Evolution of some chemical properties of soil under influence of soil erosion and different cropping systems

- Since 1968, at the Agricultural Research Station of Podu- Iloaiei, Iași County (47°12´ N latitude, 27°16´ E longitude), investigations were conducted on the influence of different crop structures and fertilizers on yield, erosion and soil fertility. The paper presented the results of investigations concerning the influence of long-term fertilization (43 years) on some chemical characteristics of Cambic Chernozem from the Moldavian Plain and on the yield of wheat and maize, placed under different crop rotations with perennial grasses and legumes. The objectives of this study was, to monitor runoff, soil loss and soil chemical properties in monocultures of wheat and corn, compared with different rotations and fallow land. The climatic conditions in the Moldavian Plain were characterized by annual mean temperature of 9.6oC and a mean rainfall amount, on 50 years, of 553.5 mm, of which 141.5 mm during September- December and 412.0 mm during January- August. In the last 20 years, the mean annual recorded quantity of rainfall was of 588.7 mm (100%), of which 369.5 mm (62.8%) determined water runoff and soil losses by erosion. Mean annual losses of soil by erosion, recorded in the last 20 years, in the Moldavian Plain, were of 0.161 t/ha in perennial grasses in the second growth year, 3.883 t/ha in beans, 6.369 t/ha in maize and 6.733 t/ha in sunflower. The crop structure, which determined, during 1991- 2010, the diminution in mean soil losses by erosion until 1.954 t/ha/year included 20 % straw cereals (wheat), 20% annual legumes (pea), 20% row crops (maize) and 40 % perennial grasses and legumes (Alfalfa + Lolium perene). After 43 years of experience, in the pea - wheat - corn - sunflower rotation + reserve field, cultivated with legumes and perennial grasses, soil organic carbon content increased with 14.7% (2.8 C g / kg), in comparison with wheat - maize rotation.