Harvest index increase during seed growth of field pea

Harvest index during seed growth has been reported to increase linearly with time for many crop species. Although the rate of harvest index increase was generally stable across experiments within a species, there are indications that it is sensitive to variations in temperature. The objective of the present study was to compare the harvest index increase for field pea (Pisum sativum L.) across 31 experiments that included a wide range of temperature environments. The change in harvest index within each experiment was well described by a linear increase with time but there was considerable variability among experiments. The increase in harvest index was also calculated as a function of thermal time after flowering. The variability was only marginally reduced. Use of thermal time was, however, superior in identifying a common point for the initiation of seed growth among the experiments.