Application Of Phosphate Fertilizers Research Articles

Effects of Phosphate-Solubilizing Bacteria, Rock Phosphate and Chemical Fertilizers on Maize-Wheat Cropping Cycle and Economics

A two-year field study was conducted to test the effects of two phosphate-solubilizing bacteria (PSB), Pantoea cypripedii (PSB-3) and Pseudomonas plecoglossicida (PSB-5), inoculated singly or together with rock phosphate (RP) fertilization on maize and wheat cropping cycle by comparing with chemical P fertilizer (diammonium phosphate, DAP), mainly in the crop yield, soil fertility and economic returns. Inoculation of PSB together with RP fertilization increased the crop growth in terms of shoot height, shoot and root dry biomass, grain yield and total P uptake in both maize and wheat crops compared to the other treatments. Soil fertility in the context of available P, enzyme activities and PSB population in both maize and wheat crops was significantly improved with PSB inoculation together with RP fertilization compared to DAP treatment. The combined use of PSB inoculation and RP fertilization was more economical due to minimal cost and maximum returns. These results suggested that PSB inoculation along with RP fertilization would be an appropriate substitute for chemical phosphate fertilizer application in sustainable agriculture systems.

Phosphorus nutrition of crops through arbuscular mycorrhizal fungi

Phosphorus (P) is one of the diffusion limited major nutrients, which is essential for plant growth. In soil, phosphorus occurs in three forms namely, soluble inorganic P, insoluble inorganic P and organic P. Uptake of P from soil solution is mediated by arbuscular mycorrhizal fungi (AMF) in addition to plant roots. AMF are ubiquitous occurring in most of the soils. They are commonly found in association with agricultural crops. It is now proved beyond doubt that AMF greatly enhance plant growth. The improved growth is mainly attributed to uptake of diffusion limited nutrients such as P, Zn, Cu, etc. from soil. The other beneficial effects are their role in the biological control of root pathogens, hormone production, greater ability to withstand water stress and synergistic interaction with beneficial microorganisms. It is believed that mycorrhizal plants absorb P only from the soluble P pools in the soil. Synergistic interactions between AMF and P-solubilizing microorganisms (PSM) are present which in turn helps plant growth. This is because PSM solubilize and release H 2 PO 4 ions from unavailable forms of P and AMF help in the uptake of H 2 PO 4 ions from soil. Field studies have shown that inoculation with efficient AMF not only increases growth and yield of crop plants but also reduces the application of phosphatic fertilizer by nearly 50%, especially in marginal soils deficient in nutrients. Though the rock phosphates available in India are of low grade and not fit for the manufacture of phosphatic fertilizer, they can be used with PSM plus AMF as a potential source of P for crop plants, thus bringing down the import of P fertilizers/rock phosphate in our country. Advantages of AMF have been attained through application of suitable AM fungal inoculum and augmenting native AM fungal activities in soil through manipulating agricultural practices in favour of these fungi.

English

Oxisols and ultisols are the major soils of Malawi but the P sorption of these soils has not been studied intensively. As of now, in terms of P fertilizer application these soils are treated   the same. This research was conducted to determine the phosphate sorption properties and external P requirements (EPR) of these soils and to derive sorption values from selected soil properties. Physical and chemical analysis showed difference in these soils. Soil exchangeable aluminium, soil pH and soil organic matter is some of the soil properties that affect P sorption and these were different in these two soils. The sorption maxima were 315.5 and 413.0 mg P kg-1 for ultisols and oxisols respectively and EPR values were 37.8 and 52.2 mg P kg-1 of soil for ultisols and oxisols respectively. Exchangeable aluminium, soil pH (H2O), and organic matter found to be highly correlating with sorption maxima. The results from this study showed that, blanket application of phosphate fertilizer may not be a good strategy because ultisols and oxisols demand different amounts of P fertilizer and this blanket application may lead to under-application or over-application of P in some areas. The results also show that farming practices which improve soil organic matter and soil pH should be encouraged.    Key words: External P requirement, P-sorption, Langmuir equation, sorption affinity, Malawi, oxisols, ultisols. &nbsp

Biochar and mycorrhizal fungi influence on nutrient uptake by two pasture species in new zealand

The symbiotic relationship between plants and mycorrhizal fungi can play an important role in enhancing nutrient uptake from the soil. Many New Zealand farm soils have elevated levels of phosphorus because of regular, long term, application of phosphate fertiliser. Much of this phosphate is not available to plants. This study aimed to investigate the effect of biochar on mycorrhizal growth and subsequent phosphorus uptake by white clover and ryegrass. The experiment was conducted in a 3×2×2 factorial design, including two biochar produced from pine at different final pyrolysis temperature (350 and 550°C), mycorrhizal inoculation (Glomus sp. arbuscular mycorrhiza) and phosphate rock, respectively. The soil sample was provided from the 10cm surface horizon of an Egmont black loam. The pots were filled with the soil sample mixed with biochar applied at 10 tha -1 .Phosphate rock was applied at a rate of 70 kg ha -1 . The seeds were inoculated by Glomus sp. arbuscular mycorrhizae before sowing. The ryegrass also contained the endophyte, AR37. Dry weight, phosphorus and nitrogen concentrations of plant tissue were measured68 days after sowing. There was an increase in both phosphorus uptake and dry weight in plants grown with the high temperature biochar (B550). There was significant increase in phosphorus uptake and herbage yield in clover plants if inoculated by mycorrhizal fungi. The results demonstrated that biochar have the potential to affect the nutrients in soil and microbial activity.

Glyphosate loss by runoff and its relationship with phosphorus fertilization.

The aim of this study was to evaluate the relationship between glyphosate and phosphate fertilizer application and their contribution to surface water runoff contamination. The study was performed in Aquic Argiudoll soil (Tezanos Pinto series). Four treatments were assessed on three dates of rainfall simulation after fertilizer and herbicide application. The soluble phosphorus in runoff water was determined by a colorimetric method. For the determination of glyphosate and aminomethylphosphonic acid (AMPA), a method based on fluorenylmethyloxycarbonyl (FMOC) group derivatization, solid phase extraction (SPE) purification, and ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was employed. The application of phosphorus fertilizer resulted in an increased loss of glyphosate by runoff after 1 day of application. These results suggest the need for further study to understand the interactions and to determine appropriate application timing with the goal of reducing the pollution risk by runoff.

Rendimento de cebola em função da dose e do modo de aplicação de fósforo

A cebola apresenta elevada resposta à aplicação de adubos fosfatados, sendo praticadas aplicações a lanço de doses de fósforo (P) maiores que as preconizadas pelas recomendações oficiais. Devido a seu sistema radicular restrito, é possível que a localização da adubação fosfatada permita o uso mais eficiente do nutriente, reduzindo a dose de P necessária para a cultura. O objetivo deste trabalho foi avaliar a resposta da cebola a doses de P aplicadas a lanço ou na linha de cultivo em um Cambissolo Húmico. Foram testadas cinco doses de P (0, 120, 240, 360 e 480 kg P2O5 ha-1) e dois modos de aplicação (a lanço e na linha de plantio), em delineamento inteiramente casualizado, com quatro repetições, em esquema fatorial 5x2. Foi usada a cultivar EPAGRI 352 Bola Precoce, plantada no dia 22/07/2014 e colhida em 15/11/2014. Houve resposta linear da cebola à aplicação de P, com incremento na produtividade de 16,7 kg e 0,08 mm de diâmetro do bulbo para cada quilograma de P2O5 aplicado. Não foi observada resposta da cultura ao modo de aplicação do P na linha de plantio ou a lanço, indicando que para essa cultura a localização do fertilizante não aumenta a eficiência da fertilização fosfatada.

ADUBAÇÃO FOSFATADA E COMPACTAÇÃO DO SOLO: SISTEMA RADICULAR DA SOJA E DO MILHO E ATRIBUTOS FÍSICOS DO SOLO

Associadas aos benefícios no solo da semeadura direta, podem ocorrer a formação de gradiente vertical de fertilidade e a de uma camada compactada provocada pelo intenso tráfego de máquinas agrícolas, podendo modificar o crescimento radicular das culturas. O objetivo deste trabalho foi avaliar as doses e formas de aplicação da adubação fosfatada e a compactação do solo pelo tráfego de máquinas nos atributos físicos e no sistema radicular da soja e do milho nas condições da Chapada dos Parecis, MT. O estudo foi realizado em Latossolo Vermelho-Amarelo distrófico argiloso em delineamento em blocos casualizados, no esquema fatorial 2 × 4 × 4 e três repetições, sendo duas formas de adubação fosfatada (a lanço e no sulco), quatro doses de P2O5 (0, 50, 100 e 150 kg ha-1) e quatro níveis de compactação (PT0, PT2, PT4 e PT8 – semeadura direta com compactação induzida por tráfego de trator em zero, duas, quatro e oito passadas, respectivamente). O tráfego de máquinas ocasionou compactação do solo em semeadura direta, aumentando a densidade do solo (Ds) e resistência do solo à penetração (RSP) e reduzindo a macroporosidade e porosidade total, sem efeito da adubação fosfatada. A resposta das espécies à forma de adubação fosfatada foi diferenciada, não apresentando influência no crescimento radicular da soja. No milho, quando fornecida a lanço proporcionou maior área de raízes na camada de 0,00-0,05 m; e, quando no sulco, foram observadas entre as camadas menores diferenças na área radicular. Nas camadas de 0,05-0,10 e 0,10-0,20 m, a RSP de 1,48 e 1,84 MPa (Us = 0,28 m3 m-3) e Ds de 1,32 e 1,35 kg dm-3, respectivamente, proporcionaram redução de 19 e 27 % no diâmetro médio das raízes do milho e aumento de 110 e 49 % no diâmetro das raízes da soja.

Metal uptake via phosphate fertilizer and city sewage in cereal and legume crops in Pakistan.

Crop irrigation with heavy metal-contaminated effluents is increasingly common worldwide and necessitates management strategies for safe crop production on contaminated soils. This field study examined the phytoavailability of three metals (Cd, Cu, and Zn) in two cereal (wheat, maize) and legume (chickpea, mungbean) crops in response to the application of either phosphatic fertilizer or sewage-derived water irrigation over two successive years. Five fertilizer treatments, i.e. control, recommended nitrogen (N) applied alone and in combination of three levels of phosphorus (P), half, full and 1.5 times of recommended P designated as N0P0, N1P0, N1P0.5, N1P1.0, and N1P1.5, respectively. Tissue concentrations of Cd, Cu, Zn, and P were determined in various plant parts, i.e., root, straw, and grains. On the calcareous soils studied while maximum biomass production was obtained with application of P at half the recommended dose, the concentrations of metals in the crops generally decreased with increasing P levels. Tissue metal concentrations increased with the application of N alone. Translocation and accumulation of Zn and Cu were consistently higher than Cd. And the pattern of Cd accumulation differed among plant species; more Cd being accumulated by dicots than monocots, especially in their grains. The order of Cd accumulation in grains was maize > chickpea > mungbean > wheat. Mungbean and chickpea straws also had higher tissue Cd concentration above permissible limits. The two legume species behaved similarly, while cereal species differed from each other in their Cd accumulation. Metal ion concentrations were markedly higher in roots followed by straw and grains. Increasing soil-applied P also increased the extractable metal and P concentrations in the post-harvest soil. Despite a considerable addition of metals by P fertilizer, all levels of applied P effectively decreased metal phytoavailability in sewage-irrigated soils, and applying half of the recommended dose of P fertilizer was the most feasible solution for curtailing plant metal uptake from soils. These findings may have wide applications for safer crop production of monocot species when irrigating crops with sewage effluent-derived waters.

Effect of Method of Sowing and Time of Di-Ammonium Phosphate (DAP) Fertilizer Application, on Yield and Yield Components of Tef ((Eragrostic tef) Trotter) At Shebedino, Southern Ethiopia

Time of DAP application and sowing method vary from farmer to farmer. Therefore, there is a need to determine time of DAP and sowing method recommendations for tef (Eragrostis tef (Zucc) Trotter). Accordingly, an experiment was conducted to evaluate the effect of sowing method and time of DAP application on yield and yield components of tef at Shebedino, Southern Ethiopia in 2012 cropping season. DZ-37 tef variety was used as a test crop. A factorial combination of planting method (row planting and broadcasting) and five times of DAP fertilize application (at planting, two, four, six and eight days before planting) was laid out in Randomized Complete Block design (RCBD) with four replications. Row sowing and DAP applied two days before planting had significantly affected days to heading and maturity, plant height, first growth rate, number of tiller and panicle, thousand seed weight, grain, straw and total biomass yields and harvest index. Days to emergence and panicle length were significantly affected by broadcasting and application of fertilizer two days before planting. Row sowing hastened heading and maturity by 1 day and increased growth rate by 23.46% than broadcasting; and DAP applied two days before planting hasten days to heading and maturity by 4 and 5 days, respectively, than DAP applied eight days before planting. Row sowing had 10, 24.8 and 23.8% more panicles, grain and biomass yields respectively, than broadcasting. DAP applied two days before sowing increased panicles, grain and biomass yields by 41.7, 62.1 and 59.6% respectively, than DAP applied eight days before sowing. Interaction of row sowing and DAP applied at the time of sowing, had 54.7 and 1.07% more 1000 seed weight and harvest index respectively, than broad casting and DAP applied at the time of sowing. Row sowing was found to be economically acceptable with Marginal Rate of Return (MRR) of 627.7% with 6775.6 Birr ha-1 more income from grain yield than broadcasting. Row sowing and DAP applied two days before planting had 80.85 Birr ha-1 more additional income from straw than broadcasting. Therefore, row sowing and DAP application two days before planting could be recommended as an economically feasible choice for the study area.

Role of arbuscular mycorrhiza in arresting reactive oxygen species (ROS) and strengthening antioxidant defense in Cajanus cajan (L.) Millsp. nodules under salinity (NaCl) and cadmium (Cd) stress

Application of phosphate fertilizers and biosolids enhances Cd contamination in arid and semi-arid regions. Increased concentration of dissolved chloride (Cl−) in saline solution increases Cd solubility and bioavailability. Nodules are soft targets for NaCl and Cd stresses due to adverse effects on their functioning. Arbuscular mycorrhizal (AM) fungi enhance plant growth in contaminated sites. Greenhouse experiments were conducted to evaluate the efficacy of Funneliformis mosseae in arresting toxic ion transport and ROS generation in pigeonpea nodules and its role in improving membrane structure and antioxidant defense. Two genotypes (Sel 85N; tolerant and ICP 13997; sensitive) were subjected to NaCl (4, 6 dS m−1) and Cd (CdCl2—25, 50 mg Kg−1 dry soil) treatments. Results indicated higher phytotoxicity of Cd than NaCl which aggravated when NaCl was added along with Cd. Increment in toxic ions caused injury to nodular membranes and increased oxidative stress (H2O2 and MDA), higher in ICP 13997 than Sel 85N. Significant increase in non-protein thiols (NP-SH) and PC levels was observed under Cd and NaCl + Cd treatments. The rapid generation of ROS was counteracted by AM-induced enzymatic activities (SOD, POD, CAT and GR), non-enzymatic components (GSH–GSSG cycling, their ratio and total glutathione) and glutathione-mediated PC synthesis.

Responsiveness of Soil Series in Southwestern Nigeria to Single Super Phosphate Fertilization

Application of Single Super Phosphate (SSP) fertilizer in soils with inadequate phosphorus (P) should elicit crop response. However, there is an indication of inconsistent response behaviour to SSP fertilizer in some Nigeria soils despite their low available P. This study identified major soil types in Southwestern Nigeria that are unresponsive to P fertilizer application under screenhouse condition and soil properties that are related to this unresponsive behaviour were determined. Soils from twenty locations in Southwestern Nigeria were selected to evaluate their response to four phosphorus fertilizer rates with a control replicated three times in a factorial arrangement laid out in randomized complete block design. Results indicated that most of the locations responded to initial P application except for Fashola 2 which produced significantly higher maize shoot yield in control soils. There were five other locations where no-response was observed. Multiple regression analysis showed that phosphorus sorption index was related to sand, organic matter and clay. Phosphorus accumulation in soil P reserves may explain the behaviour of the P-unresponsive soils irrespective of their available P levels.

Effects of Mycorrhizal Fungi with Phosphate Fertilizer Applications on Phosphate Solubilizing and Soil Properties of Grapes Orchard

The objective of this study was to efficiency determined of mycorrhizal fungi with different phosphate fertilizer application on phosphate solubilizing and soil properties of grapes orchard. The treatments were arranged in 2x5 factorials in Randomized Complete Block Design (RCBD) with 5 replications. Factor 1: two levels of mycorrhizal fungi were non-inoculation and inoculation. Factor 2: five levels of phosphate fertilizer application were 0, 27.17, 54.34, 81.52 and 108.69 g plant-1 by soil analysis recommendation. The collected data was spore number, root colonization density, phosphatases activity of mycorrhizal fungi, available phosphorus (P) in soil, soil pH and phosphorus in leaf. The results showed that the inoculation of mycorrhizal fungi increased spore number, root colonization density, phosphatases activity of mycorrhizal fungi, available P in soil and P in leaf compared with the non-inoculated. While, phosphate fertilizer at a rate 54.34 g plant-1 increased spore number, root colonization density, phosphatases activity of mycorrhizal fungi, available P in soil and P in leaf. Mycorrhizal fungi combination with 54.34 g plant-1 of phosphate fertilizer increased spore number, root colonization density, phosphatases activity and available P in soil.

A study on the impact of phosphate fertilizers on the radioactivity profile of cultivated soils in Srirangam (Tamil Nadu, India)

Phosphate fertilizers are enriched with 238U during its production from phosphate rocks. Since, application of phosphate fertilizers in modern agriculture is ever on the increase, the present study investigated the impact of phosphate fertilizers on the radioactivity profile of cultivated (fertilized) soils as against virgin soils. Thirty soil samples each from cultivated fields and virgin fields were collected from Srirangam taluk and analyzed for the activity concentrations of 238U, 232Th and 40K employing gamma ray spectrometry. Similar analysis was also undertaken in commonly used phosphate fertilizers. Among the phosphate fertilizers analyzed single super phosphate (396.3 Bq/kg) and triple super phosphate (284.2 Bq/kg) registered higher level of 238U. The mean activity level of 238U in cultivated soil (8.4 Bq/kg) was 25% higher than that of virgin soil (6.8 Bq/kg), while the mean 232Th and 40K activities in cultivated soil (98.4 Bq/kg & 436 Bq/kg) were elevated by 12.4% and 4% respectively as compared to virgin soil (87.5 Bq/kg & 419 Bq/kg). The mean radium equivalent (Raeq) value for virgin and cultivated soil samples was found to be 164.5 Bq/kg and 181.7 Bq/kg respectively. It is evident that the application of phosphate fertilizers elevated 238U level of the soil. However, the mean Raeq value for soil samples is well below the permissible limit of 370 Bq/kg and hence cultivated soils do not pose any radiological risk.

Retention of phosphorus on calcite and dolomite: speciation and modeling

The intensive application of phosphate fertilizers in agriculture has created an important source of diffuse phosphorus pollution. The interaction of phosphorus with carbonate minerals plays a role in the fate and transport of phosphorus in soil. The object of the present study was to investigate the speciation of phosphorus on two common carbonate minerals, calcite and dolomite, using a combination of batch experiments, ATR-FTIR spectroscopy, XANES analysis, and diffuse layer modeling. Within the pH range 6.0–7.0, the retention of phosphorus by calcite and dolomite is mainly attributed to the formation of amorphous calcium phosphate (Ca3(PO4)2, ACP), dibasic calcium phosphate (CaHPO4·2H2O, DCP), and hydroxyapatite (Ca5(PO4)3OH, HAP). At pH ≥ 8.0 the immobilized phosphorus takes the form of complexes =CaPO4Ca0/=sCaPO4Ca0 on the surface of calcite, followed by the formation of Ca–P phases, including ACP, DCP, and HAP, with increasing phosphorus levels (>2 mg L−1). However, the dolomite surface is initially dominated by the adsorption complex =MgHPO4Ca+ at =Mg sites, and at higher phosphorus levels it then grows due to Ca–P phases and the formation of newberyite (MgHPO4). It is interesting to note that the Mg content in dolomite favors the rapid growth of DCP at phosphorus levels >200 mg L−1. As a result, at pH ≥ 8.0, dolomite shows a stronger capacity for immobilizing phosphorus than does calcite. Dolomite therefore serves as a better phosphorus sink than calcite in calcareous soil environments.

The Influence of Long-Term Fertilization on Soil Acidification

Based on the long-term experimental field of Jilin Agricultural University as a platform. Aiming at groping for the influence of long-term fertilized of the acidity changes on soil in research area. The results show that: compared with CK group. The soil pH declined as a result of applying nitrogenous fertilizer chronically. Instead the content of exchangeable acid, exchangeable hydrogen and exchangeable aluminum increased. The content of soil organic matters reduced with the decrease of soil pH application of phosphate fertilizer and potassium fertilizer could achieve the same objective. But the Influence was not as significant as the one fertilized with N.

Factors affecting uranium and thorium fractionation and profile distribution in contrasting arable and woodland soils

This work investigated the vertical distribution and fractionation of uranium and thorium in soils under contrasting arable and woodland sites based on the same parent material. The effect of long-term application of phosphate fertilizer on U and Th concentrations in the arable soil was also assessed. The arable surface soils contained higher amounts of U compared with underlying layers and the woodland soil profile; by contrast, the Th distributions were very similar in both arable and woodland soils. The U and phosphate concentration profiles within the arable soil were broadly similar; U was strongly associated with Ca (r=0.94) and soil P content (r=0.86) whereas the U concentration profile in the woodland soil was virtually uniform with depth. The ‘excess’ U in arable soil, associated with long term P fertilizer application, was approximately 2.5kgha−1 with 80% in the top 30cm of the soil profile. A sequential extraction technique was used to fractionate U and discriminate between ‘reactive’ (non-residual) and ‘residual’ forms of U. The reactive U was adsorbed, mainly by organic matter and Fe–Mn oxides in the arable topsoil and there was a very strong relationship between reactive U and soil phosphate content in the arable soil (r=0.99, P<0.001). The ‘excess’ U accumulated in the arable topsoil was also considerably more reactive than the co-existing native U. Thus the reactive fraction of the excess U ranged from 29 to 42% compared with 14 to 15% reactivity of the native U. Thorium in both soils showed a very consistent, and low, reactivity down the soil profile at about 4% of total soil Th content (96% residual), bound almost completely to humus.

Phosphate minerals and solubility in native and agricultural calcareous soils

Generally the direct identification of naturally occurring phosphate minerals, especially the reaction products of applied phosphate fertilizer with soil constituents, is very difficult. Nevertheless the characterization of phosphate (P) minerals and the understanding of their behavior in soils are very important with respect to fertilizer management and to safeguarding water quality. The objectives of this study were to determine the P minerals detectable in different particle size fractions of native and cultivated calcareous soils that are probably products of reactions between the soil and the fertilizer, and to examine the relationships between P mineral composition, phosphate solubility, chemical fractionation, and P activity. Fifteen calcareous soils representing four soil series were collected from native pineland and wetland, cultivated vegetable fields and fruit groves in south Florida. Soil samples were separated into sand, silt and clay with and without the removal of CaCO3 and organic matter. Mineralogy of selected fractions was determined by X-ray diffraction (XRD). Relatively distinctive crystalline apatite was identified by XRD of high-density separates from carbonate-free silt fractions of selected cultivated soils, but no phosphate minerals were detected in any fraction of the corresponding native soils. Soils were also incubated under field capacity moisture content for 30days, either without P application or with 66.8mgPkg−1 soil applied as KH2PO4. Soil solutions were extracted and the concentrations of both anions and cations were determined. The activities of Ca2+ and H2PO4− calculated using the MINTEQA2 speciation program were adequate to support the stability of hydroxyapatite (HA), fluorapatite (FA) and tricalcium phosphate (TCP) minerals in farmed soils, while TCP was unstable in unfarmed soils, and the solution points of TCP were close to the equilibrium of HA. The results indicated that phosphate activities in native and heavily fertilized calcareous soils were controlled by the solubility of different phosphate minerals. Sequential fractionation data suggested that Ca–Mg-associated P accounted for a dominant proportion of total P in farmed soils, but this fraction was below the detectable limit in unfarmed soils. These findings demonstrate that the repeated heavy application of phosphate fertilizer during many years has resulted in the formation of stable, crystalline calcium phosphate minerals in these farmed calcareous soils.

Efecto de la calidad de la materia orgánica asociada con el uso y manejo de suelos en la retención de cadmio en sistemas altoandinos de Colombia

Cadmium from soils by weathering and anthropogenic activities can have produce toxic effects associate to low affinity of adsorbents forms, high solubility and mobility. It is very important to conduct studies leading to knowledge of adsorption phenomena and cadmium mobility factors and predict possible toxici-ty in High Andeansoils whose use is changing to pastures and crops with applications of phosphate fertilizer with presence of Cd in composition. High Andean soils subbasin Rio Las Piedras, (Department of Cauca), with systems of forest, crop and pasture were characterized by physical and chemical properties, highlighting strong acidity, presence of allophones, high in organic carbon, high cation exchange capacity, low density of soil. The quality of soil organic matter was assessed by different humification index obtained with the different fractions characterized to determine the influence on cadmium retention phe-nomenon and mobility factor. The retention was evaluated by Freundlich adsorption isotherms in humic acids and soils of the three systems. The K (maximum adsorption capacity) and n (retention force) values correspond to 131. 98 and 1.18 in forest soils, 340.93 and 1.19 for crop, 170.36 and 1.19 in pasture, and are lower than those of humic acids in the three systems. The quality of the organic matter has a significantly effect on these processes, better quality results in less mobility preventing groundwater contamination and bioaccumulation toxicity.

Spatial and temporal patterns of potassium on grazed permanent pastures—Management challenges

Alto Alentejo region in Southern Portugal has over 200,000ha of grazing permanent pastures. Here, the soils do not generally need potassium (K) fertilization due to the bedrock richness in K. The general objective of this study was to evaluate the specificity of the spatial and temporal soil test K dynamics, over 10 years, in a complex agro ecosystem (a bio-diverse pasture installed on a shallow soil, grazed by sheep, in Mediterranean conditions) and the potential for implementing site specific fertilizer management. A 6ha permanent pasture field was subject to two management systems: (i) 2004–2007, the field was used for grazing by sheep and improved by an annual application of super phosphate fertilizer 18%; (ii) 2007–2013, the field was left fallow. The K spatial trend and K temporal stability were evaluated by a single map of management classes. The evolution of mean soil test K concentration in the experimental field over the 10-year study ranges, in relative terms, between −21% and +16% of the overall average of the period considered (96±21mgkg−1). This study, however, shows that the experimental field is dominated by a large spatially anisotropic trend. Significant correlation coefficients were found between the soil test K concentration and altimetry (0.614), clay (0.651), sand (−0.674), test phosphorus (P) concentration (0.749), organic matter (0.882), soil moisture content (0.455), apparent soil electrical conductivity (0.436) and pasture dry matter yield (−0.499). It can be stated that the combined effects of an undulated landscape, with sparse trees and animals that selectively graze the plant species and make a heterogeneous deposition of dung and urine, provide a notable spatial variability of soil test K concentration (Spatial_CV¯ of 29.8±12.3%). The K temporal stability (Temporal_CV¯ = 18.1±8.6%), is confirmed by the predominance of moderately stable (56.6% of the experimental field) and of stable areas (25.0% of the experimental field). Within the classes identified as moderately stable and stable, around 45% of the experimental field shows soil test K concentrations below average soil test K concentration. Based on regional recommendation of 125–150mgkg−1 of K in the soil to adequately promote the development of dry-land permanent pastures, this study demonstrates the interest and the potential for using variable rate technology (VRT) for site-specific K management in pastures in Southern Portugal.

Phosphorus fractions in the vineyard soil of the Serra Gaúcha of Rio Grande do Sul, Brazil

The study aimed to evaluate the accumulation of P fractions in a vineyard soil profile with successive applications of phosphate fertilizers. In January 2010 an area was selected of native forest and a vineyard at age 33 with a history of phosphate fertilizer application, in Bento Gonçalves, Rio Grande do Sul state. Soil samples were collected from 0-5, 5-10 and 10-20 cm layers, prepared and submitted to chemical fractionation of P. The excessive application of phosphate fertilizers during 33 years in the vineyard soil increased the levels of organic and inorganic P until the 20 cm layer in all P fractions. The highest levels of P in the vineyard soil were found mainly in the labile fractions extracted with anion exchange resin and NaHCO3, which indicates high nutrient availability to plants, but also indicates the potential of transfer of solution from soil to surface run-off or percolated through the soil profile, which represents greater potential for contamination of surface and subsurface waters.