N in Crop and Crop Residues of Clover/Grass S20
Loges, R. ; Kornher, A. & Taube, F.
Institute of Crop Science and Plant Breeding, Department of Grass and Forage Science, Christian-Albrechts-University, D-24098 Kiel
|In temperate regions, symbiotically fixed
nitrogen accumulated by red clover/grass mixtures is the main nitrogen source for organic
farming systems. Clover/grass supplies nitrogen to a crop rotation either directly by
harvest residues (such as roots and stubble) or indirectly by the forage yield (after
feeding, fertilized as manure variable later in the croprotation).
The aim of the present investigation was to determine the amount of nitrogen obtained through nitrogen fixation and to follow its pathways into forage yield, harvest residues, soil-N and the yield formation of the following crop.
In a field experiment, different red clover/grass swards with different companion grasses (Lolium multiflorum/high competitive and Lolium perenne/low competitive) -with four seeding rates (0, 33, 67, 100% clover) for each companion grass - were established at four different seeding dates (autumn 1993 and 1994, spring 1994 and 1995) and examined in 1994 and 1995.The field trial was carried out without any nitrogen fertilization on a sandy, loamy cambisol near Kiel in Northern Germany. The swards were cut four times each year. In addition all mixtures were investigated in 1995 as one year green manure. The monitoring of yield formation and of the soil nitrogen dynamics of clover/grass is based on weekly sward and soil samples. The N-amount in harvest residues was determined in root and stubble samples gathered after the last cut in autumn.
The results show a high significant influence of seeding rate, companion grass species, age of ley, and form of management on clover content, dry matter and nitrogen yields and on organic matter and nitrogen in stubbles and roots, while there was no influence on light mineralizable and mineral soil-N-content during the clover/ grass period.
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