SOIL FERTILITY EVOLUTION INFLUENCED BY CROPPING SYSTEMS AND SOIL EROSION IN THE MOLDAVIAN PLATEAU

The goal of the experiments carried out during 1980-2009, at the Podu- Iloaiei Agricultural Research Station, Iasi County, was the study of water runoff and soil loss, caused by erosion, in different crops and the influence of water and soil erosion on loss of organic matter and mineral elements from soil. The results on runoff and soil losses in different crops from the Moldavian Plateau have shown that, during 1980-2009, of the total amount of 570.2 mm rainfall, 366.1 mm (64.2%) produced water runoff, which was between 6.3 mm in perennial grasses and 29.6 - 35.4 mm in maize and sunflower crops. The annual soil loss by erosion was between 0.246 t/ha in perennial grasses and 8.976 t/ha in sunflower. Erosion has affected soil fertility by removing once with eroded soil, high amounts of mineral elements, which reached 16.1-17.5 kg/ha nitrogen, 1.2-1.3 kg/ha phosphorus and 2.0-3.2 kg/ha potassium, in maize and sunflower crops. The crop structure, which determined the diminution in mean soil losses by erosion until 3.206 t/ha, included 20 % straw cereals, 20% annual legumes, 20% row crops and 40 % perennial grasses and legumes.