Mehlich-1 Extractants Research Articles

Mobility, distribution, and potential risk assessment of selected trace elements in soils of the Nile Delta, Egypt.

Environmental pollution has received considerable attention over the last 50 years. Recently, there has been an increasing interest in pollution of the Nile Delta, Egypt, which is one of the longest settled deltaic systems in the world. Pollution in the delta is increasingly recognized as a serious health concern that requires proper management of ecosystems. Therefore, this project aimed to study the distribution and assess the risk associated with selected trace elements (TEs) in different soils (i.e., marine, fluvial, and lacustrine parent materials) in the northern Nile Delta. Mehlich-3 extraction was used to determine the availability of antimony, vanadium, strontium, and molybdenum in agro-ecosystems in this area and their spatial distributions were investigated. Five indices were used to assess ecological risk. Results showed that TEs were higher in the southern part of the study area because it is affected by multiple pollution sources. The available concentrations of TEs were Sr < V < Sb < Mo. The bioavailability of Sr was highest among the studied TEs. The studied indices suggested the study area was moderately polluted by Sr and Sb. Furthermore, the results showed that marine soils had higher TE levels then lacustrine and fluvial soils. The ecological risk assessment indicated that V and Mo were of natural origin, while Sr and Sb were anthropogenically linked. Therefore, the situation calls for planning to reduce pollution sources, especially in the protected north Nile Delta, so these productive soils do not threaten human and ecological health.

Release of Heavy Metals from Dolomite Phosphate Rock after Activation with Organic Agent.

As high-grade phosphate reserves begin to diminish worldwide, low-grade phosphate rock such as that containing dolomite [CaMg(CO)] needs to be explored as a potential fertilizer. Activation of dolomite phosphate rock with humic acid substantially increased P availability by chelating Ca and Mg. However, the release potential of heavy metals during the activation process should be evaluated. In this study, an orthogonal experiment was designed to investigate the effects of major activating factors on the release of Cd, Cr, Cu, Mn, Ni, Pb, and Zn in activated fertilizers using a batch-equilibrium technique. The release potential of heavy metals from activated fertilizers was further compared with single superphosphate fertilizers made from the same dolomite phosphate rock. The activation process increased water-soluble Cr, Ni, and Zn by 39.8 to 65.7, 26.5 to 35.6, and 6.9 to 14.6 times, respectively, as compared with the original dolomite phosphate rocks, but there was a decrease in water-soluble Cd, Mn, Ni, Pb, and Zn by 1.4 to 5.4, 5.4 to 8.6, 2.3 to 3.7, 0.7 to 2.8, and 2.6 to 5.0 times, respectively, as compared with single superphosphate fertilizers. The release of heavy metals was affected by activating factors including dolomite phosphate rock type, particle size, humic acid dosage, and moisture content. Similar results were obtained with Mehlich-3 extraction, but levels of Mehlich-3-extractable heavy metals were less in activated fertilizers than in the original dolomite phosphate rocks, except Cu. These results indicate that activated fertilizers contain less bioavailable heavy metals than single superphosphate fertilizers and, therefore, are more environmentally friendly for application in agriculture.

Copper use efficiency in soybean cultivars

Abstract: The objective of this work was to evaluate the effect of copper use efficiency in soybean cultivars, grown on a typical Ultisol with a high organic matter content, on soil chemical properties and on plant grain yield, nutritional state, and physiological components. The experiment was carried out in greenhouse conditions, in a 5×4 factorial arrangement, with five soybean cultivars (TMG 1066RR, BRS 360RR, NA 6262RR, BMX Turbo RR, and BRS 359RR) and four Cu rates (0, 2, 4, and 8 mg kg-1). Under the studied soil conditions, the DTPA-TEA and Mehlich-1 extractants were efficient in determining available Cu in the soil. Regardless of the cultivars, Cu application increased grain yield (GY), shoot dry weight yield (SDWY), number of pods per pot, GY/SDWY ratio, photosynthetic rate, stomatal conductance, internal CO2 concentration, transpiration rate, and chlorophyll content. However, Cu use efficiency varied significantly among the different soybean genotypes. Except for Cu, soil chemical attributes and foliar and grain nutrient contents are not influenced by Cu rates nor by soybean cultivars.

Fertilizer and Soil Solubility of Secondary P Sources-The Estimation of Their Applicability to Agricultural Soils.

The demand for phosphorus (P) sources is increasing with the growing world population, while objections to direct agricultural use of waste P sources, such as sewage sludge, are being raised. Therefore, the need arises to employ safe and efficient secondary P fertilizer sources, originating from P-rich wastes. These recycling sources are commonly tested in accordance with the current fertilizer rules, designed originally for conventional apatite-based P fertilizers. The behavior of sewage sludge ash, an inorganic recycling secondary P source, was investigated under soil-like conditions. Standardized soil P tests, including the soil buffering capacity test and the Olsen, the Mehlich3, and water extraction methods, were employed together with standardized fertilizer P-solubility tests by neutral ammonium citrate and 2% citric acid extraction. In addition, total content and the overall soil mobility of selected metallic elements present in sewage sludge ash were investigated. The suitability of standardized soil tests for the evaluation of recycling P sources was shown. An apparent influence of Ca:Al content ratio on sewage sludge ash behavior under different soil-like conditions shows the inadequacy of the current fertilizer test and the necessity to understand soil-like behavior of secondary P sources, when considering these as possible agricultural P bearers (fertilizers).

A Comparative Study on Poaceae and Leguminosae Forage Crops for Aided Phytostabilization in Trace-Element-Contaminated Soil

When applying an aided phytostabilization in trace-element-contaminated agricultural soil, the cultivation of forage crops instead of edible crops can reduce the trace elements transfer to humans while minimizing the income loss of farmers. The objectives of this study were to compare the effect of the type of forage crops at the “family” level (Poaceae and Leguminosae) on aided phytostabilization using physical (water stable aggregation), chemical (Mehlich-3 extraction), and biological assessments (dehydrogenase activity). Pig manure and acid mine drainage sludge were used as soil amendments, and four plant species (Loliummultiflorum Lam. var. italicum and Secalecereale L. [Poaceae representatives], Viciavillosa Roth, and Trifoliumpratense L. [Leguminosae representatives]) were cultivated after amendment treatments. Chemical assessment showed that the reduction in bioavailability of trace elements was partly observed in legume crops. The positive effects of plant cultivation were determined through physical assessment. The effectiveness of pig manure as an organic amendment was determined by biological assessment. In some treatments, the synergistic effect of the incorporation of chemical stabilization with both plant families was observed but it was difficult to identify a clear distinction between the two families. The translocation of trace elements from root to shoot was low in all plants, indicating that the cultivation of the plants used in this study is safe with regards to the spread of trace elements into the environment. The results suggest that forage crop cultivation in contaminated agricultural soil could ameliorate soil quality after chemical stabilization.

The Contrasting Effects of Alum-Treated Chicken Manures and KH2PO4 on Phosphorus Behavior in Soils.

Alum [KAl(SO)⋅12HO] is often added to chicken manure to limit P solubility after land application. This is generally ascribed to the formation of Al-PO complexes. However, Al-PO complex formation could be affected by the matrix of chicken manure, which varies with animal diet. Alum was added to KHPO (as a reference material) and two manures from typical chicken farms in China, one from an intensive farm (CMIF) and another from free-ranging chickens (CMFR). These were subsequently incubated with soils for 100 d to investigate P transformations. Alum reduced water-soluble colorimetrically reactive phosphorus (RP) from soils amended with manure more effectively than in soils amended with KHPO. Alum addition lowered Mehlich-3 RP in soils with CMFR but had no influence on Mehlich-3 RP in CMIF- or KHPO-amended soils. A comparison of P in digested Mehlich-3 extracts with RP in undigested samples showed significantly increased P in digests of alum-treated CMFR only. Fractionation data indicated that alum treatment increased P in the NHF-RP (Al-P) fraction only in soils with KHPO, but not in soils with manure treatments. Furthermore, NaOH-extracted nonreactive P was markedly higher in soil with alum-treated CMFR relative to normal CMFR. The CMFR manure was assumed to contain higher concentrations of organic P because these chickens were fed grains only. These results suggest that the formation of alum-organic P complexes may reduce P solubility. By comparing alum-treated KHPO and manures, it appears that organic matter in manure could interfere with the formation of Al-PO complexes.

Phosphorus Sorption and Saturation in the Ganges Tidal Floodplain Soils of Bangladesh

The soils developed from the Ganges sediments in the coastal area of Bangladesh and India extend several thousand hectares and important from the view point of rice cultivation. Phosphorus, one of the important environmental and agricultural element, retention behavior of the Ganges floodplain soils is poorly reported. The objective of this study was to determine maximum phosphorus adsorption capacity (MPAC) and to develop Psat for 13 Ganges Tidal Floodplain soils of Bangladesh. The MPAC value and Psat based on Mehlich-3 extractions were determined. The conventional adsorption equations, such as the Langmuir, Freudlich and Temkin equations were used to describe the P sorption of the studied soils. The MPAC value varied from 1250 to 2000 mg/kg and correlated with EC (r = 0.59, p<0.05) and CEC (r = -0.74, P<0.01). The sorption capacity of the tested soils ranged from 511 to 545 mg/kg and the calculated energy of adsorption of the soils varied from 0.192 to 1.00 μg/mL and it was a positively correlated with clay (r=0.7, p<0.01) and CEC (r = 0.63, p<0.05) but negatively with silt (r= -0.80, p<0.01), pH (H2O) (r=-0.60, p<0.05) and with MPAC (r=-0.59, p<0.05) values. Phosphorus saturation indices of the studied sample demonstrated a far below the threshold critical limit of 25%.

Micronutrient concentrations vary between peat–mineral mix and substrates in revegetated sites in the Alberta oil sands

Adequate supply of micronutrients is essential for plant growth in reclaimed sites in the Athabasca oil sands region. The objectives of this study were to determine boron, iron, manganese, copper, and zinc concentrations in peat–mineral mix (PMM), tailings sand (TS), and overburden (OB) materials and to assess whether lodgepole pine (Pinus contorta) planted on PMM over TS and white spruce (Picea glauca) planted on PMM over OB had low foliar micronutrient concentrations. Micronutrient concentrations determined using LiNO3 and Mehlich-3 extractions were different between PMM and TS in the pine sites while only LiNO3 extractable boron was different between PMM and OB in the spruce sites (p iron > manganese > zinc > copper in all soil layers with concentrations ranging from 0.04 to 39.56 μg g−1. The low foliar concentration of copper in pine and spruce was consistent with low LiNO3 extractable copper in the soil in both the pine and spruce s...

Monitoring a commercial vineyard in New Zealand to maintain soil health and achieve long-term sustainability

This paper illustrates the benefits of long-term monitoring of soil and vine health in Craggy Range’s Te Muna vineyard in the Martinborough region of New Zealand. The soils at Te Muna are formed on two river terraces. The higher and older terrace, planted to Pinot Noir, is very gravelly; the lower and younger terrace, planted to Sauvignon Blanc, contains more silt and very fine sand. Both terraces are freely drained. Soil pH, organic C and available P were monitored in selected blocks on both terraces. Under current management that includes cover crops and sheep grazing in winter, soil organic C has been stable for 10 years. Because of the regular application of RPR and intermittent liming, soil pH (water) has risen from c.5.5 to 6.5–7. Values for soil available P, measured by Olsen bicarbonate and Mehlich-3 extractions, diverged over time. The Olsen test indicated satisfactory P levels: conversely, the Mehlich test showed P values rising to very high levels, confirming Western Australian experience that this acid extraction is unsuitable for soils treated with RPR. Petiole and leaf blade P concentrations confirmed these results, but they showed greater interannual variation than the soil P measurements. Overall, the long-term sustainability of the vineyard should be assured.

Optimization and Validation of an Extraction Method for Evaluating the Availability of Cu, Zn, Mn, Ni, Cr and Cd in Soil with the Use of the Mehlich-1 Extractor

The Mehlich-1 extractor is routinely used to evaluate the bioavailability of metals in soil since it has a high closeness between the amount of these elements absorbed by the plants and those available in soil, as well as being simple and practical to use. Thus, the aim of this work was to improve (optimize) a Mehlich-1 extraction method for evaluating the availability of Cu, Zn, Mn, Ni, Cr and Cd in soil using Box-Behnken type response surface method (RSM). After optimizing the soil amount, Mehlich-1 extractor volume and stirring time, the validation of the newly developed method was performed by evaluating the following parameters: matrix adjustment, linearity, linear range, limits of detection (LOD) and of quantification (LOQ), precision and accuracy. The analytical method proposed by this study can be routinely employed for the evaluation of soil toxicity since it presented advantages such as simplicity, speed and efficacy, as well as being precise and accurate.

Arsenic reactions and brake fern (Pteris vittata L.) uptake in tropical soils

In Hawaii, past use of arsenical pesticides has left elevated levels of arsenic (As) in some soils. Sorption isotherms of an Andosol and an Acrisol showed that the former required 1100 mg/kg, and the latter 300 mg/kg of added As to maintain 0.20 mg As/L in solution, the maximum allowable As level in streams/rivers in Hawaii. Greenhouse experiments were conducted on an Andosol (315 mg/kg total As), which was amended with 0, 5 g/kg compost, 5 g Fe/kg as amorphous Fe(OH)&lt;sub&gt;3&lt;/sub&gt;, or 250 mg P/kg as Ca(H&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;, and on a low-As (15 mg/kg) Acrisol, which was spiked with 0, 150 or 300 mg As/kg as Na&lt;sub&gt;2&lt;/sub&gt;HAsO&lt;sub&gt;4&lt;/sub&gt;.7 H&lt;sub&gt;2&lt;/sub&gt;O. Brake fern (Pteris vittata L.) was used as the test plant. Arsenic concentration in the fern fronds averaged 355 mg/kg in the Andosol, and 2610 and 1270 mg/kg (from consecutive plantings, 2 and 12 months after As addition, respectively) in the Acrisol spiked with 300 mg/kg of As. Chemical reactions, as suggested by sequential extractions, likely controlled the availability and uptake of soil As. Mehlich-3 extraction could be used to identify As-contaminated soils and potential phytoremediation as it correlated well with bioaccessible As and with As in fern fronds.

Iron Availability in Tropical Soils and Iron Uptake by Plants

Given the increase in crop yields and the expansion of agriculture in low fertility soils, deficiency of micronutrients, such as iron, in plants grown in tropical soils has been observed. The aim of this study was to evaluate Fe availability and Fe uptake by corn (Zea mays L.) plants in 13 different soils, at two depths. Iron was extracted by Mehlich-1, Mehlich-3, and CaCl2 (Fe-CC) and was fractionated in forms related to low (Feo) and high (Fed) crystallinity pedogenic oxyhydroxides, and organic matter (Fep) using ammonium oxalate, dithionite-citrate, and sodium pyrophosphate, respectively. In order to relate Fe availability to soil properties and plant growth, an experiment was carried out in a semi-hydroponic system in which part of the roots developed in a nutrient solution (without Fe) and part in the soil (the only source of Fe). Forty-five days after seeding, we quantified shoot dry matter and leaf Fe concentration and content. Fed levels were high, from 5 to 132 g kg-1, and Feo and Fe-CC levels were low, indicating the predominance of Fe as crystalline oxyhydroxides and a low content of Fe readily available to plants. The extraction solutions showed significant correlations with various soil properties, many common to both, indicating that they act similarly. The correlation between the Mehlich-1 and Mehlich-3 extraction solutions was highly significant. However, these two extraction methods were inefficient in predicting Fe availability to plants. There was a positive correlation between dry matter and Fe levels in plant shoots, even within the ranges considered adequate in the soil and in the plant. Dry matter production and leaf Fe concentration and content were positively correlated with Fep concentration, indicating that the Fe fraction related to soil organic matter most contributes to Fe availability to plants.

Effects of Annual Precipitation on Heavy Metals in Runoff from Soils in the US Great Plains

Deterioration of natural water resources due to runoff from agricultural land is a major problem in the US Great Plains. Changes in earth climate can create heavy storms and alter precipitation patterns which would affect the element concentrations in runoff. A 2-year study (dry and wet years) was conducted to assess the impact of annual precipitation on element concentrations in runoff from soils and element loadings to Salt Creek in the Roca watershed, NE. Both dissolved and sediment-associated forms of five elements (Al, Fe, Mn, Cu, and Zn) were determined in runoff. The amount of dissolved element in runoff during the wet year was greater than the dry year. Except for Zn, the total amount of element associated with sediment was greater than that found in dissolved form. The Mehlich3 extraction was applied to determine the reactive fraction of element in sediment. A small fraction of element associated with sediment was in reactive form, ranging from 1 to 33 % of the total element content. The sum of both the reactive fraction of element in sediment and amount of element dissolved in water were used to calculate the total bioactive element concentration (BEC) in runoff. During the dry year, the total BEC in runoff was 424, 349, 387, 5.2, and 26.8 μg/L for Al, Fe, Mn, Cu, and Zn, respectively. The corresponding total BEC during the wet year was 622, 479, 114, 3.7, and 19.8 μg/L for Al, Fe, Mn, Cu, and Zn, respectively. Further, the bioactive element loading (BEL) into Salt Creek was greater during the wet year than the dry year. Aluminum, Fe, and Mn contributed to the greatest BEL into the surface water body while Zn and Cu had the least contribution. We concluded that greater precipitation during the wet year would increase the negative impact of runoff from soils and BEL to surface water systems in the US Great Plains.

Effects of Biochar Blends on Microbial Community Composition in Two Coastal Plain Soils

The amendment of soil with biochar has been demonstrated to have an effect not only on the soil physicochemical properties, but also on soil microbial community composition and activity. Previous reports have demonstrated significant impacts on soil microbial community structure. These impacts are modulated not only by the biochar composition, but also on the soil’s physicochemical characteristics. This indicates that soil characteristics must be considered prior to biochar amendment. A significant portion of the soils of the southeastern coastal plain are severely degraded and, therefore, candidates for biochar amendment to strengthen soil fertility. In this study we focused on two common soil series in the southeastern coastal plain, utilizing feedstocks endemic to the area. We chose feedstocks in four ratios (100% pine chip; 80:20 mixture of pine chip to poultry litter; 50:50 mixture of pine chip to poultry litter; 100% poultry litter) prior to pyrolysis and soil amendment as a biochar product. Soil was analyzed for bioavailable nutrients via Mehlich-1 extractions, as well as microbial community composition using phospholipid fatty acid analysis (PLFA). Our results demonstrated significant shifts in microbial community composition in response to biochar amendment, the effects of which were greatest with 100% poultry litter biochar. Strong relationships between PLFAs and several Mehlich-1 extractable nutrients (Al, Cu, Fe, and P) were observed.

Comparison of Field-Moist and Oven-Dry Soil on Mehlich-3 and Ammonium Acetate Extractable Soil Nutrient Concentrations

Drying soil samples has been a standard step in soil processing but is known to influence the amount of extractable K. Our objectives were to evaluate the correlation between field-moist (FM) and oven-dry (OD) soil nutrient concentrations extracted with Mehlich-3 extractant and 1 mol L−1 NH4OAc and how Mehlich-3 extractable nutrient concentrations change from oven drying using loamy-textured soils. The Mehlich-3 and NH4OAc extractable K, Ca, and Mg concentrations were highly correlated (r2 > 0.95) for both FM and OD soils. The relationship between OD and FM soil-K concentrations for Mehlich-3 and NH4OAc was very similar and highly correlated (r2 = 0.92). The FM soil-K concentrations were lower than OD soil-K concentrations until an equilibrium was reached at 136 mg K kg−1 for NH4OAc and 158 mg K kg−1 for Mehlich-3 after which OD soil-K concentrations were lower than FM soil-K concentrations. Oven drying had minimal effect on Ca concentrations and decreased Mg concentrations for both Mehlich-3 and NH4OAc extractions. Oven drying increased Mehlich-3 P concentrations by 8 to 9 mg P kg−1 when OD soil concentrations were <50 mg P kg−1. The Mehlich-3 extractable Na, S, and Zn concentrations from OD and FM soils were similar. The OD soil had greater Mn concentrations and lower Cu concentrations than the FM soil. Among the Mehlich-3 extractable nutrients that are used to make fertilization decisions, K concentration was affected to the greatest magnitude and non-uniformly by oven drying, which requires field research to correlate and calibrate new agronomic recommendations.

SOIL PHOSPHORUS THRESHOLDS IN EVALUATING RISK OF ENVIRONMENTAL TRANSFER TO SURFACE WATERS IN SANTA CATARINA, BRAZIL

The State of Santa Catarina, Brazil, has agricultural and livestock activities, such as pig farming, that are responsible for adding large amounts of phosphorus (P) to soils. However, a method is required to evaluate the environmental risk of these high soil P levels. One possible method for evaluating the environmental risk of P fertilization, whether organic or mineral, is to establish threshold levels of soil available P, measured by Mehlich-1 extractions, below which there is not a high risk of P transfer from the soil to surface waters. However, the Mehlich-1 extractant is sensitive to soil clay content, and that factor should be considered when establishing such P-thresholds. The objective of this study was to determine P-thresholds using the Mehlich-1 extractant for soils with different clay contents in the State of Santa Catarina, Brazil. Soil from the B-horizon of an Oxisol with 800 g kg-1 clay was mixed with different amounts of sand to prepare artificial soils with 200, 400, 600, and 800 g kg-1 clay. The artificial soils were incubated for 30 days with moisture content at 80 % of field capacity to stabilize their physicochemical properties, followed by additional incubation for 30 days after liming to raise the pH(H2O) to 6.0. Soil P sorption curves were produced, and the maximum sorption (Pmax) was determined using the Langmuir model for each soil texture evaluated. Based on the Pmax values, seven rates of P were added to four replicates of each soil, and incubated for 20 days more. Following incubation, available P contents (P-Mehlich-1) and P dissolved in the soil solution (P-water) were determined. A change-point value (the P-Mehlich-1 value above which P-water starts increasing sharply) was calculated through the use of segmented equations. The maximum level of P that a soil might safely adsorb (P-threshold) was defined as 80 % of the change-point value to maintain a margin for environmental safety. The P-threshold value, in mg dm-3, was dependent on the soil clay content according to the model P-threshold = 40 + Clay, where the soil clay content is expressed as a percentage. The model was tested in 82 diverse soil samples from the State of Santa Catarina and was able to distinguish samples with high and low environmental risk.

EFICIÊNCIA DE MÉTODOS ANALÍTICOS NA PREDIÇÃO DA DISPONIBILIDADE DE FÓSFORO PARA ARROZ IRRIGADO EM SOLOS CATARINENSES

Os solos cultivados com arroz irrigado no Estado de Santa Catarina apresentam características mineralógicas e químicas distintas dos solos utilizados nos estudos de calibração do extrator Mehlich-1, para estimar a disponibilidade de fósforo do solo para as plantas. Desse modo, o objetivo deste trabalho foi avaliar a eficiência dos extratores Mehlich-1, Mehlich-3, Resina em lâminas, Olsen e EDTA na predição da disponibilidade P para plantas de arroz cultivadas em sistema de alagamento em solos representativos de lavouras orizícolas do Estado de Santa Catarina. O experimento foi conduzido em casa de vegetação, com cinco solos oriundos de várias lavouras orizícolas, em 2014. Foram adicionados aos solos quatro concentrações de P, correspondendo a 0, ¼, ½ e 1,0 vez a quantidade de P para atingir 0,2 mg L-1 de P na solução do solo (com base na capacidade de adsorção de cada solo). Foram usadas três repetições por tratamento, dispostas no delineamento completamente casualizado. Após cinco dias da adição dos níveis de P, as unidades experimentais constituídas por vasos de 8 L contendo 3,5 kg de solo seco foram amostradas para determinar o P disponível do solo por cinco métodos químicos. Na sequência, essas foram alagadas e cultivadas com seis plantas de arroz por 46 dias, quando se quantificaram a massa de matéria seca e o P absorvido pela parte aérea das plantas. A eficácia dos métodos Mehlich-1, Mehlich-3, Resina em lâminas, Olsen e EDTA foi avaliada por correlação linear entre a quantidade de P extraída dos solos e a quantidade absorvida pelas plantas. A quantidade de P absorvida pelas plantas de arroz aumentou com o acréscimo das doses de P aplicadas, variando com o tipo de solo. A maior recuperação do P adicionado aos solos foi obtida pelo extrator EDTA, seguido pelo Olsen. O P extraído pelo EDTA e Mehlich-3 evidenciou melhor correlação com quantidade de P absorvida pelo arroz. O agrupamento dos solos segundo características relacionadas à adsorção de P no solo melhora a eficiência de todos os métodos em predizer a disponibilidade de P em solos cultivados com arroz no sistema de inundação.

Methods to Quantify Nickel in Soils and Plant Tissues

In comparison with other micronutrients, the levels of nickel (Ni) available in soils and plant tissues are very low, making quantification very difficult. The objective of this paper is to present optimized determination methods of Ni availability in soils by extractants and total content in plant tissues for routine commercial laboratory analyses. Samples of natural and agricultural soils were processed and analyzed by Mehlich-1 extraction and by DTPA. To quantify Ni in the plant tissues, samples were digested with nitric acid in a closed system in a microwave oven. The measurement was performed by inductively coupled plasma/optical emission spectrometry (ICP-OES). There was a positive and significant correlation between the levels of available Ni in the soils subjected to Mehlich-1 and DTPA extraction, while for plant tissue samples the Ni levels recovered were high and similar to the reference materials. The availability of Ni in some of the natural soil and plant tissue samples were lower than the limits of quantification. Concentrations of this micronutrient were higher in the soil samples in which Ni had been applied. Nickel concentration differed in the plant parts analyzed, with highest levels in the grains of soybean. The grain, in comparison with the shoot and leaf concentrations, were better correlated with the soil available levels for both extractants. The methods described in this article were efficient in quantifying Ni and can be used for routine laboratory analysis of soils and plant tissues.

Relationship between Soil Phosphorus and Phosphorus Budget in Grass Sward with Varying Nitrogen Applications

Changes in soil available P usually relate to P budgets, but the sensitivity of the relationship to N fertilization is poorly understood. Four P rates (0, 15, 30, and 45 kg ha⁻¹) as main plots and four N rates (0, 60, 120, and 180 kg ha⁻¹) as subplots were applied each year from 1999 to 2006 to a timothy (Phleum pratense L.) sward established in 1998 on a gravelly sandy loam soil (Typic Fragihumods). Soil available P was assessed using water (Cp) and Mehlich-3 (PM₃) extractions. Annual P budgets were calculated as the difference between applied P and P offtake and were then summed over the duration of the experiment to determine the cumulative P budget (Bcum). Over the 8-yr study, Bcum (−148 to 286 kg P ha⁻¹), Cp (0.13 to 0.94 mg L–¹), and PM₃ (22.3 to 111.7 mg kg⁻¹) were affected by both P and N fertilization. The Cp and PM₃ were linearly related to Bcum and the relationship was similar among N rates [Cp = 0.0016Bcum + 0.3 (r² = 0.86, P < 0.001) and PM₃ = 0.20Bcum + 47.7 (r² = 0.90, P < 0.001)]. A positive or negative Bcum of 100 kg P ha⁻¹ would then raise or deplete Cp by 0.16 mg L–¹ and PM₃ by 20 mg kg⁻¹. The relationship between Bcum and soil available P was not affected by N applications in this gravelly sandy loam soil.

EXTRACTION METHODS AND POTASSIUM AVAILABILITY FOR SOYBEAN IN THE PARANA STATE’S SOILS, BRAZIL

Evaluating the potassium (K) availability to the plants can be performed by different methods. In general, multielement methods are employed and they are used for K due to increase operational of soil testing laboratory. T he efficacy of ammonium acetate, Mehlich-1, Mehlich-3 and ion exchange resin soil K extractantsin determining the K availability for soybean [ Glycine max L. (Merrill) ], in different Parana’s soils, were investigated in this study. Twelve soil samples, collected from the upper layer 0–0.20 m, were cultivated with soybean for 42 days in greenhouse conditions. The average amount of available soil K extracted in test soils was found, displayed in decreasing order: ammonium acetate > Mehlich-3 > Mehlich-1 = ion exchange resin. The correlation coefficients between the K extracted content by ammonium acetate, Mehlich -1, Mehlich-3 and ion exchange resin and the K accumulated amount in the plants were, respectively, 0. 90, 0.77, 0.88 and 0.89 . The efficacy of ammonium acetate, Mehlich-3 and ion exchange resin extractants in assessing plant-available K in soils from Parana State were similar. The Mehlich-1 was the least efficient in estimating plant-available K in Parana’s soils. Normal 0 21 false false false PT-BR X-NONE X-NONE