Pig slurry versus mineral fertilization on corn yield and nitrate leaching in a Mediterranean irrigated environment

Over the last 20 years, in many regions of Spain, there has been an intensification of pig production. Most of the resulting pig slurry (PS) is applied to agricultural fields and so it is important to determine the availability of nitrogen for the crops and to assess the risk of adverse environmental effects such as nitrate leaching. The effects of a single application of three different doses of PS: 50, 100 and 150 m(3) ha(-1), were compared with a control mineral treatment in an irrigated Mediterranean environment. Development and crop yield of corn and the amount of nitrate leached were evaluated during 3 years in a Typic Xerofluvent soil. No significant differences for aboveground biomass, corn yield and nitrogen plant uptake were observed between the different fertilization schemes. Nitrate concentrations in the soil solution at the 0.9-1.2 m depth were higher for the control treatment (44.7 mg NO3--N l(-1)) than for the slurry treatments (ranging from 19.9 to 28.0 mg NO3--N l(-1)), indicating a higher susceptibility to nitrate leaching for the control mineral treatment. The high unaccounted losses in the N budget for the slurry treatments and the unexpectedly decrease in the ratio between nitrate leaching and applied nitrogen with increased N doses proves that there is a need to examine the slurry N cycle in the soils with especial emphasis in the immobilization of ammonium slurry in Mediterranean conditions. (C) 2003 Elsevier B.V. All rights reserved.