Premium
Simulating the Nutritive Value of Timothy Summer Regrowth
Author(s) -
Jing Qi,
Bélanger Gilles,
Baron Vern,
Bonesmo Helge,
Virkajärvi Perttu
Publication year - 2013
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2012.0331
Subject(s) - forage , dry matter , zoology , agronomy , neutral detergent fiber , phleum , winter wheat , environmental science , mathematics , biology
The process‐based grass model, CATIMO, simulates the spring growth and nutritive value of timothy ( Phleum pratense L.), a forage species widely grown in Scandinavia and Canada, but the nutritive value of the summer regrowth has never been simulated. Our objective was to improve CATIMO for simulating the N concentration, neutral detergent fiber (NDF), in vitro digestibility of NDF (dNDF), and in vitro true digestibility of dry matter (IVTD) of summer regrowth. Daily changes in summer regrowth nutritive value were simulated by modifying key crop parameters that differed from spring growth. More specifically, the partitioning fraction to leaf blades was increased to increase the leaf‐to‐weight ratio, and daily changes in NDF and dNDF of leaf blades and stems were reduced. The modified CATIMO model was evaluated with data from four independent experiments in eastern and western Canada and Finland. The model performed better for eastern Canada than for the other locations, but the nutritive value attributes of the summer regrowth across locations (range of normalized RMSE = 8–25%, slope < 0.17, R 2 < 0.10) were not simulated as well as those of the spring growth (range of normalized RMSE = 4–16%, 0.85 < slope < 1.07, R 2 > 0.61). These modeling results highlight knowledge gaps in timothy summer regrowth and prospective research directions: improved knowledge of factors controlling the nutritive value of the timothy summer regrowth and experimental measurements of leaf‐to‐weight ratio and of the nutritive value of leaves and stems.