Cover plants and mineral nitrogen: effects on organic matter fractions in an oxisol under no-tillage in the cerrado

Cover plants are essential for the sustainability of no-tillage systems in tropical regions. However, information on the effects of these plants and N fertilization on soil organic matter fractions is still scarce. This study evaluated the effect of cover crops with different chemical composition and of N topdressing on the labile and humified organic matter fractions of an Oxisol of the Cerrado (savanna-like vegetation). The study in a randomized complete block design was arranged in split-plots with three replications. Four cover species were tested in the plots and the presence or absence of N topdressing in the subplot. The following cover species were planted in succession to corn for eight years: Urochloa ruziziensis; Canavalia brasiliensis M. ex Benth; Cajanus cajan (L.) Millsp; and Sorghum bicolor (L.) Moench. In general, the cultivation of U. ruziziensis increased soil C levels, particularly of C in the humic acid and particulate organic C fractions, which are quality indicators of soil organic matter. The C in humic substances and mineral organic C accounted for the highest proportions of total organic C, demonstrating the strong interaction between organic matter, Fe and Al oxides and kaolinite, which are predominant in these weathered soils of the Cerrado.

SWEET SORGHUM PERFORMANCE AFFECTED BY SOIL COMPACTION AND SOWING TIME AS A SECOND CROP IN THE BRAZILIAN CERRADO

ABSTRACT Increasing attention has recently been given to sweet sorghum as a renewable raw material for ethanol production, mainly because its cultivation can be fully mechanized. However, the intensive use of agricultural machinery causes soil structural degradation, especially when performed under inadequate conditions of soil moisture. The aims of this study were to evaluate the physical quality of aLatossolo Vermelho Distroférrico (Oxisol) under compaction and its components on sweet sorghum yield forsecond cropsowing in the Brazilian Cerrado (Brazilian tropical savanna). The experiment was conducted in a randomized block design, in a split plot arrangement, with four replications. Five levels of soil compaction were tested from the passing of a tractor at the following traffic intensities: 0 (absence of additional compaction), 1, 2, 7, and 15 passes over the same spot. The subplots consisted of three different sowing times of sweet sorghum during the off-season of 2013 (20/01, 17/02, and 16/03). Soil physical quality was measured through the least limiting water range (LLWR) and soil water limitation; crop yield and technological parameters were also measured. Monitoring of soil water contents indicated a reduction in the frequency of water content in the soil within the limits of the LLWR (Fwithin) as agricultural traffic increased (T0 = T1 = T2>T7>T15), and crop yield is directly associated with soil water content. The crop sown in January had higher industrial quality; however, there was stalk yield reduction when bulk density was greater than 1.26 Mg m-3, with a maximum yield of 50 Mg ha-1 in this sowing time. Cultivation of sweet sorghum as a second crop is a promising alternative, but care should be taken in cultivation under conditions of pronounced climatic risks, due to low stalk yield.

Changes in Soil Organic Carbon Fractions in Response to Cover Crops in an Orange Orchard

ABSTRACT The cultivation of cover crops intercropped with fruit trees is an alternative to maintain mulch cover between plant rows and increase soil organic carbon (C) stocks. The objective of this study was to evaluate changes in soil total organic C content and labile organic matter fractions in response to cover crop cultivation in an orange orchard. The experiment was performed in the state of Bahia, in a citrus orchard with cultivar ‘Pera’ orange (Citrus sinensis) at a spacing of 6 × 4 m. A randomized complete block design with three replications was used. The following species were used as cover crops: Brachiaria (Brachiaria decumbes) – BRAQ, pearl millet (Pennisetum glaucum) – MIL, jack bean (Canavalia ensiformis) – JB, blend (50 % each) of jack bean + millet (JB/MIL), and spontaneous vegetation (SPV). The cover crops were broadcast-seeded between the rows of orange trees and mechanically mowed after flowering. Soil sampling at depths of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m was performed in small soil trenches. The total soil organic C (SOC) content, light fraction (LF), and the particulate organic C (POC), and oxidizable organic C fractions were estimated. Total soil organic C content was not significantly changed by the cover crops, indicating low sensitivity in reacting to recent changes in soil organic matter due to management practices. Grasses enabled a greater accumulation of SOC stocks in 0.00-0.40 m compared to all other treatments. Jack bean cultivation increased LF and the most labile oxidizable organic C fraction (F1) in the soil surface and the deepest layer tested. Cover crop cultivation increased labile C in the 0.00-0.10 m layer, which can enhance soil microbial activity and nutrient absorption by the citrus trees. The fractions LF and F1 may be suitable indicators for monitoring changes in soil organic matter content due to changes in soil management practices.

Quinoa (Chenopodium quinoa) reaction to herbicide residue in a Brazilian Savannah soil

The quinoa (Chenopodium quinoa Willd.) cultivation, one of the most promising in double cropping with soybeans or maize, depends on weed control. The objective of this work was to evaluate quinoa reaction to herbicide residue in a savannah soil. Six herbicide treatments, trifluralin, pendimethalin, clomazone, imazaquin, trifluralin + imazaquin and control, were applied, prior to summer cultivation of soybean, in a Dark-Red Latosol (typic Haplustox). Soybean cultivar BR 9 Savana was grown and soil samples were collected at 15, 38, 100, 145 and 206 days after treatment and stored at -5ºC. Bioassays were conducted in greenhouse, using quinoa, cultivar Q18. Imazaquin was the most harmful to quinoa seedlings, up to 206 days after application, followed by clomazone 15-38 days after application; trifluralin and pendimethalin had no residual effect. These results suggest that a broad-base screening should be conducted.

GUS gene expression driven by a citrus promoter in transgenic tobacco and 'Valencia' sweet orange

The objective of this work was the transformation of tobacco and 'Valencia' sweet orange with the GUS gene driven by the citrus phenylalanine ammonia-lyase (PAL) gene promoter (CsPP). Transformation was accomplished by co-cultivation of tobacco and 'Valência' sweet orange explants with Agrobacterium tumefaciens containing the binary vector CsPP-GUS/2201. After plant transformation and regeneration, histochemical analyses using GUS staining revealed that CsPP promoter preferentially, but not exclusively, conferred gene expression in xylem tissues of tobacco. Weaker GUS staining was also detected throughout the petiole region in tobacco and citrus CsPP transgenic plants.

Desarrollo larvario y número de estadios larvarios de "Pseudaletia unipuncta" alimentada con dos variedades de maíz y dos dietas semisintéticas

Pseudaletia ( Mythimna) unipuncta (Haworth) es una plaga defoliadora del maíz presente año tras año en la Cuenca del Ebro, que realiza en el maíz daños esporádicos pero a veces devastadores. La implantación creciente de maíz resistente a taladros ha producido, en la zona del presente estudio, la disminución casi total de los daños debidos a los taladros Sesamia nonagrioides (Lefebvre) y Ostrinia nubilalis (Hübner). Sin embargo, no se sabe aún cómo el incremento de maíz transgénico puede afectar a las poblaciones de P. unipuncta. Actualmente no hay datos sobre biología o parámetros del desarrollo de la especie en la Península Ibérica necesarios para evaluar los posibles efectos de las nuevas variedades utilizadas. Para ello es necesario primero establecer un método de cría adecuado y posteriormente iniciar los estudios sobre la biología de la misma. En el presente trabajo se planteó conocer diferentes parámetros del desarrollo larvario de poblaciones locales de P. unipuncta alimentada sobre hoja de maíz (variedades Tietar y PR33P66) y sobre dos dietas semisintéticas, una a base de alubias. Phaseolus vulgaris, y otra a base de maíz, Zea maya. Los resultados mostraron que las larvas desarrolladas en dieta a base de alubias sufrieron menor mortalidad, que las desarrolladas con planta o sobre la otra dieta, además el peso de las pupas resultantes fue mayor y presentaron menos malformaciones. En cuanto al numero de estadios larvarios, la mayoría pupó tras seis mudas larvarias, necesitando, las de dieta de maíz, estadios larvarios adicionales. Estos resultados indican que la dieta a base de alubias es la más adecuada para posteriores trabajos con esta especie.

Peatlands and plantations in Sumatra, Indonesia : Complex realities for resource governance, rural development and climate change mitigation

Peatlands play a crucial role in Indonesia's economic development, and in its stated goal of reducing greenhouse gas emissions. Improved peatland management - including a national moratorium on the granting of any new conversion licenses - forms a cornerstone of Indonesia's climate change mitigation commitment. At the same time, rapid expansion of the plantation sector is driving wide-scale drainage and conversion of peat swamp ecosystems. The province of Riau, in central Sumatra, finds itself at the crossroads of these conflicting agendas. This essay presents a case study of three islands on Riau's east coast affected by industrial timber plantation concessions. It examines the divergent experiences, perceptions and responses of communities on the islands. A mix of dramatic protests, localised everyday actions and constructive dialogue has succeeded in delaying or perhaps halting one of the concessions, while negotiations and contestation with the other two continue. With the support of regional and national non-governmental organisations and local government, communities are pursuing alternative development strategies, including the cultivation of sago, which requires no peat drainage. While a powerful political economy of state and corporate actors shapes the contours of socio-environmental change, local social movements can alter trajectories of change, promoting incremental improvements and alternative pathways.

Estudo da biodisponibilidade de metais nos sedimentos da Lagoa da Pampulha

The presence of metals in the sediments of Pampulha Lake was investigated in order to determine the bioavailability of metals in these sediments for the cultivation of vegetables such as lettuce. The chemical analyses of metals and As were accomplished by the k0 neutron activation technique. The plans for recovering this lake foresee the removal of the deposited sediments and transport of the discarded material to a specific area after the dam. The present study suggests that this strategy of discarding sediments doesn't imply any risk for the local population, in relation to the bioavailability of metals in these sediments.

A rota dos estudos sobre a cochonilha em Portugal e no Brasil no século XIX: caminhos desencontrados

For imparting an intense and long-lasting red to fabrics, cochineal remained in high demand during the eighteenth and nineteenth centuries. This period witnessed, accordingly, several initiatives aimed at producing the precious dye: publication of specialized texts, cultivation of the cactus and the insect from which the dye is extracted, and, also, attempts to obtain the secrets of production through espionage. The present paper analyses certain aspects of the measures adopted by the Portuguese government towards Brazil in this field. The work shows how people sought to take part in the network of cochineal production (yet they were unsuccessful most of the time).

Bioprocessos para remoção de dióxido de carbono e óxido de nitrogênio por micro-algas visando a utilização de gases gerados durante a combustão do carvão

The aim of this work was to study the removal of CO2 and NO by microalgae and to evaluate the kinetic characteristics of the cultures. Spirulina sp. showed µmax and Xmax (0.11 d-1, 1.11 g L-1 d-1) when treated with CO2 and NaNO3. The maximum CO2 removal was 22.97% for S. obliquus treated with KNO3 and atmospheric CO2. The S. obliquus showed maximum NO removal (21.30%) when treated with NO and CO2. Coupling the cultivation of these microalgae with the removal of CO2 and NO has the potential not only to reduce the costs of culture media but also to offset carbon and nitrogen emissions.

Nitrato de amônio ocluído em zeólita 4A: lixiviação e absorção de nitrogênio no cultivo de milho

Systematic studies were undertaken in the intra zeolitic media to better understand the ability of zeolite type LTA in occluded nitrogen used in fertilizer and soil conditioning. We have measured the dry matter production from the cultivation of corn in a greenhouse for about 40 days, and also the amounts of nitrogen absorbed, retained and lost by leaching. The dry matter production in the cultivation with different concentrations of nitrogen occluded in the zeolite, was more efficient than the traditional fertilizer, which demonstrated better use of nitrogen to reduce leaching losses, which implies a possible reduction of costs for nitrogen.

Uutto-olosuhteiden vaikutus kasviperäisen indigon saantoon

Indigo on väriaine, jota valmistetaan petrokemianteollisuuden välituotteena syntyvästä aniliinista. Indigolla on kuitenkin pitkä historia. Sitä on valmistettu perinteisesti eri viljelykasveista, joista Euroopassa merkittävin on ollut morsinko. Luonnonmukaisten tuotteiden suosion kasvaessa on ryhdytty selvittämään morsingon viljelyn potentiaalia. Viljelyn kannattavuuden kannalta olennaista on kasvin lehdissä esiintyvien indigon esiasteiden mahdollisimman täydellinen eristäminen. Indigoa tuotetaan uuttamalla indigon esiasteet veteen. Esiasteet hajoavat synnyttäen indoksyyliä, josta hapen vaikutuksella muodostuu indigoa. Syntynyt indigo saostuu ja laskeutuu pohjalle. Samalla kuitenkin tapahtuu epätoivottuja sivureaktioita, jotka vähentävät indigon saantoa. Tutkimuksen tavoitteena oli laboratorio- ja kenttäkokeiden avulla löytää indigon saantoa parantavat uutto-olosuhteet. Kokeiden perusteella havaittiin, että indigon saantoon vaikuttavat positiivisesti pH:n laskeminen, lämpötilan nostaminen, morsingon lehtien pilkkominen ja uuttoliuoksen sekoittaminen. Uuttoliuoksen suolapitoisuuden havaittiin puolestaan vaikuttavan indigon saantoon negatiivisesti. Laboratoriokokeiden perusteella havaittu pH:n laskemisen vaikutus indigon saantoon todistettiin myös kenttäolosuhteissa. Kokeiden havaintojen perusteella esitettiin olosuhteiden indigosaantoa parantavien vaikutusten johtuvan kahdesta tekijästä: indoksyylin stabiloitumisesta happamassa ympäristössä, jolloin sivureaktioiden osuus vähenee, sekä aineensiirron paranemisella sekoituksen, faasien rajapinnan kasvamisen ja etenkin lehtien vahakerroksen rikkoutumisen kuuman veden ja hapon vaikutuksesta.

Soil salinization and maize and cowpea yield in the crop rotation system using saline waters

The use of saline water and the reuse of drainage water for irrigation depend on long-term strategies that ensure the sustainability of socio-economic and environmental impacts of agricultural systems. In this study, it was evaluated the effects of irrigation with saline water in the dry season and fresh water in the rainy season on the soil salt accumulation yield of maize and cowpea, in a crop rotation system. The experiment was conducted in the field, using a randomized complete block design, with five replications. The first crop was installed during the dry season of 2007, with maize irrigated with water of different salinities (0.8, 2.2, 3.6 and 5.0 dS m-1). The maize plants were harvested at 90 days after sowing (DAS), and vegetative growth, dry mass of 1000 seeds and grain yield were evaluated. The same plots were utilized for the cultivation of cowpea, during the rainy season of 2008. At the end of the crop, cycle plants of this species were harvested, being evaluated the vegetative growth and plant yield. Soil samples were collected before and after maize and cowpea cultivation. The salinity of irrigation water above 2.2 dS m-1 reduced the yield of maize during the dry season. The high total rainfall during the rainy season resulted in leaching of salts accumulated during cultivation in the dry season, and eliminated the possible negative effects of salinity on cowpea plants. However, this crop showed atypical behavior with a significant proportion of vegetative mass and low pod production, which reduced the efficiency of this strategy of crop rotation under the conditions of this study.

Estado e embates socioterritoriais na Bolívia do século XXI

Recent results of presidential elections in Latin America suggest a turn to the left in various countries. In Bolivia, such a movement includes the victory of an Aymara Indian who is also a leader of coca farmers. The article proposes an interpretation of this event, describes and discusses the main actions of the new government, stressing the reactions they provoked, and explores the class, ethnic and territorial dimensions of the resulting conflicts. The regional aspects of the fights, seen in connection with the country's historical regionalism, are highlighted and their basic conditions are investigated.

Propuesta para el desarrollo de un clúster frutícula en el de partamento de Cundinamarca

El departamento de Cundinamarca cuenta con una gran riqueza agrícola a lo largo de su extensión territorial. Su ubicación geográfica lo hace poseedor de múltiples escenarios óptimos para la siembra de un sinnúmero de frutas y hortalizas que juegan un impacto importante en la economía de la región. En este trabajo de grado se analiza específicamente la situación económica y social que rodea al cultivo del mango en las provincias del Tequendama y Alto Magdalena partiendo de la caracterización de este producto agrícola y de la región e implementando la guía del “manual de minicadenas productivas” de la ONUDI. El objetivo principal inicial del proyecto de investigación era realizar una propuesta para el desarrollo de un clúster frutícola en el Departamento de Cundinamarca, sin embargo, en la elaboración del documento principal de este proyecto fue posible determinar que aún no se cuentan con los factores necesarios para desarrollar un modelo asociativo de esta índole, los problemas sociales y de comercialización representan grandes obstáculos para su creación. Aquí se presentará un modelo de asociación basado en la estructura ejemplar de la Federación Nacional de Cafeteros de Colombia y un modelo de comercialización diseñado congruentemente con las necesidades y desafíos que se evidencian en la región, cuya implementación dependerá de la iniciativa de organismos gubernamentales, comerciales o educativos que logren ver en el proyecto, tal como nosotros lo hicimos, un gran potencial.