EFFECT OF UNDERSOWN CATCH CROPS CULTIVATED IN CONVENTIONAL AND ORGANIC FARMING SYSTEMS ON THE MINERAL NITROGEN CONTENT OF SOIL DETERMINED IN AUTUMN AND SPRING

摘要

The aim of the studies performed in 2007-2010 was the determination of the effects of undersown catch crops on the mineral nitrogen content concerning to both, conventional or organic fanning systems. The undersown catch crops were incorporated with a plough in autumn, or were left on the soil surface as mulch. The content of mineral nitrogen in the soil profile was determined in autumn and spring. A field experiment was set up at the Zawady Experimental Farm of the Siedlce University of Natural Sciences and Humanities, and 2 factors were examined. Factor I: undersown catch crop: control (without), autumn-incorporated biomass (serradella, Westerwold ryegrass) and bio-mass left on the soil surface as a mulch until spring (serradella, Westerwold ryegrass); factor II: farming system: conventional and organic. Ammonium and nitrate contents were determined twice (in autumn and spring) in 2 soil strata (0-30 and 31-60 cm). The obtained results have demonstrated that the cultivation of under-sown catch crops leads to reduction of mineral nitrogen content in the soil in autumn but increases it in spring. Mineral nitrogen contents in the soil profiles determined both in spring and autumn were significantly higher in conventional than in organic farming system. Undersown catch crops which remained on the soil surface as mulch till spring significantly reduced the soil mineral nitrogen content in spring compared with the autumn-incorporated under-sown catch crops.