Long-term effect of tillage systems, straw and green manure combinations on soil organic matter

Continuous straw application increased the quantity of mobile humus substances by 22.7% compared to the plots without straw. Straw in combination with catch crop for green manure incorporation and rotovating and no-tillage increased mobile humus substances by 53.2% and 58.8% compared with conventional ploughing. Only long-term application of straw increased the quantity of mobile humic acids by 40.6% compared with the plots without straw. The rate of mobile humic acids from total amount of mobile humus substances in the treatments without straw amounted to 39.8%, while with straw this content increased to 45.6%. Reduced tillage systems without primary tillage had no significant effect on mobile humic acids but tended to increase soil organic matter quality.