Crop-livestock systems are regaining their importance as an alternative to unsustainable intensive farming systems. Loss of biodiversity, nutrient pollution and habitat fragmentation are a few of many concerns recently reported with modern agriculture. Integrating crops and pastures in no-till systems can result in better environmental services, since conservation agriculture is improved by system diversity, paths of nutrient flux, and other processes common in nature. The presence of large herbivores can positively modify nutrient pathways and soil aggregation, increasing soil quality. Despite the low diversity involved, the integration of crops and pastures enhances nature's biomimicry and allows attainment of a higher system organization level. This paper illustrates these benefits focusing on the use of grazing animals integrated with crops under no-tillage systems characteristic of southern Brazil.

-Integrated crop-livestock systems (ICLS) are designed to exploit synergisms and emergent properties resulting from interactions between different soil-plant-animal-atmosphere compartments that integrate themselves at different spatial-temporal scales. In this review, a panorama of the evolution of studies based on ICLS is presented. Specific keywords were used as search terms to construct a database of 450 articles from 93 national and international journals published up to and including 2013. These articles were classified according to the region of origin within Brazil (subtropical or tropical) and categorized regarding the studied components: soil, plant, animal and 'others'. Within these components, groups of variables that could characterize the different thematic lines were listed. The number of publications worldwide has been increasing, and Brazil is one of the main suppliers of scientific work within this area. Although the number of scientific studies seeking better understanding of ICLS may have increased in Brazil, further studies with a systematic view and with larger temporal and spatial scales are still required to help identify interactions between diverse biotic and abiotic factors that define new properties that emerge from these systems.Key words: Conservation agriculture. Sustainability. Scientific production. Agricultural technology. Systematic approach.RESUMO -Os sistemas integrados de produção agrícola e pecuária são caracterizados como sistemas planejados para explorar sinergismos e propriedades emergentes, resultado de interações entre os diferentes compartimentos solo-plantaanimal-atmosfera, que se integram em diferentes escalas espaço-temporais. Nesta revisão é apresentado um panorama da evolução das pesquisas embasadas em uma produção integrada entre os diferentes compartimentos. Considerou-se o período até 2013 e palavras-chave como fator de busca, sendo construída uma base de dados, partindo de um universo de 450 artigos em 93 periódicos nacionais e internacionais. Estes artigos foram classificados de acordo com a região de origem do Brasil: subtropical ou tropical; e categorizados quanto aos componentes: solo, planta, animal e outros. Dentro desses componentes foram elencados grupos de variáveis que caracterizassem diferentes linhas temáticas. As publicações no mundo têm aumentado e o Brasil está entre os principais provedores de trabalhos científicos nessa área. Embora seja crescente o número de trabalhos científicos no Brasil, que buscam melhor compreensão dos sistemas integrados de produção agrícola e pecuária, as pesquisas com visão sistêmica e de maior escala temporal e espacial ainda necessitam de mais estudos, para que possam detectar interações entre os diversos fatores bióticos e abióticos e novas propriedades que emergem destes sistemas.Palavras-chave: Agricultura conservacionista. Sustentabilidade. Produção científica. Tecnologia agropecuária. Enfoque sistêmico.

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The study of factors influencing animal intake can provide a better understanding of the dynamics of the pasture ecosystem and serve as a basis for managing livestock in a more efficient way. We measured different sward surface heights of tall fescue in the process of short-term intake rate of sheep. There was a significant effect of sward surface height on herbage mass ( P < 0.001), leaf lamina mass ( P < 0.001), other species mass ( P = 0.02), bite mass ( P = 0.01) and short-term intake rate ( P = 0.03) of sheep. There was a quadratic fit between time per bite and bite mass ( P = 0.006). Multivariate analysis showed that the short-term intake rate and bite mass were positively correlated (r = 0.97), bite rate and total jaw movement rate were positively correlated but both were negatively correlated with time per bite. The sward surface height of tall fescue corresponding to the maximum short-term herbage intake rate was 22.3 cm. The underlying processes were driven by the bite mass, which was influenced by the leaf lamina bulk density and its consequences upon time per bite. This sward surface height can be adopted as a pre-grazing target for rotational stocking systems to optimize sheep nutrition on pastures.

Effective integrated weed management in agricultural landscapes depends on the ability to identify and manage processes that drive weed dynamics. The current study reports the effects of grazing management and crop rotation strategies on the seedbank and emerged weed flora in an integrated crop-livestock system (ICLS) experiment during a 12-year period under no-tillage in sub-tropical southern Brazil. During winter, Italian ryegrass cover crops were grazed by sheep: grazing management treatments included two stocking methods (continuous and rotational) and two forage allowances (10 and 20 kg of herbage dry matter available per 100 kg animal live weight). During summer, the crop rotation treatments involved either soybean-maize or soybean-soybean in succession with winter-grazed cover crops. The treatments were part of a factorial randomized complete block design. Treatment effects were evaluated on the weed seedbank and emerged weed flora populations during winter-grazed cover crop and summer crop growth as well as during the harvest phase. The current results demonstrate that crop rotation and grazing management exhibited interactive effects on the determination of weed outcomes in an ICLS. However, overall, compared with moderate forage allowance, high forage allowance during the winter-grazed cover crop caused lower emerged weed flora in subsequent crops (20% reduction during crop growth and 90% reduction at crop harvest) and 48% reduction in seedbank size. High forage allowance promoted more residue from winter-grazed cover crop biomass, which remained during the summer crop phases and probably resulted in a physical barrier to weed emergence.

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Weeds are a major constraint on food and feed production, and the excessive use of herbicides to control them is a global concern for food security, human health, and environmental sustainability. Under no-tillage systems, cover crop residues provide a physical barrier to weed emergence that reduce weed infestations and reliance on herbicides. In integrated crop-livestock systems, cover crops provide fodder to grazing animals, adding an additional source of revenue for farmers; however, grazing can cause a trade-off because it reduces biomass during the cover crop season and residues left on the soil surface in the next cash crop, which may increase weed infestation. In the current study, it was hypothesized that there is an optimal cover crop forage allowance during the grazing period that maximizes beef production while retaining enough cover crop biomass and residue to minimize weed infestations and maintain grain yield of the subsequent cash crop. Therefore, the effects of cover crop (mixed black oat + Italian ryegrass) forage allowances (based on sward height) during the winter grazing period on weed infestations, beef production, and soybean grain yield during the next summer season were evaluated. The experiment was conducted in several commercial fields involving two experimental protocols (one short-term and one long-term experiment) in Southern Brazil, and the results demonstrated that a moderate forage allowance in winter cover crops (i.e., maintaining 17.8 cm of winter grazed cover crop sward height) reduced weed infestations and increased soybean and beef production when compared with a lower forage allowance (i.e., < 10.7 cm of winter grazed cover crop sward height) or a higher forage allowance (i.e., > 17.8 cm of winter grazed cover crop sward height). Therefore, the current study provides evidence that it is possible to optimize forage allowance to sustainably intensify arable cropping systems using winter cover crops for direct grazing.

RESUMOProdutores no Sul do Brasil estão procurando diversificar a propriedade aumentando a eficiência de produção através da integração lavoura-pecuária. O objetivo foi determinar o efeito do pastejo e da adubação nitrogenada na decomposição dos resíduos da pastagem anual de inverno no milho. A cobertura de Avena strigosa Schreb mais Lolium multiflorum L. foi semeada em abril de 2002, em Ponta Grossa -PR. A combinação de tratamentos com e sem nitrogênio, com e sem pastejo foi aplicada sobre a pastagem de inverno. O período de pastejo ocorreu de junho à outubro de 2002, a pastagem foi dessecada em 11 de outubro e o milho semeado vinte dias depois, tendo sido aplicados duas doses de nitrogênio (0 e 150 kg.ha -1 ). A pastagem de inverno, cortada, foi colocada em sacos de nylon que foram espalhados sobre o solo, e recolhidos em cinco épocas com intervalos de três semanas para análise de matéria seca residual. Os dados foram submetidos a análise de variância. Ajustes de modelo matemático indicaram que a redução da massa seca ocorreu de acordo com o modelo quadrático em função do tempo. A decomposição dos resíduos da pastagem foi afetada pelos tratamentos impostos (p<0,02), pelas doses de nitrogênio no milho (p<0,01) e suas interações. Na última data de avaliação (132 dias do período experimental) foram verificadas diferenças (p<0,01) apenas para os tratamentos sobre a pastagem de inverno. Tratamentos que receberam adubação nitrogenada no inverno resultaram em decomposição maior nas áreas com e sem pastejo.Palavras-chave: pastejo, nitrogênio, decomposição, Zea mays L. ABSTRACTProducers in southern Brazil are seeking to diversify farm income and increase production efficiency by integrating livestock grazing of winter annual forages within rotations of summer grain crops. Our objective was to determine grazing and nitrogen fertilization effects on decomposition of winter annual forage residues in corn. A winter cover of oat (Avena strigosa Shreb) and annual ryegrass (Lolium multiflorum L.) was no-till seeded in April 2002 near Ponta Grossa, PR in southern Brazil. Treatment combinations of N fertilizer (0 or 150 kg ha ). Above ground forage biomass residue was hand-clipped, placed in small nylon bags that were scattered on the soil immediately after corn planting, and recovered after five periods of three weeks each for determination of residual dry matter. Results were submitted to analysis of variance. The loss of residual dry matter followed a quadratic function on time. Decomposition of winter annual forage residue was affected by winter treatment (P<0.02), corn N rate (P<0.01), and by their interaction . At the last collection period (132 days after corn planting) differences (P<0.01) were detected only for the winter treatments. Treatments receiving winter-applied N had greater decomposition of residue regardless of the grazing treatment imposed on the winter forage cover.