effects of surface soil removal (simulated erosion) and fertilizer application on wheat yield

an experiment involving erosion simulation was conducted at the soil and water con-servation research center of the university of tehran. a split-factorial plot with four replications was designed. five soil desurfacing treatments of blank, 5, 10, 15, and 20 cm of soil surface removal (e0, e5, e10, e15, and e20) were carried out, respectively. fertilizer treatments were 0, 65, and 130 kg ha-1 of urea (equal to 0, 30, and 60 kg ha-1 of pure n) and 0, 107, and 214 kg ha-1 of triple super phosphate (equal to 0, 50, and 100 kg ha-1 of p2o5). wheat (triticum aestivum), sardary cultivar, was cultivated in november 2001. to-tal precipitation was 223 mm during the growing season and 336 mm for the whole year (23 september 2001–22 september 2002). in order to reduce the effect of drought stress, three supplementary irrigations were applied during the growing season (13mm each). the crop was harvested in july and plant density recorded. grain, dry matter and straw yields, as well as 1,000 grain weight were determined. the results showed that erosion had a significant effect (p