Effects of long-term soil and crop management on the yield and on the fertility of eroded soil

The goal of the experiments carried out during 1980-2010, at the Podu-Iloaiei Agricultural Research Station - Romania, was the study of water runoff and soil losses, caused by erosion, in different crops, the annual rate of erosion processes under the influence of anti-erosion protection by different crops, the influence of water and soil erosion on the losses of organic matter and mineral elements from soil. In the study period of the total amount of 565.5 mm rainfall, 356.8 mm (63.1%) produced water runoff, which was between 7.98 mm in perennial grasses, in the second year of vegetation, and 29.7 to 31.2 mm, in maize and sunflower crops. The investigations concerning the potential erosion, conditioned by geomorphologic, soil and climatic factors, have shown that in the NE region of Romania, the mean soil losses by erosion in bare fallow were of 18.2 t ha -1 year -1 . On cultivated land the mean annual soil losses, caused by erosion, registered during 1980-2010, were of 0.20 t ha -1 in perennial grasses, on the second growth year, 4.33 t ha -1 in beans, 8.14 t ha -1 in maize and 8.72 t ha -1 in sunflower. The mean annual nitrogen, phosphorus and potassium leaches, due to erosion, were comprised between 19.18 and 20.32 kg ha -1 in row crops (maize and sunflower) and between 2.51 and 5.23 kg ha -1 year -1 in wheat and peas crops. The obtained results on soil erosion in different crop rotations, shown that in 16% slope fields from the Moldavian Plateau, soil losses by erosion were diminished below the allowable limit of 4 t ha-1 year-1 only in four-year crops rotations with one or two reserve fields, cultivated with legumes and perennial grasses.