Modelling Phenological Development of Regrowth Lucerne (Medicago sativa L.) Using APSIMX

Xiumei Yang1, Hung T. Ta1, Hamish E. Brown2, Edmar I. Teixeira2, José M. Jáuregui3, Derrick J. Moot1

1Agriculture and Life Sciences Department, Lincoln University, Canterbury, Lincoln 7647, New Zealand, PO Box 85804,,

2 The New Zealand Institute for Plant and Food Research Ltd., Private Bag 4604, Christchurch, New Zealand

3Animal Production Department, National University of Litoral, Kreder 2805, Esperanza (3080), Santa Fe, Argentina


Predicting lucerne phenological development is important for optimising defoliation scheduling and other management events. This study provides a simple framework to quantify the phenological response of a semi-dormant (fall dormancy 5; FD5) lucerne to environmental factors. This response was used to create algorithms for the APSIMX model, which was verified using two different fall dormancy classes (dormant FD2 and non-dormant FD10). The framework includes lucerne node appearance, height, and flowering in response to temperature and photoperiod (Pp). An evaluation of methods for calculating thermal time (Tt) indicated that the “Moot model” to define cardinal temperature most accurately computed Tt. A Tb (base temperature) of 1˚C had the lowest CV% and highest P value. In the vegetative phase, the phyllochron increased from 23 to 45˚Cd/primary leaf as Pp decreased from 16 to 12.5 h; the “heightchron” and mean Pp displayed a poor polynomial relationship (R2=0.44). In the reproductive phase, the phyllochron was consistent across Pp at 68˚Cd/primary leaf and the crop had a longer “heightchron” than in the vegetative stage. Tt to 50% bud initiation decreased as Pp increased. There was close agreement between predicted and observed values of node number and time to 50% bud initiation across genotypes.


The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

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David Marland Photography Graham Centre for Agricultural Innovation, Charles Sturt University

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