Distribution and erosive potential of rainfall in the state of Tocantins, BrazilAbstract -The objective of this work was to determine rainfall erosivity values and to generate its spatial-temporal distribution maps in the state of Tocantins, Brazil. Pluviometric historical series from 97 rain gauges were analyzed, covering the period from 1985 to 2009. Erosivity was estimated by equations in which the independent variable was the average monthly rainfall or the Fournier rainfall index (Rc). Geostatistics was applied for mapping erosivity both monthly and annually. Annual erosivity values varied between 6,599 and 14,000 MJ mm ha -1 h -1 , with peak in December when it reached values up to 2,800 MJ mm ha -1 h -1 per month. From May to September, erosivity values had lower than the critical one, considered 500 MJ mm ha -1 h -1 per month. Three priority regions were identified for soil and water conservation planning activities: mid-west region of the state, in the neighborhood of Cantão State Park, with greatest erosivity; northern region of the state, especially during the first quarter of the year; and southern region of the state, in the fourth quarter.

Nitrogen fertilization is an important step for watermelon (Citrullus lanatus) production due to its influence over yield, fruit quality, and disease severity. Currently, the gummy stem blight (Didymella bryoniae) and the downy mildew (Pseudoperonospora cubensis) can be taken as the most important watermelon diseases, since they impose severe impairment to the crop. Furthermore, studies focusing on plant responses to nitrogen fertilization regarding fruit yield and quality, and disease resistance are rare. Hence, the present study aimed at evaluating the effect of nitrogen doses on fruit yield and quality, and on disease prevalence in watermelon. Two experiments were carried out at the Universidade Federal de Tocantins, employing sprinkler irrigation, in an area previously used to grow watermelon. The experimental design was blocks at random, with five treatments (N doses, applied twice as side-dressing, in kg ha-1, as follows: T1= control treatment without N, T2= 20, T3= 40, T4= 80, and T5= 120), and four replications. Urea (45% N) was used as the N source. In the first assay, the highest fruit yield and average weight were observed when 40 kg ha-1 of N were applied. The highest severity of the gummy stem blight was observed when the highest nitrogen doses were applied (80 and 120 kg ha-1). In the second assay, the highest severity levels of the gummy stem blight, as well as of mildew, were observed again when N doses were the highest (80 and 120 kg ha-1). The lowest severity levels for both diseases were observed in the control treatment.

Este trabalho teve como objetivo avaliar o crescimento e a produtividade da cultivar Nordestina da mamoneira em ambientes de baixo nível tecnológico e de alto nível tecnológico. O delineamento foi o de blocos casualizados em esquema fatorial, com cinco repetições. Os tratamentos foram constituídos por dois níveis tecnológicos e cinco épocas de avaliação. No baixo nível tecnológico, não foi realizada adubação e irrigação da cultura e a semeadura foi feita em covas. No alto nível tecnológico, foi realizada a adubação química, calagem do solo, uma aração, duas gradagens, semeadura em sulcos e irrigação por aspersão convencional. Foram avaliadas as características altura da planta, diâmetro do caule, área foliar, massa fresca da folha e do caule, massa seca da folha e do caule, razão de área foliar, índice de área foliar e a produtividade. Houve diferença significativa entre os níveis tecnológicos em todas as características avaliadas. No baixo nível tecnológico a ausência de adubação no plantio e a falta de irrigação durante o período de condução do experimento, prejudicou o desenvolvimento das plantas. Com relação à produtividade, o alto nível tecnológico apresentou uma maior produtividade, 3.794 Kg ha-1. No baixo nível tecnológico, a produtividade foi de 1.683 Kg ha-1.

Combinations of species, cultivars, clones and structural arrangements are cited as possibilities that may determine the interactions between these system components and management, needing to be better understood, especially in relation to shading capacity. In this sense, the present study aims to evaluate the light interception of Eucalyptus spp. clones at different structural arrangements for integrated production systems. An experiment was installed in randomized blocks design with five replications, in factorial scheme 4 x 2. Four structural arrangements A1 = Triple row (3,5 x 3,5 x 3,5) + 88 m; A2 = Double row (3,5 x 3,5) + 44 m; A3 = Single row 4 x 22 m; and A4 = Single row 4 x 11 m and two hybrids clones of Eucalyptus urophylla x E. grandis. For the estimation of the luminosity characteristics, the CI-110 imager equipment was used for estimate: the leaf area index, the average leaf angle, the coefficient of transmission, the sunflecks and the photosynthetically active radiation. Data were analyzed by variance analysis and the averages of the values of characteristics were compared by the Tukey test at 5% probability. The single row arrangement A4 promoted to the clones the greater shading capacity, characterized by high values of leaf area index, lower values of photosynthetically active radiation and by the densification of the arrangement of the other rows of alleys.

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