Long-term effect of fertilizer and crop residue on soil fertility in the Moldavian Plateau

anglais. Since 1965, at the Agricultural Research Station of Podu- Iloaiei, Iasi County, Romania (47°12´ N latitude, 27°16´ E longitude), investigations were conducted on the influence of different fertilizer systems on production and soil fertility. For wheat and maize crops, placed in a three-year rotation (pea - wheat - maize), three fertilization systems were experienced: (1) mineral fertilization with nitrogen and phosphorus rates until N140P100; (2) manure fertilization (20, 40, and 60 t/ha), with and without mineral fertilization and (3) mineral fertilizers + hashed residue applied in autumn under the base ploughing. The paper presented the results of investigations concerning the influence of long-term fertilization (46 years) on some chemical characteristics of Cambic Chernozem from the Moldavian Plateau. The climatic conditions in the Moldavian Plain were characterized by annual mean temperature of 9.6 deg C 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. After 46 years of experiences, in pea-wheat-maize crop rotation, the content of organic carbon from soil has decreased by 22.3% (4.2 g/kg soil) at the unfertilized control and by 14.4% (2.7 g/kg soil) at the rate of N120P80. In wheat and maize, nitrogen uptake by weeds was between 7 and 9.5 kg/ha from all the plots. Applying moderate rates of mineral fertilizers (N80P60), together with 6 t/ha wheat straw or 40 t/ha manure, has determined the increase in organic carbon content from soil by 0.5 and, respectively, 2.8 g/kg.

roumain; moldave. Incepand cu anul 1965, la Statiunea de Cercetari Agricole Podu- Iloaiei, judetul Iasi (47°12´ N latitude, 27°16´ E longitude), cercetarile efectuate au urmarit influenta diferitelor sisteme de fertilizare asupra productiei si a fertilitatii solului. Pentru culturile de grau si de porumb, amplasate intr-o rotatie de trei ani (mazare - grau - porumb), au fost experimentate trei sisteme de fertilizare: (1) minerala cu azot si fosfor, cu doze de pana la N140P100; (2) fertilizarea cu gunoi de grajd (20, 40, si 60 t/ha), cu si fara fertilizare minerala si (3) ingrasaminte minerale + resturi vegetale, aplicate in toamna, sub aratura de baza. Lucrarea prezinta rezultatele cercetarilor privind influenta fertilizarii de lunga durata asupra unor insusiri chimice ale cernoziomului cambic din Podisul Moldovei. Conditiile climatice din Campia Moldovei se caracterizeaza prin temperaturii medii anuale de 9.6 deg C si o cantitate medie de precipitatii, pe 50 de ani, de 553,5 mm, din care 141,5 mm in perioada septembrie-decembrie si 412 mm in perioada ianuarie-august. Dupa 46 de ani de experimentare, in rotatia culturilor mazare-grau-porumb, continutul de carbon organic din sol a scazut cu 22,3% (4,2 g/kg sol) la varianta martor nefertilizata si cu 14,4% (2,7 g/kg sol) la doza de N120P80. La culturile de grau si porumb, cantitatile de azot consumate de buruieni au fost cuprinse intre 7 si 9,5 kg/ha la toate variantele. Aplicarea unor doze moderate de ingrasaminte minerale (N80P60), impreuna cu 6 t/ha paie de grau sau cu 40 t/ha gunoi de grajd, a determinat cresterea continutului de carbon organic din sol cu 0,5 si, respectiv, 2,8 g/kg.