Uptake and above- and below-ground allocation of soil mineral-N and fertilizer-15N in a perennial grass ley (Festuca pratensis).
A perennial Festuca pratensis ley was grown during 3 years in a field experiment at Kjettslinge, Sweden. N uptake, defined as the flow of N into the crop during one growing season, was estimated from frequent sampling of aboveground and belowground plant parts during the 2nd and 3rd year. Total N content was determined in living and dead plant parts. If calculated from significant increases of N in the whole crop, N uptake in 1982 was 33 g/m2, of which 23 g/m2 was removed at harvest. If N in roots dying during the growing season was included, total annual N uptake was 38 g/m2. In a 2nd experiment the uptake of fertilizer N and soil mineral N using 15N-labelled fertilizer in small enclosed plots was examined. 92% of the applied fertilizer N (20 g N/m2) was recovered in the crop during 1982. The rest of the fertilizer N passed through the crop and was recovered in the belowground dead organic material. Results indicated that all applied fertilizer N as well as an additional 18 g/m2 from the soil mineral N pool was taken up.