The field was cultivated during 2 years before soil sampling(2011 and 2012) with a corn/cereal succession (corn/oat/corn/wheat) under a no-tillage system. The treatments were applied twice a year during two years (before the summer - corn; and the winter crops - oat or wheat) on soil surface with residues of the preceding crop (a few days before sowing the next crop). The
average daily temperature was obtained from the University meteorological station, located approximately 500 m from the experiment. The amount of rainfall and irrigationwater at each site was measured using rain gauges. The average annual rainfall was 1700 mm, and the mean annual temperature was 19.9 C