The crop rotation and the irrigation influence on soil fertility parameters and on the wheat yield in the Crisurilor plain condition.

The paper is based on the researches carried out in a long term trial placed in 1990 on the preluvosoil from Agricultural Research and Development Station Oradea. In comparison with unirrigated and irrigated wheat-monocrop, in wheat-maize crop rotation, structure degree increased with 10% and 13% and in the wheat-maize-soybean with 23% and 24%. In comparison with the bulk density registered in the wheat monocrop in the wheat-maize crop rotation the average value on the 0-20 cm depth decreased with 2.1% in unirrigated variant and with 1.3% in the irrigated variant; the differences registered in the wheat-maize-soybean were of 5.6% and 3.4%. As consequence, the values of the total porosity increased in comparison with the values registered in wheat monocrop; the values of the air porosity increased, too. Penetration rezistance had the smallest values in wheat-monocrop: 17.3 kgf/cm 2 and 19.5 kgf/cm 2 ; in wheat-maize crop rotation, the values of the penetration decreased and in the wheat-maize-soybean crop rotation were registered the smallest values. In these conditions, in comparison with the wheat monocrop variant, in the wheatmaize crop rotation, the values of the hydraulic conductivity increased with 16.3% in unirrigated conditions and with 20.2% in irrigated variat; in the wheat-maize-soybean crop rotation, the differences were bigger: 33.9% and 51.8%. All the years studied, the smallest values of the wheat yield were registered in the wheat-monocrop; the yield increased in the wheat-maize crop rotation and the biggest yields were registered in the with-maize-soybean crop rotation. The irrigation determined the yield gains very significant statistically every year studied.