Mulching and soil tillage influence on the thermal behaviour of a Luvisol surface layer

Important energy exchanges at soil surface regulate the thermal environment within top soil layer and the boundary layer above it. By this reason, the application of mulches or the modelling of micro relief by soil tillage are common practises to modify the thermal regime of a soil. The aim of this study is to compare the effect on thermal behaviour of a Luvisol resulting of soil tillage and the application of stubble mulch and, different amounts of straw mulch. For this purpose, experiments were performed from January to May 2007 in a field sowed with winter wheat. Temperatures were measured with copper-constantan (Type T) thermocouples placed over straw and over stubble, at soil surface and at 2, 4 and 8 cm depth. Temperatures above canopy were also recorded. Daily mean temperatures and thermal amplitudes in the top soil layer covered by straw mulch were smaller than those verified either by stubble mulch or with soil tillage. Daily minimum temperatures in mobilized plots or covered by stubble mulch were smaller than those verified in plots covered by straw mulch, therefore being the former treatments more susceptible to frost than the later ones. Thermal differences between the four plots decreased significantly with wheat growth. Implications of these techniques of soil temperature control for crop growth are also discussed

Mulching and soil tillage influence on the thermal behaviour of a Luvisol surfacel layer

Important energy exchanges at soil surface regulate the thermal environment within top soil layer and the boundary layer above it. By this reason, the application of mulches or the modelling of micro relief by soil tillage are common practises to modify the thermal regime of a soil. The aim of this study is to compare the effect on thermal behaviour of a Luvisol resulting of soil tillage and the application of stubble mulch and, different amounts of straw mulch. For this purpose, experiments were performed from January to May 2007 in a field sowed with winter wheat. Temperatures were measured with copper-constantan (Type T) thermocouples placed over straw and over stubble, at soil surface and at 2, 4 and 8 cm depth. Temperatures above canopy were also recorded. Daily mean temperatures and temperature amplitudes in the top soil layer covered by straw mulch were smaller than those verified either by stubble mulch or with soil tillage. Daily minimum temperatures in mobilized plots or covered by stubble mulch were smaller than those verified in plots covered by straw mulch, therefore being the former treatments more susceptible to frost than the later ones. Thermal differences between the four plots decreased significantly with wheat growth. Implications of these techniques of soil temperature control for crop growth are also discussed

Clima e estado do tempo. Factores e elementos do clima. Classificação do clima

O sistema climático é um sistema composto, fechado mas não isolado (i.e., não há entrada ou saída de massa mas permite trocas de energia com o exterior, o espaço), constituído por vários subsistemas limitados por participações permeáveis e diatérmicas. Os subsistemas são a Atmosfera - invólucro gasoso que envolve o globo terrestre, a Litosfera - massas de terra da superfície do globo, a Hidrosfera - água líquida distribuída à superfície do globo, a Criosfera - grandes massas de gelo e depósitos de neve, e a Biosfera – seres vivos. A entrada de energia no Sistema Climático tem, fundamentalmente, origem solar e é de natureza radiante. A maior parte da energia emitida pelo Sol provém da sua Fotosfera. O estado do tempo e o clima descrevem o mesmo sistema, o Sistema Climático, mas referem-se a escalas temporais diferentes. O clima de uma região ou local é o conjunto das condições meteorológicas predominantes nessa região ou local durante um longo intervalo do tempo, com uma duração mínima de três décadas. O clima é caracterizado pelos valores médios dos diferentes elementos meteorológicos, pela variabilidade destes (estatísticas de ordem mais elevada como variâncias, covariâncias, correlações,..) e por informação sobre a ocorrência de eventos extremos. O estado do tempo refere-se às condições meteorológicas instantâneas e à evolução diária dos sistemas sinópticos individuais. A descrição do clima ou do estado do tempo é feita a partir do conhecimento de um conjunto de valores de grandezas meteorológicas. Estes parâmetros, variáveis no tempo e no espaço, são os elementos climáticos ou meteorológicos. A fenomenologia atmosférica assim como o estado do tempo e respectiva evolução são objecto de estudo da Meteorologia enquanto que o clima e sua dinâmica o é da Climatologia. A Meteorologia observa os fenómenos ao mesmo tempo que os explica, sendo por isso uma ciência analítica, explicativa e prospectiva; a Climatologia é o estudo do ambiente atmosférico constituído por uma série de estados da atmosfera (clima), sendo uma ciência de síntese e retrospectiva. Os princípios teóricos da Meteorologia são, basicamente, os da física (termodinâmica, mecânica, óptica, dinâmica, etc…), pelo que usa frequentemente o cálculo vectorial e diferencial. A Climatologia usa, fundamentalmente, a estatística. Fenómenos atmosféricos de microescala e de escala local são objecto de estudo da Micrometeorologia e da Microclimatologia, domínios científicos assentes no conceito de camada limite atmosférica - camada de ar aderente à superfície terrestre resultante da acção do vento e do atrito e da variação térmica dessa mesma superfície, com espessura variável (no espaço e no tempo), desenvolvendo-se até onde se faça sentir a influência da superfície sobre a qual se forma, sendo normalmente constituída por duas sub-camadas (laminar e turbulenta), ao longo das quais são transportados momento, energia e massa

Effect of reduced doses of a post-emergence herbicide to control grass and broad-leaved weeds in no-till wheat under Mediterranean conditions

A study was carried out over two years (2004/2005 and 2005/2006) on a private farm in the Alentejo region (Évora), in the South of Portugal where rainfed wheat is sown at the start of the winter rainfall season. The wheat crop was established using no-till as this technology provides the necessary machine bearing capacity of the soil to assure the post-emergence application of herbicides at different weed development stages. Mesosulfuron-methyl (3%) and iodosulfuron-methyl-sodium (0.6%) and mefenpyr-diethyl (9%) were used at three doses and two dates with three different application volumes. The results of this study indicate that using lower doses than recommended (0.4 kg ha−1) this herbicide controls the annual grass weeds (Avena sterilis L. and Lolium rigidum G.) better than some broad-leaved weeds. For all doses and volume combinations, the application at the first weed development stage (beginning of tillering for grass weeds and 3–4 pairs of leaves for broad-leaved weeds) provided higher grain yields. The lower efficiency of control of more developed grass and broad-leaved weeds and a longer period of competition between crop and weeds for the second application date (complete tillering for grass weeds and 5–6 pairs of leaves for broad-leaved weeds) were responsible for the significantly lower crop yields for this application date. Within each application date no significant differences were obtained between all dose/volume combinations, indicating that the reduction of dose is possible. At the later application date, the lower herbicide dose seems to require a lower application volume to provide maximum grain yield

Effect of different doses of post-emergence-applied iodosulfuron on weed control and grain yield of malt barley (Hordeum distichum L.), under Mediterranean conditions

A study was carried out over a two year period (2009/2010 and 2012/2013) on an experimental farm in the Alentejo region (Beja), in southern Portugal where rainfed malt barley (Hordeum distichum L.) is sown at the end of autumn or beginning of winter (November– December). The aim of this experiment was to study the efficiency of the herbicide iodosulfuron-methyl-sodium to control post-emergence broadleaved weeds in this cereal crop. The malt barley crop was established using no-till farming. This technology provides the necessary machine bearing capacity of the soil to assure the post-emergence application of herbicides at two diferente weed development stages. The herbicide iodosulfuron-methyl-sodium was applied at three doses (5.0, 7.5, and 10.0 g a. i. · ha–1) and at two different broadleaved weed development stages (3 to 4 and 6 to 7 pairs of leaves), that also corresponded to two diferente crop development stages (beginning of tillering and complete tillering). The results indicated that early herbicide application timing provided a significantly higher efficiency for all the applied herbicide doses, but this better weed control was not reflected in a higher crop grain yield. The lack of a higher crop grain yield was probably due to a crop phytotoxicity of the herbicide, when used at an early application timing

Weed management in winter wheat (Triticum aestivum L.) influenced by different soil tillage systems

In this study, weed management in winter wheat influenced by different soil tillage systems was investigated. The experiment was carried out under Mediterranean conditions on a Luvisol, during two growing seasons (1996/1997 and 1999/2000). Two factors (different soil tillage systems and post-emergence weed control) were studied, with two levels each: Two soil tillage systems and two levels of post-emergence weed control. The conventional soil tillage system, performed for seedbed preparation after the emergence of a high percentage of weeds, increases the appearance of monocotyledons, especially Lolium rigidum Gaud. in wheat crops, when compared to their establishment in no-till system. As a consequence of the higher number of monocotyledons there is an increase in weed-crop competition. Without post-emergence herbicide treatment, the wheat crop yield is lower in the treatments with the conventional soil tillage system and yield reduction is less under no-till system compared to the respective treatments with post-emergence herbicide application

Segurança Alimentar em Cabo Verde: objetivos das políticas públicas e resultados alcançados

Por meio de entrevistas guiadas junto a especialistas do setor público, de ONG’s e de organismos internacionais de ajuda ao desenvolvimento, com experiência na implementação de políticas públicas, este artigo veicula uma análise comparativa entre concepção e aplicação de políticas públicas para a segurança alimentar em Cabo Verde. Concluiu-se que as políticas de bem-estar social são insuficientes para responder à necessidade premente de um desenvolvimento sustentável da agricultura, com foco na qualidade de vida. Nesta perspectiva de avaliação do caráter sustentável de políticas econômicas e sociais, o estudo considerou notadamente o lugar de associações comunitárias na concepção e implementação de políticas públicas. Apesar de não haver impedimentos legais à organização de associações, também não existem mecanismos que promovam sua participação no processo de desenvolvimento.Through guided interviews with experts from the public sector, NGOs and international development aid agencies with experience in the implementation of public policies, this article makes a comparative analysis between practice and theory in the implementation of public policies for security food in Cape Verde. It is concluded that social welfare policies are not entirely safeguarded and that to give this answer there is a pressing need to have an effective sustainable development policy for agriculture, improving the focus on quality of life and in fair economic and social policies and environmentally sustainable. Although there are no legal impediments for the organization of associations, there are also no mechanisms that promote participation in the development process

Hybrid Conceptual Model for Assessing Quality, Production and Satisfaction (SQual4Agri), in Agricultural Production Units, in Cape Verde

In Cape Verde, small family farming production suffers continuously from limited essential resources such as water and soil for a steady development. This situation is further aggravated by the lack of financial resources. We have developed a hybrid and multidimensional conceptual model for improvement of those small farming units by bringing together concepts of quality management, farmers’ satisfaction evaluation and production capabilities. The model we have built was the result of an inquiry based on Focus Group study with 15 farmers and it was carried out in 2019. We name the model as SQual4Agri and this is a step toward improvement in small family based agricultural organization, namely in productivity, responsibility sharing, communication and quality management

Hidrologia Agrícola - Sebenta para a unidade curricular de hidrologia agrícola

Com esta sebenta pretendemos fornecer aos alunos as fundamentações teóricas e as aplicações práticas que sustentam a unidade curricular de Hidrologia Agrícol

Segurança Alimentar em Cabo Verde

No âmbito da palestra apresentada no 11º Encontro das Fundações da CPLP, sob o lema Segurança Alimentar: O papel das Fundações no Desenvolvimento de Politicas Públicas de Desenvolvimento, escolheu–se para fins deste trabalho, fazer uma análise comparativa, atravéz de entrevistas guiadas a quatro especialistas do sector publico, de ONG e de organismos internacionais de ajuda ao desenvolvimento com experiência na implementação de políticas públicas para que fizessem uma comparação entre a pratica e a teoria na implementação de politicas públicas para a segurança alimentar em Cabo Verde. Concluiu-se que as políticas de bem-estar social não estão de todo salvaguardas e que para dar esta resposta existe uma necessidade premente de se ter uma política efetiva de desenvolvimento sustentável da agricultura, melhorando o foco na qualidade de vida e em políticas económicas e sociais justas e sustentável do ponto de vista ambiental. Apesar de não haver impedimentos legais a organização de associações também não existe mecanismos que promovam a participação no processo de desenvolvimento