Extractability of P in major soils of Angola as affected by P fertilizers and lime application

Phosphorus (P) deficiency is the major constraint to crop production in most tropical soils (Sahrawat et al., 2001). In Angola, such constraint (i.e, low concentration and low P solubility) has also been reported to limit crop production in many agricultural soils (Ucuassapi, 2006). These soils may require application of inorganic P through soluble and relatively reactive phosphate rock sources, and lime (Dobermann et al., 2002; Murphy, 2007). However, appropriate P management strategies may require information on the fate of applied P and its interaction with the colloidal constituents. Therefore, information on the different P fractions (inorganic and organic) after the application of different rates of P fertilizers and lime, as fractionated sequentially by the Hedley modified procedure (Tiessen and Moir, 1993) is crucial for making appropriate fertilizer and lime rate recommendations for crops (Islam et al., 2010)

(Des)Conhecimento da presença de produtos de origem animal em suplementos alimentares

Poster apresentado no XIX Congresso de Nutrição e Alimentação: Nutrition 20 > 30 Act For Tomorrow. 9-10 Setembro 2020, Centro de Congressos de Lisboa, Portugal.N/

Phosphorus desorbability in soils with andic properties from the Azores, Portugal Desorção de fósforo em solos com propriedades ândicas do Arquipélago dos Açores (Portugal)

Desorbability of phosphorus (P des) at P sorption maxima in eighteen horizons (surface and subsurface) of soils with andic properties from the Azores, Portugal, was determined by eight successive extractions using distilled water (H2O), calcium chloride (CaCl2), Bray 2 (B2), Mehlich 3 (M3), Egnér-Riehm (ER) and Olsen (OL) methods. The highest proportions of P des by the B2, M3, ER and OL methods (29-100%) were obtained in soils with weak andic properties (Vitrandic Haplustepts, Typic Haplustepts and Andic Haplustepts), indicating that P can be easily lost from these soils to nearby water bodies, through surface runoff and subsurface drainage. In contrast, low proportions of P des (4-57%) by these methods were obtained in allophanerich (Acrudoxic Hydrudands and Typic Placudands) and non-allophanic soils (Acrudoxic Hydrudands and Alic Hapludands), indicating that large amounts of P can be sorbed in an unavailable form by these soils. Of the six methods used, the proportions of P des obtained by H2O and CaCl2 were consistently lower than those obtained by the B2, M3, ER and OL methods. The proportion of P des obtained by the B2 method was highly correlated with other methods (M3, ER and OL) suggesting that the B2 is also an effective method to extract P in most of the studied soils. The proportions of P des obtained by different methods were negatively correlated with Feo and Fed, correlatios being stronger than with Alo, Ald, Alp and Fep contents. This indicates that Feo and Fed plays an important role in desorbability of P in studied soils.A proporção de P desorvido no solo (P des) após oito extracções sucessivas com água destilada (H2O), cloreto do cálcio (CaCl2) e pelos métodos Bray 2 (B2), Mehlich 3 (M3), Egnér-Riehm (ER) e Olsen (OL) foi determinada em dezoito horizontes (superficiais e subsuperficiais) de pedónes representativos de Andossolos dos Açores, enriquecidos com P no seu máximo desorção. As proporções de P des por estes extractantes foram comparadas e correlacionadas com os constituintes coloidais do solo. Observou-se uma grande variação da proporção de Pdes para qualquer dos extractantes, consoante a constituição coloidal do solo. As proporções de P des obtidas pela H2O e CaCl2 foram bastante menores do que as observadas para os outros extractantes, em qualquer dos horizontes dos solos estudados. Os Vitrandic Haplustepts, Typic e Andic Haplustepts, que apresentam reduzido teor de alofana e em que as propriedades ândicas estão fracamente expressas, mostraram elevada proporção de Pdes (29-100%) pelos métodos de B2, M3, ER e OL. Os fosfatos aplicados como fertilizantes neste tipo de solos ficarão facilmente disponíveis para as plantas, mas, provavelmente, serão facilmente perdidos por drenagem e erosão do solo. Assim, a aplicação de fertilizante de fósforo nesses solos deverá ser a estritamente necessária e em quantidades limitadas, de modo a minimizar as perdas de P e naturalmente a eutroficação dos cursos de água e lagoas das proximidades. Pelo contrário, tanto os horizontes superficiais como sub-superficiais dos outros pédones (Typic Placudands, Acrudoxic Hydrudands, Acrudoxic Hapludands e Alic Hapludands) mostraram uma baixa proporção de P des, sugerindo uma forte retenção e indisponibilidade do P quando aplicado a estes solos. Nestas circunstâncias, será preferível a aplicação de grandes quantidades de fertilizante de libertação lenta e contínua de P. Dos seis métodos estudados, as proporções de P des usando H2O e CaCl2 foram inferiores às obtidas com B2, M3, ER e OL. O P des obtido com B2, M3, ER e OL mostrou uma forte correlação entre eles. B2 revelou-se o extractante mais eficaz na remoção de P na maioria dos solos em estudo. As proporções de P des observadas para os extractantes mostraram uma correlação negativa com os teores de Ald, Alo, Alp, Feo, Fed, and Fep e com os valores de Alo + ½ Feo, e de retenção de P. Contudo, a correlação entre as proporções de Pdes obtidas com CaCl2, B2, M3, ER e OL com componentes ferruginosos (Feo, Fed) foi mais forte do que com componentes de Al (Alo, Ald)

Properties and related management implications of major soils in Bukidnon, Philippines

Os dados foram recolhidos e registados pelo técnico da ESACB João Nunes sob a supervisão da Prof.ª Maria do Carmo Horta Monteiro.Dados climáticos relativos ao ano de 1986, recolhidos e registados no Posto Meteorológico da Escola Superior Agrária do Instituto Politécnico de Castelo Branco

P adsorption and desorption capacities of selected Andisols from the Azores, Portugal Capacidade de adsorção e de desorção de P em Andossolos dos Açores, Portugal

Phosphorous adsorption maxima (P-ads max) and the amounts of P desorbed (P-des) using Langmuir equation and eight successive extractions with 0.01M CaCl2, were determined on sixteen horizons of Andisols from the Azores, Portugal. Results showed that the values of P-ads max and the proportions of P desorbed (P-des) were highly influenced by allophane, Alo, Ald, and Fed contents, and by the values of Alo + ½ Feo and ferrihydrite + allophane. P-des were negatively correlated with these constituents, but not with allophane. Vitrandic Haplustepts and Typic Udivitrands, and Typic Hapludands containing low amounts of allophane, Alo, Ald, and Fed showed low values of P-ads max, but high P-des values. Phosphate ions applied as fertilizer on these soils are highly available for plant use, but maybe easily lost through surface runoff, subsurface drainage and soil erosion. They may require restricted amounts of P fertilizer, and P losses should be controlled to minimize eutrophication of nearby water bodies. Conversely, Typic Placudands containing large amounts of allophane, and Acrudoxic Hydrudands and Typic Hapludands containing large amounts of organic C showed high values of P-ads max, but low P-des, indicating unavailability of P when retained by these soils. Large amounts of slow P-releasing fertilizer may be required for better crop use.A adsorção máxima de P (P-ads max) e a quantidade de P desorvido no solo (P-des), foram determinadas em 16 horizontes superficiais e subsuperficiais de Andossolos dos Açores, Portugal, usando equação de Langmuir e oito extracções sucessivas com cloreto do cálcio. Os valores de P-ads max mostraram uma correlação positiva com os teores de Alo, Ald, Fed, alofana, ferihidrite + + alofana, e com valores de Alo + ½ Feo. Por outro lado, os resultados de P-des, mostraram uma correlação negativa com os mesmos constituintes, excepto com alofana. Vitrandic Haplustepts, Typic Udivitrands e Typic Hapludands mostraram um valor de P-ads max baixo, mas com elevado teor de P-des. Iões fosfato adicionados como fertilizante neste tipo de solos ficam disponíveis para utilização pelas plantas, mas provavelmente, serão facilmente perdidos por drenagem e erosão do solo. Estes solos podem necessitar de quantidades limitadas de fertilizante de fósforo, com controlo das perdas deste elemento para minimizar a eutroficação dos cursos de água das proximidades. Por outro lado, os Typic Placudands com elevado teor de alofana e os Acrudoxic Hydrudands, com elevado teor de carbono orgânico, têm elevado valor de P-ads max e baixo teor de P-des, indicando indisponibilidade do P quando retido por estes solos. Neste caso, poderá ser preferível o uso de grandes quantidades de fertilizante de libertação lenta de P

Effects of biochar on available P fractions, soil properties and P uptake by plant in P fertilized Ferralsols from Angola

Low phosphate (P) availability is one of the major problems in most Ferralsols from Angola, due to the strong ability of these soils to adsorb P, thereby limiting its bioavailability for crop production (Ucuassapi, 2006). Application of biochar as soil amendment, along with superphosphate and rock phosphate fertilizers may be useful in increasing supply of available P. However, appropriate P management strategies may require information on the fate of biochar and applied P fertilizers in the soil as well as on their interaction with soil colloidal constituents. Therefore, information on soil P availability using different methods, and P forms (inorganic and organic) by Hedley modified fractionation procedure (Tiessen and Moir, 1993), early plant growth performance and P content in plant after biochar amendment along with different rates of P fertilizers, is crucial for making appropriate fertilizer and biochar recommendations for crops

The growth of oil palm, cocoa and rice in Malaysia as affected by acid sulfate soil infertility.

Soils along the coastal plains in Malaysia usually contain pyrite (FeS2). When these areas are drained, pyrite in the sediments oxidizes releasing acidity and A1, and jarosite is formed. This paper summarizes the results of studies on the acid sulface soils planted to oil palm, cocoa and rice. A glasshouse study conducted to test the growth of oil palm on acod sulfate under waterlogged and well drained conditions indicated that the best growth was observed on the non-jarositic freely topsoil. Oil palm was found to be moderatley yolerant to soil acidity. The growth was only affected if A13+ activities were aboved 100uM and pH below 4.3. The result from our study indicated that cocoa was sensitive to the presence of A1 in acid sulfate soil. As the amount of A1 in the cocoa leaves increased, the relative plant height of cocoa seedlings decreased. The critical value for A13+ activities in the soil were 10uM. A study was conducted in the Kelantan Plains, in the Northeast coast state of Peninsular Malaysia to determine the effects of line and organic fertilizer application on rice yield planted on an acid sulfate soil. After applying 4 t of ground magnesium limestone per ha in combination with 0.25 t per ha of organic fertilizer, a rice yield of 7.5 t/ha was obtained in the 2nd season. This is comparable to the rice production in the gragary area of Malaysia. If properly managed, acid sulfate soils in Malaysia can be used for cultivation of oil palm and rice