Integrated fertilizer and irrigation management to reduce nitrate leaching in Central Spain

Cropping systems that fail to manage N and irrigation, with the objective of reducing losses of N, are frequently associated with elevated concentrations of nitrate N in soil and ground water. A Longterm (4-yr) field experiment was carried out at La Poveda Field Station (30 km southeast of Madrid, Spain) with the objective of assessing whether the effect of traditional cultivation practices (irrigation and fertilization) can be reduced. The experiment was conducted on a Typic Xerofluvent soil and a crop sequence (corn-wheat-corn-oat) traditional in the area. Four fertilizer treatments (unfertilized check, urea, floranid [a slow-release N fertilizer] and municipal organic waste [MOW] compost) were combined with two irrigation schedules (traditional and improved) in two sets of 24 plots, Seasonal drainage was estimated by the zero flux plane-water balance equation and nitrate concentration was measured at the soil depth of deep percolation (1.4 m) by a ceramic cup extraction system. Nitrate leaching could be attributed to both irrigation schedule and fertilizer type. Within fertilizer treatments, reductions of nitrate losses between irrigation schedules of 52, 51, 66, and 81% were found for the unfertilized check, urea, floranid, and MOW compost, respectively, Grain yields in the whole crop sequence were not affected by fertilizer or irrigation managements.