Potassium fertilization for long term no-till crop rotation in the central-southern region of Paraná, Brazil

Fertilization programs for annual crops in the state of Paraná, southern Brazil, are based on studies that focused on conventional tillage and were established more than 30 years ago. The primary purpose of this study was to assess potassium (K) fertilization on long-term (>30 years) no-tillage soybean, corn, wheat, and barley crops grown in rotation on Oxisols in the central-southern region of Paraná. A total of 47 experiments were carried out from 2008 to 2013, three of which addressed K calibration and the other 44, crop response to K fertilization. Critical K soil-test value and interpretation classes were established from the ratio between relative crop yield [RY = (yield without K/max yield) × 100] and soil K levels. Winter cereals were found to be more demanding of K than were soybean and corn; also, the former governed critical K soil-test value for crop rotation: 0.23 cmolc dm-3 in the 0.00-0.20 m soil layer. Recommended fertilization rates for soils in the low and medium soil K levels were established by using the build-up approach for soil correction; and those for the high and very high soil K levels were established by removing K at harvest and assessing economic return in crop response experiments. The K rates calculated for the high yield classes exceeded those currently recommended for use in Paraná

Sampling layer for soil fertility evaluation in long-term no-tillage systems

In no-tillage (NT) systems, there is no plowed layer since the soil is not tilled. Thus, the soil layer for fertility evaluation can be defined as the one in which the fertility indices are affected by the surface application of lime and fertilizers and soil properties have the closest relationship with crop yields. The objective of this study was to determine the most appropriate soil layer under long-term NT for sampling for fertility evaluation in the South-Central region of Paraná, Brazil. A total of 99 field experiments of crop rotations were performed, including soybean, corn, barley, wheat, and white oat, all on Oxisols (Hapludox). Despite the surface application, lime and fertilizers increased base saturation (V) and available K to a depth of 0.20 m. The relationship with crop yields was high for V and low for available K for both soil layers (0.00-0.10 and 0.00-0.20 m); for P, however, the relationships with soybean and corn yields were strongest in the 0.00-0.20 m layer. Thus, considering the soil layer fertilized by the surface application of lime and potassium fertilizers and the highest relationship of soil P contents with the yield of the main crops of the crop rotation, the 0.00-0.20 m layer is the most appropriate for soil fertility evaluation under long-term no-tillage systems

Phosphorus fertilization for high yield of soybean, maize, and winter cereal crops in rotation in oxisols under long-term no-till in the south central region of Parana, Brazil

O Estado do Paraná não dispõe de um sistema de recomendação de adubação para rotação de culturas em plantio direto (PD). Em razão disso, utiliza indicações geradas para culturas individuais há mais de 30 anos e em preparo convencional. Este estudo teve como objetivo consolidar a calibração de P e avaliar a resposta das culturas à adubação fosfatada, visando à proposição de um sistema de indicações técnicas para a adubação fosfatada das culturas da soja, do milho, do trigo e da cevada cultivadas em sistema de rotação em Latossolos com longo histórico de PD (>30 anos) na região centro-sul do Paraná, que se caracteriza por possuir alto potencial produtivo. Três experimentos de calibração foram conduzidos de 2008 a 2013 e consistiram na criação de níveis de P pela aplicação de doses a lanço de até 640 kg ha-1 de P2O5. Quarenta e quatro experimentos de resposta a P foram conduzidos entre as safras de 2011 a 2012/13, tendo como foco avaliar a resposta das culturas a P em solos com distinta disponibilidade do nutriente. Os rendimentos relativos [RR = (rendimento sem P/rendimento máximo) × 100] das culturas e os teores de P no solo (Mehlich-1) foram relacionados, obtendo-se os teores críticos e as classes de disponibilidade de P no solo. Para a estimativa das doses nas classes de disponibilidade Baixa e Média, foram utilizadas as curvas de resposta à adubação de P, seguindo a filosofia de suficiência (adubação de cultura) Nas classes de disponibilidade Alta e Muito Alta, as doses foram com base na exportação pelos grãos. Os cereais de inverno se evidenciaram mais exigentes e determinaram o teor crítico de P de 8 mg dm-3 para a rotação de culturas, considerando a camada de 0-20 cm. As doses de P indicadas para soja, milho, trigo e cevada em solos em PD de longa duração são superiores às de adubação atualmente indicadas no PR, o que, ao menos em parte, justificam-se pelas altas produtividades das culturas e alta capacidade de retenção de P dos solos da região. Embora adotada a filosofia de suficiência/adubação de cultura para a indicação das doses de adubação fosfatada em solos abaixo do teor crítico, estima-se que as doses estipuladas para as culturas elevem o teor de P no solo ao teor crítico após um ciclo da rotação de culturas (três anos).Although the State of Parana, Brazil, has adopted crop rotation and no-till (NT) systems, fertilizer application is still based on recommendations developed more than 30 years ago for monocropping under conventional tillage because fertilizer recommendations developed specifically for crop rotation under NT are lacking. The objective of our study was to consolidate P calibration and evaluate crop responses to P fertilization so as to propose a system of technical recommendations for P fertilization for soybean, maize, wheat, and barley grown in a crop rotation system in Oxisols under long-term (>30 years) NT systems in the high yield potential South-Central region of Parana. Three calibration trials were conducted from 2008 to 2013, consisting of P broadcast application rates of up to 640 kg ha-1 P2O5. Forty-four P fertilization trials were carried out over the 2011-2012/13 growing seasons to evaluate yield response to P fertilization rates in Oxisols with different levels of P availability. Relative crop yield [RR = (yield without P/maximum yield) × 100] and soil P availability (Mehlich-1) were compared to obtain P critical levels and generate soil P availability classes based on crop response. For soils in the Low and Medium availability classes, recommended P fertilizer application rates were based on the yield response curve following the nutrient sufficiency approach For soils in the High and Very High availability classes, P fertilizer recommendations were based on P removal through grain harvest. The winter cereal crops were more demanding to achieve maximum yields - the soil critical P level for the crop rotation system was determined at 8 mg dm-3 based on the requirement of these crops, considering the 0-20 cm soil layer. The recommended P fertilization rates for soybean, maize, wheat, and barley in Oxisols under long-term NT developed in our study are higher than the current P fertilization rates used in Parana, which is explained in part by the high crop yields and high P adsorption capacity of soils in the region. Although the nutrient sufficiency approach was used to determine P fertilization rates in the soils below the critical level, it is estimated that the P rates recommended for the crops will raise soil P availability above the critical level after a full crop-rotation cycle (3 years)

Assessing Nitrogen Limitation in Inoculated Soybean in Southern Brazil

Core Ideas Soybean yield did not respond to low starter fertilizer N rates in soils with high organic matter content. Nitrogen limitation tended to be greater in low compared with medium-high yield levels. Nitrogen limitation is potentially related to lower contribution of N coming from biological nitrogen fixation (BNF) and mineralization. Overcoming potential N limitation in soybean [Glycine max (L.) Merr.] is a critical factor for sustaining plant nutrient demand and improving productivity. Following this rationale, a set of studies were executed in southern Brazil with the goals of quantifying yield response to early season fertilizer N rates (up to 40 kg ha−1), “starter N fertilization,” and to understand if soybean seed yields are limited by N (testing a non-limiting N scenario) when grown in soils with medium to high organic matter content. The main key outcomes of this research were: (i) starter N fertilization did not increase yields compared with non-fertilized soybean, potentially highlighting the absence of an early season N limitation; and (ii) N limitation was observed when soybean yields were compared with non-limiting N scenario and it tended to be greater in low compared with medium-high yield levels, potentially connected with co-limitations on both N sources (N2 fixation and mineralization) to satisfy soybean N demand. Producing soybean in a sustainable manner implies focus on production practices to conserve and, potentially, to increase soil organic matter on a long-term basis. Furthermore, it requires enhancing the biological N2 fixation process for satisfying the large plant N demand for achieving high soybean yields. Future research should be focused on understanding factors governing biological N2 fixation and N mineralization processes in soybean grown in soils with medium-high organic matter content.Fil: Ambrosini, Vítor Gabriel. Universidade Federal do Rio Grande do Sul; BrasilFil: Vieira Fontoura, Sandra Mara. Fundação Agrária de Pesquisa Agropecuária; BrasilFil: Paulo de Moraes, Renato. Fundação Agrária de Pesquisa Agropecuária; BrasilFil: Carciochi, Walter Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Ciampitti, Ignacio Antonio. Kansas State University; Estados UnidosFil: Bayer, Cimélio. Universidade Federal do Rio Grande do Sul; Brasi