A quantitative examination of the growth of swards of Medicago truncatula cv. Jemalong

Abstract

Shoot dry matter yield data for swards of Medicago truncatula cv. Jemalong established on two occasions at Adelaide in 1975 have been used to examine the influence of sowing rate on the seasonal growth pattern of this species.

The patterns of dry matter growth are assessed: (i) by the use of a logistic function; (ii) by a growth stage approach involving an initial phase of approximately exponential growth (stage I) followed by a phase of almost constant growth rate (stage II). Two methods are given for determining the duration of these stages. It was found that stage I1 began at a shoot dry weight of about 300 g m^-2, irrespective of sowing rate.

End-of-season yield at about 10 t ha^-1 was largely independent of sowing time and of sowing density. A maximum crop growth rate of 14.9 g m^-2 d^-1 was recorded for low density and late sowing. Sowing density had a marked effect on the shape of the growth curves; both the maximum crop growth rate and the average crop growth rate in stage II decreased with increase in sowing rate for each time of sowing.