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

English. The investigations conducted during 1995-2010 at the Podu- Iloaiei Agricultural Research Station, Iasi 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).

Romanian; Moldavian; Moldovan. Cercetarile efectuate in perioada 1995-2010, la Statiunea de Cercetare-Dezvoltare Agricola Podu-Iloaiei, judetul Iasi, au urmarit influenta diferitelor doze de ingrasaminte minerale asupra productiei de grau si porumb si a insusirilor fizice si chimice ale solului. Eroziunea solului a determinat reducerea procentului de macro agregate cu 14,5% la solul slab erodat si cu 37,7% la solul puternic erodat. Procentul de agregate hidrostabile a fost cuprins intre 73,5% la solul neerodat de la baza pantei terenului si 45,7% la solul puternic erodat. Pe terenurile slab si puternic erodate, continutul de carbon organic din sol, dupa 44 de ani de experimentare, a scazut cu 16.8 - 24.9% (3.3 - 4.9 g / kg sol), la martorul nefertilizat si cu 12.2 - 18.3% (2.4 - 3.6 g / kg sol), la doza de N120P80. Pe terenurile slab si puternic erodate, sporurile medii de productie obtinute, pentru fiecare kg de ingrasaminte aplicate, au fost cuprinse intre 9.6 si 11.3 kg la grau si intre 11.9 si 13.06 kg la porumb (N80P60-N160P100).