THE INFLUENCE OF FERTILIZATION AND EROSION ON MAIZE CROP, GROWN ON ERODED SOIL, AND ON SOIL AGROCHEMICAL AND BIOLOGICAL CHARACTERISTICS

Podu – Iloaiei have studied the influence of different fertilizer systems on yield in wheat and maize crops, and placed in a three-year rotation (pea – wheat – maize). The erosion process has determined the differentiation of average maize yield, according to slope and erosion. The mean annual losses of yield registered in wheat in the last 10 years, caused by erosion, were of 1296 kg/ha (22.1%). On weakly eroded lands, mean maize yields obtained during 1997-2006, were comprised between 3227 kg/ha at the unfertilized control, and 7678 kg/ha at rates of N70P70+ 60 t/ha manure. On highly eroded lands, the mean yield obtained under unfertilized was of 2346 kg/ha. Average yield increases obtained by applying 60 t/ha manure, every two years, were of 41.3 kg grains per t of manure applied. Mineral fertilizers (N100P100) resulted in obtaining mean yield increases of 13.6 kg grains/kg a.i. of applied fertilizer. On slightly eroded lands, maintaining a good supply level in soil nutritive elements was done by the annual use of fertilizer rates of at least N100P100 or N70P70+ 40 t/ha manure, applied once in two years, or N70P70 + 6 t/ha straw. On highly eroded lands, maintaining a good plant supply in mineral elements was done at rates of N140 P100K70 or N70P70 + 40 t/ha manure. The total number of microarthropods from soil, at the depth of 0-30 cm had values between 22.4 samples/100 cm2 in the fertilized plot with N70P70 + 6 t/ha straw, and 78.5 samples/cm2 in the fertilized plot with N70P70+40 t/ha manure. In most of the fertilization variants, the highest values were registered in Collembole. In case o