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International audience; Crop losses from pests threaten global food security and safety. In the last six decades, pest control using chemical pesticides has resulted in important yield gains per unit area, worldwide. However, the long-term sustainability of chemical pest control has been increasingly thrown into doubt due to the negative impact on human health, biodiversity, and the environment. Consequently, there is an urgent need to improve the science of crop protection in order to tackle the five key challenges of 21st century agriculture holistically: (i) maintaining or improving agricultural productivity, (ii) producing healthy food, (iii) reducing the negative impacts of agriculture on ecosystem and human health, (iv) ensuring the economic viability of farms, and (v) adapting agriculture to climate change. Agroecological Crop Protection (ACP) can be a powerful approach to address these challenges, as we demonstrate in this paper. ACP is the application of the principles of agroecology to crop protection in order to promote virtuous and sustainable changes in agriculture and food systems. ACP combines multiple approaches and disciplines including ecology, agroecology, and Integrated Pest Management. It promotes a crop protection system compatible with healthy agricultural and food systems, agroecological principles and the “one health” approach. We predict that ACP will meet the challenge of pesticide-free agriculture in the future. In this paper, we will first present the scientific, agricultural and social components of ACP. We will then analyze the research approaches, questions, methods and tools needed to adopt ACP. Finally, we suggest key mechanisms to facilitate the transition to ACP, which will ultimately provide sustainable food, feed, and fuel in a context of major global change.

The political and territorial reintegration strategy that had been implemented in Cambodia to establish peace and order in the late 1990s caused the degraded evergreen forestlands to be allocated to the demobilized Khmer Rouge families in the western regions of the country. The increasing regional demand for cereals and tubers and the highland saturation in central rice areas have driven massive immigration of smallholder farmers. Almost half a million hectares of those forestlands were thus converted in less than 15 years for annual upland cash crops development. This dramatic expansion of agricultural area, without any plan for sustainability, has exerted tremendous pressures on the natural forest resources and on biodiversity. Its effects rapidly spread on the water and soil resources of Cambodia. With conventional practices and more frequent flooding and incidents of drought, smallholder farmers could hardly sustain their livelihoods, which are mainly based on annual upland farming. Farmers with investment capacity have shifted to planting tree crops and/or to animal production in order to cope with the hazardous phenomena. This case story presents the collaborative R&D program between farmers and researchers in Battambang and Kampong Cham provinces in Cambodia. The program aimed to restore soil fertility and build the resilience of smallholder farmers to the effects of climate change while improving crop productivity and profitability of the smallholder farmers. Using the Diagnosis, Design, Assessment, Training and Extension (DATE) methodology, the project implementers designed, tested, and evaluated crop production systems that are grounded on the principles of conservation agriculture (CA). DATE is a multi-scale, multi-stakeholder participatory approach. It integrates scientific and tacit knowledge, and is composed of four components: agrarian systems diagnosis, field experiment, on-farm assessment, and pre-extension. A number of CA-based cropping systems have been designed and validated in the program: (1) mono-cropping of maize in association with pigeon pea or mungbean as relay crops, (2) biannual rotation cropping of maize with soybean or cassava, and (3) intensified cropping of maize and cassava. Synergizing this with the benefits of CA, each system has the capacity for climate change adaptation and mitigation, to retain soil fertility, and to increase smallholder farmers' profitability. Based on the results, pigeon pea is the most suitable crop for mollisols used with maize since it can improve the water retention capacity of the soil, reduce soil evaporation, and reduce mineral nitrogen inputs. Moreover, its grain can be sold or used as animal feed to augment farmers' income, a characteristic that smallholders look for in an agricultural production system. Likewise, shifting mungbean to be sown by hand broadcast after harvesting early maize significantly reduces farmers' risks and costs, thereby improving their productivity. Shifting to CA-based cassava production (a key annual crop) using chisel to operate strip tillage on planting rows after the early maize harvest also enables farmers to significantly minimize risks and costs. These risks and costs are estimated to be about USD (United States Dollar) 300–400 per hectare and USD 200 per hectare, respectively. Designing CA-based cropping systems based on the DATE methodology presents clear benefits. DATE is a holistic approach for identifying technical, socioeconomic, and institutional elements for a sustainable and more inclusive intensification of smallholder farmers' agricultural production systems. However, designing such innovative techniques is a combination of context-specific and context-generic features. These issues need to be taken into account should such innovation be replicated in other regions. In addition, this action-research program should be a continuous process; the agro-technical performances of the introduced cropping systems should be continuously validated in multiple locations and for several years. The outcomes of the cropping systems should also be continuously monitored such that their impacts on natural resources (e.g., soil organic carbon, nutrient cycles, xenobiotic dynamic, etc.) can be determined and measured accurately.

The continuous use of plowing for grain production has been the principal cause of soil degradation. This project was formulated on the hypothesis that the intensification of cropping systems by increasing biomass-C input and its biodiversity under no-till (NT) drives soil restoration of degraded agro-ecosystem. The present study conducted at subtropical [Ponta Grossa (PG) site] and tropical regions [Lucas do Rio Verde, MT (LRV) site] in Brazil aimed to (i) assess the impact of the continuous plow-based conventional tillage (CT) on soil organic carbon (SOC) stock vis-à-vis native vegetation (NV) as baseline; (ii) compare SOC balance among CT, NT cropping systems, and NV; and (iii) evaluate the redistribution of SOC stock in soil profile in relation to soil resilience. The continuous CT decreased the SOC stock by 0_58 and 0_67MgCha_1 y_1 in the 0- to 20-cm depth at the PG and LRV sites, respectively, and the rate of SOC sequestration was 0_59 for the PG site and ranged from 0_48 to 1_30MgCha_1 y_1 for the LRV site. The fraction of C input by crop residues converted into SOC stock was ~14_2%at the PGsite and ~20_5% at the LRV site. The SOC resilience index ranged from 0_29 to 0_79, and it increased with the increase in the C input among the NT systems and the SOC sequestration rates at the LRV site. These data support the hypothesis that NT cropping systems with high C input have a large potential to reverse the process of soil degradation and SOC decline.

Cambodia has been identified to be one of the most affected countries by climate change. In the past two decades, migration from the central plains to the peripheral areas changed drastically the development of the uplands, inducing tremendous degradation of natural resources. The promotion of cropping systems based on ecological intensification is of paramount importance to strengthen the resilience of small-scale farming, to mitigate the effect of climate change and to advance in farm sustainability. The aim of this study was to quantify the short-term impact of conservation agriculture (CA, direct seeding + use of cover/relay crops), on soil organic C (SOC), soil total N (STN), labile C fractions (particulate organic C - POC and permanganate oxidizable organic C - POXC), β-glucosidase and arylsulfatase activities. Established in 2009, the experimental plots were laid out in a randomized complete block design (3 replicates) with: (i) soybean under conventional tillage (CT), (ii) soybean under conservation agriculture (CA1), and (iii) soybean in bi-annual rotation with maize under conservation agriculture (CA2). Several cover/relay crops were associated prior to and with the main crops. Soil sampling was conducted in 2011 and 2013 at 0-5, 5-10, 10-20, and 20-40 cm depths. Biomass-C inputs ranged from 2.2 to 7.8 Mg C ha-1 yr-1 under CT and CA respectively, emphasizing the difference of supply of fresh organic matter. On average, CA increased SOC and STN stocks at 0-5 cm depth by 20% and 25% when compared with CT. β-glucosidase and arylsulfatase activities at 0-5 cm depth was 28% and 36% greater in CA1 and CA2 soils. In addition, CA2 (rotational sequence and higher biomass-C inputs) showed a better increasing trend of labile C fraction (HWEOC and POXC) and β-glucosidase and arylsulfatase activities than CA1. Conservation agriculture shows potential for the long term improvement of Cambodia uplands. (Texte intégral)

La connaissance des différentes unités agronomiques au niveau d'un terroir et leur utilisation par les agriculteurs est indispensable si l'on veut adapter les propositions de systèmes SCV aux contraintes du milieu. Ces unités agronomiques sont définies de manière à constituer des ensembles homogènes, pour lesquels les systèmes de cultures que l'ont peut proposer sont identiques. Ainsi, l'origine d'un sol n'est pas vraiment discriminante (il ne s'agit pas d'unités pédologiques), mais on s'attache avant tout à prendre en compte les caractères discriminant les possibilités de culture. Dans la zone agro-écologique de moyenne altitude, avec longue saison sèche, la différenciation agronomique des sols se fait sur la base de leur niveau de fertilité, de leur compaction, et de leur régime hydrique (en saison et en contre-saison). Ainsi, les pratiques agronomiques peuvent faire évoluer une parcelle d'une unité à une autre. Par exemple, un sol compacté sur lequel on installe des plantes de couvertures au système racinaire très puissant, peut ainsi évoluer en quelques années vers un sol non compacté. De même, la fertilité du sol peut évoluer, dans un sens ou dans un autre. En pratique, on peut distinguer ces unités en se basant sur la couleur du sol, la flore en place et les performances des cultures conduites par les paysans.

Présentation de l'éditeur : Agriculture in whatever age, under whatever natural, economic and social conditions, has to feed the human being. To fulfil this mission, the sector has to overcome continuous and changing challenges to achieve notable developments. The Green Revolution, through developing and introducing high-yielding crop varieties and advanced crop management techniques, saved billions people from starvation. The advent of biotechnology, in its turn, has speed up the agricultural growth to meet food demands of the world's booming population. Continuous demographic pressure and rapid market integration have created necessity to further agricultural developments to meet not only food security, but also the increased demands for nutrition security, food safety, energy, etc., while the global climate change has created needs for capturing synergies between agricultural production and environmental protection. New breakthroughs to trigger the second Green Revolution have therefore become necessary. Thus, it is now the right time for us to consider the means to make "the Double-Green Revolution" to become a reality. Conservation Agriculture (CA) has demonstrated potential to meet this goal through designing and promoting the adoption of environment-sound and climate-resilient agricultural production systems. Increasing interests and efforts have been given to CA research for development in the Southeast Asia during the last 15 years. As a result, a new stage has been reached with the formation of the Conservation Agriculture Network for Southeast Asia (CANSEA) in 2009, in which efforts have been maintained to adapt concepts of CA to small scale farmers dealing with a great diversity of climate, land, topography and economy conditions. Enormous inputs are needed for the Southeast Asia to design specific and diverse CA innovations appropriate for local farmers and to promote their large scale adoption. This requires involvement of a wide range of stakeholders from both private and public sectors. This is the reason for us to gather together at the 3rd International Conference on Conservation Agriculture in Southeast Asia. At this conference, the results of a tremendous amount of creative work dedicated to CA development worldwide will be presented. The methods and tools for designing relevant CA innovations and the experience and proposals for their adoption will be shared. This volume compiles a picture portfolio of abstracts selected through a peerreview process for oral and poster presentations at the conference. Main topics addressed in this volume include (1) Agrarian transitions in the Southeast Asian uplands and highlands; (2) Impacts of agricultural systems on agricultural ecosystem sustainability; (3) Farming and cropping system design to sustainably intensify production; (4) Synergizing concepts of CA and Agroforestry; (5) Potentials and constraints of CA for rural development, and (6) Conditions, strategies, barriers and opportunities for scaling-up CA. This compilation represents a state and the art of CA research for development worldwide and the possible applications for the Southeast Asia

O sistema plantio direto é apontado como alternativa para a mitigação do CO2 atmosférico. O objetivo desse trabalho foi avaliar o efeito do uso da terra e de sistemas de produção no aumento do conteúdo e do estoque de carbono e nitrogênio em agro-ecossistema tropical e subtropical. Este trabalho foi realizado em uma área experimental há 29 anos comparando sistemas de manejo em um Latossolo Vermelho de textura muito argilosa (675 g kg-1) em Ponta Grossa, PR (PG) e outra com 8 anos de manejo em um Latossolo Vermelho Amarelo de textura argilosa (490 g kg-1) em Lucas do Rio Verde - MT (LRV). Em PG os tratamentos consistiram em quatro sistemas de uso da terra sendo: Preparo convencional (PC), preparo mínimo (PM), plantio direto (PD) e o solo sob vegetação nativa (VN) de floresta. Em LRV os tratamentos consistiram de Preparo convencional (PC), plantio direto (PD) e o solo sob vegetação nativa (VN) de cerrado.O conteúdo de carbono orgânico total (COT) e nitrogênio total (NT) foi determinado por combustão seca até um metro de profundidade. O estoque de COT e NT foram calculados em massa equivalente usando o solo sob vegetação nativa como referencia. O estoque de COT e NT na VN em PG e LRV na camada de 0-5 cm foi o dobro em relação ao PC e 30% superior ao PD. Em PG, na camada de 0-40 cm o estoque de COT e NT no PD (137,7 Mg C ha-1; 8,3 Mg N ha-1) foi próximo ao da VN (145,7 Mg C ha-1; 9,3 Mg N ha-1) e quando comparado ao PC foi superior em 17,4 Mg C ha-1 e 2,4 Mg N ha-1 cuja taxa anual de acúmulo foi de 0,58 Mg C ha-1 e 83 kg N ha-1 em 29 anos de experimentação. Em LRV o estoque de COT em 13 anos sob PC reduziu 27% (20,1 Mg C ha-1) na camada de 0-40 cm em relação ao cerrado e a taxa de perda foi de 1,55 Mg ha-1 ano-1. O PD com predominância de gramíneas (sorgo + B. ruziziensis e milho + B. ruziziensis) na safrinha foram os sistemas com os maiores aportes anuais de biomassa (acima de 20 Mg ha-1) e também apresentaram os maiores estoques de C (120,0 e 121,7 Mg C ha-1 até 1 m de profundidade) e diferiram significativamente de PC (104,1 Mg C ha-1). Em LRV, a diferença entre todos os sistemas em PD comparados ao PC variou de 5,8 a 16,5 Mg C ha-1 na camada 0-40 cm, e a taxa de acúmulo foi de 0,73 a 2,06 Mg C ha-1 ano-1. O aporte de resíduos culturais para manter o balanço positivo de C neste ecossistema é em torno de 13 Mg C ha-1 ano-1. (Texte intégral)

A estrutura do solo está estreitamente relacionada com o fluxo de ar e água no perfil do solo com impacto no desenvolvimento do sistema radicular e na produção das culturas. A conversão da vegetação natural em área agricola e o uso intensivo do solo com o preparo provoca mudanças profundas na estrutura. O objetivo deste trabalho foi avaliar as alterações que a adoção do plantio direto (PD) de longa duração promoveu na estrutura do solo, em comparação ao preparo convencional (PC) tendo como referência o solo sob vegetação nativa (VN). Essa avaliação foi conduzida na área experimental do Instituto Agronômico do Paraná (IAPAR) em Ponta Grossa - PR (PG) em um Latossolo Vermelho de textura muito argilosa (675 g kg-1 de argila) com 29 anos de manejo. A separação dos agregados foi realizada por via úmida e os agregados com tamanho entre 8 a 19 mm da camada de 0-5 cm foram utilizados para as medidas de porosimetria com injeção de mercúrio e a análise qualitativa pelo método de microscopia eletrônica de varredura (MEV) acoplada com raios-X. A proporção dos macroagregados com tamanho entre 8 a 19 mm foram superiores no PD (79,5%) aos encontrados na VN (58,4%) e no PC (38,1%). No entanto, na VN o conteúdo de C orgânico (82,1 g kg-1) foi superior ao PD (48,4 g kg-1) e 2,3 vezes superior ao PC (35,3 g kg-1) na camada de 0-5 cm. A técnica de MEV associada com raios-X mostrou que a estrutura do macroagregado foi afetada significativamente pelo uso da terra. Na VN, foi observado planos de fraqueza com a presença de compostos orgânicos cimentando a superfície e baixa microporosidade em seção com escala de 5 ?m. Em contraste, no PD observou-se elevada rugosidade da superfície apresentando elevada microporosidade na superfície deste plano de fraqueza. Ao contrario, no PC observou-se uma estrutura semi-aberta com revestimento de compostos orgânicos descontínuos deixando as partículas de minerais descobertas. O volume total da microporosidade foi respectivamente de 0,253, 0,291, 0,351 cm3 g-1 para VN, PC e PD, enquanto o volume dos poros maiores do que 360 ?m foi de 0,125, 0,114 e 0,102 cm3 g-1 para o VN, PC e PD, respectivamente. A vegetação nativa apresentou maior macroporosidade (> 360 ?m) enquanto no PD maior volume de microporos. Esta mudança na estrutura dos agregados é de extrema importância quando se refere ao potencial de estabilização da matéria orgânica do solo. (Texte intégral)

O objetivo desse trabalho foi avaliar o efeito de diferentes usos do solo no conteúdo e estoque de C nas frações particulada (COP) e associada aos minerais (COAM) da MOS. Este trabalho foi realizado em um Latossolo Vermelho de textura muito argilosa (675 g kg-1) em Ponta Grossa, PR (PG) com 29 anos e outra em um Latossolo Vermelho Amarelo de textura argilosa (490 g kg-1) em Lucas do Rio Verde - MT (LRV) com 8 anos de manejo. Em cada situação (PG, LRV) os tratamentos consistiram de três modos de uso da terra: preparo convencional (PC), plantio direto (PD) e o solo sob vegetação nativa (VN) de floresta. As frações COP e COAM foram separadas pelo método da tamisação em via úmida em sete profundidades de amostragem (0-5; 5-10, 10-20; 20-40; 40-60; 60-80; 80-100 cm) e o conteúdo de C total de cada fração foi determinado por combustão seca. As frações COP e COAM foram afetadas pela conversão das terras e o PC gerou as maiores perdas de C na fração particulada. Em PG, na camada de 0-5 cm o PC resultou em uma perda de carbono orgânico de 45,7 g kg-1 sendo 37% na fração COP, indicando menor migração de C para a fração COAM. Em condição Subtropical na camada 0-40 cm o COP e o COAM diminuiram de 14,5 e 77,5 Mg C ha-1 na vegetação nativa para 6,0 e 61,5 Mg C ha-1 quando converteu para PC, representando 59% e 21% de decrescimo devido ao preparo do solo. O COP e o COAM apresentou, 86% (4,86 Mg C ha-1) e 20% (12,14 Mg C ha-1) respectivamente, mais C sob PD do que em PC. O ganho de C (17 Mg C ha-1) no Latossolo Vermelho na camada 0-20 cm, com a conversão em PD foi atribuído as duas frações, sendo 27% ao COP e 73% ao COAM. Em contraste com a região subtropical, o COP representou em média 19% do estoque total de C em relação ao Cerrado, e variou nos sistemas de plantio direto de 14% a 17% até 1 m de profundidade. Na camada 0-20 cm o COP e o COAM diminuiram de 15,3 e 35,4 Mg C ha-1 da VN para 7,5 e 27,3 Mg C ha-1 no PC, representando 51% e 23% de redução devido ao preparo. O COP e o COAM apresentou em média, 24% (2,35 Mg C ha-1) e 21% (9,91 Mg C ha-1) respectivamente, mais C sob PD do que em PC. (Texte intégral)

A perda de carbono (C) orgânico devido ao uso inadequado do solo afeta as propriedades químicas, físicas e biológicas e torna o solo uma fonte de CO2 para a atmosfera. O objetivo desse estudo foi avaliar o efeito de sistemas de uso do solo no conteúdo carbono orgânico total (COT), C oxidável (Cox) e C recalcitrante (CRec) da matéria orgânica do solo (MOS) em região sub-tropical e tropical. Este trabalho foi realizado em Ponta Grossa (PG, PR região subtropical) em um Latossolo Vermelho (675 g kg-1 de argila) com 29 anos sob preparo convencional (PC) e plantio direto (PD), e em Lucas do Rio Verde (LRV, MT, região tropical), em um Latossolo Vermelho Amarelo (490 g kg-1 de argila) com 8 anos sob PC e PD. Nos dois locais foi selecionada a vegetação nativa (VN) de cerrado (LRV) e floresta (IAPAR) como referência. A profundidade de amostragem nos dois locais foi: 0-5; 5-10, 10-20; 20-40; 40-60; 60-80; 80-100 cm. O conteúdo de COT (80,7 g kg-1) em PG na camada de 0-5 cm em solo sob VN foi 2,3 vezes superior ao PC (35,0 g kg-1) e a perda total em 29 anos foi de 45,7 g kg-1 cuja taxa anual foi de 1,58 g kg-1. Em contraste, o conteúdo de COT no PD (62,5 g kg-1) foi 1,29 vezes inferior ao VN e recuperou 34,1% do COT perdido com o PC em relação ao VN. Em região tropical a perda de C (VN = 38,3 g kg-1) com o PC (18,3 g kg-1) foi de 20 g kg-1 representando 52,2 % e 2,5 g kg-1 ano-1 de C e 1,6 vezes superior à região subtropical. Da mesma forma a recuperação com os sistemas de produção em PD (23,8 g kg-1) recuperaram 30,0% do COT em relação ao PC. Abaixo da camada de 20 cm não se constatou diferenças significativas entre os sistemas de uso do solo. O conteúdo de COx apresentou a mesma tendência do COT. Foi observado que a proporção de C recalcitrante aumentou com a diminução do C em profundidade e variou de 14% na camada superficial para 49% nas camadas mais profundas. Em condição subtropical, o conteúdo do CRec diferiu significativamente entre os modos de uso da terra na camada superficial do solo com 16,3, 7,7 e 9.0 g kg-1 em VN, PC e PD, respectivamente. Conteúdo semelhante de CRec foi constatado de 5-10 cm até 100 cm de profundidade entre os usos da terra, embora o conteúdo de COT foram diferentes entre os tipos de manejo. Em LRV, o conteúdo do CRec não alterou nas camadas superficiais até 1 m de profundidade independente do uso da terra e sistemas de produção. (Texte intégral)

A perda de C com a conversão da vegetação natural em área de produção agrícola é influenciada pela zona climática, pela classe de solo e sua textura e a intensidade do preparo utilizada. O objetivo do trabalho foi avaliar o efeito da conversão do solo sob vegetação natural em área de produção agrícola no estoque de C total, o C orgânico particulado (COP), o C associado aos minerais (COAM) em ecossistemas contrastantes (Tropical e Subtropical). Este trabalho foi realizado em um Latossolo Vermelho (675 g kg-1 de argila) em Ponta Grossa, PR (PG) com 29 anos sob preparo convencional, em um Latossolo Vermelho Amarelo (490 g kg-1 de argila) em Lucas do Rio Verde - MT (LRV) com 8 anos sob preparo e em um Neossolo Quartzarênico (770 g kg-1 de areia) em Luiz Eduardo de Magalhães - BH (LEM) com 4 anos sob preparo. Em PG, o estoque no COAM (234,0 Mg ha-1) foi 2,1 e 5,8 vezes mais elevado do que em LRV (COAM = 108,1 Mg ha-1) e LEM (39,8 Mg ha-1), enquanto o estoque de C no COP foi semelhante entre os ecossistemas (24,0 Mg ha-1 em PG; 25,2 Mg COP ha-1 em LRV e 27,4 Mg ha-1 em LEM) embora as diferenças no material de origem sejam contratantes. A média do estoque de COP em PG foi de 9,3% do estoque total de C, enquanto essa fração foi responsável por 19% em LRV e 35% do estoque total de C em LEM até 1 m de profundidade. Comparativamente, mais COP poderia ser mineralizado no Latosolo Vermelho Amarelo (LRV) e no Neossolo Quartzarênico indicando que o impacto da conversão na fração de C lábil gera perdas espressivas na fertilidade química, fisica, biologica do solo. Em cada ecossistema o preparo resultou em uma taxa de perda anual na camada 0-40 cm de 0,88; 1,55 e 0,40 Mg C ha-1 ano-1, para PG, LRV e LEM, respectivamente. Essas perdas ocorrem em maior expressão no COP do que no COAM. Em ambiente subtropical o COP e o COAM diminuiram na camada 0-40 cm de 17,6 e 128,1 Mg C ha-1 na vegetação nativa para 7,8 e 112,5 Mg C ha-1, representando 55% e 12% de decréscimo devido ao preparo do solo. No ambiente tropical, o estoque de COP de LRV e LEM reduziu de 18,8 e 11,4 Mg C ha-1 para 9,9 e 8,7 Mg C ha-1 com o preparo enquanto o estoque de COAM decresceu em LRV de 59,9 para 46,6 Mg C ha-1 e em contraste, em LEM o COAM não foi afetado com o PC. (Texte intégral)

O fluxo de C oriundo dos resíduos culturais é o suprimento para a formação das frações lábeis da Matéria Orgânica do Solo (MOS) e torna-se fundamental para a formação dos agregados e do C estável com o passar do tempo. O objetivo deste trabalho foi avaliar as alterações nos compartimentos lábeis da MOS afetado por diferentes sistemas de manejo do solo em ambiente sub-tropical e tropical. A pesquisa foi realizada em experimentos de longa duração implantados no Instituto Agronômico do Paraná (IAPAR), em Ponta Grossa-PR e na estação experimental da Fundação Rio Verde, em Lucas do Rio Verde (LRV), Mato Grosso. Foram avaliados três sistemas de uso da terra em cada ambiente: Vegetação Nativa (VN), Plantio direto (PD) e Preparo convencional (PC). O C orgânico dissolvido (COD) extraível em água quente e polissacarídeos totais (PT) foram analisados nas amostras coletadas nas camadas de 0-5, 5-10, 10-20, 20-40, 40-60, 60-80 e 80-100 cm do perfil do solo. Independentemente dos tratamentos, a concentração média do COD diminuiu significativamente com a profundidade do solo. Em Ponta Grossa, a média do conteúdo de COD no solo sob VN (2,16 g kg-1) representou 2,7% do COT na camada 0-5 cm e reduziu até 1,5% do COT (0,21g C kg-1) na camada de 80-100 cm de profundidade. A porcentagem de C em PT no solo sob VN representou 20% do COT a 0-5 cm e 29% na camada 80-100 cm. O conteúdo de COD no solo sob VN e em PD, foi positivamente correlacionada com o conteúdo de PT sugerindo que os carboidratos solúveis foram os componentes predominantes do COD. O conteúdo de COD e PT na camada de 0-5 cm na VN e no PD foi significativamente superior em relação ao PC. Na camada 0-5 cm o conteúdo de COD e PT sob PC, reduziu 57% e 41%, respectivamente. Em LRV na VN, o conteúdo de COD e C em PT representou 2,1% e 13% do COT respectivamente na camada 0-5 cm e 0.6% e 27% na camada 80-100 cm. Os conteúdos de COD e PT foram significativamente afetados pelas mudanças de uso da terra na camada superficial com menores valores medidos sob PC (COD: 0,39 g kg-1; PT: 6,5 g kg-1) em comparação com VN (COD: 0,82 g kg-1; PT: 11,3 g kg-1) e PD (COD: 0,65 g kg-1; PT: 11,3 g kg-1). (Texte intégral)

O monitoramento do conteúdo de carbono (C) do solo em diferentes usos da terra é essencial para a realização de inventários e das estimativas sequestro. O método mais usado no mundo está baseado na oxidação do C por via úmida (C-CH) descrito originalmente por Walkley e Black em 1934. Embora o método padrão para a quantificação do C total no solo seja pelo método da combustão seca (C-CS), a maioria dos laboratórios ainda usam a oxidação por via úmida. O objetivo desse trabalho foi avaliar: a) o efeito do uso da terra (solo sob vegetação nativa, preparo convencional - PC, preparo mínimo - PM, plantio direto - PD), do gradiente textural (150 a 720 g kg-1 de argila) e da profundidade de amostragem no fator de correção usado para corrigir o C orgânico determinado por combustão umida, b) propor modelos lineares que reduzem o erro entre os dois métodos analíticos e c) ser uma ferramenta útil para a comparação dos estoques de C orgânico passados e atuais em ecossistemas tropical e subtropical. Para esses objetivos foram coletadas amostras de duas condições climáticas contrastantes: região subtropical (Ponta Grossa/PR, Carambei/PR, Tibagi/PR) e região tropical (Lucas do Rio Verde/MT - LRV e Luís Eduardo de Magalhães/BA - LEM), totalizando cinco locais. Independente dos locais e sistemas de uso da terra constatou-se estreita correlação entre os dois métodos de análise. No modelo linear, a importância de cada fator (uso da terra, gradiente textural e profundidade) muda entre as localidades. Na condição subtropical a profundidade de amostragem para Carambeí e Tibagi, o conteúdo de argila para Tibagi e as interações "uso da terra profundidade" para Ponta Grossa e "uso da terra silte" para Carambeí foram significativas na expressão do fator de correção entre C-CS e C-CH. Na condição tropical, a profundidade para LEM e a interação "uso da terra silte" para LRV foram significativas. Este fator de correção variou em média de 1,38 a 1,59 na condição subtropical e de 1,20 a 1,49 na condição tropical. Maiores fatores nos solos subtropicais refletem o maior conteúdo de C quimicamente estabilizado, inacessibilidade espacial de C dentro de microagregados e intima interação com a fração associada aos minerais conduzindo a uma oxidação parcial de C pelo método de Walkley-Black. O conjunto de dados possibilitou elaborar três modelos cobrindo a grande variação de clima, solos e uso da terra. (Texte intégral)

O efeito do preparo do solo proporciona a ruptura dos agregados expondo o carbono (C) protegido entre e intra-agregado à ação decompositora da microbiota. O objetivo desse trabalho foi avaliar o efeito de diferentes usos da terra e de sistemas de produção proteção e acúmulo de C nos agregados do solo em ecossistema subtropical e tropical. Este trabalho foi realizado em Ponta Grossa - PR (PG) em um Latossolo Vermelho de textura muito argilosa (675 g kg-1) há 29 anos com diferentes manejos e em Lucas do Rio Verde - MT (LRV) em um Latossolo Vermelho Amarelo de textura argilosa (490 g kg-1) com 8 anos de manejo. Os tratamentos consistiram em três usos da terra sendo: Preparo convencional (PC), plantio direto (PD) e uma vegetação nativa (VN) de cerrado (LRV) e floresta (IAPAR). A separação das classes de agregados (8, 4, 2, 1, 0.5, 0.25, 0.053 mm) foi realizada através da tamisação por via úmida em cada uso da terra e sistemas de produção em três profundidades de amostragem (0-5, 5-10, 10-20 cm). O conteúdo de C orgânico (COT) de cada classe foi determinado pelo método da combustão seca. Em PG, o PD proporcionou a porcentagem de agregados com tamanho entre 8 a 19 mm e maior diâmetro médio em todas as profundidades amostradas. Entretanto, o maior conteúdo de C foi constatado no solo sob VN em todas as classes de agregados. Em contraste, o conteúdo de C no PC foi constante nas diferentes classes de agregado. O PC afetou significativamente a agregação com uma proporção maior de agregados menores do que 2 mm e um conteúdo de C menor em cada classe. Na camada 0-5 cm o conteúdo medio de C diminui de 74,9 g kg-1 sob VN para 49,2 g kg-1 no PD e 33,4 g kg-1 no PC, representando 34% e 55% de perda devido ao uso da terra. Em LRV, a diferença significativa no tamanho medio do agregado e no conteudo de C foram observadas entre o VN e o PC e nos sistemas de produção em PD. Em LRV o conteúdo de C foi melhor distribuído nas classes de agregado e no VN o conteudo de C foi de 41,2 g kg-1 nos agregados > 8 mm e descrescendo para 15,6 g kg-1 nos agregados de 0.053 a 0,250 mm. O maior conteúdo de C foi nos sistemas de produção em PD com aporte de biomassa superior a 7,5 Mg C ha-1 ano-1. (Texte intégral)

In the four southern districts (Kenthao, Paklay, Boten, and Thongmixay) of Xayabury province, the current cropping systems are based on cash crop production. Maize is the main crop under rainfed conditions and covers more than 30,000 ha in the region. Land preparation is based mainly on plowing, which degrades soil and destroys infrastructures (paddy fields and roads). These deteriorations result from growing pressure on agricultural systems and farmers' lack of access to affordable labour. This study sought to analyze soil aggregation, soil water-holding capacity, and soil biological activity under tillage and notillage conditions in relation to the cropping sequence. Three cropping sequences were investigated: 1. maize monoculture; 2. two-year rotational sequence, maize - rice bean; 3. two-year rotational sequence, maize + Brachiaria ruziziensis - rice bean.). Each year of the sequence was represented under no-till (NT) and tillage (CT) practices. Independent of depth, soil aggregation was greater under no-till conditions and enhanced by crop rotation and higher dry matter production (maize + B. ruziziensis / rice bean). Soil macrofauna, that is, the number of species and amount of biomass, was increased with no-till and the cropping sequence. Earthworms increased with no-till and for some cropping sequences amounted to more than 50% of the total macrofauna biomass. The cropping sequences produced a limited amount of dry matter. The main challenge was to increase biomass productivity (above-ground and below-ground) to recover ecosystem functions (recycling of nutrients, carbon sequestration, high biological activity, integrated weed and pest management, etc.) in a medium-term process (five years). Generating and adapting intensive cropping sequences (high production of aboveground and belowground biomass combined with a high diversity) under no-tillage systems with smallholders is an essential step in achieving long-term land sustainability, to obtain more reliable harvests and higher farm profits.

The Plain of Jars is an acid, infertile savannah grassland covering an area of about 60,000 ha in the western region of Xieng Khouang Province, northeastern Lao PDR. In this ecology, farming systems are mainly based on lowland rice cultivation and extensive livestock production. An increase in rice production and intensification of the livestock industry are two key components in the Lao government's poverty alleviation strategy for this area. The main agronomic constraints for developing crops and forage systems are related to serious unfavourable soil chemical characteristics. Low pH, along with nutrients deficiencies (in nitrogen, phosphorus, potassium, calcium and magnesium) and high levels of aluminium saturation probably have a negative effect on the growth of upland crops, as well as many pasture species. Moreover, severe phosphorus deficiency generates animal health problems. Since 2004, the Lao National Agro- Ecology Programme (PRONAE) has been working on innovative farming systems based on direct seeding mulch-based cropping system (DMC) principles, as a technical approach, and on a progressive in situ validation process with smallholders as a Research & Development (R&D) approach. The advantages of the methodology are presented through the case of a DMC system developed in 2005 by the project to intensify rice-beef production in the Plain of Jars. The farming system initially proposed was a 5-year rotational sequence where improved pasture land was implemented in the first year, fattening activities conducted in the following three years and pasture regenerated in the fifth year using rice as a cash crop to finance pastureland re- implantation. Costs and benefits of the system were simulated according to the data collected in the creation sites. At the end of the 5 years, an average net income of 160 $US/ year/ha and an average labour productivity of 2.5 US$ per ha and working day were expected. The system was then proposed to 89 families forming 16 farmers' groups in 12 different villages for an in situ validation covering 76 ha. Even though promising results have been described at the creation site, 3-years of continuous validation have revealed several constraints for mass extension. In- field monitoring and interviews with farmers showed the main constraints to be (i) Market channels' constraints or malfunctioning, (ii) Fencing costs and maintenance, (iii) Production costs rising faster than benefits, (iv) Credit access and supply, (v) Technical skills required for good-quality pastureland implementation and management and (vi) Cattle fattening management. This feedback has given rise to development-related discussions and proposals regarding credit access, market channel functioning and training supports to be provided to farmers. This feed back has also given rise to new research topics, such as (i) how to generate higher incomes during the first year of implementation and (ii) how to reduce fertilizer use (main production cost) while maintaining at the same time improved pastureland productivity. New farming systems based on direct sowing of rice associated with forage species on degraded native pastureland have therefore been tested at creation sites and are currently under validation with farmer groups. This rice-beef system "creation- validation" process shows (i) the need to maintain research activities in the development process and (ii) the merits of the "creation site / farmer validation group" system for determining the potential for technology dissemination.

The National Agroecology Programme (PRONAE) and the Southern Xayabury Application Point (PASS) of the Capitalization and Rural Development Support Programme (PCADR) have developed an approach in the provinces of Xayabury and Xieng Khouang that relies on direct sowing mulch-based cropping systems (DMC). This approach has provided relevant alternatives to traditional agricultural practices which can no longer ensure the foundations of sustainable agriculture. In view of the results obtained, be they socio-economic or environmental, the Council of Ministers asked the Ministry of Agriculture and Forestry (MAF) to promote these techniques throughout the country, and called for this approach to be included in university and school courses. It is in that context that the Sector-based Agroecology Programme (PROSA), whose main aim is to define and implement a national strategy for the dissemination of Conservation Agriculture based on agroecological techniques (DMC), operates. This strategy is based on implementing an Agroecology Action Plan relying on the necessary incorporation of natural capital in rural development policies. The plan involves programming activities, setting in place decision-making and operational processes and bringing into play financial, material and human resources on both a central and local level (province, district and sub-district). The finest level of intervention comprises groups of farmers linked to service centres set up by the government within the districts (Kum Ban Pattana). On each level, the agroecology action plan is to arise from an integrated and concerted approach, in which each category of rural development stakeholders is committed to a process in which their needs and skills are acknowledged by all. Likewise, on each level, it is necessary to define, in a concerted manner, the initiatives that have to be taken (diagnosis, planning, implementation, monitoring-appraisal), the tools required (training of the different stakeholders, organization and structuring of the State sector and of the private sector, contractualization between stakeholders) and the fields of involvement (extension, local development funding arrangements, management of natural resources, equipment management, organization of supply and marketing chains, etc.). Each of the two pilot provinces, Xayabury and Xieng Khouang, is in the process of defining its Provincial Action Plan in Agroecology. An initial diagnosis of farming systems and their envi ronmental impacts, along with the needs and contributions of each category of stakeholders, has been completed. The provinces then gave priority to defining decision making and operational processes, and setting in place financial arrangements for the Provincial Action Plans. Initially, two funding tools are under consideration: constitution of a development fund, and agricultural credit. On a central level, the decision-making and operational processes are directly attached to the Ministry of Agriculture and Forestry, notably via the Planning Department. The creation of a Research and Service Provider Centre in support of local and national development is envisaged. Likewise, on a central level, it is a matter of facilitating the implementation of training plans for the different stakeholders. Lastly, the inclusion of agroecology in university and school courses is under way. Also for the educational sector, it is necessary to define a training plan to strengthen the skills and abilities of teachers. The creation of a national, or even regional network associating agricultural faculties and agricultural schools would enable an economy of scale by more effectively taking advantage of complementarities and decentralization to a more functional local level.

Over the past fifteen years, farming systems have changed drastically in the Lao PDR, with swidden systems giving way to more modern agricultural technologies in many areas. In southern Xayabury, agricultural intensification is causing rotational cultivation systems and fallow periods to disappear. These are gradually being replaced by 'resource-mining' agriculture that has serious social and environmental costs, including increased soil erosion (leading to destruction of roads and paddy fields), loss of soil fertility, and chemical pollution of the environment. On elevated plains in the upper part of the Nam Ngum river basin (Xieng Khouang province), large areas of savannah grasslands are under-utilised by smallholders whose main farming systems are based on lowland paddy fields, livestock production with extensive grazing on savannah grasslands, and off-farm activities. Given this situation, the Lao National Agro-Ecology Programme (PRONAE) has implemented an iterative research-development approach based on conservation agriculture. The objectives are to find innovative systems that can revert the present 'resource-mining' practices in southern Xayabury to systems based on conservation agriculture, and to develop alternatives systems for the plains of Xieng Khouang province. Direct seeding mulch-based cropping systems with residue management were evaluated and validated by farmer groups in five villages in southern Xayabury over four seasons. Positive results (increased net income and labour productivity) are evident from these direct seeding systems, and with growing interest observed there is potential for widespread adoption. Results show that the level of dissemination of direct seeding mulch-based cropping systems differs greatly among the villages surveyed depending on their environmental and socio-economic conditions. On the elevated plains of Xieng Khouang province, the economic and technical viability of cattle fattening was analysed. Fattening on improved pastureland (using Brachiaria ruziziensis) during the rainy season appears very efficient, with high growth rates recorded. During trials in 2005 weight gain and seed production of B. ruziziensis earned a gross income of US$879 over 1.5 ha, covering all expenses for fencing, fertiliser, seeds, and bull management for the first year. The income generated by this fattening programme in 2006 was $362/ha, the equivalent of a paddy rice yield of 1.8 t/ha, which is unlikely in this ecology. Development of specific market channels for seeds could indirectly improve pasture management, avoid high stocking rates and generate new income that could be invested in fertilisers and animal care. The approach followed by PRONAE highlights the collaboration process progressively developed with all of the stakeholders (smallholders, agronomists, District Agriculture and Extension Office staff, development projects, policy-makers and the private sector). One of the main challenges involved with this approach is the transfer to extension agencies and the private sector, over the medium term, of a research-development programme with systems and technologies based on the main principles of conservation agriculture (permanent soil cover, no soil disturbance, and diversified crop rotations with use of relay and/or cover crops).

Since the 1990s, in the southern districts of Xayabury province in the Mekong corridor, traditional farming systems have changed through extensive agricultural development based on cash crops. This development, by way of intensification, depends on local market accessibility, transfer of technologies from Thailand and the increasing financial capacities of local enterprises. Thai inputs, heavy mechanisation and technical skills are imported and cropping is largely opportunistic, following Thai market demand. Due to its low labour requirements and high labour productivity, maize is widely sown and spreads to new areas every year (more than 15,000 ha was sown in southern Xayabury in 2004), while crop rotation tends to be abandoned. Land preparation, based on burning residues and ploughing on steep slopes, has allowed for cultivation of large upland areas. As a result of this development, combined with land allocation and increasing population density, fallow periods are disappearing. Such 'resource-mining' agriculture generates land erosion - leading to destruction of roads and paddy fields - and is also responsible for fertility loss, yield decline and chemical pollution. To rehabilitate the areas most degraded by these practices, combinations of multicropping, animal husbandry and off-farm activities can provide a balanced distribution of farming activities over time and space. Such strategies reduce climatic and economic risks in a fragile ecosystem. In light of this, the Lao National Agro-Ecology Programme has implemented a holistic research approach which emphasises generation and adaptation of direct seeding mulch-based cropping (DMC) systems with village communities and groups of smallholders. From a large range of technologies that were tested, maize production using direct seeded grain on former crop residues under no-tillage systems has been implemented. Results achieved under various conditions are presented in this paper: yields, labour inputs, costs, net income and labour productivity are all observed. Positive results are evident from DMC on residues. Despite agronomic and economic successes, however, various constraints limit the dissemination of these systems. A gender-disaggregated survey was carried out with all groups of smallholders to identify the main constraints of this first level of DMC systems on residues. The major limiting factors appear to be: i) drudgery of labour for land preparation, so limiting cultivated area; ii) access to inputs (market and financial constraints); iii) problems of appropriate equipment for sowing; iv) technical skills required; and v) calendar flexibility.

Conservation agriculture and direct seeding mulch-based cropping (DMC) systems greatly modify plant and soil interaction. Plants commonly provide energy that fuels biological processes and either directly or indirectly creates structure within soils. Under DMC systems 7 large biomass is produced both above and below ground, thereby influencing soil parameters. Different methods can be used to measure soil characteristics, but simple and cheap tools for on-site recording are not common. This study attempts to analyse the physical soil parameters (water-stable aggregate, bulk density and soil permeability) of various ecosystems: savannah grassland, pine forest, ploughed upland rice fields, and improved Brachiaria ruziziensis and Stylosanthes guianensis pasture lands. The results show that these forage species have a clear effect on soil structure: medium soil particles (

In the vicinity of Phonsavanh (provincial capital of Xieng Khouang, on the Plain of Jars) as in many other areas of Laos, livestock production remains one of the main components of farming systems. In Pek district of Xieng Khouang, it accounts for more than 50% of household income. Cattle raising remains traditional, based on free grazing on clear forest, savannah grassland, and crop residues after harvesting. Poor soil conditions, and lack of both fodder resources and economic incentives are the main constraints limiting extension of livestock production. The savannah grassland here is characterised by acidic soils, high aluminium saturation, and local weed species that produce low amounts of biomass and have low palatability; the main species are Themeda triandra, Hypparhenia and Cymbopogon nardus. More than 60,000 ha of savannah grasslands is present in Xieng Khouang province, mainly located in the districts of Pek, Phoukhouth and Paxay. Since 2004 the Lao National Agro-Ecology Programme (PRONAE) has been introducing innovative cropping systems based on direct-seeding to regenerate lands and diversify farming production. These systems integrate crops and livestock through the use of forage species and cover crops. At the same time thematic adjustment are carried-out, testing simple technologies such as forage species. Promising fodder productivity results were obtained on the Plain of Jars and it was then decided to test these forage species under grazing conditions. The present study seeks to evaluate the agronomic and economic components of cattle fattening in the vicinity of Phonsavanh using improved forages and other inputs. Cattle fattening appeared to be very efficient during the rainy season with a mean growth rate of 364 g.day-1 recorded. The local cattle seem well adapted for fattening and showed a good response to improved fodder. The technical and economical results are clearly positive. However, economic incentives and technical and political support must be better defined if efficient and productive livestock systems are to be developed in such an environment. Forage seed production has to be promoted to improve pasture management, to avoid high stocking rates and to generate new income that could be invested in fertilisers and animal care.

Farming systems throughout the Lao PDR have changed drastically over the last 15 years due to a range of factors. In some areas where market forces are prevalent, shifting cultivation systems have given way to more conventional high-input agricultural systems. In other more remote areas, the traditional swidden system with long rotations has been put under pressure primarily due to modification of land access and increasing population pressure. In southern Xayabury in the Mekong corridor, where there is access to the Thai market, land preparation has become based on burning residues and ploughing on steep slopes. Because of the environmental and financial costs of land preparation, farmers are shifting to herbicides, which lead to chemical pollution, while crop residues and weed mulch are usually burned, thereby increasing mineral losses and erosion on bare soil. In mountainous areas such as Xieng Khouang Province, the rationale of shifting cultivation is collapsing as farmers use land for longer periods of cropping and return more frequently to each field. A holistic research approach has been implemented in Xayabury and Xieng Khouang to find direct seeding mulch-based cropping (DMC) systems that are compatible with farmers' strategies and which can be reproduced inexpensively on a large scale. The methodological framework, based on five main components, emphasises the process of adaptation and validation by farmer groups, meaning that priorities are defined by smallholders in light of the constraints of their farming systems and the overall environmental conditions.