Integrated fertilizer and irrigation management to reduce nitrate leachingin Central Spain

Cropping systems that fail to manage N and irrigation, with the objective o f reducing losses of N, are frequently associated with elevated concentrati ons of nitrate N in soil and ground water. A Longterm (4-yr) field experime nt was carried out at La Poveda Field Station (30 km southeast of Madrid, S pain) with the objective of assessing whether the effect of traditional cul tivation practices (irrigation and fertilization) can be reduced. The exper iment was conducted on a Typic Xerofluvent soil and a crop sequence (corn-w heat-corn-oat) traditional in the area. Four fertilizer treatments (unferti lized check, urea, floranid [a slow-release N fertilizer] and municipal org anic waste [MOW] compost) were combined with two irrigation schedules (trad itional and improved) in two sets of 24 plots, Seasonal drainage was estima ted 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 cu p extraction system. Nitrate leaching could be attributed to both irrigatio n schedule and fertilizer type. Within fertilizer treatments, reductions of nitrate losses between irrigation schedules of 52, 51, 66, and 81% were fo und for the unfertilized check, urea, floranid, and MOW compost, respective ly, Grain yields in the whole crop sequence were not affected by fertilizer or irrigation managements.