Influence of some organic residues on wheat and maize yield and eroded soil fertility

Abstract

Investigations conducted during 2003-2009 at the Podu-Iloaiei Agricultural Research Station, Iaşi County, have studied the influence of different sewage sludge rates, crop residues and manure rates on yield quality and quantity and soil agrochemical characteristics. Trials were set up in a five year-crop rotation (soybean-wheat-maize-sunflower-wheat). Sewage sludge was applied every two years at rates of 20, 40 and 60 t/ha, with different mineral fertilizer rates, differentiated according to the growing plant. In wheat, we have used Gabriela Variety, and in maize, Oana Hybrid. The mean yield increases obtained during 2003-2009, by applying the rate of 60 t/ha sewage sludge, were of 1877 (93%) in winter wheat and of 2102 kg/ha (57%) in maize. After 7 years since the application of a rate of 60 t/ha sewage sludge, soil pH has increased 0.4 units, while phosphorus and potassium content from soil has increased by 39 and 115 mg/ kg soil, respectively. Sewage sludge from the Iaşi Water Treatment Station, which was applied every two years at rates of 40 and 60 t/ha, has determined the increase in the organic carbon content from soil by 3.4 g/kg (20.5%) and 4.7 g/kg (28.3%), respectively, compared to the unfertilized variant. Applying wheat and maize residues, at the rate of 6 t/ha DM, has determined the increase by 1.4-1.7 g/kg soil (8.2-9.9%) in the content of organic carbon from soil, compared to the mineral fertilization (N80P60), and by 1.9-2.2 g/kg (11.5-13.3%), compared to the unfertilized control.