Influence of the Irrigation on Soil Properties in a Long Term Trial from Oradea

The paper is based on the researches carried out in the long term trial placed on the preluvosoil from Oradea in 1976, for establishing the soil water balance. In the irrigated variant the soil moisture was determined 10 to 10 days for maintaining the soil water reserve on irrigation depth (0 – 50 cm for wheat and bean, 0 – 75cm for maize, sunflower, soybean, sugarbeet, potato and alfalfa 1st year and 0 – 100 cm for alfalfa nd year) between easily available water content and field capacity. Thus, an average irrigation rate of 2560 m³/ha was used in the 9 experimental crops. The average of the annual rainfall for the 1976 – 2010 period was pf 625.0 mm. The technologies used were correlated with the needes of the crops, such as melioration, crop rotation, chemical fertilizers in accordance with the chemical export on the yield, manure (20 t/ha) used in potato and sugarbeet. After 35 years of irrigation use the soil structure degree (38.62%) did not decrease when compared to the unirrigated maize – wheat crop rotation (37.01%). Bulk density, total porosity, penetration resistance and hydraulic conductivity have worse values than the ones in the unirrigated variant. The humus content is very close to the humus content determined in 1976, the phosphorus and the potassium content increased very much in comparison with the initial content (117 ppm vs 22.0 ppm); (180.0 ppm vs 102 ppm). The use of the adequate fertilization system and of the irrigation water with a good qaulity (SAR = 0.52; CSR = -1.7; pH = 7.2 did not determine a decrease of the pH value of the soil