O escoamento da água oriunda das terras agricultadas é o principal fator poluente dos mananciais hídricos nas áreas rurais. Devido a esse fato, faz-se necessário o desenvolvimento e a aplicação de tecnologias que venham a reduzir descargas de resíduos indesejáveis. Nesse sentido, conduziu-se um experimento na área experimental do Departamento de Engenharia Rural - ESALQ/USP, Piracicaba - SP, com o objetivo de avaliar o efeito de diferentes condições de solo, (feijão, gramínea e solo nu) e diferentes práticas de controle de erosão (sulco de infiltração, terraço de infiltração e sem práticas de controle de erosão), buscando-se estimar o escoamento superficial. O delineamento estatístico adotado foi o em blocos aleatorizados, em esquema fatorial 3x3, perfazendo 9 tratamentos com 3 repetições. O período de coleta de dados pluviométricos foi de 06 de dezembro de 2007 a 11 de abril de 2008; para isto, utilizou-se de um pluviômetro, com 21,1 cm de diâmetro, instalado na área experimental. Observando-se as perdas de água, em relação às estruturas, tem-se em ordem decrescente de eficiência: Terraço, Sulco e Rampa; e com relação às coberturas, tem-se em ordem decrescente de eficiência: Feijão, Capim e Solo Nu.

The tomato crop plays an important environmental, economic and even social role, especially for creating employment and income. The present work aims to evaluate the effects of potassium (K) drip fertigation and of conventional K fertilization on the tomato crop quality. The experiment was conducted under field conditions, in the period between August 2011 and December 2011, in Fortaleza, CE, Brazil. The experimental design was in randomized blocks in a factorial arrangement and the treatments corresponded to doses (D1 = 200, D2 = 400 and D3 = 800 kg K2O ha-1) and K fertilizing methods (F1 - Fertigation and F2 - Conventional fertilization), plus an additional control (without K fertilization) for each fertilizing method, with four replicates. The following variables were analyzed: fruit firmness (FF), soluble solids content (SS), titratable acidity (TA), pH and SS/TA ratio. K fertilization through fertigation (400 kg K2O ha-1) increases SS and the SS/TA ratio of the tomato fruits. Thus, K fertigation is the most promising method, since it allows the use of a lower K dose.

The objective of this study was to evaluate the effects of the addition of parts of leguminous trees on the growth and nutrition of maize (Zea mays L.), as well as on the chemical attributes of a degraded soil, 65 days after applying the residues. The experiment was conducted in pots, in a randomized block design with ten treatments and four replicates. The evaluated treatments were: T1 - No residues of leguminous trees, T2 - Leaves of Mimosa caesalpiniifolia, T3 - Branches of Mimosa caesalpiniifolia, T4 - Leaves + branches of Mimosa caesalpiniifolia, T5 - Leaves of Mimosa hostilis, T6 - Branches of Mimosa hostilis, T7 - Leaves + branches of Mimosa hostilis, T8 - Leaves of Gliricidia sepium, T9 - Branches of Gliricidia sepium and T10 - Leaves + branches of Gliricidia sepium. Pots were filled with soil from a degraded area and residues were added in the form of green mass after sowing the maize. Residues of leguminous trees positively influenced maize growth at 65 days after application and favored the accumulation of nitrogen, phosphorus and potassium in the shoots. Green fertilizers improved soil chemical attributes at 65 days after application, especially nitrate-N (NO3 --N), ammonium-N (NH4 +-N), total inorganic N (NO3 --N + NH4 +-N) and K, demonstrating that these species are good options for recovering degraded areas in the semi-arid region of Ceará.

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RESUMOA curva de regulação e a histerese de uma válvula reguladora de pressão, utilizada em pivô central foram obtidas de avaliações conduzidas em laboratório, conforme ISO (1993). Após uma mudança no corpo da válvula efetuada pelo fabricante do equipamento, realizou-se novo ensaio utilizando o mesmo procedimento técnico efetuado por LIMA (2001) e LIMA et al. (2003. A modificação resultou em uma melhoria na regulação da pressão e uma redução na variação da histerese tendo sido corrigida uma vibração na mola do antigo regulador quando a pressão de entrada no mesmo chegava aos 63,3 mca. Todos os modelos se adequaram aos padrões exigidos por ISO (1993). PALAVRAS CHAVE: regulação de pressão, histerese, pivô central Behavior of the Center Pivot Pressure Controllers After Their Internal Modification ABSTRACTThe performance curve and hysteresis of a regulating valve of pressure used in center pivots were provided from evaluations carried out in laboratory, according to ISO (1993). As the manufacturer has changed the valve body of pressure controllers, new trials were made by using the same technical procedure followed by LIMA (2001) andLIMA et al. (2003). As a result, the mentioned modification has contributed both to improve pressure regulation and to reduce hysteresis variation and a spring vibration that usually happened into the old regulator when reaching 63,3 mca inlet pressure no longer exists. All regulators tested were considered suitable in agreement with standards required from ISO (1993).

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Ground covering and practical erosion control effects in the water and soil losses by runoff The main pollutants of water resources from agricultural areas are organic matter, sediments, nutrients and pesticides, carried out mainly by runoff from farming lands. Considering this fact, it is very important the development and application of technologies to reduce such undesirable residues discharges, that were analyzed in this study. The experiment was carried out in the experimental area at ESALQ / USP, Piracicaba-SP, Brazil, with the objective to evaluate the effect of different ground coverings, wide base terraces and infiltration furrows in slopes, searching esteem the water infiltration capacity and soil losses by runoff. The adopted statistical delineation in the experiment was randomized blocks, in 3x3 factorial diagram (torrent containment structures x ground covering), making 9 treatments with 3 repetitions, being considered each block a repetition. The torrent containment structures have been: infiltration furrows, infiltration terrace and slope (without containment structure) and the ground coverings have been: bean, grass and naked ground (without ground covering). The pluviometric data collection began in December, 06, 2007 and finished in April, 11, 2008, for such, was used a rain gauge, with 21.1 cm of diameter, installed inside of the experimental area. Observing the ground losses, with relationship to the structures, we have in sequence of decreasing efficiency: Terrace, Furrow and Slope; and with relationship to the covering: Grass, Bean and Naked Ground. Observing the water losses, with relationship to the structures, we have in sequence of decreasing efficiency: Terrace, Furrow and Slope; and with relationship to the covering: Bean, Grass and Naked Ground. A draining coefficient average (C) was calculated for each treatment that is for the respective treatments: 0.18 (Bean Terrace), 0.18 (Grass Terrace), 0.24 (Bean Furrow), 0.26 (Grass Furrow), 0.29 (Grass Slope), 0.31 (Bean Slope), 0.42 (Naked Ground Terrace), 0.44 (Naked Ground Furrow) and 0.52 (Naked Ground Slope). Had to the replant of the beans, it had a bigger land movement in the parcels with this ground covering, thus favoring to an increase in the ground disaggregation, consequently, an increase in it drags of ground particles and a bigger water infiltration.

RESUMO: Para a recuperação de áreas degradadas em região semiárida é oportuno a avaliação de cultivares mais tolerantes a estresse hídrico, e o milheto é um cultura que possui potencial de uso para produção vegetal em regiões com baixas precipitações, assim, objetivou-se estudar cultivares de milheto em função de lâminas de irrigação, em solo degradado coletado em Irauçuba-CE. O estudo foi conduzido em pleno sol, em vasos com 12,5 dm 3 de solo, o qual apresentava baixa fertilidade natural, coletado em Irauçuba-CE. As cultivares avaliadas foram ADR500, BRS1501, BRS1502, BRS1503 e IPABulk-1, com quatro lâminas de irrigação: 100, 80, 60 e 40% em função da evapotranspiração da cultura (ETc), a qual foi mensurada por um tanque classe "A". Logo, o delineamento utilizado foi inteiramente casualizado em esquema fatorial, com três repetições. Até o 34° dia após a germinação das plantas a quantidade de água aplicada era equivalente a 100% da ETc, e após iniciou-se a aplicação das diferentes lâminas, sendo as plantas conduzidas por mais 14 dias, cujas variáveis biométricas e de clorofila foram mensuradas, e esta última avaliada, também, três dias após a aplicação das lâminas e ao final do ensaio. A diminuição da lâmina afetou as variáveis altura, comprimento de raiz, número de folhas vivas, total e índice SPAD (Soil Plant Analysis Development), independente da cultivar. Dentre as variáveis apenas diâmetro e índice SPAD apresentaram significância para a interação cultivares e lâminas na menor quantidade de água aplicada (40%), sendo que os menores valores foram verificados para as cultivares ADR500 e BRS1501, respectivamente. Para número de folhas vivas e