O feijão caupi ou feijão de corda é uma das principais culturas da atividade econômica no nordeste brasileiro e apresenta boa tolerância à seca e às altas temperaturas, tendo sua produtividade condicionada pelo estresse hídrico advindo dos longos períodos de seca na região. Assim, objetivo do trabalho foi a avaliação do potencial do polímero hidrorretentor na melhoria da retenção de água, das características biométricas e da produtividade da cultura do feijão caupi em solo de textura arenosa. O delineamento experimental foi em blocos inteiramente casualizados, com sete tratamentos e quatro repetições. Cada parcela foi composta por um vaso com capacidade de 7L, com solo e a devida quantidade de polímero hidrorretentor ou ausência do mesmo (testemunha). Foram semeadas quatro sementes por vaso e, após a germinação, realizou-se o desbaste, mantendo-se duas plântulas. Durante e ao final do ciclo da cultura, foram avaliados parâmetros biométricos e de produtividade, e determinadas a umidade e a curva de retenção de água no solo. A utilização do polímero hidrorretentor aumentou a retenção de água e melhorou grande parte das propriedades morfológicas e produtivas da cultura. Dentre as dosagens avaliadas, as proporções de 1,50; 2,00 e 4,00 g L-1 se apresentaram como as que mais favoreceram ao desenvolvimento vegetal.

Cowpea, a short-cycle legume with large production in the North and Northeast regions, has its productive potential limited by edaphic characteristics and degradation processes of soil physical quality, such as compaction. This process may interfere with plant development and productivity by restricting root system growth, aeration, water and nutrient availability. The objective of this work was to analyze the interference of different levels of compaction in the soil physical characteristics, root growth, development of the aerial part and productivity of cowpea. The experiment was conducted in a greenhouse following a completely randomized design with a control (control) and four levels of soil compaction, with four replications. Each experimental unit was composed of PVC tubes composed of a 0.05-m layer of gravel, cotton fabric and a 0.04-m layer of soil. The different levels of compaction were obtained using a proctor socket and a wooden base. Based on the value of penetration resistance (PR) of 1.00 MPa, soil reached the macroporosity considered as critical theresohold for soil aeration. Results indicate that the higher the PR of the soil, the lower the development of the root system and the aerial part. The productive aspects of cowpea presented better results in plants grown in soils with a level of resistance to penetration close to 0.8 MPa.

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The aim of this work is to define indices of soil chemical quality in intense agricultural activity area surrounding Sobradinho Lake, State of Bahia, Brazil, by means of multivariate statistical techniques. Based on the factor scores, it was determined soil chemical quality index for depths of 0-0.10, 0.10-0.20 and 0.20-0.40 m, respectively, classifying soils as good, fair and poor, according to the performance of its attributes. Then realized the Discriminative Analysis in order to validate the results obtained and, knowing the chemical soil attributes that influence and are associated with soil quality in agriculture of the region. In this way, among the main results could be observed that the attributes exchangeable sodium percentage (ESP) and organic matter (OM) stood out as indicators of soil quality. The ESP was the more important attribute in discrimination models in the depths of 0.00-0.10 and 0.10-0.20 m and OM in the 0.20-0.40 m layer. These variables are the main responsible for discrimination and classification of soil groups. In general, the chemical quality of soils is not considered ideal mainly due to the low contents OM and the extremely sandy texture, denoting environmental fragility.Resumo: O objetivo deste trabalho foi a definição de índices de qualidade química do solo em área com agricultura intensiva do entorno do Lago de Sobradinho, Estado da Bahia, Brasil, por meio de técnicas de estatística multivariada. Com base nos escores fatoriais, foi determinado o índice de qualidade do solo química (ICSQ) para profundidades de 0-0,10, 0,10-0,20 e 0,20-0,40 m, respectivamente, classificando os solos como bom, regular e ruim, de acordo com o desempenho de seus atributos. Em seguida, realizou-se a análise discriminante (AD) com o objetivo de validar os resultados obtidos, bem como, conhecer os atributos químicos do solo, que influenciam e estão associados à qualidade do solo na área agrícola da região. Dessa maneira, dentre os principais resultados pôde-se observar que os atributos PST, teores de Na + e de MO se destacaram como indicadores de qualidade do solo. PST foi o atributo de maior peso relativo nos modelos de discriminação dos sítios amostrados nas profundidades de 0,0-0,10 e 0,10-0,20 m e, teor de MO na profundidade de 0,20-0,40 m. Essas variáveis foram as principais responsáveis pela discriminação e classificação dos grupos de solo. Em geral, a qualidade química dos solos não é considerada ideal, principalmente devido ao baixo conteúdo de MO e à textura extremamente arenosa, denotando fragilidade ambiental.Palavras-chave: análise multivariada, atributos químicos, manejo do solo, solos arenosos.

Excessive tillage operations under inadequate conditions can raise the cost of agricultural production and lead to soil degradation without adequate crop response. The objective of this study was to evaluate the onion crop response to soil water contents and tillage systems. Three tillage systems were evaluated: P1 (plowing + two harrowings + two seedbed raising operations), P2 (two harrowings + one seedbed raising operation), P3 (one harrowing + one seedbed raising operation); and four soil water contents: 12, 15, 23 and 26%. The experiment was conducted in the irrigated perimeter of Tourão, Juazeiro, BA, Brazil (9° 24’ 7.3” S; 40° 26’ 8.7” W and altitude of 368 m), in 2017, and was installed in split plots, in a randomized block design, with four repetitions. Water contents were arranged in the plots and tillage systems in the subplots. Crop response to the applied treatments was evaluated through the determination of the emergence speed index of the seedlings, regularity of the longitudinal distribution of seedlings, final stand, total and marketable yields of the crop and yield per bulb transverse diameter class. The variation of soil water content had a quadratic effect on the variables emergence speed index, final stand and total onion yield. The treatments did not significantly affect the longitudinal distribution of plants and marketable yield. The tillage system composed of one harrowing and one seedbed raising operation showed to be the most appropriate for onion cultivation by direct seeding.