Timothy yield and nutritive value under climate change in Canada

Timothy (Phleum pratense L.) is a dominant forage grass in Canada but its performance under projected future climate conditions has not been evaluated. This study combined the grass model CATIMO (Canadian Timothy Model) with baseline (1961-1990) and projected future (2040-2069) climate scenarios to assess the response of timothy to climate change at 10 sites across Canada. Projected future conditions are expected to have the following effects on timothy: (i) earlier growth onset (10-site average: -21 d; range: -4 to -40 d), date of first harvest (-15 d; -11 to -25 d), and date of second harvest (-20 d; -17 to -29 d), along with a later end to the growing season (+12 d; 0 to +18 d); (ii) increased dry matter (DM) yield at first harvest (+355 kg ha-1; -917 to +826 kg ha-1) but decreased DM yield at second harvest (-427 kg ha-1; +47 to -936 kg ha-1); (iii) increased neutral detergent fiber (NDF) concentration at first harvest (+22 g kg-1 DM; -22 to +94 g kg-1 DM) but a small decrease (-3 g kg-1 DM; +7 to -30 g kg-1 DM) at second harvest; and (iv) decreased NDF digestibility at first harvest (-6 g kg-1 NDF; +7 to -30 g kg-1 NDF) and second harvest (-23 g kg-1 NDF; -11 to -35 g kg-1 NDF). The longer growing season (+581°C-d to +1219°C-d) is expected to result in an additional harvest by 2040 to 2069. © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.