Release of phosphorus forms from cover crop residues in agroecological no-till onion production

Cover crops grown alone or in association can take up different amounts of phosphorus (P) from the soil and accumulate it in different P-forms in plant tissue. Cover crop residues with a higher content of readily decomposed forms may release P more quickly for the next onion crop. The aim of this study was to evaluate the release of P forms from residues of single and mixed cover crops in agroecological no-till onion (Allium cepa L.) production. The experiment was conducted in Ituporanga, Santa Catarina (SC), Brazil, in an Inceptisol, with the following treatments: weeds, black oat (Avena sativa L.), rye (Secale cereale L.), oilseed radish (Raphanus sativus L.), oilseed radish + black oat, and oilseed radish + rye. Cover crops were sown in April 2013. In July 2013, plant shoots were cut close to the soil surface and part of the material was placed in litterbags. The bags were placed on the soil surface and residues were collected at 0, 15, and 45 days after deposition (DAD). Residues were dried and ground and P in the plant tissue was determined through chemical fractionation. The release of P contained in the tissue of cover crops depends not only on total P content in the tissue, but also on the accumulation of P forms and the quality of the residue in decomposition. The highest accumulation of P in cover crops occurred in the soluble inorganic P fraction, which is the fraction of fastest release in plants. Black oat had the highest initial release rate of soluble inorganic P, which became equal to the release rate of other cover crop residues at 45 DAD. Weeds released only half the amount of soluble inorganic P in the same period, despite accumulating a considerable amount of P in their biomass. The mixtures of oilseed radish + rye and oilseed radish + black oat showed higher release of P associated with RNA at 45 DAD in comparison to the single treatments

Formas de fósforo em folhas e suas relações com a composição do mosto e a produção em videiras

The objective of this work was to evaluate phosphorus forms in grape leaves and their relationships with must composition and yield in grapevines grown in a Typic Hapludalf with different available P contents. Two experiments were carried out with Vitis vinifera cultivars, one with 'Tannat' and the other with 'Cabernet Franc' grapes. Experiment 1 consisted of two vineyards of 'Tannat', with the following P content in the soil: V1, 11.8 mg kg-1 P; and V2, 34.6 mg kg-1 P. Experiment 2 consisted of two vineyards of 'Cabernet Franc', with the following P content in the soil: V1, 16.0 mg kg-1 P; and V2, 37.0 mg kg-1 P. Leaves were collected at flowering (FL) and veraison (V), and, after their preparation, P forms were evaluated. Yield and must composition were assessed. The highest yield was observed in V2 of experiment 1 and in V2 of experiment 2. Total P content and P forms in leaves at FL and V have no relationship with yield parameters; however, total P content in leaves has a relationship with anthocyanin content in the must of 'Tannat' grapevines. Therefore, P fractionation in leaves predicts neither grapevine yield nor must composition.O objetivo deste trabalho foi avaliar as formas de fósforo em folhas e suas relações com a composição do mosto e a produção em videiras cultivadas em um Argissolo Vermelho distrófico típico, com diferentes teores de P disponível. Dois experimentos foram realizados com cultivares de Vitis vinifera, um com uvas 'Tannat' e outro com 'Cabernet Franc'. O experimento 1 consistiu de dois vinhedos de 'Tannat', com os seguintes teores de fósforo no solo: V1, 11,8 mg kg-1 de P; e V2, 34,6 mg kg-1 de P. O experimento 2 consistiu de dois vinhedos de 'Cabernet Franc', com os seguintes teores de fósforo no solo: V1, 16,0 mg kg-1 de P; e V2, 37,0 mg kg-1 de P. Coletaram-se as folhas ao florescimento (FL) e ao início da maturação (IM), e, após a preparação delas, analisaram-se as formas de P. A produtividade e a composição do mosto foram avaliadas. A maior produtividade foi observada no V2 do experimento 1 e no V2 do experimento 2. O teor total de P e suas formas nas folhas ao FL e IM não apresentam relação com os parâmetros produtivos; no entanto, o teor de P total nas folhas apresenta relação com o teor de antocianinas no mosto de videiras 'Tannat'. Portanto, o fracionamento de P nas folhas não prediz a produtividade da videira nem a composição do mosto

Espécies e atividade de alumínio na solução de solo arenoso com adição de dejetos líquidos de suínos

The application of slurry may reducing the bioavailability the aluminum (Al), by increasing the concentration of soluble ligands. The study aimed to assess how the long-term use of pig slurry is able to modify the exchangeable Al content, activity, and distribution of chemical species of Al in soil solution. Soil samples of Typic Hapludalf were obtained from an experiment conducted for eight years with 19 pig slurry applications of 0, 20, 40 and 80 m3 ha-1 at the Federal University of Santa Maria, in Santa Maria, Rio Grande do Sul (RS), Brazil. The soil samples was collected stratified in layers, to determine exchangeable Al content and extract the solution. The soil solution concentrations of the main cations, anions, dissolved organic carbon and pH were assessed. The distribution of the chemical species of Al and the activity of the Al3+ species was obtained through Visual Minteq software. The history of pig slurry applications did not modify the exchangeable Al content and had little impact on Al3+ activity in soil solution. Pig slurry applications reduce the phytotoxic potential of Al by increasing the concentration of soluble inorganic ligands, thus increasing the proportion of AlHPO4+ and AlSO4+ in soil solutionO objetivo deste trabalho foi avaliar o efeito das aplicações de dejetos líquidos de suínos no teor de Al trocável, na atividade e na distribuição das espécies químicas de Al na solução do solo. Amostras de um Argissolo foram obtidas de um experimento conduzido durante oito anos, com 19 aplicações de 0, 20, 40 e 80 m3 ha-1 de dejetos líquidos de suínos. As amostras de solo foram coletadas em camadas, para determinação do Al trocável e extração da solução do solo pelo método da pasta de saturação. Na solução, foram determinados as concentrações dos principais cátions e ânions, o carbono orgânico dissolvido e o pH. A distribuição das espécies químicas de Al e a atividade da espécie Al3+ foram obtidas pelo programa Visual Minteq. A aplicação de dejetos líquidos de suínos não altera o teor de Al trocável no solo e a atividade de Al3+ na solução do solo. A baixa atividade de Al3+ nas camadas superficiais não apresenta risco de toxidez para a maioria das culturas. A adição de dejetos líquidos de suínos aumenta a proporção das espécies AlHPO4+ e AlSO4+ na solução do solo, por incrementar a concentração de ligantes inorgânicos solúveis

Respostas de culturas à adubação sulfatada e deposição de enxofre atmosférico

Solos com baixo teor de argila e matéria orgânica apresentam baixa disponibilidade de enxofre (S) e, por isso, as culturas podem responder à adubação sulfatada. No entanto, a mobilidade de S no perfil do solo e sua deposição atmosférica pela água da chuva dificultam o estabelecimento do nível de suficiência do nutriente no solo. Este trabalho objetivou avaliar a resposta de culturas à adubação sulfatada e quantificar o S atmosférico depositado no solo pela água da chuva. Os cultivos avaliados (mamoneira, trigo, feijão-de-porco e milheto) foram realizados entre 2006 e 2009, em um Argissolo Vermelho distrófico arênico. As doses de S aplicadas em cada cultivo foram de 0, 5, 10 e 20 kg ha-1, utilizando-se gesso agrícola como fonte de S. Avaliaram-se a produção de matéria seca e o acúmulo de S na parte aérea do milheto e do feijão-de-porco, e a produção e o teor de S nos grãos de mamona e de trigo. Determinou-se o teor de S disponível no solo até 60 cm de profundidade e a deposição de S pelas precipitações. A maior produção de grãos da mamona e de matéria seca do segundo cultivo de feijão-de-porco foi obtida com aplicação de 14,5±0,35 kg ha-1 de S. Mesmo com teores de S abaixo dos níveis de suficiência, não houve respostas do trigo, do milheto e do primeiro cultivo de feijão-de-porco à adubação sulfatada. O aporte de S atmosférico ao solo foi de 4,5 kg ha-1 ano-1 e pode ter contribuído para a ausência de resposta desses cultivos

Release of Phosphorus Forms from Cover Crop Residues in Agroecological No-Till Onion Production

ABSTRACT Cover crops grown alone or in association can take up different amounts of phosphorus (P) from the soil and accumulate it in different P-forms in plant tissue. Cover crop residues with a higher content of readily decomposed forms may release P more quickly for the next onion crop. The aim of this study was to evaluate the release of P forms from residues of single and mixed cover crops in agroecological no-till onion (Allium cepa L.) production. The experiment was conducted in Ituporanga, Santa Catarina (SC), Brazil, in an Inceptisol, with the following treatments: weeds, black oat (Avena sativa L.), rye (Secale cereale L.), oilseed radish (Raphanus sativus L.), oilseed radish + black oat, and oilseed radish + rye. Cover crops were sown in April 2013. In July 2013, plant shoots were cut close to the soil surface and part of the material was placed in litterbags. The bags were placed on the soil surface and residues were collected at 0, 15, and 45 days after deposition (DAD). Residues were dried and ground and P in the plant tissue was determined through chemical fractionation. The release of P contained in the tissue of cover crops depends not only on total P content in the tissue, but also on the accumulation of P forms and the quality of the residue in decomposition. The highest accumulation of P in cover crops occurred in the soluble inorganic P fraction, which is the fraction of fastest release in plants. Black oat had the highest initial release rate of soluble inorganic P, which became equal to the release rate of other cover crop residues at 45 DAD. Weeds released only half the amount of soluble inorganic P in the same period, despite accumulating a considerable amount of P in their biomass. The mixtures of oilseed radish + rye and oilseed radish + black oat showed higher release of P associated with RNA at 45 DAD in comparison to the single treatments