Water is the most limiting resource for global crop production. The projected increase of dry spells due to climate change will further increase the problem of water limited crop yields. Besides low water abundance and availability, water limitations also occur due to restricted water accessibility. Soil penetration resistance, which is largely influenced by soil moisture, is the major soil property regulating root elongation and water accessibility. Until now the interactions between soil penetration resistance, root system properties, water uptake and crop productivity are rarely investigated. In the current study we quantified how interactive effects between soil penetration resistance, root architecture and water uptake affect water accessibility and crop productivity in the field. Maize was grown on compacted and uncompacted soil that was either tilled or remained untilled after compaction, which resulted in four treatments with different topsoil penetration resistance. Higher topsoil penetration resistance caused root systems to be shallower. This resulted in increased water uptake from the topsoil and hence topsoil drying, which further increased the penetration resistance in the uppermost soil layer. As a consequence of this feedback, root growth into deeper soil layers, where water would have been available, was reduced and plant growth decreased. Our results demonstrate that soil penetration resistance, root architecture and water uptake are closely interrelated and thereby determine the potential of plants to access soil water pools. Hence, these interactions and their feedbacks on water accessibility and crop productivity have to be accounted for when developing strategies to alleviate water limitations in cropping systems.

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INTRODUCTIONThe olive moth, Prays oleae (Bern.) (Lepidoptera: Yponomeutidae), is one of the most serious pests of olives in the Mediterranean basin. This moth has three generations a year, attacking in succession flowers, fruits, and leaves. Usually the leaf generation does not affect very much the trees, but the damage by the flower and the fruit generations can often lead to significant losses (Bento, 1999). In response to the growing requirement for more efficient methods to control the pest, research is needed on economic thresholds (ET), which could enable the growers to determine the need for intervention with a specific control measure and to apply integrated systems for olive cropping. In this work a mathematical model is presented which aims to establish the economic thresholds for the flower (anthophagous) generation of P. oleae in the Tràs-os-Montes region (north-eastern Portugal).

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Indicadores de qualidade física do solo representam uma importante ferramenta no estudo das alterações que ocorrem no solo em função de ações de uso e manejo. Objetivou-se com este estudo utilizar o intervalo hídrico ótimo (IHO) e o índice-S (declividade da curva de retenção de água no solo no ponto de inflexão) para quantificar as alterações físicas do solo promovidas pelo sistema de pastagem, tendo como referência um solo sob mata. O estudo foi realizado em um Latossolo Amarelo distroférrico típico sob mata nativa e pastagem, onde foram coletadas amostras deformadas e indeformadas nas profundidades de 0-5 e 25-30 cm, utilizadas para determinação do carbono orgânico do solo e análises físicas. Os valores de índice-S, com exceção do solo sob mata (0-5 cm), estiveram abaixo do limite sugerido para separar solos com boa e pobre qualidade estrutural. O IHO foi fortemente reduzido no solo sob pastagem, chegando a atingir valor zero. O principal fator limitante para a disponibilidade de água foi a resistência à penetração, que exceto em mata (0-5 cm), atuou como limite inferior do IHO em todas as áreas e profundidades avaliadas. Os indicadores de qualidade física do solo, IHO e índice-S, apresentaram conformidade quanto à avaliação da qualidade física dos solos estudados e indicaram as alterações físicas promovidas no solo sob sistema de pastagem.

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For several decades, the Acai orchards (acaizais) have directly influenced the survival of the families in the Amazonian floodplains. In this period, the production of the Acai fruit for local consumption was ceased and became an export item produced in intensive management, resulting in an increase in orchards in the floodplains and the emergence of dryland plantations, no longer representing a typical extractive activity in the Amazon. The objective of this study was to map the classes of use and coverage, and the occurrences of the Acai orchards massifs, as well as to analyze the physical and chemical parameters of five islands in the municipality of Igarapé-Miri, State of Pará, Brazil, where there is a great occurrence of productive Acai orchards. This work evaluated the following islands: Jarimbu, Mamangal, Itaboca, Mutirão, and Buçu, where geolocalized collections were carried out in the areas with the highest occurrence of Acai orchards, both to assist in the classification of images and for soil sampling. August 2019 Planet images were processed using the unsupervised method, where seven classes of cover use were obtained: hydrography, exposed soil, urban, alluvial, lowland, arboreal, and agriculture areas. Therefore, occurrences of productive orchards were identified and correlated to the good attributes of soil fertility in the floodplains under continuous flooding and sedimentation. The correlation confirmed the higher productivity of Acai in the Alluvial and Lowland classes, which predominate in the evaluated area, presenting soils considered fertile with a loam-clay-silty and loam -silty texture, high base saturation (greater than 50%), high organic matter content, and significant presence of potassium and phosphorus.