THE INFLUENCE OF CROP ROTATION, CATCH CROP AND MANURE ON SOIL ENZYME ACTIVITIES IN ORGANIC FARMING

A field experiment was carried Out in an organic certified field of the Experimental Station of the Lithuanian University of Agriculture during 2003-2008 on a Calc(ar)i Epihypogleyic Luvisol (LVg-p-w-cc). Factor A of the experiment - crop rotations with a different ratio of nitrogen fixing crops: I - 43% (grass-clover -> grass-clover -> winter wheat -> spring barley -> peas -> winter wheat -> spring barley), II - 43% (grass-clover -> winter wheat -> peas -> spring barley -> grass-clover -> winter wheat -> spring barley), III - 29% (grass-clover -> potato -> oat -> spring barley -> peas -> winter wheat -> spring barley), IV - 14% (grass-clover -> winter wheat -> potato -> spring barley -> winter rape -> winter wheat -> spring barley). Factor B - catch crop: 1) without catch crop, 2) with catch crop. Factor C - farmyard manure: 1) without farmyard manure, 2) with farmyard manure. The objective of this investigation was to determine the influence of crop rotation, catch crop for green manure and farmyard manure on soil enzyme (urease and saccharase) activities in organic farming. The highest activity of urease and saccharase in 2007 was in the soil in the crop rotation, where perennial grasses and peas had been grown. The activity of urease increased from 14.3 to 60.0% and that of saccharase from 14.8 to 28.3%, compared to the other crop rotations. In the crop rotation with 14% of nitrogen fixing crops, the catch crop increased the activity of urease by 100% and the activity of saccharase by 43.6% in the soil, compared to the treatments without catch crop. Farmyard manure 30 Mg ha(-1) significantly stimulated the activity of soil urease in 2008, while the activity of saccharase was not significantly influenced. Crop rotation and catch crop for green manure had no significant effect on soil hydrolase activity. The activity of soil urease directly depended on total nitrogen (r = 0.50, P < 0.05), mineral nitrogen (r = 0.50, P < 0.05), organic carbon 0.56, P < 0.05), and content of potassium (r = 0.59, P < 0.05).