ABSTRACT: Organic fertilization effect on physical-chemical properties in no-tillage systems in tropical soils has been widely investigated, but little is known about the effects of this practice on the mineralogy of the clay fraction. This study aimed to evaluate the clay-fraction mineralogy of two subtropical soils, fertilized with organic residues in long-term no-tillage systems. An Alfisol fertilized with 0, 40, and 80 m3 ha-1 yr-1 pig slurry was evaluated for eight years, and an Oxisol with 0, 8, and 16 Mg ha-1 of wood shavings with pig slurry, for six years. Soil samples from the layers 0.00-0.04, 0.04-0.08, and 0.16-0.20 m were collected and subjected to chemical extractions with DCB and oxalate, X-ray diffractometry, and thermal analysis. No mineralogical changes in the clay fraction were observed in either the Alfisol or Oxisol. The chemical dissolution data indicated no significant differences among the tested treatments with regard to the re-precipitation of low-crystallinity oxides. However, the increase in zinc extracted by DCB and zinc extracted by oxalate in the treatments with residue application was clear. The crystallinity data efficiently indicated the effects of residue rates on soil mineralogy only in the Alfisol; the increasing slurry rates induced a reduction in the percentage of hematite, increase in the percentage of goethite, increase in the Gt/Gt+Hm ratio and decreased the mean crystal diameter of goethite and hematite.

Resumo: O objetivo deste trabalho foi determinar as alterações em atributos químicos de um Latossolo Vermelho após aplicações sucessivas de composto orgânico de dejeto líquido de suínos com maravalha, em sistema plantio direto. O experimento foi conduzido em Chapecó, SC, em Latossolo Vermelho, de setembro de 2005 a agosto de 2011. Foram aplicadas anualmente as doses de 0, 2, 4, 8 e 16 Mg ha-1 de composto de dejeto líquido de suínos com maravalha, além de um tratamento com adubação mineral (NPK). Após seis aplicações, coletaram-se amostras de solo nas camadas de 0-4, 4-8, 8-12, 12-16, 16-20, 20-40 e 40-60 cm e avaliaram-se os atributos químicos. As maiores doses do composto orgânico incrementaram o pH do solo e reduziram a acidez potencial. As aplicações de composto orgânico derivado de dejeto de suínos e maravalha promoveram alterações nos atributos químicos do Latossolo Vermelho avaliado, especialmente nas camadas superficiais do solo, com maior ênfase para aumento do pH do solo e dos teores de P, K, Cu e Zn. A utilização de 4 Mg ha-1 do composto mantém os atributos químicos do solo semelhantes aos do tratamento NPK, que seguiu recomendação oficial para os estados do Rio Grande do Sul e de Santa Catarina, além de manter os teores de P nas camadas superficiais dentro do limite crítico ambiental para solos com altos teores de argila.

Abstract: The objective of this work was to determine changes in the chemical attributes of an Oxisol after successive applications of organic compounds with pig slurry and wood shavings, under a no-tillage system. The experiment was conducted in the municipality of Chapecó, in the state of Santa Catarina, Brazil, in an Oxisol, from September 2005 to August 2011. The doses of 0, 2, 4, 8, and 16 Mg ha-1 compound with pig slurry and shavings were applied annually, as well as a treatment with mineral fertilizer (NPK). After six applications, soil was collected at the 0-4, 4-8, 8-12, 12-16, 16-20, 20-40, and 40-60-cm layers and the chemical attributes were evaluated. The highest doses of the organic compound increased soil pH and reduced potential acidity. The applications of the organic compound derived from swine manure and wood shavings promoted changes in the chemical attributes of the evaluated Oxisol, especially in the upper soil layers, with greater emphasis on increased soil pH and P, K, Cu, and Zn contents. The use of 4 Mg ha-1 of the compound maintains the soil chemical attributes similar to those of the NPK treatment, which followed official recommendation for the states of Rio Grande do Sul and Santa Catarina, besides keeping the P content in the surface layers within the environmental critical limit for soils with high clay content.

O dejeto líquido de suínos (DLS) representa importante fonte de nutrientes às plantas e sua utilização como adubo para as culturas significa a possibilidade de maior ciclagem de nutrientes no ambiente. Este trabalho objetivou avaliar como as doses de DLS, aplicadas ao longo de alguns anos, podem impactar a produção de grãos, de matéria seca e o acúmulo de nutrientes em culturas de grãos comerciais e em plantas de cobertura do solo. O experimento foi realizado na área experimental da Universidade Federal de Santa Maria, em Santa Maria, RS, no período de maio de 2000 a janeiro de 2008. Nesse período, foram implantadas 19 culturas de grãos e de cobertura de solo, sendo aplicado DLS antes da semeadura de cada cultura, nas doses de 0, 20, 40 e 80 m³ ha-1. O aumento da dose de DLS aplicada ao longo de anos promoveu o incremento da disponibilidade de nutrientes, notadamente de P, mas também de nutrientes que podem ser potencialmente tóxicos às plantas, especialmente Cu e Zn. A recuperação aparente de nutrientes pelas culturas de grãos comerciais e de cobertura do solo diminuiu à medida que aumentou o número de aplicações de doses de DLS no solo. A produção de matéria seca acumulada das culturas e a produção de grãos de milho foram maiores com a dose anual de 80 m³ ha-1 de DLS. Entretanto, a produtividade de grãos de feijão elevou até 20 m³ ha-1 de DLS, evidenciando que, na definição da dose, deve ser considerada a cultura a ser estabelecida.

Pig slurry (PS) represents an important nutrient source for plants and using it as fertilizer makes greater nutrient cycling in the environment possible. The aim of this study was to assess how PS application over a period of years can affect grain yield, dry matter production and nutrient accumulation in commercial grain and cover crops. The experiment was carried out in an experimental area of the Universidade Federal de Santa Maria, in Santa Maria, RS, Brazil, from May 2000 to January 2008. In this period, 19 grain and cover crops were grown with PS application before sowing, at rates of 0, 20, 40 and 80 m³ ha-1. The highest PS rate led to an increase in nutrient availability over the years, notably of P, but also of nutrients that are potentially toxic to plants, especially Cu and Zn. The apparent recovery of nutrients by commercial grain and cover crops decreased with the increasing number of PS applications to the soil. Accumulated dry matter production of the crops and maize grain yield were highest at an annual application rate of 80 m³ ha-1 PS. However, common bean yield increased up to 20 m³ ha-1 PS, showing that the crop to be grown should be considered to define the application rate.