Effects of long-term fertilization on the fertility of erosion-affected soils from the Moldavian Plateau

Abstract

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 maize yield. On slope lands, the high rate fertilization of maize crop (N140P100) has determined, in the latest ten years, an average yield increase of 103% (3373 kg/ha), against the control, and applying a rate of N70P70+40 t/ha manure resulted in getting a very close yield increase (99%, 3258 kg/ha). The minimum supply level of mobile phosphorus in soil (37-72 ppm) in pea-wheat-maize rotation (37 ppm) was maintained in case of annual application of a rate of N100P80. The total carbon content in Cambic Chernozem from the Moldavian Plain has registered significant increases at higher rates than N140P100 and in case of organo-mineral fertilization. The annual fertilization of wheat and maize, at the rate of 70 kg N + 70 kg P2O5/ha + 6 t/ha stalks of wheat, has determined, compared to the unfertilized variant, the increase in the content of organic carbon from soil by 14.5% (2.4 g organic C/kg) on weakly eroded soils, and by 29.5% (4.2 g organic C/kg) on highly eroded soils. During the long-term fertilizing of wheat and maize with high rates of mineral fertilizers (N140P100), on highly eroded lands, the total content of carbon has increased by 16.9% (2.4 g organic C/kg soil), against the unfertilized control. Applying moderate rates of mineral fertilizers (N70P70), together with 60 t/ha manure, has determined, after 43 years of testing, the increase by 32% (5.3 g organic C/kg) in the content of organic carbon from soil, on weakly eroded soils, and by 42.3% (6.0 g organic C/kg soil) on highly eroded soils, compared to the unfertilized control. On 16% slope arable lands from the Moldavian Plateau, the mean annual soil losses by erosion, registered during 1986-2007, were of 1.640 t/ha in winter wheat, 4.618 t/ha in beans, 1.89 t/ha in the field cultivated with perennial grasses and legumes on the second year of vegetation, 9.176 t/ha in maize and 9.6 t/ha in sunflower.