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Resultados da Pesquisa
Item Soil profile internal drainage for a central pivot fertigated coffee crop(Universidade Federal de Viçosa, 2011-11) Bortolotto, Rafael Pivotto; Bruno, Isabeli Pereira; Dourado-Neto, Durval; Timm, Luís Carlos; Silva, Adilson Nunes da; Reichardt, KlausCoffee cultivation via central-pivot fertigation can lead to fertilizer losses by soil profile internal drainage when water application is excessive and soils have low water retention and cation adsorption capacities. This study analyses the deep water losses from the top 1 m sandy soil layer of east Bahia, Brazil, cultivated with coffee at a high technology level (central-pivot fertigation), using above normal N fertilizer rates. The deep drainage (Q) estimation is made through the application of a climatologic water balance (CWB) program having as input direct measures of irrigation and rainfall, climatological data from weather stations, and measured soil water retention characteristics. The aim of the study is to contribute to the understanding of the hydric regime of coffee crops managed by central-pivot irrigation, analyzing three scenarios (Sc): i) rainfall only, ii) rainfall and irrigation full year, and iii) rainfall and irrigation dry season only. Annual Q values for the 2008/2009 agricultural year were: Sc i = 811.5 mm; Sc ii = 1010.5 mm; and Sc iii = 873.1 mm, so that the irrigation interruption in the wet season reduced Q by 15.7%, without the appearance of water deficit periods. Results show that the use of the CWB program is a convenient tool for the evaluation of Q under the cited conditions.Item Nitrate leaching through climatologic water balance in a fertigated coffee plantation(Universidade Federal de Viçosa, 2013-11) Bortolotto, Rafael Pivotto; Bruno, Isabeli Pereira; Dourado-Neto, Durval; Timm, Luís Carlos; Silva, Adilson Nunes da; Reichardt, KlausNitrate losses from soil profiles by leaching should preferentially be monitored during high rainfall events and during irrigation when fertilizer nitrogen applications are elevated. Using a climatologic water balance, based on the models of Thornthwaite and Penman Monteith for potential evapotranspiration, drainage soil water fluxes below the root zone were estimated in a fertigated coffee crop. Soil solution extraction at the depth of 1 m allowed the calculation of nitrate leaching. The average nitrate concentration in soil solution for plots that received nitrogen by fertigation at a rate of 400 kg ha -1 , was 5.42 mg L -1 , surpassing the limit of the Brazilian legislation of 10.0 mg L -1 , only during one month. For plots receiving 800 kg ha -1 of nitrogen, the average was 25.01 mg L -1 , 2.5 times higher than the above- mentioned limit. This information indicates that nitrogen rates higher than 400 kg ha -1 are potentially polluting the ground water. Yearly nitrate amounts of leaching were 24.2 and 153.0 kg ha -1 for the nitrogen rates of 400 and 800 kg ha - 1 , respectively. The six times higher loss indicates a cost/benefit problem for coffee fertigations above 400 kg ha -1 .Item Nitrogen fertilizer (15 N) leaching in a central pivot fertigated coffee crop(Universidade Federal de Viçosa, 2012-07) Bortolotto, Rafael Pivotto; Bruno, Isabeli Pereira; Reichardt, Klaus; Timm, Luís Carlos; Amado, Telmo Jorge Carneiro; Ferreira, Ademir de OliveiraNitrogen has a complex dynamics in the soil-plant-atmosphere system. N fertilizers are subject to chemical and microbial transformations in soils that can result in significant losses. Considering the cost of fertilizers, the adoption of good management practices like fertigation could improve the N use efficiency by crops. Water balances (WB) were applied to evaluate fertilizer N leaching using 15 N labeled urea in west Bahia, Brazil. Three scenarios (2008/2009) were established: i) rainfall + irrigation the full year, ii) rainfall only; and iii) rainfall + irrigation only in the dry season. The water excess was considered equal to the deep drainage for the very flat area (runoff = 0) with a water table located several meters below soil surface (capillary rise = 0). The control volume for water balance calculations was the 0 – 1 m soil layer, considering that it involves the active root system. The water drained below 1 m was used to estimate fertilizer N leaching losses. WB calculations used the mathematic model of Penman-Monteith for evapotranspiration, considering the crop coefficient equal to unity. The high N application rate associated to the high rainfall plus irrigation was found to be the main cause for leaching, which values were 14.7 and 104.5 kg ha -1 for the rates 400 and 800 kg ha - 1 of N, corresponding to 3.7 and 13.1 % of the applied fertilizer, respectively.Item Balanço hídrico de um solo podzolizado de Lins e Marília cultivado com cafeeiros(Instituto Agronômico (IAC), 1986-07) Pereira, Antônio RobertoO balanço hídrico de um solo podzolizado de Lins e Marília cultivado com cafeeiros de diferentes idades e tamanhos, ou seja, 'Mundo Novo' com livre crescimento (18 anos; altura - 3m), 'Mundo Novo' recepado (3 anos; altura - 2m) e 'Catuaí' (4 anos; altura - 1,5m), foi realizado no período entre duas colheitas (1971/72), na Estação Experimental de Pindorama, utilizando a técnica de moderação de nêutrons até 2,4m de profundidade. Este tipo de solo reteve cerca de 1mm de água por centímetro de profundidade quando submetido à tensão de 15atm. A ocorrência de uma camada adensada entre 60 e 90cm de profundidade ajudou a reter a umidade na parte superior do solo, dificultando a drenagem profunda. Os armazenamentos mínimo e máximo observados representaram, respectivamente, 500 e 620mm para o 'Catuaí', 460 e 600mm para o recepado, e 390 e 590mm para o livre crescimento. De modo geral, pode-se dizer que: (a) o lote com livre crescimento evapotranspirou 97% do total de chuva e não contribuiu efetivamente com os reservatórios subterrâneos; (b) o recepado evapotranspirou 94% do total de chuva e teve uma drenagem profunda efetiva de 55mm; (c) o 'Catuaí' evapotranspirou 88% do total de chuva e teve uma drenagem profunda efetiva de 152,6mm.