Sustentabilidad del monocultivo de soja y otras alternativas agrícolas, en relación a los recursos suelo y agua, en la Región Centro-Norte de Córdoba. Sustainability of soybean monoculture and another agricultural alternatives, in relation to soil and water natural resources, in the north-central area of Cordoba (Argentina).

En este proyecto se pretende demostrar que existen alternativas sustentables al monocultivo de soja y económicamente factibles si se consideran los costos ambientales.Se cumplirán los siguientes objetivos específicos:- Caracterizar la sensibilidad de indicadores de calidad del suelo: infiltración, densidad aparente, penetrometría, C orgánico, fracciones de la MO y un índice químico de disponibilidad de N. - Medir escurrimiento y erosión en dos microcuencas con manejos contrastantes donde existe instrumental instalado y registros desde hace mas de 10 años.- Establecer rangos para las situaciones encontradas en los suelos representativos de la región.- Integrar los parámetros considerados en un sistema de diagnóstico de calidad/salud del suelo, para las condiciones de la región. - Aplicar el sistema de Calidad/salud del suelo para situaciones con monocultivo de soja y otras alternativas.- Calibrar y aplicar el modelo de simulación de la materia orgánica AMG, al monocultivo de soja y otras alternativas, a distintas escalas temporales y espaciales.- Estimar los costos ambientales de monocultivo a partir de los datos obtenidos.- Extrapolar los resultados del monocultivo y las otras alternativas a los suelos característicos, para estimar la sustentabilidad de los suelos en el centro-norte de la provincia de Córdoba.Se trabajará en dos áreas piloto en campos de productores, con y sin erosión hídrica. Se evaluarán parámetros indicadores del estado de los suelos, se los integrará en un sistema, se evaluarán los suelos con situaciones de monocultivo de soja y manejos contrastantes y se los correlacionará con su historial de intervención antrópica. Se brindará una herramienta apta para el ordenamiento territorial.

Water erosion in no-tillage monoculture and intercropped systems along contour lines

Water erosion is the major cause of soil and water losses and the main factor of degradation of agricultural areas. The objective of this work was to quantify pluvial water erosion from an untilled soil with crop rows along the contour, in 2009 and 2010, on a Humic Dystrupept, with the following treatments: a) maize monoculture; b) soybean monoculture; c) common bean monoculture; d) intercropped maize and bean, exposed to four simulated rainfall tests of on hour at controlled intensity (64 mm h-1). The first test was applied 18 days after sowing and the others; 39, 75 and 120 days after the first test. The crop type influenced soil loss through water erosion in the simulated rainfall tests 3 and 4; soybean was most effective in erosion control in test 3, however, in test 4, maize was more effective. Water loss was influenced by the crop type in test 3 only, where maize and soybean were equally effective, with less runoff than from the other crops. The soil loss rate varied during the runoff sampling period in different ways, demonstrating a positive linear relationship between soil and water loss, in the different rainfall tests.

Cycling of nutrients and silicon in pigeonpea and pearl millet monoculture and intercropping

In a no-tillage system, cover crops must be used that combine shoot dry matter production and nutrient recycling. The aim of this study was to evaluate shoot dry matter production, decomposition rate and macronutrient and silicon release from pigeonpea and pearl millet in monoculture and intercropping systems. A randomized block design was used with a 3 x 6 factorial arrangement, with four replications. The first factor consisted of three cover crops (pigeonpea, pearl millet and intercropping of these cover crops) and the second consisted of six sampling times [0, 18, 32, 46, 74 and 91 days after desiccation (DAD)]. Pearl millet produced greater amounts of shoot dry matter and content of N, P, K, Ca, Mg, S, C and Si and had a higher decomposition rate and macronutrient and Si release than the other cover crops. The rates of decomposition and daily nutrient release from shoot dry matter were highest in the first period of evaluation (0-18 DAD). Over time, the C/N, C/P and C/S ratios increased, while C/Si and the decomposition rate decreased. Potassium was the nutrient most quickly released to the soil, especially from pearl millet residue. Silicon had the lowest release rate, with 62, 82 and 74 % of the total content in the shoot dry matter remaining in the last evaluation of pearl millet, pigeonpea and in the intercrop system, respectively. The shoot dry matter from the intercrop system had a different decomposition rate than that from the pearl millet monoculture and pigeonpea. Plants with greater shoot dry matter production and lower C/Si ratio are more effective in a no-tillage system for providing a more complete and persistent soil cover.

Decomposition of Arachis pintoi and Hyparrhenia rufa litters in monoculture and intercropped systems under lowland soil

Tropical grasslands under lowland soils are generally underutilized and the litter of forage legumes may be used to recover these degraded pastures. The objective of this work was to study the dynamics of litter decomposition of Arachis pintoi (pinto peanut), Hyparrhenia rufa (thatching grass) and a mixture of both species in a lowland soil. These treatments were analyzed in three areas: grass monoculture, legume monoculture and legume intercropped with the grass during the dry and wet seasons. Litter bags containing the legume, grass or a mixture of both species were incubated to estimate the decomposition rate and microorganism colonization. Decomposition constants (K) and litter half-lives (T1/2) were estimated by an exponential model whereas number of microorganisms in specific media were determined by plate dilution. The decomposition rate, release of nutrients and microorganisms number, especially bacteria, increased when pinto peanut was added to thatching grass, influenced by favorable lignin/N and C/N ratios in legume litter. When pinto peanut litter was incubated in the grass plots, 50% N and P was released within about 135 days in the dry season and in the wet season, the equivalent release occurred within 20 days. These results indicate that A. pintoi has a great potential for nutrient recycling via litter and can be used to recover degraded areas.

Interactions of onion (Allium cepa) and yellow wax bean (Phaseolus vulgaris) in monoculture and intercropping with weeds, Chenopodium album and Amaranthus hybridus

Intercropping systems are seen as advantageous as they can provide higher crop yield and diversity along with fewer issues related to pests and weeds than monocultures. However, plant interactions in intercropped crop species and between crops and weeds in these systems are still not well understood. The main objective of this study was to investigate interactions between onion (Allium cepa) and yellow wax bean (Phaseolus vulgaris) in monocultures and intercropping with and without the presence of a weed species, either Chenopodium album or Amaranthus hybridus. Another objective of this study was to compare morphological traits of C. album from two different populations (conventional vs. organic farms). Using a factorial randomized block design, both crop species were planted either in monoculture or intercropped with or without the presence of one of the two weeds. The results showed that intercropping onion with yellow wax bean increased the growth of onion but decreased the growth of yellow wax bean when compared to monocultures. The relative yield total (RYT) value was 1.3. Individual aboveground dry weight of both weed species under intercropping was reduced about 5 times when compared to the control. The poor growth of weeds in intercropping might suggest that crop diversification can help resist weed infestations. A common garden experiment indicated that C. album plants from the conventional farm had larger leaf area and were taller than those from the organic farm. This might be associated with specific evolutionary adaptation of weeds to different farming practices. These findings contribute to the fundamental knowledge of crop-crop interactions, crop-weed competition and adaptation of weeds to various conditions. They provide insights for the management of diversified cropping systems and integrated weed management as practices in sustainable agriculture.

Impact of teak and eucalypt monoculture on soils in the highlands of Kerala

Impact of teak and eucalypt monoculture on soils in the highlands of kerala .The thesis is arranged under nine chapters. The first chapter introduces the topic, reviews the literature pertaining to the study and presents the aims and objectives of the study. The second chapter briefly describes the study location. experimental design and sampling methodology. The third chapter deals with physical properties of plantation soils. The fourth and fifth chapters cover the chemical properties and macro- and micro nutrient status in plantation soils. The organic matter fractions in plantation soils are described in sixth chapter. First part of the seventh chapter presents the results of factor analysis and the second part deals with fertility index of plantations. All these chapters are self-contained with separate introduction, materials and methods and results and discussions. A general discussion of the results is included in the eighth chapter. The ninth chapter includes conclusions and summary A study that traces the variation in physical and chemical properties and nutrient status of teak soils with age of plantations, till the end of a rotation period is thus highly pertinent. Such a study, with an adjacent natural forest as a reference stand will not only generate information that will help us to understand the pattern of variation in soil properties, but will also aid us in formulating better management strategies. The data generated by such a study will be more useful if accompanied by information on soil changes following a short rotation plantation crop. As Eucalypt, a short rotation crop is the second major plantation crop in Kerala, it was chosen for the study.

Monoculture of Leafcutter Ant Gardens

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cycling of nutrients and silicon in pigeonpea and pearl millet monoculture and intercropping

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Modelling predicts positive and negative interactions between three Australian tropical tree species in monoculture and binary mixture

Computer modelling promises to. be an important tool for analysing and predicting interactions between trees within mixed species forest plantations. This study explored the use of an individual-based mechanistic model as a predictive tool for designing mixed species plantations of Australian tropical trees. The 'spatially explicit individually based-forest simulator' (SeXI-FS) modelling system was used to describe the spatial interaction of individual tree crowns within a binary mixed-species experiment. The three-dimensional model was developed and verified with field data from three forest tree species grown in tropical Australia. The model predicted the interactions within monocultures and binary mixtures of Flindersia brayleyana, Eucalyptus pellita and Elaeocarpus grandis, accounting for an average of 42% of the growth variation exhibited by species in different treatments. The model requires only structural dimensions and shade tolerance as species parameters. By modelling interactions in existing tree mixtures, the model predicted both increases and reductions in the growth of mixtures (up to +/- 50% of stem volume at 7 years) compared to monocultures. This modelling approach may be useful for designing mixed tree plantations. (c) 2006 Published by Elsevier B.V.

Responses of neotropical mangrove seedlings grown in monoculture and mixed culture under treatments of hydroperiod and salinity

We investigated the combined effects of salinity and hydroperiod on seedlings of Rhizophora mangle and Laguncularia racemosa grown under experimental conditions of monoculture and mixed culture by using a simulated tidal system. The objective was to test hypotheses relative to species interactions to either tidal or permanent flooding at salinities of 10 or 40 g/l. Four-month-old seedlings were experimentally manipulated under these environmental conditions in two types of species interactions: (1) seedlings of the same species were grown separately in containers from September 2000 to August 2001 to evaluate intraspecific response and (2) seedlings of each species were mixed in containers to evaluate interspecific, competitive responses from August 2002 to April 2003. Overall, L. racemosa was strongly sensitive to treatment combinations while R. mangle showed little effect. Most plant responses of L. racemosa were affected by both salinity and hydroperiod, with hydroperiod inducing more effects than salinity. Compared to R. mangle, L. racemosa in all treatment combinations had higher relative growth rate, leaf area ratio, specific leaf area, stem elongation, total length of branches, net primary production, and stem height. Rhizophora mangle had higher biomass allocation to roots. Species growth differentiation was more pronounced at low salinity, with few species differences at high salinity under permanent flooding. These results suggest that under low to mild stress by hydroperiod and salinity, L. racemosa exhibits responses that favor its competitive dominance over R. mangle. This advantage, however, is strongly reduced as stress from salinity and hydroperiod increase.

Performance and quality of wood in a clone of Eucalyptus in monoculture and silvipastoral system.

Este trabalho foi desenvolvido com o objetivo de avaliar e comparar o desempenho e as variações na qualidade da madeirade árvores de eucalipto implantadas em sistema silvipastoril e em monocultivo. Os dados foram coletados em 13 árvores amostras aos 36 meses de idade, selecionadas em função do intervalo de confiança da média dos diâmetros a altura do peito (DAP), e da posição das árvores na faixa de plantio no sistema silvipastoril, com face de exposição sul, norte e central. Foram avaliadas as variáveis DAP, altura total e altura comercial, volume e conicidade do tronco, densidade básica e deslocamento da medula. Concluiu-se que no sistema silvipastoril as árvores apresentaram maior DAP, menor altura total e maior conicidade do tronco que no monocultivo. O DAP não diferiu em relação à posição na faixa de plantio, porém as árvores com face de exposição norte foram mais baixas e cônicas. A densidade básica e o deslocamento da medula não foram influenciados pelo sistema de cultivo.

Soil microbilogica properties and available nitrogen for corn in monoculture and intercropped with forage.

2016