Carbon distribution and variations in nitrogen-uptake between catch crop species in pot experiments

Chicory (Cichorium intybus L.) and perennial ryegrass (Lolium perenne L.) are seen as suitable catch crops species in Sweden. Pot experiments were conducted to study C distribution and variations in nitrogen uptake between several varieties of chicory and perennial ryegrass for comparison.A soil amended with Ca(¹⁵NO₃) (109 and 145 mg N kg⁻¹ soil) and glucose (2.5 g C kg⁻¹ soil) was incubated for 10 days to promote the immobilization of added ¹⁵N; therefore, N was supplied to plants through the remineralization of the immobilized ¹⁵N. In experiment 1 four varieties of chicory and one variety of perennial ryegrass were grown for 60 days in greenhouse conditions. In experiment 2, only two varieties of chicory and one ryegrass were grown in soil with high-N rate of fertilization. In the later experiment, pots were moved from greenhouse to a growth chamber with ¹⁴CO₂ atmosphere for a pulse labelling of the plants 7–10 days before harvest.At both levels of N supply, dry weights of taproots were higher in the chicory cultivars Cassel and Fredonia than in cultivars Puna and Salsa. The opposite was found for dry weights of small roots. There were significant differences in N uptake between chicory varieties. Cassel and Fredonia together with the ryegrass were significantly more effective in securing nitrate than the other two varieties. Significantly higher amounts of labelled-N were found in taproots of Cassel than in Puna. The opposite trend was found for small roots. Similar results were measured for amounts of radioactivity (kBq pot⁻¹) of newly fixed C transferred to roots. Amounts of labelled-N measured in soil residues for both crop species were significantly higher at the low level of N supply than at the high level of N. There was no significant increase in plant uptake of soil-N (native-N) either between chicory varieties or between chicory and ryegrass, when the high level of N was supplied.The importance of these results is discussed in relation to the suitability of chicory species as catch crop and as plant material for breeding.