Sorry, the document appears to be unavailable. Please contact the AER administrator.
Nitrogen, including 15N-labelled fertilizer nitrogen, in components of a grass sward.
A sward of perennial ryegrass cv. S23 grown during 1979-81 was treated on 20 April with 130 kg N/ha as ammonium nitrate doubly labelled with 15N, followed on 9 June and 21 July by unlabelled NH4NO3 at the same rate. Plots were unirrigated or were irrigated during early June-late July. Herbage was harvested on 4 successive occasions between 9 June and 20 Oct. Mean N conc. in plant components at the 4th harvest were herbage, 2.52%, stubble, 2.32%, dead leaf tiller 1.16%, roots 1.65%. Irrigation increased herbage yield at the 2nd harvest but had no effect on herbage N conc. Of the labelled fertilizer N, a mean of 47.6% was recovered in herbage at the 1st harvest, with only 5.3% recovered at the subsequent 3 harvests. Mean values for recovery in other components of the sward at the 4th harvest were stubble, 0.3%, dead leaf litter, 1.0%, roots 7.1%, and soil to a depth of 30 cm, 13.2%. Overall recovery of labelled fertilizer N in herbage, stubble, leaf litter, roots and soil was 74-75%. N losses may have resulted from leaching and/or denitrification.