Critical plant and leaf N concentrations of an ageing timothy sward
Quantifying the level of N nutrition of grass swards requires the definition of a critical concentration, that is the minimum N concentration required to achieve maximum shoot growth.The critical plant N concentration Nc ; g kg‐1 dry matter (DM) of a tall fescue sward was first defined as a function of shoot biomass (SB ; t DM ha‐1 ) (Nc ＝ 48.0 × SB‐0.32 ) by Lemaire and Salette (1984) ; this was later validated for timothy by B langer and Richards (1997 ).The N nutrition index ( NNI) is calculated by dividing the observed N concentration by Nc.The NNI was then successfully related to the leaf N concentration of the upper sward layer Leaf N ＝ 4.0 ＋ (37.9 × NNI) ; Gastal et al., 2001) , hence making it possible to establish the N nutrition index by simply analyzing leaf N concentration.These models of critical plant and leaf N concentrations were determined on young swards ( ＜ 3 years).Our objective was to determine the critical plant and leaf N concentrations of older timothy ( Phleum p ratense L.) swards.
Phleum p ratense nitrogen N nutrition index model
G.Bélanger G.F.Tremblay
Agriculture and Agri-Food Canada,2560 Hochelaga Blvd.,Quebec,Canada GIV 2 J3
国际会议
呼和浩特
英文
2008-06-29（万方平台首次上网日期，不代表论文的发表时间）