Source analysis of PAHs in soils using molecular diagnostic indices suggested that PAHs in soils originated from both petrogenic and pyrolytic sources. Our results can be used to set baseline values of PAHs in urban residential soils of Florida and monitor changes in soil metals and PAHs values over a period of time due to anthropogenic inputs.

Predicting Phosphorus Desorption from Acid Piedmont Rice Soils of Bangladesh

A laboratory experiment was conducted at the Bangladesh Rice Research Institute, Gazipur during 2003 to determine phosphorus (P) desorption characteristics for 10 acid piedmont rice soils of Bangladesh. Soil samples were analyzed for sand, silt and clay, pH, organic carbon, available P, Mehlich-3 (M3) extractable P and dithionite extractable Fe (FeD). Desorption of phosphorus (release pattern) from different soils varied from 1.34 to 19.17 ppm. Phosphorus desorption was affected by the increased shaking time up to one hour. In almost all the studied soils, the highest desorbed P was extracted at one hour shaking time, beyond which there was again re-adsorption in most of the soils. Soil properties, particularly, pHKCl, ?pH, organic carbon and clay content were found to be important soil variables in determining phosphorus desorption in piedmont soils. The increase in ?pH and organic carbon increased P desorption, while an increase in clay and Fe tended to decrease in P desorption. Equations were proposed for predicting ?, ?, and K of famous Sharpley’s equation and were tested for better prediction of P desorption in Piedmont soils of Bangladesh. Sharpley’s equations for Piedmont soils resulted in a strong relationship (R2 = 0.86) between measured and predicted P desorption. The equations recommended by Sharpley to predict values for ?, ? and K has provided a good prediction of P desorption for our Piedmont rice soils.