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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, Klaus
Nitrate 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 .