The influence of reduced tillage, winter crops and ecologically managed long-term mono- and multi-component swards on soil humic substances

Abstract

Chemical analyses of soil humic substances were performed at the Chemical Research Laboratory of the LIA. A field experiment (Experiment 1) was established on a glacio-lacustrine clay loam on a silty clay Endocalcari–Endohypogleyic Cambisol. The study investigated two soil tillage systems: conventional (CT) and reduced (RT). The study also encompassed crop rotations with different structures: 0, 25, 50, 75 and 100% winter crops in a crop rotation. Experiment 2 compared the influence of long-term legume swards on soil humic substances in an Epicalcari–Endohypogleic Cambisol. The swards were used for five years under ecological management. No fertilisers or pesticides were used. There were 2.6 times more labile humic acids (HA) in the topsoil in RT compared with CT. A significant effect on the increase of labile HA content was determined in crop rotations with≥50% winter crops. The highest amount of mobile HA accumulated in soil under a four-component sward (Galega+Trifolium repens+Onobrychis+Festulolium). Reduced soil use resulted in qualitative changes in HA determined by Fourier transform infrared (FT-IR) spectroscopy. The analytical methods used are appropriate for evaluating sensitivity to changes in soil management and are helpful for the development of reduced soil use systems. However, labile and mobile carbon pools are more sensitive than humus.

Keywords:

• soil
• humus
• mobile HS
• labile HS
• FT-IR
• reduced tillage
• winter crops
• swards
• ecological management

Acknowledgements

We gratefully acknowledge financial assistance of the Lithuanian Foundation for Science. Many thanks to Prof. Michael A. Fullen from the University of Wolverhampton (UK) for scientific comments and suggestions to improve the English in this paper.