Soil quality and crop yields, after utilization of sewage sludge on agricultural land, in the Moldavian Plain, Romania

anglais. Investigations conducted at the Podu-Iloaiei Agricultural Research Station, Iasi County, have studied the influence of different sewage sludge rates on yield quality and quantity and soil agrochemical characteristics. Trials were set up in a five year-crop rotation, winter rape- wheat-maize-sunflower-wheat. Sewage sludge was applied every 2 years at rates of 20, 30, 40 and 60 t/ha, with different mineral fertilizer rates, differentiated according to the growing plant. The Cambic Chernozem used for experiments had a clayey-loam texture (410 g clay, 310 g loam and 280 g sand), a weakly acid reaction and a mean supply with mobile phosphorus and a very good one with mobile potassium. Applying rates of 30 t/ha sewage sludge has resulted in the accumulation of mobile phosphate stock in soil of 57 mg/kg and the microelement content, mobile forms from soil, was of 7.9 mg/kg at Cu, 1.4 mg/kg at B, 6.8 mg/kg at Zn and 186 mg/kg at manganese. The combined use of mean rates of mineral fertilizers (N100P80), together with 40 t/ha sewage sludge has resulted in improving soil chemical characteristics and getting yield increases in winter rape of 1854 kg/ha (108 %). After 8 years since the application of a rate of 30 t/ha sewage sludge, soil pH has increased 0.4 units, while phosphorus and potassium content from soil has increased by 30 and 52 mg/ kg soil, respectively. Sewage sludge from the Iasi Water Treatment Station, which was applied every two years at rates of 20 and 30 t/ha, has determined the increase in the organic carbon content from soil by 2.9 g/kg (18%) and 4.4 g/kg (28%), respectively, compared to the unfertilized variant. The copper and zinc content from grains in wheat and maize crops, fertilized with 30 t/ha sewage sludge, was by two-four times higher, compared to the unfertilized control.

roumain; moldave. Cercetarile efectuate la Statiunea de Cercetare Dezvoltare Agricola Podu-Iloaiei, jud. Iasi, au urmarit influenta diferitelor doze de namoluri asupra cantitatii si calitatii productiei si asupra insusirilor agrochimice ale solului. Experientele au fost organizate intr-un asolament de 5 ani - rapita de toamna-grau-porumb-floarea soarelui-grau. Namolurile s-au aplicat o data la 2 ani, in doze de 20, 30, 40 si 60 t/ha, impreuna cu diferite doze de ingrasaminte minerale, diferentiate in functie de planta de cultura. Cernoziomul cambic folosit pentru experiente are o textura luto-argiloasa (410 g argila, 310 g lut si 280 g nisip), o reactie slab acida , un nivel mediu de aprovizionare cu fosfor mobil si unul foarte bun cu potasiu mobil. Aplicarea unor doze de 30 t/ha namol orasenesc a determinat acumularea unei rezerve de fosfati mobili in sol de 57 ppm, iar continutul de microelemente, forme mobile in sol, a fost de 7.9 mg/kg Cu, 1.4 mg/kg B, 6.8 mg/kg Zn si 186 mg/kg mangan. Folosirea combinata a dozelor medii de ingrasaminte minerale (N100P80), impreuna cu 40 t/ha namol fermentat, a imbunatatit caracteristicile chimice ale solului si a determinat, in comparatie cu varianta martor nefertilizata, cresterea productiei la rapita de toamna cu 1854 kg/ha (108 %). Dupa 8 ani, prin aplicarea dozei de 30 t/ha namol fermentat, pH-ul solului a crescut cu 0.4 unitati si continutul de fosfor si potasiu din sol a crescut, fata de varianta martor netratata, cu 30 si, respectiv, 52 mg/kg sol. Namolurile fermentate de la Statia de epurare Iasi, aplicate o data la 2 ani, in doze de 20 si 30 t/ha, au determinat cresterea continutului de carbon organic din sol, in comparatie cu varianta netratata, cu 2.9 (18%) si, respectiv, 4.6 g/kg (28%). Continutul de cupru si zinc din boabe la culturile de grau si porumb, fertilizate cu 30 t/ha namol, a fost de doua-patru ori mai mare, comparativ cu varianta martor nefertilizata.