To estimate the effects of biological measures – various catch crops in combination with different straw incorporation methods – on the reduction of soil physical degradation and nitrogen leaching complex, a research was conducted at the Lithuanian Institute of Agriculture Joniškelis Experimental Station on an Endocalcari–Endohypogleyic Cambisol during the period 2003–2005. Incorporation of straw and the biomass of catch crops, especially of white clover (Trifolium repens L.) and Italian ryegrass (Lolium multiflorum Lamk.) mixture, tended to improve soil physical state and decrease soil bulk density. Catch crops grown with undersown crops reduced soil moisture content, whereas surface loosening by stubble breaking tended to increase soil moisture. On incorporating straw, moisture content was found to be significantly higher (by 4.1%) compared with the control treament. Better soil moisture conditions, in the year of catch crop and straw incorporation aftereffect, were identified for barley in the treatments where catch crop biomass was incorporated in combination with straw.

In the autumn, with a high rainfall rate during the post-harvest period of primary crops, undersown red clover (Trifolium pratense L.) and a mixture of white clover (Trifolium repens L.) and Italian ryegrass (Lolium multiflorum Lamk.) reduced N_min. content in the soil as well as the risk of leaching by 10.9% and 13.1%, respectively, as compared with the treatment without catch crops. On the background of shallow incorporation of straw and mineral N45 incorporation intended to accelerate straw mineralization, white mustard (Sinapis alba L.) grown as a catch crop reduced N_min. content in the soil by 9.5%. In the year of aftereffect, in spring, after autumn-incorporated nitrogen-rich biomass of legumes grown as catch crops, and straw, N_min. content in the soil and lysimetric water significantly declined.

Keywords: clay loam, physical degradation of soil, nitrogen immobilisation, catch crops, nitrogen leaching