Changes of lignin concentration and C:N in oilseed rape, wheat and clover residues during their decomposition in the soil

Z. Kriauciuniene², R. Velicka¹, S. Raudonius¹ and M. Rimkeviciene²

¹Department of Soil Management, Lithuanian University of Agriculture, Studentu 11,Akademija, LT-53361 Kaunas dist., Lithuania, e-mail: rimantas.velicka@lzuu.lt
²Experimental Station of Lithuanian University of Agriculture, Noreikiskės,LT-53363 Kaunas dist., Lithuania, e-mail: zita.kriauciuniene@lzuu.lt

Abstract:

Field experiments were conducted in 2003–2005 at the Experimental Station of the Lithuanian University of Agriculture to study the changes of lignin concentration and C:N in roots and top residues of winter and spring oilseed rape (Brassica napus L.), winter wheat (Triticum aestivum L.) and red clover (Trifolium pratense L.) after 14, 33, 63, 85 and 116 weeks of decomposition in the soil. Correlation between lignin concentration and amount of dry matter as well as the ratio of carbon and nitrogen in investigated crop residues were estimated.Investigation of crop residue decomposition during the period of 116 weeks showed thatstubble and roots of winter and spring oilseed rape decompose more slowly than their threshing remains, or stubble, and roots of winter wheat and red clover. Dry matter and lignin decomposed and the ratio of carbon and nitrogen in winter oilseed rape residues decreased more slowly than that of spring oilseed rape residues.The ratio of carbon and nitrogen in the decomposing crop residues decreased mostintensively during the 33–63 week period. After that, the concentration of lignin started to decrease, but its significant decline in all investigated crop residues was estimated after 116 weeks of decomposition. Lignin was most decomposed from its concentration peak in the stubble of red clover (37.9%) and least in winter oilseed rape roots (12.8%).Negative correlation between lignin concentration and dry matter amount and betweenlignin concentration and C:N was established in winter and spring oilseed rape, winter wheat and red clover top and root residues decomposing in the soil.

Key words:

Brassica napus, crop top and root residue, decomposition, dry matter, lignin, organic carbon and nitrogen ratio, Trifolium pratense., Triticum aestivum

Weed suppression by increasing spring rape crop density

A. Marcinkevičienė, S. Raudonius and R. Velička

Lithuanian University of Agriculture, Studentu 11, Akademija, Kaunas district, LT-53067,Lithuania, e-mail: lzuustotis@hotmail.com, steponas.raudonius@lzuu.lt

Abstract:

Field experiments were conducted in 2003 and 2004 at the Experimental Station of the Lithuanian University of Agriculture to study the influence of different spring rape (Brassica napus L.) densities (50.1–100, 100.1–150, 150.1–200, 200.1–250, 250.1–300, 300.1–350, 350.1–400, 400.1–450 plants m-2) on weed abundance. Increase of crop density and herewith increase of canopy should intensify the competition ability of spring rape plants and suppress weeds better. The results show that light intensity on the soil surface decreases when the assimilation area of spring rape leaves and total crop biomass increases. Weed density decreases when spring rape crop is densier. A significant negative relationship exists between weed biomass and spring rape leaf area index (LAI) (r = -0.62, P < 0.05), as well as between weed biomass and spring rape biomass (r = -0.67, P < 0.01). A significant positive correlation appears between weed abundance and light intensity on soil surface (r = 0.68, P < 0.01).

Key words: