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Bacterial inoculants have been used in agriculture to improve plant performance. However, laboratory and field requirements must be completed before a candidate can be employed as an inoculant. Therefore, this study aimed to evaluate the parameters for inoculant formulation and the potential of Bacillus subtilis (B70) and B. pumilus (B32) to improve phosphorus availability in maize (Zea mays L.) crops. In vitro experiments assessed the bacterial ability to solubilize and mineralize phosphate, their adherence to roots, and shelf life in cassava starch (CS), carboxymethyl cellulose (CMC), peat, and activated charcoal (AC) stored at 4 °C and room temperature for 6 months. A field experiment evaluated the effectiveness of strains to increase the P availability to plants growing with rock phosphate (RP) and a mixture of RP and triple superphosphate (TS) and their contribution to improving maize yield and P accumulation in grains. The B70 was outstanding in solubilizing RP and phytate mineralization and more stable in carriers and storage conditions than B32. However, root adherence was more noticeable in B32. Among carriers, AC was the most effective for preserving viable cell counts, closely similar to those of the initial inoculum of both strains. Maize productivity using the mixture RPTS was similar for B70 and B32. The best combination was B70 with RP, which improved the maize yield (6532 kg ha-1) and P accumulation in grains (15.95 kg ha-1). Our results indicated that the inoculant formulation with AC carrier and B70 is a feasible strategy for improving phosphorus mobilization in the soil and maize productivity.

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Resumen El fósforo (P) es un elemento fundamental para toda la vida en la tierra, y no presenta un sustituto en la producción de alimentos. El suministro de P desde las reservas de rocas fosfóricas está concentrado en unos pocos países y, en las próximas décadas podría verse gravemente afectado. Por lo que el contexto geopolítico debería ser considerado al evaluar la situación. Sin embargo, no existen datos fiables y transparentes sobre la producción, el comercio, el uso y las pérdidas de dicho nutriente. Por lo tanto, ¿hay realmente una escasez física o son limitaciones de tipo económicas, políticas o técnicas? Si bien ya se están buscando soluciones a diferentes escalas para lograr una mayor resiliencia de los agroecosistemas, se necesitan acciones urgentes para comprender, proteger y preservar nuestro planeta y sus limitados recursos, como el P, de una manera sostenible, rentable y segura.

Abstract Phosphorus (P) is an essential element for all life on earth, and has no substitute in food production. The supply of P from phosphate rock reserves is concentrated in a few countries and could be severely affected. Whereby the geopolitical context should be considered when assessing the situation. However, there are no reliable and transparent data on the production, trade, use and losses of this nutrient. So is there really a physical shortage or are they economic, political or technical constraints? Although solutions are already being sought at different scales to achieve greater resilience of agroecosystems, actions are urgently needed to understand, protect and preserve our planet and its limited resources, such as phosphorus, in a sustainable, profitable and safe way.

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Improving phosphorus (P) use efficiency is a challenge to promote a circular economy and greening the phosphorus cycle towards planetary sustainability. The disruptive innovation for phosphate fertilizers may help to reduce some unwelcome reactions that occur to P in soils. Monoammonium phosphate (MAP) coating with biodegradable organic polymers and the addition of magnesium (Mg) - a nutrient with a synergistic effect on the uptake of P, zinc (Zn), and boron (B) - emerge as a smart strategy to applying these micronutrients uniformly in soils. The objectives of this study were: to characterize the coated-MAP with biodegradable organic polymers, quantify the diffusion and availability of P in the soil, and evaluate the corn crop nutrition and yield during two crop seasons. The treatments were: MAP, MAP coated with biodegradable organic polymer (BOP), MAP + BOP + 1.3% of Zn + 0.33% of B, and MAP + BOP + 1.76% of Mg. The laboratory tests showed that the diffusion of MAP-based fertilizers was: MOMg (7.86 mm) = MO (8.82 mm) = MAP (8.84 mm) = MOM (8.51 mm) after 432 h. Coatings did not cause delays in the P-release in water at 25 °C since more than 95% of P was released within 24 h. In the field trials, the application of Mg, Zn, and B in the MAP coating did not increase nutrient leaf concentration. In the summer crop season, grain yield increased up to the P-rates of 85 kg of P2O5 ha-1, reaching the value of 6731 kg ha-1. Physical and chemical characteristics of MAP-fertilizers tend to improve with the coatings. The addition of biodegradable organic polymers, Mg, B, and Zn, as MAP-coatings did not enhance P diffusion, release, and availability in the soil and the crop nutrition. Coated-MAP improved corn yield only in the 2nd crop season.

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This paper reports the hydrochemistry and activity concentration of the natural radionuclides 238U, 234U, and 210Po for three compartments of the hydrological/hydrogeological system in Araxá city, Minas Gerais State, Brazil: 1) mineral waters from the prominent springs Dona Beja (DBS) and Andrade Júnior (AJS), occurring at Barreiro area; 2) surface waters from Barreiro area and vicinity; and 3) rainwater. According to the Rule for Mineral Waters in Brazil (Register 7841) for temperature, the DBS water is cold (< 25 °C), while AJS is hypothermal (25-33 °C). The TDS (Total Dissolved Solids) concentration of DBS is low (70 mg/L), but high in AJS (2898 mg/L). The hydrogeochemical facies corresponded to sodium-(bi)carbonate for AJS and sodium/potassium-bicarbonate for DBS. The hydrochemical differences of DBS and AJS waters reflect the distinct characteristics of their respective aquifer systems. The DBS classification for TDS is the same of the Barreiro basin surface waters (mean TDS = 102 mg/L). Such value is somewhat higher than that of the rainwater and surface waters used for human consumption at Araxá city (TDS < 50 mg/L). The dataset reported in this paper indicated that fluoride and barium exceeded the WHO limits proposed in 2011 for drinking water. Among the natural radionuclides analyzed here that offer potential hazards for the human health is 210Po, whose WHO's limiting value of 100 mBq/L in drinking water was exceeded in rainwater, thus, restricting the use of this resource as a possible supply of drinking water for the local community.

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Phosphate-solubilizing bacteria can release phosphorus (P) from insoluble minerals and benefit either soil fitness or plant growth. Bulk sized P compounds have been suggested but little is known about solubilization of nanosized materials such as hydroxyapatite nanoparticles (HANP). A screening of the initial 43 strains from vanilla rhizospheres for phosphate solubilization with bulk Ca3(PO4)2 was carried out. Subsequently, 6 strains were selected on bulk rock phosphate (RP) and HANP. Two kinetics experiments were run out regarding evaluation at 5, 10 and 20 days after inoculation (dai). Bacterial biomass production was similar in both experiments; the lowest biomass was found at 20 dai. In all cases, bacteria reduced the original culture medium pH; which was related with phosphate solubilization from the production of organic acids. Citric acid was produced by all strains. Enterobacter cloacae CP 31 was the most interesting bacterium: produced the lowest culture pH at 20 dai (4) with both Ca3(PO4)2 and RP, and 3.7 at 10 dai with HANP correlating with high soluble P concentration (536, 64 and 13 mg L-1 with these P sources, respectively). This bacterium should be tested as an inoculant in plants to reveal its potential as plant promoter growth and HANP to suggest its role in the potential use of nano-P fertilizers.

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Rice is the world's most consumed and in-demand grain. Ecuador is one of the main rice-consuming countries in Latin America, with an average per capita consumption of 53.2 kg per year. Rice cultivation takes place under flooding conditions, which favors the mobilization and subsequent accumulation of heavy metals in the plant. This study's principal objective was to evaluate the contamination of cadmium (Cd) and lead (Pb) in the rice cultivation system in the province of Guayas. To this end, extensive sampling of water, soil and rice grains was carried. Water samples were analyzed to determine physicochemical properties and concentrations of dissolved Cd and Pb. Physicochemical properties, total organic carbon (TOC), total content of nitrogen (N), iron (Fe), manganese (Mn), phosphorus (P), bioavailable phosphorus (P mehlich), Cd and Pb were determined in soil samples. In addition, to understand the dynamics of Cd and Pb mobility and bioavailability, an extraction of six randomly selected soil samples was carried out. The concentration values of the total Cd and Pb content in the rice cultivation system did not exceed the maximum recommended limit for soil, water and rice grains. However, 85% of the total Cd was in the soluble or exchangeable fraction of the soil, while the Pb was strongly bound to crystalline iron oxyhydroxides. It was established that the TOC, N, Fe, and P mehlich have a significant correlation (p < 0.05) with the overall concentration of Cd and Pb in the rice farming soil. The Cd and Pb present in rice do not represent a dietary health risk to the population of Ecuador.

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The mineral exploration of rare earth elements (REEs) and their entry into the soil via fertilizers has generated concern about environmental impacts and human health risks. We evaluated 60 samples of limestone, gypsum and phosphate fertilizers marketed in Brazil in order to characterize their contents, signature and solubility of REEs. The fertilizers from igneous origin presented the largest accumulation of REEs. Accumulation of the light REEs Ce, La, Nd, Pr, Sm and Eu were larger than the heavy REEs (Y, Dy, Gd, Er, Yb, Ho, Tb and Lu). The solubility of fertilizers produced from sedimentary sources was greater than that of igneous sources. The mean annual REEs contribution of SSP and organo-mineral + phosphate rock (both of igneous origin) to soils was > 4000 t year-1, with highest additions for Ce, La, Nd and Y. Thus, phosphate fertilization and liming were considered to be significant sources of REEs and soils receiving continuously high doses of these inputs are likely to be enriched in REEs. Risk assessment studies are necessary to evaluate the impact of these REEs additions to soils on human health.

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The aim of this study is to determine the amounts of radionuclides' activity present in samples of feed for young and adult chicken and feed for dairy and beef cattle, as well as in dicalcium phosphate (DCP) (CaHPO4), used as a nutritional supplement for animal feed. Radioactivity in these samples is due to the presence of the 238U and 232Th radioactive series, as well as their daughter. In addition, as it is for environmental samples, the activity of 40K should be an important source of radioactivity in all analyzed samples. Gamma rays were measured using a standard spectroscopy system, with a high-resolution HPGe detector. Measured activities in feed samples ranged from 0.23 to 1.51 Bq.kg-1, 0.67 to 4.21 Bq.kg-1, 0.29 to 1.63 Bq.kg-1 and 236 to 402 Bq.kg-1 for 226Ra, 228 Ra, 228 Th and 40K, respectively. Measured activities in DCP samples were 46.6 Bq.kg-1, 83 Bq.kg-1, 4.20 Bq.kg-1 and 16.61 Bq.kg-1 for 40 K, 226 Ra, 228 Ra and 228 Th, respectively. Although 40K activity has reached hundreds of Becquerel in feed samples, it should not represent a risk to human health, not even to animals, since potassium is an essential mineral to living organisms.

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The development of piatã grass fertilized with phosphorus sources with different solubilities in water was evaluated. The experiment was developed in the unit of Aquidauana of UEMS, MS, from February to August, 2012. Four treatments were evaluated: control (without phosphorus fertilization), slow solubility, fast solubility (readily available), and mixed solubility sources of phosphorus (FH Pasture(r)). It was adopted a randomized blocks design with four blocks and four replicates in a total of 16 pastures (0.5 ha each one). Measurements were performed weekly to evaluate structural characteristics and morphogenic variables of the plants. Data were submitted to a variance analysis according to the model. When necessary, the means of treatments with different phosphorus fertilizer sources were compared with the control using the Dunnett test and with other treatments by using student's t test. The significance level of 5% was adopted in all analysis. No significant effect was observed (P 0.05) in the evaluated traits in the first year of the experiment.(AU)

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The development of piatã grass fertilized with phosphorus sources with different solubilities in water was evaluated. The experiment was developed in the unit of Aquidauana of UEMS, MS, from February to August, 2012. Four treatments were evaluated: control (without phosphorus fertilization), slow solubility, fast solubility (readily available), and mixed solubility sources of phosphorus (FH Pasture(r)). It was adopted a randomized blocks design with four blocks and four replicates in a total of 16 pastures (0.5 ha each one). Measurements were performed weekly to evaluate structural characteristics and morphogenic variables of the plants. Data were submitted to a variance analysis according to the model. When necessary, the means of treatments with different phosphorus fertilizer sources were compared with the control using the Dunnett test and with other treatments by using student's t test. The significance level of 5% was adopted in all analysis. No significant effect was observed (P 0.05) in the evaluated traits in the first year of the experiment.

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O melhor aproveitamento do P, tanto o aplicado no cultivo quanto o residual do solo, em razão do uso de calcário em solos argilosos cultivados e adubados por muitos anos, pode ser viável. Objetivando avaliar o efeito do aumento do pH do solo e da aplicação de adubo fosfatado e calcário na semeadura sobre a disponibilidade de P e o seu acúmulo em plantas de soja, realizaram-se dois experimentos em Latossolo Vermelho Distrófico-LVD e Latossolo Vermelho Distroférrico-LVDf, argilosos, com elevados níveis de fertilidade. O delineamento experimental foi blocos casualizados, num fatorial 4x2x2: quatro níveis de pH, duas doses de P e duas de calcário, com quatro repetições. Cultivaram-se plantas de soja em vaso até a floração. Avaliaram-se o peso da massa seca, teor e acúmulo de P na parte aérea; teor de P e P remanescente no solo. A disponibilidade de P nos solos aumentou com a elevação do pH. Para o LVdf, houve interação entre pH e doses de P, os teores de P no solo aumentaram com o pH e com a aplicação de P. Para o LVD, houve interação entre pH e doses de calcário. O P remanescente foi reduzido pelo aumento do pH em ambos os solos. Nos dois experimentos, com o aumento do pH do solo houve incremento na produção de massa seca e de P acumulado. Em solos argilosos e com alto teor de P, a elevação do pH aumenta a disponibilidade de P, proporcionando maior produção de massa seca de soja.

The best P employment, both applied in the culture as the P soil residual, is possible, due limestone use in clayey soils cultivated and fertilized for many years. Aiming at evaluating the pH increase in the soil and the effect of the application of phosphated fertilizer and lime on the sowing on the P availability and its accumulation in soybean plants, two experiments in oxisols, Haplortox (one LVD and the other LVDf), with high fertility levels, were carried out. The experimental design was random blocks, in a 4x2x2 factorial, being four pH levels, two P doses and two limestone doses, with four repetitions. Soybean plants were cultivated in vases up to flowering. The dry mass weight, P contents and accumulation in the area, P content and P remaining in the soil, were evaluated. P availability in soils increased with pH elevation. For the LVDf, there was an interaction between the pH and the P doses, the P contents in the soil increased with the pH and with the P application. For the LVD, there was an interaction between the pH and the doses of lime applied. The P remaining was reduced by the pH increase in both soils. In both experiments, with the pH increase in the soil, there was an increment in the dry mass production and P accumulated. In clayey soils with a high P content, the pH elevation increases the P availability, providing greater soybean dry mass production.

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The corn plants were evaluated with different phosphate fertilizer sources and aluminum (Al) concentrations in a sandy substrate. A totally randomized experiment design was set up with two corn plants in the pots containing 2 kg of a sandy substrate, two phosphate sources (Triple Super Phosphate - TSP or Arad Phosphate - AP) and four Al concentrations. When Al concentrations increased, pH (CaCl2) substrate values decreased. There was an increase in the calcium and phosphorus contents in the sandy substrates that received the TSP and AP sources. The calcium, magnesium, phosphorus, and potassium concentrations of the corn plant's shoot were higher in the TSP than without P and AP sources. When the Al concentration increased, the concentration values of the former elements decreased. The dry mass production of the corn plants responded positively to P sources. As the Al concentration increased, the dry mass values decreased significantly in the TSP source.

Foram avaliadas plantas de milho submetidas a diferentes fontes de fertilizantes fosfatados e diferentes concentrações de alumínio em um substrato de areia. O experimento foi conduzido com duas plantas por vaso contendo 2 kg de areia, duas fontes de fósforo (Fosfato Supertriplo -TSP ou Fosfato de Arad -AP) e quatro concentrações de Al. Com o aumento das concentrações de Al houve diminuição dos valores de pH (CaCl2) do substrato. Os valores de cálcio e fósforo aumentaram no substrato nos tratamentos com TSP e AP. As concentrações de cálcio, magnésio, fósforo e de potássio das plantas de milho foram maiores em TSP do que nos tratamentos sem P ou com AP. Como o aumento da concentração de Al observou-se redução na concentração de cálcio, magnésio, fósforo e de potássio nas plantas. A produção de massa seca da parte aérea respondeu positivamente com as fontes de P. Com o aumentou da concentração de Al os valores de massa seca diminuíram significativamente com TSP.

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Conduziu-se este estudo, com o objetivo de avaliar os efeitos de doses de adubos fosfatados sobre a cultura da soja e do milho, em cultivos sucessivos. O experimento foi realizado em casa de vegetação da UFGD, em vasos contendo amostras de 5,5 dm³ de um Latossolo Vermelho Distroférrico argiloso, sendo utilizado como fontes de fósforo (P) o superfosfato triplo (SFT) e o fosfato natural de Arad (FNA). O FNA foi utilizado sob duas formas. Em uma, considerou-se o P total (Arad T) e, em outra, apenas a fração de P solúvel em ácido cítrico a 2% (Arad SA), resultando em três fatores de estudo, cada um em seis níveis de P (0, 56, 112, 224, 336 e 560), expressos em mg dm-3. A soja foi semeada em dezembro de 2006 e ao final do ciclo, efetuou-se a colheita, avaliando-se a produtividade de grãos, teores de P na folha e no solo. Após o cultivo da soja, semeou-se o milho, cuja colheita das plantas ocorreu aos 76 dias após a semeadura, sendo avaliados a produção de massa seca da parte aérea e teores de P na folha. O índice de eficiência agronômica foi calculado para ambas as culturas. Conclui-se que, para o primeiro cultivo (soja), o SFT apresentou um melhor desempenho no que se refere à produtividade de grãos, quando comparado ao FNA. No cultivo do milho em sucessão a soja, o FNA tendeu a equiparar-se ao SFT nos atributos avaliados.

The aim of this study was to evaluate the effects of phosphate fertilizer rates on soybean and corn crops, in crop rotation. The experiment was carried out in a greenhouse at the Grande Dourados University, in pots with samples of 5.5 dm³ clayey Dystropherric Red Latosol, where the triple superphosphate (TSP) and the Arad rock phosphate (ARP) were used as P source. Two kinds of ARP were used. In one, the total P (Arad T) was considered while in the other, only the P soluble fraction in citric acid at the concentration of 2% (Arad SA) was considered, resulting in three factors of study, each with six levels of P (0, 56, 112, 224, 336, and 560 mg dm-3). The soybean was sowed in December 2006 and in the end of the cycle, the crop was harvested and evaluated for grain yield, P concentration in leaves and in the soil. After the soybean crop, it was turn for the corn sowing, which harvest occurred 76 days after sowing. The shoot dry matter and P concentrations in leaves were evaluated. The Index of Agronomic Efficiency was calculated for both crops. We concluded that the TSP caused a better soybean grain yield, when compared to the ARP. In the corn crop succeeding the soybean crop, the ARP tended to be similar to the TSP values in the attributes evaluated.

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Despite the small mobility of phosphates and liming, addition of these materials on the soil surface, without incorporation, has often increased crop yield. However, it is unknown the behavior of plant roots developed in a soil with only a thin layer chemically ameliorated, as well as the result of combining large amounts of lime and phosphates on P availability. This study was carried out to evaluate the effect of surface addition of lime and phosphates on maize dry mattert yield as well as on some soil and root parameters. Lime rates applied on the soil surface were equivalents to 0, 1/8, 1/4 e 1/2 of the quantity required to raise the pH-H2O of a 17 cm soil layer depth to 6.0 (5.0 g kg-1), which was also added but incorporated into the soil. Phosphorus was applied at rate of 100 mg P kg-1, as diammonium phosphate (DAP) or triple superphosphate (TSF). The experiment was set in a greenhouse using pots containing 5.0 kg (dry base) of an acid Oxisol where five maize plants were grown for 26 days after emergence. Addition of lime on the soil surface improved the chemical characteristics of the most superficial soil layer (0 to 2.5 cm). Increases on maize dry matter yield due to surface liming occurred only with the smallest lime rate, which had the same efficiency of the integral rate incorporated into the soil. Liming increased P uptake regardless of rates applied or forms of ad

Apesar da baixa mobilidade dos fosfatos e do calcário, a aplicação desses insumos na superfície do solo, sem incorporação, tem freqüentemente aumentado o rendimento vegetal. Desconhece-se, entretanto, o comportamento das raízes em relação à existência de apenas uma camada superficial de solo melhorada quimicamente, assim como da combinação de grandes quantidades de calcário e fosfatos na disponibilidade de P. O presente trabalho objetivou avaliar o rendimento de matéria seca de milho e alterações em atributos de solo e de raízes ocasionados pela combinação de doses de calcário e de fertilizantes fosfatados, ambos aplicados sobre a superfície de um Latossolo Bruno ácido, em casa-de-vegetação. As quantidades de calcário aplicadas na superfície equivaleram a 0, 1/8, 1/4 e 1/2 da dose necessária para elevar o pH-H2O de uma camada de 17 cm para 6,0 (5,0 g kg-1), a qual foi também utilizada, porém incorporada ao solo. O P foi aplicado na dose de 100 mg kg-1, na forma de fosfato diamônio (DAP) e de superfosfato triplo (SFT). Foram cultivadas cinco plantas de milho por vaso (5,0 kg de solo, base seca) durante 26 dias após a germinação. A adição de calcário sobre a superfície do solo ocasionou melhorias significativas na composição química da camada mais superficial do solo (0 a 2,5 cm). O benefício da calagem superficial no rendimento de matéria seca da parte aérea do milho somente oco

RESUMEN

Despite the small mobility of phosphates and liming, addition of these materials on the soil surface, without incorporation, has often increased crop yield. However, it is unknown the behavior of plant roots developed in a soil with only a thin layer chemically ameliorated, as well as the result of combining large amounts of lime and phosphates on P availability. This study was carried out to evaluate the effect of surface addition of lime and phosphates on maize dry mattert yield as well as on some soil and root parameters. Lime rates applied on the soil surface were equivalents to 0, 1/8, 1/4 e 1/2 of the quantity required to raise the pH-H2O of a 17 cm soil layer depth to 6.0 (5.0 g kg-1), which was also added but incorporated into the soil. Phosphorus was applied at rate of 100 mg P kg-1, as diammonium phosphate (DAP) or triple superphosphate (TSF). The experiment was set in a greenhouse using pots containing 5.0 kg (dry base) of an acid Oxisol where five maize plants were grown for 26 days after emergence. Addition of lime on the soil surface improved the chemical characteristics of the most superficial soil layer (0 to 2.5 cm). Increases on maize dry matter yield due to surface liming occurred only with the smallest lime rate, which had the same efficiency of the integral rate incorporated into the soil. Liming increased P uptake regardless of rates applied or forms of ad

Apesar da baixa mobilidade dos fosfatos e do calcário, a aplicação desses insumos na superfície do solo, sem incorporação, tem freqüentemente aumentado o rendimento vegetal. Desconhece-se, entretanto, o comportamento das raízes em relação à existência de apenas uma camada superficial de solo melhorada quimicamente, assim como da combinação de grandes quantidades de calcário e fosfatos na disponibilidade de P. O presente trabalho objetivou avaliar o rendimento de matéria seca de milho e alterações em atributos de solo e de raízes ocasionados pela combinação de doses de calcário e de fertilizantes fosfatados, ambos aplicados sobre a superfície de um Latossolo Bruno ácido, em casa-de-vegetação. As quantidades de calcário aplicadas na superfície equivaleram a 0, 1/8, 1/4 e 1/2 da dose necessária para elevar o pH-H2O de uma camada de 17 cm para 6,0 (5,0 g kg-1), a qual foi também utilizada, porém incorporada ao solo. O P foi aplicado na dose de 100 mg kg-1, na forma de fosfato diamônio (DAP) e de superfosfato triplo (SFT). Foram cultivadas cinco plantas de milho por vaso (5,0 kg de solo, base seca) durante 26 dias após a germinação. A adição de calcário sobre a superfície do solo ocasionou melhorias significativas na composição química da camada mais superficial do solo (0 a 2,5 cm). O benefício da calagem superficial no rendimento de matéria seca da parte aérea do milho somente oco

RESUMEN

The objective of this study was to evaluate residual effects of phosphate fertilizers (triple superphosphate, Yoorin thermophosphate, North Caroline rock phosphate and Arad rock phosphate) and the efficiency of chemical phosphorus extractants. The fertilizers were applied to pots using a Xantic Ferralsol and three levels of phosphorus (50, 100 e 200 mg dm-3). Pots were planted with rice. Phosphorus rates increased both dry matter and phosphorus accumulation; triple superphosphate had the highest values of dry matter; Mehlich 1 was the best extractant to evaluate rock phosphates while the resin method was for soluble fertilizers. Soil phosphorus values estimated using Mehlich 1 and 3 and resin extraction were well correlated among themselves and gave similar results. The "E value" was correlated with dry matter to North Caroline phosphate, Arad phosphate and Yoorin termophosphate. All extractants were efficient and similar.

O objetivo foi avaliar o efeito residual de fertilizantes fosfatados e a eficiência de extratores químicos na avaliação da disponibilidade de fósforo no solo e estudar o aproveitamento do fósforo dos adubos fosfatados. Quatro fontes de P (Superfosfato Triplo, Termofosfato Yoorin, Fosfato Natural da Carolina do Norte e Fosfato Natural de Arad) e três doses (50, 100 e 200 mg dm-3) foram aplicadas em Latossolo Vermelho Amarelo, onde foram cultivadas plantas de arroz. Houve efeito residual das doses de fósforo aplicadas, resultando em aumento de matéria seca; o teor de fósforo extraído do solo aumentou com as doses de fósforo; o extrator Mehlich 1 apresentou maiores valores de P para os fosfatos naturais. Para as fontes solúveis, a resina extraiu mais fósforo, sendo similar ao Mehlich 1; o valor E correlacionou-se com a matéria seca para o fosfato Carolina do Norte, fosfato Arad e termofosfato Yoorin; todos os extratores foram eficientes e similares para avaliar a disponibilidade de fósforo para a planta; além de se considerar os diversos extratores, é necessário considerar a fonte utilizada.

RESUMEN

The objective of this study was to evaluate residual effects of phosphate fertilizers (triple superphosphate, Yoorin thermophosphate, North Caroline rock phosphate and Arad rock phosphate) and the efficiency of chemical phosphorus extractants. The fertilizers were applied to pots using a Xantic Ferralsol and three levels of phosphorus (50, 100 e 200 mg dm-3). Pots were planted with rice. Phosphorus rates increased both dry matter and phosphorus accumulation; triple superphosphate had the highest values of dry matter; Mehlich 1 was the best extractant to evaluate rock phosphates while the resin method was for soluble fertilizers. Soil phosphorus values estimated using Mehlich 1 and 3 and resin extraction were well correlated among themselves and gave similar results. The "E value" was correlated with dry matter to North Caroline phosphate, Arad phosphate and Yoorin termophosphate. All extractants were efficient and similar.

O objetivo foi avaliar o efeito residual de fertilizantes fosfatados e a eficiência de extratores químicos na avaliação da disponibilidade de fósforo no solo e estudar o aproveitamento do fósforo dos adubos fosfatados. Quatro fontes de P (Superfosfato Triplo, Termofosfato Yoorin, Fosfato Natural da Carolina do Norte e Fosfato Natural de Arad) e três doses (50, 100 e 200 mg dm-3) foram aplicadas em Latossolo Vermelho Amarelo, onde foram cultivadas plantas de arroz. Houve efeito residual das doses de fósforo aplicadas, resultando em aumento de matéria seca; o teor de fósforo extraído do solo aumentou com as doses de fósforo; o extrator Mehlich 1 apresentou maiores valores de P para os fosfatos naturais. Para as fontes solúveis, a resina extraiu mais fósforo, sendo similar ao Mehlich 1; o valor E correlacionou-se com a matéria seca para o fosfato Carolina do Norte, fosfato Arad e termofosfato Yoorin; todos os extratores foram eficientes e similares para avaliar a disponibilidade de fósforo para a planta; além de se considerar os diversos extratores, é necessário considerar a fonte utilizada.

RESUMEN

In order to evaluate the direct and residual effects of ordinary granulated superphosphate as compared to magnesium thermophosphate (Yoorin), supplied at four rates (0,50,100 and 200 ppm), seven successive croppings were carried out in the glasshouse. Available phosphorus was assessed after the third, fourth and seventh harvest by using Mehlich 1, Bray 1, anión exchange resin and isotopic dilution (E value). The highest correlation coefficients between available P and either total dry matter or total P content was found to occur with data provided by Mehlich 1 and resin. Phosphorus extracted by Bray 1 as well as that estimated by the E value showed lower "r" coefficients.

Em condições de casa-de-vegetação foram feitos sete cultivos sucessivos para avaliar o efeito direto e residual do superfosfato simples granulado e do termofosfato magnesiano (Yoorin) fornecidos em quatro doses (O, 50,100 e 200 ppm). O fósforo disponível foi determinado depois do terceiro, quarto e último cultivos usando-se os extratores de Mehlich 1, Bray 1, resina e a técnica de diluição isotópica (valor E). De um modo geral, os coeficientes de correlação mais altos entre P disponível e matéria seca ou fósforo total absorvido, foram encontrados com os dados obtidos com resina e Mehlich 1, seguindo-se os obtidos com Bray 1 e, em último lugar, os com o valor E.

RESUMEN

In order to evaluate the direct and residual effects of ordinary granulated superphosphate as compared to magnesium thermophosphate (Yoorin), supplied at four rates (0,50,100 and 200 ppm), seven successive croppings were carried out in the glasshouse. Available phosphorus was assessed after the third, fourth and seventh harvest by using Mehlich 1, Bray 1, anión exchange resin and isotopic dilution (E value). The highest correlation coefficients between available P and either total dry matter or total P content was found to occur with data provided by Mehlich 1 and resin. Phosphorus extracted by Bray 1 as well as that estimated by the E value showed lower "r" coefficients.

Em condições de casa-de-vegetação foram feitos sete cultivos sucessivos para avaliar o efeito direto e residual do superfosfato simples granulado e do termofosfato magnesiano (Yoorin) fornecidos em quatro doses (O, 50,100 e 200 ppm). O fósforo disponível foi determinado depois do terceiro, quarto e último cultivos usando-se os extratores de Mehlich 1, Bray 1, resina e a técnica de diluição isotópica (valor E). De um modo geral, os coeficientes de correlação mais altos entre P disponível e matéria seca ou fósforo total absorvido, foram encontrados com os dados obtidos com resina e Mehlich 1, seguindo-se os obtidos com Bray 1 e, em último lugar, os com o valor E.