Premium
Improvement of Time‐Driven Models of Lamina Cocksfoot Digestibility by a Process‐Based Model to Take Account of Plant N Nutrition and Defoliation
Author(s) -
Duru M.
Publication year - 2008
Publication title -
journal of agronomy and crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.095
H-Index - 74
eISSN - 1439-037X
pISSN - 0931-2250
DOI - 10.1111/j.1439-037x.2008.00331.x
Subject(s) - lamina , tiller (botany) , nitrogen , residual , yield (engineering) , mathematics , complement (music) , agronomy , fertilizer , biology , botany , chemistry , physics , biochemistry , organic chemistry , algorithm , complementation , gene , phenotype , thermodynamics
For management purposes, models of lamina digestibility (D W ) that are thermal time driven (T sum ) fail to account for plant nitrogen status (0 < Ni < 1) and defoliation intensity (residual sheath height: S r ). The objective of this paper was to enrich them using a functional processed‐based model, which assumes that the decline in D W over time depends on the metabolic : structural tissue ratio and plant ageing. An experiment combining two N fertilizer rates and two defoliation regimes (differences in S r ) for two spring and two summer regrowth was done to analyse D W of laminae (youngest fully expanded) and tiller (whole green lamina) levels. For laminae, we show that both processes contribute to explain the decline in D W at a rate that depends on Ni but not on S r . For tillers, consistent results were found justifying the use of a simple model: D W = f(+Ni; −Ni × T sum ; −S r ). Two different databases (from experiment and commercial farms) were used for validation: RMSD varied from 35 to 49 g kg −1 . The process‐based model strengthened the empirical model and improved the comprehensiveness of how management practices change D W. We used both models to create applications for reasoning yield in function of herbage mass in complement than in function of time.