Long-term effects of crop residues and fertilization on production and soil fertility

The investigations conducted during 1995-2010 at the Podu- Iloaiei Agricultural Research Station, Iași County, have studied the influence of different mineral fertilizers rates on wheat and maize yield and soil agrochemical characteristics. Soil erosion caused a reduction in the percentage of aggregate by 14.5% to slightly eroded soil and 37.7% in the strongly eroded soil. The percentage of water stable aggregates was comprised between 73.5% in non eroded soil, at the bottom of slope land and 45.7% at the highly eroded soil. On weakly and highly eroded lands the content of organic carbon from soil, after 44 years of experiences, has decreased by 16.8-24.9% (3.3-4.9 g/kg soil) at the unfertilized control and by 12.2- 18.3% (2.4-3.6 g/kg soil) at the rate of N120P80. On weakly and highly eroded lands the mean yield increases, obtained for each kg of a.i. of applied fertilizer, were comprised between 9.6 and 11.3 kg in wheat and between 11.9 and 13.06 kg in maize (N80P60-N160P100)