Exportação de nutrientes em tangerinas produzidas em sistema orgânico no subtrópico brasilero

The knowledge on the amount of nutrients exported by citrus fruit is an adequate tool to estimate nutrient demand reposition and this information about mandarin is very scarce. In this context, the objective of this study was to determine the nutrient content and exportation by mandarin fruits harvest, in an orchard managed under organic production system. An experiment was carried out in an organic orchard of adult mandarin trees (23 years), located in Rio Grande do Sul State (Brazil). The total content of macronutrients and micronutrients was determined in the mandarin fruits and the exportation was estimated by average yields in two seasons (2013/2014 and 2014/2015). The average exportation of macronutrient was 3.3, 2.3, 1.3, 0.4 and 0.3 kg t-1 for N, K, Ca, P and Mg, respectively; and of micronutrients was 6.3, 4.6, 1.5, 0.7 and 0.5 g t-1 for Fe, B, Zn, Mn and Cu, respectively. The N exportation in mandarin fruits does not comply with the current information used for citrus fertilizer recommendations, where the K is the nutrient most exported. Regarding micronutrients, besides the exported amounts vary among the literature, the magnitude order follows the same observed in our study. We propose these new standards for reposition of macronutrients and micronutrients in established mandarin orchards under organic management, contributing to a more accurate fertilizer recommendation.O conhecimento sobre a quantidade de nutrientes exportados por frutas cítricas é uma ferramenta adequada para estimar a reposição de nutrientes, e estas informações para tangerinas são escassas. Nesse contexto, o objetivo deste estudo foi determinar o teor e a exportação de nutrientes pela colheita de frutos de tangerineiras, em um pomar manejado sob sistema orgânico de produção. Um experimento foi realizado em um pomar orgânico de tangerineiras adultas (23 anos), localizado no Rio Grande do Sul, Brasil. O teor total de macronutrientes e de micronutrientes foi determinado nos frutos de tangerina, e a exportação foi estimada pela produtividade média de duas safras (2013/2014 e 2014/2015). A exportação média de macronutrientes foi de 3,3; 2,3; 1,3; 0,4 e 0,3 kg t -1 para N, K, Ca, P e Mg, respectivamente; e de micronutrientes foi de 6,3; 4,6; 1,5; 0,7 e 0,5 g t-1 para Fe, B, Zn, Mn e Cu, respectivamente. A exportação de N pelas tangerinas não condiz com as informações atuais utilizadas para recomendações de adubação em citros, sendo o K o elemento mais exportado. Em relação aos micronutrientes, além de as quantidades exportadas variarem entre a literatura, a ordem de magnitude segue a mesma observada em nosso estudo. Propomos esses novos padrões para reposição de macronutrientes e de micronutrientes em pomares estabelecidos de tangerina sob manejo orgânico, contribuindo para uma recomendação de adubação mais precisa

Crop response to gypsum application to subtropical soils under no-till in Brazil : a systematic review

The use of gypsum to improve the root environment in tropical soils in the southeastern and central-western regions of Brazil is a widespread practice with well-established recommendation criteria. However, only recently gypsum began to be used on subtropical soils in South of Brazil, so available knowledge of its effect on crop yield is incipient and mainly for soils under no-till (NT) systems. Avaiable studies span a wide range of responses, from a substantial increase to a slight reduction in crop yield. Also, the specific conditions leading to a favorable effect of gypsum application on crop yield are yet to be accurately identified. The primary objectives of this study were to examine previously reported results to assess the likelihood of a crop response to gypsum and to develop useful recommendation criteria for gypsum application to subtropical soils under NT in Brazil. For this purpose, we examined the results of a total of 73 growing seasons, reported in 20 different scientific publications that assessed grain yield as a function of gypsum rates. Four different scenarios were examined, by the occurrence or not of high subsurface acidity (viz., Al saturation >20 % and/or exchangeable Ca 3 cmolc dm-3) failed to increase crop yield, irrespective of the soil water status. Under these conditions, high gypsum rates (6-15 Mg ha-1) may even reduce grain yield, possibly by inducing K and Mg deficiency. On the other hand, applying gypsum to soils with high subsurface acidity increased yield by 16 % in corn (87 % of cases) and by 19 % in winter cereals (83 % of cases), whether or not the soil was water-deficient. By contrast, soybean yield was only increased by gypsum applied in the simultaneous presence of high soil subsurface acidity and water deficiency (average increase 27 %, 100 % of cases)

ELEMENTOS-TRAÇO NO PERFIL DO SOLO DE POMAR CÍTRICO APÓS ADUBAÇÃO ORGÂNICA DE LONGO PRAZO

A utilização de resíduos agroindustriais como fonte de nutrientes para sistemas de produção orgânica tem sido uma alternativa viável em muitos locais. Entretanto, a presença de componentes indesejáveis nesses resíduos, como os elementos-traço (ETs), pode resultar em contaminação ambiental quando utilizados de forma excessiva e continuada. Nesse contexto, o objetivo deste trabalho foi avaliar o impacto do uso de um resíduo agroindustrial da região de Montenegro/RS, Brasil, nos atributos químicos ao longo do perfil de um Argissolo Vermelho Distrófico espessarênico sob um pomar de tangerineiras manejado em sistema orgânico de produção, conduzido por longo prazo sob diferentes manejos e doses de adubação. Os tratamentos consistiram em diferentes manejos da adubação orgânica, com uso de plantas de cobertura do solo e aplicação de composto e biofertilizante líquido, em doses comumente utilizadas pelos produtores. Altas doses do composto orgânico ocasionaram o incremento de ETs, em especial na camada superficial do solo, aumentando o risco de contaminação ambiental. Onde as doses foram maiores, houve maior pH e teores de matéria orgânica no solo e menor mobilidade dos elementos-traço no perfil, pelo efeito na precipitação e complexação destes elementos.Palavras-chave: contaminação, matéria orgânica, mobilidade, pH, resíduo.

INTENSIDADE DE IRRIGAÇÃO E MANEJO DA ADUBAÇÃO NITROGENADA DE COBERTURA NO MILHO EM SISTEMA DE PLANTIO DIRETO CONSOLIDADO

O objetivo desta pesquisa foi avaliar como o manejo da adubação nitrogenada em cobertura no milho e os volumes de irrigação afetam a dinâmica do nitrogênio no perfil do solo e o rendimento de grãos de milho. Para isso, foi avaliada uma área experimental que vem sendo cultivada em sistema plantio direto há 22 anos. Os tratamentos constaram da combinação de manejos de nitrogênio em cobertura (testemunha sem nitrogênio em cobertura, dose única de 300 kg ha-1 e essa dose parcelada em duas vezes) e volumes de irrigação (20 e 100 mm). As amostragens de solo foram realizadas dez dias após a primeira adubação de N em cobertura e dez dias após a segunda adubação de nitrogênio em cobertura. Independentemente do volume, a irrigação promoveu o aumento nos teores de nitrato nas camadas subsuperficiais (20-30 e 30-40 cm) após a aplicação das doses de nitrogênio em cobertura. O parcelamento da adubação nitrogenada foi uma alternativa eficiente para diminuir os teores de nitrato nas camadas subsuperficiais do solo, para ambos os volumes de irrigação. Entretanto, isso não se refletiu em ganho de produtividade e em retorno econômico quando comparado à aplicação única de nitrogênio em cobertura, independentemente do volume de irrigação

SOIL AND PASTURE WATER STATUS IN A LONG TERM INTEGRATED CROP-LIVESTOCK SYSTEM PERSPECTIVE

Integrated crop-livestock systems have been indicated as alternatives to intensify land use. However, the soil water dynamics for proper water resources management is still poorly understood in such systems. This study aimed to assess the impact of grazing intensities on soil and black oat plants water status in a long-term, no-tillage, integrated soybean-beef cattle system. The experiment has been carried out since 2001 with a soybean and cattle grazing on black oat + ryegrass pasture succession. Treatments consist of different grazing intensities regulated by the pasture sward height, namely: intensive grazing (10 cm sward height), moderate grazing (20 cm sward height) and non-grazed. Soil bulk density was determined after soybean harvest. Soil moisture and water status of the black oat plants were monitored from the pasture sowing until the animal removal from the area, by the evaluation of leaf temperature and water potential. Grazing season begins with similar surface soil bulk density among the evaluated systems. The intensive grazing store less water in the soil profile, with greatest water stress degree of black oat plants along the evaluated period. The proper grazing management (moderate intensity) allowed black oat plants to keep leaf temperature and water potential similar to non-grazed condition, regardless of differences in soil moisture

Ciclagem de carbono e nitrogênio em sistema integrado de produção de soja e bovinos de corte sob diferentes intensidades de pastejo

The objective of this work was to evaluate the effect of grazing intensity on the decomposition of cover crop pasture, dung, and soybean residues, as well as the C and N release rates from these residues in a long‑term integrated soybean‑beef cattle system under no‑tillage. The experiment was initiated in 2001, with soybean cultivated in summer and black oat + Italian ryegrass in winter. The treatments consisted of four sward heights (10, 20, 30, and 40 cm), plus an ungrazed area, as the control. In 2009–2011, residues from pasture, dung, and soybean stems and leaves were placed in nylon‑mesh litter bags and allowed to decompose for up to 258 days. With increasing grazing intensity, residual dry matter of the pasture decreased and that of dung increased. Pasture and dung lignin concentrations and C release rates were lower with moderate grazing intensity. C and N release rates from soybean residues are not affected by grazing intensity. The moderate grazing intensity produces higher quality residues, both for pasture and dung. Total C and N release is influenced by the greater residual dry matter produced when pastures were either lightly grazed or ungrazed.O objetivo deste trabalho foi avaliar o efeito da intensidade de pastejo na decomposição dos resíduos da pastagem utilizada como cultura de cobertura, do esterco e da soja, bem como a liberação de C e N desses resíduos, em um sistema integrado de produção de soja e bovinos de corte, em plantio direto e em longo‑prazo. O experimento foi iniciado em 2001, com soja cultivada no verão e aveia‑preta + azevém no inverno. Os tratamentos consistiram de quatro alturas de pasto (10, 20, 30 e 40 cm), além de uma área sem pastejo, como controle. Em 2009–2011, resíduos da pastagem, do esterco, e do caule e das folhas de soja foram alocados em sacos de decomposição feitos com malha de nylon e decompostos até 258 dias. Com o aumento da intensidade de pastejo, a matéria seca residual da pastagem diminuiu e a do esterco aumentou. A concentração de lignina e as taxas de liberação de C da pastagem e do esterco foram menores com a intensidade de pastejo moderada. A liberação de C e N do resíduo de soja não é afetada pela intensidade de pastejo. A intensidade moderada de pastejo produz resíduos de maior qualidade, tanto para a pastagem quanto para o esterco. Já a quantidade total de C e N liberada é influenciada pela maior quantidade de matéria seca residual produzida quando a pastagem foi submetida ao pastejo leve ou não foi pastejada

Reconnecting nature and agricultural production : mixed cropping systems as a way forward sustainable intensification

In the last decades, population growth worldwide boosts agricultural demand for food production. This huge driver rendered global food production more and more specialized, so agricultural landscapes became uniform and monotonic. The loss of diversity is a strong evidence of how modern agricultural landscapes have been disconnecting from nature. Evidence of environmental side- effects from this pathway are abundant in literature. Now, society is pressing towards changing practices aiming for healthy diets and sustainable food production systems. This raises the question: how to reconnect nature and agriculture in the context of future food production? In this review we propose a reconnection process based on the principles of ecological intensification or sustainable intensification. The integrated crop-livestock systems (ICLS) are the most consolidated technological pathway to reconcile crop production with natural processes. These systems are diverse and can partially mimic natural ecosystems exploring the synergies of natural biological processes, while achieving high levels of food production. ICLS promote soil improvements and mitigate greenhouse gas (GHG) emissions, reducing the agricultural share of global warming and climate change. Besides, these systems are more efficient in the use of nutrients and can optimize the use of other inputs such as pesticides. We present evidence of soil health and biogeochemical cycle restoration in addition to system stability improvement, and assume those symptoms as evidence of mixing crops and livestock fostering reconnection with natural processes

Livestock integration into soybean systems improves long‐term system stability and profts without compromising crop yields

Climate models project greater weather variability over the coming decades. High yielding systems that can maintain stable crop yields under variable environmental scenarios are critical to enhance food security. However, the efect of adding a trophic level (i.e. herbivores) on the long-term stability of agricultural systems is not well understood. We used a 16-year dataset from an integrated soybean- beef cattle experiment to measure the impacts of grazing on the stability of key crop, pasture, animal and whole-system outcomes. Treatments consisted of four grazing intensities (10, 20, 30 and 40 cm sward height) on mixed black oat (Avena strigosa) and Italian ryegrass (Lolium multiforum) pastures and an ungrazed control. Stability of both human-digestible protein production and proftability increased at moderate to light grazing intensities, while over-intensifcation or absence of grazing decreased system stability. Grazing did not afect subsequent soybean yields but reduced the chance of crop failure and fnancial loss in unfavorable years. At both lighter and heavier grazing intensities, tradeofs occurred between the stability of herbage production and animal live weight gains. We show that ecological intensifcation of specialized soybean systems using livestock integration can increase system stability and proftability, but the probability of win–win outcomes depends on management