Split nitrogen application strategies in seed production of two contrasting cultivars of timothy (Phleum pratense L.)
Title:
Split nitrogen application strategies in seed production of two contrasting cultivars of timothy (Phleum pratense L.)
Author:
Havstad, L. T. Aamlid, T. S.
Appeared in:
Acta agriculturae Scandinavica. Section B, Soil and plant science
Paging:
Volume 56 (2006) nr. 4 pages 241-254
Year:
2006-12-01
Contents:
Split nitrogen (N) application to seed crops of timothy (Phleum pratense L.) was evaluated in 20 field trials, 11 in the south-Norwegian cultivar 'Grindstad' (origin 59°N) and nine in the north Norwegian cultivar 'Vega' (origin 67°N) in southeast (58-61°N) and central (63-64°N) Norway during 1998-2000. Three N rates (25, 50 or 75 kg N ha-1) at the start of growth were combined with four N rates (0, 25, 50 or 75 kg N ha-1) at the start of tiller elongation (Z 31). On average for all trials, the highest seed yield was obtained when a total rate of 75 kg N ha-1 was split into a main application of 50 kg N ha-1 at the start of growth and a supplemental application of 25 kg N ha-1 at Z 31. In both cultivars, the optimal N rate at Z 31 was uncorrelated with soil mineral N (NO3+NH4) in early spring and only weakly correlated (r2=0.16-0.17, p% = 2-5) with the N concentration of aboveground plant material at Z 31. In 'Grindstad', a better correlation (r2=0.46, p% < 0.1) was obtained between the optimal N rate at Z 31 and measurements by the hand-held chlorophyll meter Hydro N-Tester™ on the last fully developed leaf. The equation (HTN model) Optimal N input (kg N ha-1) at Z 31 = - 0.37×measured HNT value at Z 31+156 was further evaluated in ten on-farm trials during 2001-2002. Compared to the fixed N levels 0, 25 or 50 kg N ha-1, the HNT model predicted optimal N rates at Z 31 in 2002, but not in 2001, when less rainfall caused less lodging than in 1998-2000 and 2002. Nevertheless, we conclude: 1) that the spring N rates to timothy seed crops should be split into an early and a late application, and 2) that the HTN model will help in adjusting the second N rate at Z 31 in 'Grindstad'.
Journal description