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Forskningsartikel2007Vetenskapligt granskad

Modelling carbon dynamics in mixed grass-red clover swards

Torssell B, Eckersten H, Kornher A, Nyman P, Bostrom U


Growth and carbon dynamics in mixed grass-red clover leys were simulated using a growth model for pure stands based oil radiation use, allocation within plant and loss of biomass. The model and its parameter values were taken from previous applications of the model to pure swards of grass and red clover grown in the same experiment at the same sites and years. The field data used comprised above-ground dry matter production and proportion of clover in a mixture of red clover (Trifolium pratense L.), timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis Huds.) in two seasonal growth cycles during two consecutive years, sampled at six sites in Central and Southern Sweden. On average for all fields, the proportion of clover decreased with increased nitrogen application. It increased from the first to the second cut, but decreased from the first to the second year. The model most often underestimated above-ground biomass when using proportion of clover and estimates of radiation use efficiency (epsilon) and root allocation fraction (b(r)) from values in the pure stands (Method 1). This discrepancy suggested that epsilon might be higher for the mixed stand than the pure stands. Values of e and br for the mixed stands were therefore derived by calibration to the observed above-ground biomass (Method 2). The radiation use efficiency (epsilon) of the mixed stand was on average 6% higher than estimates of epsilon from pure stand values and proportion of clover. Overall, the variation in radiation use efficiency of mixed stands due to cutting and year was similar to that of pure stands of grass and clover, whereas the relationship to N treatment was weak and more similar to that of clover. The explanation that variations in biomass production were due to changes in root allocation seems reasonable. No variations in radiation use efficiency or root allocation fraction could be related to the proportion of clover. The variations due to cutting and year overwhelmed any such effect. (C) 2006 Elsevier Ltd. All rights reserved

Publicerad i

Agricultural Systems
2007, Volym: 94, nummer: 2, sidor: 273-280 Utgivare: ELSEVIER SCI LTD