Chemical modifications in acid soils caused by addition of gypsum or limestone

Os benefícios do calcário aplicado sobre a superfície do solo no rendimento vegetal podem estar associados à melhoria na composição química das águas de percolação. Esse trabalho objetivou avaliar alterações na fase sólida e na solução percolada em dois solos ácidos (Latossolo Bruno Álico e Cambissolo Húmico Álico), ocasionadas pelo método de aplicação (na superfície ou incorporado) de corretivos da acidez (CaCO3 e MgCO3) e de gesso agrícola. O CaCO3 foi utilizado na dose equivalente a 0,25 daquela necessária para elevar o pH a 6,0, e os demais em doses molares equivalentes. O CaCO3 foi ainda incorporado nas doses de 0; 0,5; 1,0 e 1,5 vez a necessidade de calcário para pH 6,0. Em colunas de lixiviação, com 1,5 kg de solo, percolou-se água destilada durante 12 semanas num volume de 200 mL semana-1. Os corretivos da acidez, quando incorporados aos solos, aumentaram o pH das duas fases, diminuíram o Al trocável, porém não afetaram o Al percolado; quando foram aplicados na superfície, não afetaram nenhum parâmetro da solução percolada, e alteraram a composição química somente da camada de 0 a 2,0 cm de profundidade. O gesso agrícola diminuiu o pH do solo e da solução percolada, não afetou o Al trocável, mas percolou muito mais Ca, Mg e Al que os corretivos da acidez, principalmente quando foi incorporado ao solo. A mobilidade dos cátions integrantes dos corretivos foi muito pequena, e a aplicação de calcário na superficie dos solos não afetou a composição química da solução coletada 30 cm abaixo.The increase on crop yield caused by lime addition on the soil surface may be associated to improvements in the chemical composition of the percolating water. This study was carried out to evaluate chemical changes in the solid phase and in the percolating water in two acid soils (Oxisol and Inceptisol) caused by the application method (incorporated or on soil surface) of gypsum, CaCO3, or MgCO3. Calcium carbonate was used at a rate equivalent to 0.25 of that recommended by the SMP method to raise soil water pH to 6.0; gypsum and MgCO3 were used at the same molarity rate. Additional CaCO3 were (0, 0.50, 1.0 and 1.5 times that recommended by the SMP method) was also incorporated. Treated soil samples (1.5 kg) were transferred to leaching columns, and distilled water (200 mL column-1 week-1) were added on soil surface during twelve weeks. Incorporation of lime (CaCO3 and MgCO3) into the soils increased pH of both phases, decreased exchangeable Al, but had no effect on Al in the percolated solution. When carbonates were applied on soil surface, they had no effect on the leached solution, and affected the chemical composition of the solid phase only in the top 2.0 centimeters. Addition of gypsum decreased soil and solution pH, had no effect on exchangeable Al, but leached greater amounts of Ca, Mg and Al than limestone, especially when gypsum was incorporated. Cation mobility from limestone materials was negligible, and surface liming had no chemical effects in the solution collected 30 cm below soil surface

Alterações na composição química do solo e no desenvolvimento inicial de plântulas de milho ocasionadas pela aplicação superficial de calcário e fertilizantes fosfatados

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 addition, but had no effect on root parameters probably due to the high P values in the soil. The smaller values for soil P caused by diammonium phosphate, relatively to triple superphosphate, had no negative effect on root parameters, P uptake, or dry matter yield of 26-days old maize plants. Therefore, in absence of water deficit, addition of lime and P fertilizers over the soil surface improves the initial growth of maize plants.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 ocorreu com a menor dose aplicada (1/8 de SMP), cujo efeito foi semelhante ao proporcionado pela dose integral (1,0 SMP) incorporada. A calagem aumentou a absorção de P, independente da dose ou da forma de aplicação, porém não influenciou nenhum atributo radicular provavelmente devido ao alto teor de P no solo. Os menores valores de P no solo ocasionados pela adição de DAP relativamente ao SFT não se refletiram negativamente nos parâmetros radiculares, na absorção de P, nem tampouco no rendimento de matéria seca, nos primeiros 26 dias de desenvolvimento do milho. Não havendo déficit hídrico, portanto, a adição de calcário e de P sobre a superfície do solo melhora o desenvolvimento inicial das plântulas de milho

Carbon indices to assess quality of management systems in a Subtropical Acrisol

Management systems to improve soil quality are essential for agricultural and environmental sustainability. We assessed the quality of soil management systems applied to a subtropical Acrisol in terms of the carbon management index (CMI), the stratification ratio for total organic carbon (SR-TOC) and light fraction of organic matter (SR-LF). In addition, we examined their relationship to chemical, physical and biological soil quality indicators, as well as to maize yield. The study was conducted on a long-term experiment (18 years) in southern Brazil involving two different systems [no tillage (NT) and conventional tillage (CT)], two cropping systems [black oat/maize (O/M) and black oat + vetch/maize + cowpea (OV/MC)] and two nitrogen fertilizer rates for maize (0 and 180 kg ha–1). Based on the three indices, the best managements for soil quality comprised NT (50-212 % better than CT), legume cover crops (10-47 % better than O/M) and N fertilization (8-33 % better than no fertilizer). All three indices proved accurate to assess the impact of soil management systems, especially SR-LF, which showed increased sensitivity and close relationships with chemical, physical and biological soil quality indicators. On the other hand, a poor relationship was observed between soil C indices and maize yield, which was improved only by legume cover crops and N fertilization. The results showed that the association of no-till system to an abundant supply of crop residues is key to ensure high soil quality and crop yields in humid subtropical regions

Carbon storage in labile fractions of soil organic matter in a tropical no-tillage Oxisol

A reserva de carbono na matéria orgânica (MO) do solo é uma importante estratégia para atenuar a concentração de dióxido de carbono na atmosfera. O objetivo deste trabalho foi avaliar o efeito do plantio direto (PD), durante seis anos, sob quatro sistemas de cultura de outono na sucessão comercial soja-milho (guandu-anão-milheto, crotalária-sorgo, girassol-aveia-preta e nabo forrageiro-milho), no armazenamento de carbono nas frações particulada (>53 µm) e associada aos minerais (53 µm) and mineral-associated (<53 µm) SOM fractions of a clayey Oxisol from Brazilian Cerrado region. In comparison to conventional tillage (CT) under summer cash-crops, NT increased the total organic carbon (TOC) stocks in the surface soil layer (0–5 cm). In the top 20 cm layer, NT soil under wild radish-maize had 9% (4.66 Mg ha-1) more TOC than the conventionally tilled soil. On the other hand, C storage in NT soil under other cropping systems was statiscally similar to the CT soil. The C stocks in the particulate SOM fraction increased by 37 to 52% in NT soil (0–20 cm) in comparison to CT. The higher sensitivity to soil management changes made the particulate organic matter a more adequate soil quality index compared to the TOC stocks. The C stock in the mineral-associated SOM fraction was not affected by soil management systems, which can be related to the short-term under NT and or to the highly stable soil microaggregates in this clayey Oxisol. The preferential C storage in the labile SOM fraction is an environmental benefit, which is expected to occur only under continuous no-tillage and crop residues addition

Nitrous oxide emissions in maize on mollisols in the Pampas of Argentina

The objectives of this study were i) to measure the soil N2O fluxes in a cropping system currently adopted by farmers of the region (FP), and in an ecologically intensified cropping system (EI) over two consecutive maize growing seasons (2011–12 and 2012–13), and ii) to relate N2O fluxes to soil factors. Gas fluxes were measured using vented static chambers, from October through April in each season. Fluxes of N2O ranged from 3 to 88 μg N2O-N m−2 h−1 in 2011–12, and between 3 and 97 μg N2O-N m−2 h−1 in 2012–13. There was a significant (p 0.05) effect on cumulative N2O emissions, which were, on average across two seasons, 558 g N2O-N ha−1 for the EI treatment and 578 g N2O-N ha−1 for the FP treatment. Cumulative N2O emissions tended to be 20% greater over 153 days in 2012–13 compared with over 156 days in 2011–12 mainly due to differences in total and timing precipitations. As there were no differences in cumulative N2O emissions between managements but grain yield was higher under EI, this treatment had lower yield-based N2O emissions (75 g N2O-N Mg−1 grain) compared with FP treatment (94 g N2O-N Mg−1 grain). The results showed that a moderate increase in N rate (10 kg N ha−1), combined with N split-application and UAN (urea-ammonium nitrate) as N source, as well as other crop management practices, can be a viable alternative to improve maize productivity without increasing the N2O environmental impact.EEA BalcarceFil: Picone, Liliana. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Bayer, Cimélio. Universidade Federal do Rio Grande do Sul. Faculdade de Agronomia. Departamento de Solos; BrasilFil: Videla, Cecilia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina.Fil:. Rizzalli, Roberto Héctor. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina.Fil: Casanave Ponti, Sheila M. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Andrade, Fernando Héctor. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: García, Fernando O. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina

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

Alterações físicas e químicas num cambissolo húmico de campo nativo após a correção da acidez

Farmers are introducing annual crops under native grass utilizing different soil management and limestone application methods. In order to know better the changes of physical and chemical soil properties caused by these interferences , the effect of methods and rates of liming under native grass to corn cultivation were evaluated in the following systems: 1) NT 1.0i – no-tillage, incorporated liming at the experiment implantation , with rates of 0, 0.25, 0.5, 1.0 and 1.5 SMP; 2) NT 1.0s – no-tillage with superficial liming at the experiment implantation with the same rates; 3) NT 0.3s – no-tillage with superficial liming at the experiment implantation with the same rates divided and reapplied each three years. The completely randomized blocks design was used. The trial was set in a humic cambissol with native grass, located in Lages, SC. The soil had a water ph of 4.4. Its limestone necessity was 24 Mg ha-1 to rise to pH until 6.0. The following soil properties were determined: soil bulk density; soil particle density; macroporosity; microporosity; total porosity; penetration resistance; saturated hydraulic conductivity; aggregated stability; organic carbon; water ph; particle size distribution and flocculation degree by four layers of 0.05 m each, until the depth of 0.20 m. The incorporated limestone corrected soil acidity in the layer of 0-0.10 m, while the superficial limestone with integral rate corrected the layer of 0.0-0.05 m. Soil revolving with plowing and disk harrowing to incorporate limestone was beneficial to soil quality, reducing bulk density, microporosity, penetration resistance and increasing total porosity, macroporosity and flocculation degree. However, this soil preparation system also promoted loss of soil quality because it decreased the aggregate stability and the organic carbon content. The limestone rates, increased soil pH but did not modify soil physical properties.Os agricultores estão introduzindo culturas anuais em áreas de campo nativo, utilizando diferentes sistemas de manejo e métodos de correção da acidez. Para conhecer melhor as mudanças nas propriedades físicas e químicas do solo destas interferências sobre o campo nativo, avaliou-se o efeito de métodos de aplicação e doses de calcário em área de campo nativo para cultivo de milho nos sistemas: 1) PD 1,0i - plantio direto com calcário incorporado na implantação do experimento nas doses de 0, 0,25, 0,5, 1,0 e 1,5 SMP; 2) PD 1,0s - plantio direto com calcário superficial nas mesmas doses na implantação do experimento e; 3) PD 0,3s - plantio direto com calcário superficial nas mesmas doses e divididas em três vezes, reaplicadas a cada três anos. O experimento em blocos casualizados foi instalado em um cambissolo húmico de campo nativo em Lages, SC, com pH em água de 4,4 e necessidade de calcário de 24 Mg ha-1 para elevar o ph até 6,0. Foram determinadas: densidade do solo e de partículas; macro, micro e porosidade total; resistência à penetração; condutividade hidráulica saturada; estabilidade de agregados; carbono orgânico; pH em água; distribuição do tamanho das partículas e; grau de floculação em quatro camadas de 0,05 m cada uma, até os 0,20 m de profundidade. A incorporação do calcário corrigiu a acidez do solo na camada de 0-0,10 m, enquanto a aplicação superficial com dose integral corrigiu apenas a camada de 0,0-0,05 m. O revolvimento do solo no campo nativo, com lavração e gradagem para incorporação do calcário, foi benéfico para a qualidade do solo quanto a redução da densidade, da microporosidade, da resistência à penetração e ao aumento da porosidade total, da macroporosidade e do grau de floculação. Houve prejuízos à qualidade do solo pela redução da estabilidade dos agregados e do conteúdo de carbono. As doses de calcário não modificaram as propriedades físicas avaliadas, apenas elevaram o pH do solo

Monitoring plant and soil nitrogen status to predict nitrogen fertilization in corn

O objetivo deste trabalho foi comparar o monitoramento do teor de N na planta com base no índice do teor relativo crítico de clorofila na folha (TRCC) e no índice de suficiência (IS), determinados pelo clorofilômetro, e avaliar a integração de características de planta e de solo no monitoramento de N no sistema solo-planta em milho. Foram conduzidos dois experimentos em Eldorado do Sul, RS. Os tratamentos foram sistemas de manejo de N, que diferiram quanto à época, dose e critério para decidir pela aplicação de N (com monitoramento e sem monitoramento). Nos sistemas monitorados, o TRCC e o IS foram usados para indicar a época de aplicação de N em cobertura e testou-se o monitoramento integrado, usando o TRCC e o teor de nitrato no solo. O rendimento e os incrementos no rendimento de grãos e na margem bruta, bem como as eficiências técnica, econômica e de uso do N foram maiores nos sistemas monitorados que nos sistemas sem monitoramento. A eficiência do monitoramento, com base no TRCC e no IS e na intregração entre o teor de nitrato no solo e o TRCC, foi similar. O monitoramento com base na integração entre o teor de nitrato no solo e o TRCC não incrementou a eficiência de uso do N no ambiente avaliado.The objective of this work was to compare the monitoring of corn plant nitrogen status using two indexes of leaf relative chlorophyll content (critical leaf relative chlorophyll content – CRCC and sufficiency index – SI) determinated by chlorophyll meter and to evaluate the integration between plant and soil characteristics for monitoring the N content of the soil-plant system in corn. Two field experiments were conducted in Eldorado do Sul, State of Rio Grande do Sul, Brazil. The treatments were different N management systems, with different N application times and N rates, carried out with or without monitoring. In the monitored systems, CRCC and SI were used to indicate when N side-dress should be performed and it was tested, using the CRCC and soil nitrate content, one integrated monitoring system. Grain yield and grain yield increase, gross profit increase and the technical, economic and N use efficiency were often higher in the monitored systems than in the systems without monitoring. The efficiency of the monitoring methods, using the CRCC and using the SI and integrating the CRCC and soil nitrate content, was similar. Monitoring corn N status integrating the CRCC and soil nitrate content did not improve nitrogen use efficiency in the tested environment

Additives on in vitro ruminal fermentation characteristics of rice straw

The objective of this study was to evaluate the effects of mineral and protein-energy (MPES), exogenous fibrolytic enzyme supplements (ES), combination of MPES + ES, and straw without supplement (WS) on digestibility, fermentation kinetic parameters, cumulative gas production, methane, CO2 production, and volatile fatty acid concentration of rice straw of low and high nutritional value, estimated by in vitro techniques. The experimental design was randomized and factorial 2 × 4: two straws (low and high nutritional value) incubated with four supplements (MPES, ES, MPES + ES, and WS) and their interactions. Four experimental periods were used, totaling four replications per treatment over time. Data were analyzed by PROC MIXED of SAS. The in vitro dry matter and organic matter digestibilities of the rice straw with high nutritional value was improved by MPES, while the combination of MPES + ES supplements inhibited the digestibility of this straw. Dietary carbohydrate and nitrogen increased through MPES and MPES + ES supplements resulted in an increase in NH3-N concentration and a decrease in CO2 production due to the microbial mass formation. However, this increase was not enough to improve organic matter degradability parameters, cummulative gas production, gas production kinetics, and acetate:propionate ratio and reduce methane emissions. The straw with high nutritional value showed greater content of nitrogen fraction a, effective degradability, cummulative gas production, and methane and CO2 productions comparing with low-nutritional value straw. The use of MPES and MPES + ES supplements can be used as strategy to mitigate CO2 in ruminant production systems that use rice straw

Adequacy of side dress nitrogen rates in corn based on soil and plant indicators

O objetivo deste trabalho foi testar uma metodologia para determinar doses ótimas de N a serem aplicadas em cobertura, no estádio V6 do milho, com base em características de solo e de planta, e verificar quais os indicadores mais precisos para a predição da dose de N a ser aplicada. O experimento foi conduzido em Eldorado do Sul, RS, em dois anos agrícolas. Os tratamentos consistiram de cinco doses de N, aplicadas em duas épocas. Além do rendimento de grãos, determinaram-se, no estádio V6, o teor relativo de clorofila na folha, as massas de matéria seca da folha e da planta, o teor e a quantidade de N acumulados na folha e na planta, teores de nitrato, amônio e N mineral no solo. As características de planta foram mais eficientes para a predição da dose de N em cobertura no milho, nos dois anos agrícolas, do que as características de solo, com destaque para massa de matéria seca e N acumulado na planta, seguidas pelo teor relativo de clorofila na folha. É possível desenvolver ou adaptar a metodologia testada, para predição de doses ótimas de N em cobertura em milho, a partir de características de planta e de solo, desde que se possua uma rede de ensaios com uma curva de reposta a esse nutriente.The objective of this work was to test one methodology to determine nitrogen (N) optimum rate to side dress at V6 corn stage, using soil and plant characteristics, and to verify which are the most precise indicators of N rate application. A field experiment was carried out in Eldorado do Sul, RS, Brazil, in two growing seasons. The treatments were five N rates applied in two timings. The following variables were measured: corn grain yield, leaf relative chlorophyll content, leaf and plant dry weight, N content and accumulated in the leaf, and plant and soil nitrate, ammonium and N mineral contents were measured at V6. From the evaluated characteristics, the most precise to predict optimum N rate for side dressing in corn were plant dry weight, N accumulated in the plant and leaf relative chlorophyll content. The results show that is possible to adapt or to develop a method to predict the optimum N rates for side dressing, using soil and plant characteristics, since there is a N response curve available from a group of experiments