Improving Soil Primary Productivity Conditions with Minimum Energy Input in the Mediterranean

A collective well-succeed enterprise for good agriculture worldwide is possible through the synergetic effects of a series of favourable factors, among them, basically that associated to an adequate management of agricultural practices, improvement in soil tillage technologies, soil protection and conservation measures, animal and plant-breeding programs, genetic engineering and plant fertilization, all practices directed to augment the potential net production and productivity of the best biological varieties or cultivars available. A modern, intensive agricultural production system requires high levels of energy inputs, as compared to a traditional system. One should, for instance, just compare these two different production systems in terms of their global efficiency, but the IPS brought some negative environmental impacts, now diagnosed worldwide. In the Mediterranean areas the seasonal distribution of precipitation is harmful to plant (crop) dry matter (DM) production which can be increased by adequately combining a good management of all input factors with a special care to natural resources protection, namely soil and water conservation. In this work two fertile soils were managed under two alternative (TS = traditional mechanized system and DS = direct-seeding system) production systems during a ten-year period and their physical and chemical characteristics were compared in terms of agro-physical optimization to produce DM. The parameters that have been evaluated were: soil profile evolution texture and coarse elements, bulk density and soil resistance to the penetrometer, consistency limits; aggregates stability, organic matter (SOM) and nitrogen (N) contents and C/N ratio, cation-exchange capacity (CEC) and associated parameters, pores connectivity and soil-water retention curve. From an agronomic perspective the DM production has been also estimated in order to evaluate the ecological sustainability of eventual improvements in soil-water conservation were justified by the alternative system. Results enable to conclude that, inter alia, the alternative system under the perspective of the “Conservation Agriculture Paradigm” (Dumanski, R. et al., 2006) revealed to be prone to conserve more soil and water resources with interesting marginal gain in water and so in DM production. These results are well in the scope of the international concerns on adopting improved common policies for food security and problems associated to water scarcity, worldwide

DELIMITING TREE TERRITORY FROM SOIL WATER BALANCE EQUATION: A CASE STUDY

A usual problem linked to the apparent complexity of soil-plant interactions with the climatic forcing (as rainfall) is the need to compute the “active soil depth” (zr), available for water storage. Moreover, zr truncates the bottom depth of the control soil column, where drainage takes place, in the computation framework of a supply-demand-storage approach, in solving the soil water balance (SWB) equation at a site. Since the difficulty to estimate zr can lead to arbitrariness to set an operational value to it, our objective was to derive zr as the integral value of a unique soil layer of homogeneous properties. Our experimental scheme to solve the SWB equation involved a sample of ten young, 5 to 6 years-old, evergreen cork-oak (Quercus suber L.) trees, grown on a sandy loam soil (porosity is s), nearby Évora, Portugal. To achieve that goal, we have assembled several measurements techniques to assess the relevant water mass flux density terms, in the soil-plant-atmosphere continuum, as expressed per unit horizontal ground surface area (Ap), so justified by dimensional analysis. A steady-state IRGA (Li-1600M) apparatus was used to measure a discrete time series on instantaneous maximum diffusive conductance (gs) of sunlit leaf samples from four trees, under saturating light and soil water comfort, during spring season (in 2002). Further, gs was up-scaled to the corresponding daily foliage transpiration rate (Tr), which, in turn, was scaled up to plant root water uptake rate (U), using the derived sunlit leaf area index (Li) as the linear scale factor. In the same time period, the mean soil water variation rate (∆S), as induced by U, has been thermo-gravimetrically determined on collected soil core samples. Both ∆S and Tr was related to the spring season depletion phase of the ASW, lasted for a 30-day long period, the volumetric soil water () residence time (RT), under site conditions. Assumption of water mass conservation for the SWB problem in the rooted soil, as well as for whole-plant water capacitance, implies U matches ∆S, the depth-integrated value of variation, throughout zr domain. Results showed zr can be estimated as a cumulative and directly proportional function of observed Tr and RT, without vertical discretization of the soil column. Model output showed an effective maximum rooting depth (or an equivalent lateral expansion) of 1754 mm (1.75 m), which is interpreted as the mean radius of an ellipsoidal zone of influence, in all directions; it was 1.32 times greater than the mean tree high. The product zr s gives the “effective” soil depth, ca. 0.70 m, in this case study. Extension of the approach can be either determining U for pounded water land use system (e.g., rice cultivation) or estimating the plant density in irrigated orchards, enhancing water management

Contributo para a determinação do coefiente cultural do sobreiro (Quercus suber L.): um estudo de eco-hidrologia agroflorestal

O estudo da importância hidrológica do sobreiro (Quercus suber L.) justifica-se no âmbito da gestão agroflorestal do erritório, hidrologia florestal, ecologia e micro-climatologia. O objectivo do presente estudo foi a determinação do integral anual da transpiração de um sobreiral através do que, em hidrologia agro-florestal, se designa "coeficiente cultural" (medida relativa do uso da água pelas plantas). problema foi resolvido no âmbito do balanço hídrico no solo enraizado e do balanço energético à superficie, em tomo da árvore e ao nível do ecossistema. A metodologia utilizada consistiu na detalhada caracterização geométrica, hidrológica e termo-radiativa dos compartimentos do contínuo solo-planta-atmosfera (SPAC) e na modelação matemática de vários processos eco-hidrológicos do ecossistema estudado. De entre diversos tópicos tratados, a investigação permitiu estabelecer: (1) a relação matemática empírica entre a transpiração sazonal (medida na folha) e a correspondente variação (AA) da água do solo enraizado, sem se proceder à discretização vertical do solo; (2) a expressão matemática que define a extensão do enraizamento, designado "dimensão linear de enraizamento" Z,(max); (3) a formulação hidrodinâmica da relação biométrica AxIAF, entre a área seccional de fluxo (Ax) no xilema do tronco e a área foliar (AF) total, em função da variável de fluxo adimensional ETJW, sendo u' a densidade de fluxo da seiva bruta. O índice de área foliar (LAI) é o escalar que unifica os procedimentos (1), (2) e (3). procedimento (1) permitiu converter a média sazonal da transpiração máxima em AA correspondente e determinar o "coeficiente cultural de base" (Kb), parâmetro em (3). O procedimento (3) ofereceu o quadro formal para estimar a curva sazonal dos integrais diários de u', em função da evapotranspiração de referência (ET,,) estimada pela equação de Penman-Monteith, em que u' é limitado pelo produto entre Kb e a função ge(D) de redução da condutância estomática difusiva, g, elo défice de pressão de vapor atmosférico. A combinação entre (1) e (2) levou à determinação de Zr(max) que limita o volume de controlo do solo em torno da árvore, onde a variação da água disponível afecta ge. balanço hídrico pôde resolver-se, inicialmente, sem o balanço energético que depois o refinou e confirmou. Do diversificado painel dos resultados, pudemos concluir que o Kb (0.85-0.92) e a transpiração do sobreiro em conforto hídrico (transpiração potencial: TP), ao contrário do que correntemente se possa pensar, se inserem em categorias de limites flexíveis, onde figuram as mesófitas e as higrófitas. O mesmo se concluiu para outros parâmetros bio-hidrológicos do sobreiro, tais como a condutância hidráulica da planta, a condutância estomática, a relação Ax/AF e o índice de área xilémico da árvore. No ano exemplificado, a transpiração representou ~80% da evapotranspiração do ecossistema, (563-574 mm/ano), determinada em torno da árvore ou para um sobreiral equivalente cobrindo completamente o solo, enquanto que ascendeu à terça parte de ETo anual e a 62% da precipitação acumulada em 2002, mas perfazendo 71 % da precipitação média anual. A água disponível armazenada no domínio Z,(max) do solo enraizado justificou o integral anual da transpiração estimada com base no fluxo de seiva. Além disso, z,(max), que resulta das relações eco-hidrológicas entre a dinâmica da água do solo e a dinâmica das raízes finas colectoras, permitiu predizer uma densidade arbórea média de 43 árvores por hectare, consistente com dados disponíveis referentes a "montados" no Alentejo (Portugal) e em Sevilha (Espanha). O balanço energético, além de fundamentar e confirmar o balanço hídrico, forneceu informação necessária a vários fins, nomeadamente, para a determinação da resistência difusiva total da superfície e para a calibração pragmática da equação de Penman-Monteith ao nível da "folha-gigante", da árvore e da plantação esparsa. A natureza biofisica da abordagem adoptada nesta investigação perspectiva a sua aplicação à gestão da água em agro-ecossistemas sujeitos à rega, nomeadamente, pomares, olivais e vinhas. ### /ABSTRACT- Landscape and agro-forestry systems management are issues of national concern, justifying experimental studies to evaluate the impact of tree plantations or natural ecosystems on local hydrology. In Portugal, this kind of agro-forestry survey programs are still rare in the mediterranean-type agro-forestry ecosystems, namely in the secondary type of forest called "montado", based on the sclerophyllous evergreen corkoak (Quercus suber) and holm-oak (Quercus rotundifolia) species. The "montado" plays important socio-economic and ecological roles in Portugal. In the eco-hydrologic perspective of mutual interactions between the hydrologic cycle and the ecosystems, this study quantifies the annual water use () of cork-oak tree based on the concept of (maximum) "basal crop coefficient", Kcb, the actual plant water use relative to the reference evapotranspiration rate, ETO, in a daily basis. For that, both water and energy balances have been solved around tree and then scaled up to the plantation level. For the water balance computations, under water-unsaturated soil and from mid-spring to early-summer (year 2002), we have quantified the spatial (vertical) water variations and temporal (seasonal) water use patterns of a young-aged, at six years old, plantation of cork-oak trees without understore, in a site located in the Central Alentejo district, Portugal. The energy and water balance flux approaches for the vegetated surface have been supported either by measuring or by determining global solar radiation, net radiation, latent heat, sensible heat and soil heat conduction taken at the experimental site, during the wet seasons in 2001 and 2002. To asses the water vapour (vH20) loss by trees, soil, tree and the atmosphere have been properly characterized. This involved (1) the hydrologic and geometric properties and reservoir capacity of the control soil column for seasonal mass water balance around tree; (2) leaf, foliage and stand diffusive stomatal conductance (ge) and transpiration rates; additionally, (3) the total leaf area index (LAI) has been discriminated into its sunlit and shaded leaf area index component layers per tree to determine the dual-source foliage transpiration rate for the representative tree and so at the (sparse) canopy level. For long time series of actual daily tree transpiration (o per unit ground area, both Kb and daily ET,, estimated by the Penman-Monteith equation, are needed, being U derived from the sap mass flux density, u', and the xylem area index (XAI)as described bellow. To continuously estimate U, based on u', we have first formulated an ecological version of the hydrodynamic continuity equation which defines the biometric ratio AX/AF between the (trunk) effective sapwood cross sectional area (Ax) and total one-side leaf area (AF), as a linear function of the non-dimensional flux ratio ET0/u,. Since it is assumed a hydrologic principle underlying stomatal conductance (ge) regulation, to identify the soil domain, zr(max), where the seasonal variation (ΔA) of the available soil water determines g, we wrote and verified the equation for Zr(max), related, to that for sap flow via LAI Among several results, this investigation has enable one to establish: a) an empirical, but physically-based, mathematical relationship between U and ΔA, without the need to descretize the rooted soil column; b) a mathematical expression to estimate the soil rooting domain, Zr(max), whose native available soil water matches the annual tree water use base on the sap flow. For an ecosystem with full ground cover (C is 1), results showed that a null water balance assumption corresponded to an expected maximum actual evapotranspiration, , of 563-574 mm/yr in 2002, also both null bare soil evaporation and ecosystem water wield (WY), being the sun between the canopy water interception (E) and U. For such a scenario U and Ei accounted for, respectively, ~80% and 20% of tree, or of the equivalem homogeneous canopy, . For the young plantation (C was 0.08) reduced accordingly to 154 mm and WY rised to 349 mm per year. For full ground cover, it was meaningful to note that, despite the total annual rainfall was greater than the mean annual precipitation (), U corresponded to ~75% of . This means that the annual rainfall does not determine the tree annual water use for the study tree species which is ecologically adapted to the site climate and soil water temporal dynamics. The study also permitted one to clarify that the hydrodynamic definition of Ax/AF, linked to truncation of the total "rooting length" into the tree territory, allows one to determine the ecosystem tree density, under the actual soil and climate conditions, consistent with published inventories for the montado ecosystem. Finally, we concluded that the mean seasonal maximum transpiration rate of the cork-oak tree as well as its Kcb (0.85-0.92) belong to numerical ranges with flexible boundaries which are convergent to those of mesophyte and hygrophyte plant species

Procedures for vigor tests based on the thermal stress tolerance of cucumber seeds

O presente trabalho foi realizado com o objetivo de identificar métodos, baseados na tolerância das sementes ao estresse térmico, eficientes para a avaliação do potencial fisiológico das sementes de pepino. O trabalho foi desenvolvido em três épocas, utilizando-se lotes de sementes dos cultivares Safira e Jóia, abrangendo testes de germinação, emergência de plântulas, envelhecimento acelerado e deterioração controlada. Concluiu-se que o teste de deterioração controlada (com ajuste do teor de água para 24%, período de 48 h a 45 ºC) e de envelhecimento acelerado tradicional e com solução saturada de cloreto do sódio (a 41 ºC por 96 h) é sensível para a avaliação do potencial fisiológico de sementes de pepino.The objective of this research was to identify reliable methods based on the thermal stress tolerance of cucumber seeds, which would be efficient for evaluating their physiological potential. The study was conducted in three experimental phases using seed lots of Safira and Joia cultivars and included procedures for the assessment of seed physiological potential from germination, field emergence, controlled deterioration and accelerated ageing tests. Results indicated that the controlled deterioration (24% water content/ 48 h / 45 ºC), and the traditional and saturated salt accelerated ageing (41 ºC for 96 h) tests are sensitive to differences in the physiological quality of cucumber seed lots.FAPES

Cucumber (Cucumis sativus) seed priming methods and germination at different temperatures

O condicionamento fisiológico é uma técnica utilizada para a embebição controlada de sementes e tem como benefícios, aumentar a rapidez e uniformidade na emergência de plântulas e a tolerância das sementes a condições ambientais adversas. O presente trabalho teve como objetivo estudar procedimentos para o condicionamento fisiológico e verificar o desempenho das sementes quando colocadas para germinar sob diferentes temperaturas. Foram utilizados lotes de sementes dos cultivares Safira e Jóia, testando-se o osmocondicionamento a -0,1MPa e -0,2MPa até que as sementes do cv. Safira atingissem o teor de água de 29%, e do cv. Jóia, 32%. Os efeitos do condicionamento foram avaliados pela porcentagem e velocidade de germinação a 15, 20, 25, 30 e 35 ºC. Verificou-se que o osmocondicionamento em papel embebido em solução de PEG -0,2MPa é benéfico ao desempenho de sementes de pepino, favorecendo a velocidade de germinação para a maioria dos lotes e temperaturas testados, com resultados mais expressivos em lotes de menor vigor expostos a temperaturas subótimas.Seed priming is a technique that involves the controlled hydration of seeds and has beneficial effects such as increased velocity and uniformity of seedling emergence and increased seed tolerance to unfavorable environmental conditions. We defined procedures for seed priming and verified seed performance at different temperatures using seed lots of C. Sativus cultivars Safira and Joia submitted to osmopriming (-0.1 and -0.2 MPa) to a seed moisture content of 29% for cv. Safira and 32% for cv. Joia. The effects of osmoconditioning were evaluated by percentage and speed of germination at 15, 20, 25, 30 and 35 ºC. The results indicated that seed osmopriming between sheets of paper towel moistened with -0.2 MPa polyethylene glycol (PEG) solution is efficient for cucumber seeds, affecting the speed of seed germination for almost every seed lot and temperature tested. Results were particularly good when seed from low-vigor lots were exposed to sub-optimal temperatures.FAPES

“Metrópoles de papel” na Amazônia: Horizontes lefebvrianos na produção do espaço em Macapá-Santana, Brasil

“Paper metropolises” are urban centers in established metropolitan regions that present no functionalities of a metropolis, in terms of political, economic, and social influence, as well as the flow of information, capital, and people. Thus, this study has sought to understand the conception, perception, and experience of a “paper metropolis” located in the Brazilian Amazon based on Henri Lefebvre’s understanding of the production of urban space. Using a historiographical approach, and a literature and documentary review, it was possible to understand that the conceived space is essentially the result of joint actions among political and economic actors that prioritize the institutionalization of space rather than its production, thereby reflecting the lack of perception and experience of the population in relation to metropolitan space. Thus, particular intra-urban dynamics transform the metropolitan spaces into a product that does not necessarily fit into Lefebvrian theory, creating new horizons for apprehending the socio-spatial production of what constitutes paper metropolises.“Metrópoles de papel” são centros urbanos de regiões metropolitanas institucionalizadas que não apresentam funcionalidades de uma metrópole, tais como influências político-econômicas e sociais, além do tráfego de informações, capital e pessoas. Assim, este estudo buscou compreender a concepção, a percepção e a vivência de uma "metrópole de papel" localizada na Amazônia brasileira com base no entendimento da produção do espaço urbano de Henri Lefebvre. Utilizando uma abordagem historiográfica, análises de recursos bibliográficos e documentais possibilitaram apreender que o espaço concebido é fruto essencialmente de ações conjuntas entre agentes políticos e econômicos que priorizaram a institucionalização do espaço em vez de sua produção, repercutindo na ausência de percepção e vivência por parte da população com relação ao espaço metropolitano. Por conseguinte, dinâmicas intraurbanas peculiares tornam a produção dos espaços metropolitanos um produto que não necessariamente se encaixa na teoria lefebvriana, criando novos horizontes para a apreensão da produção socioespacial do que se constituem as metrópoles de papel

A aferição da modalidade epistêmica em enunciados sob escopo de advérbios de dúvida

Seguindo a perspectiva da Sociolinguística Variacionista, concebemos a variação inerente ao sistema linguístico. Avaliamos a frequência de alternância subjuntivo/indicativo em orações dubitativas na comunidade de fala da Cidade do México e, por hipótese, supomos que a modalidade seja um fator condicionador dessa alternância. Desse modo, o presente trabalho configura-se como um ensaio analítico de uma categoria discursivo-pragmática conflituosa, a modalidade.  O objetivo básico neste trabalho é o de buscar formalizar parâmetros para a aferição da modalidade epistêmica irrealis apreensível no discurso. Nesse sentido, concebendo sua influência como fator condicionador na alternância subjuntivo/indicativo em orações dubitativas não subordinadas, poderemos avaliar sua atuação, nos termos de Labov (1972), como variável independente