Grain yield for both growing seasons is shown in Fig. 3. Overall, wheat yield ranged between 500 and 5000 kg ha-1 with an average yield of 3000 kg ha-1 for the growing season 2008/09 and 3500 kg ha-1 for the growing season 2009/10. The HS zone was more productive than the AS zone during both years (Fig. 3); but the plots showing higher production in 2009 had lower yields in 2010. In the HS zone the 30 and 90 N yields for the growing season 2009/10 had the same yield range, while the AS plots showed high yield variability, except for some plots in 2009 located in the north-east area of the field.