Effect of varying evaporative demand on the relationship between actual and potential evapotranspiration at different soil moisture deficits in potato (Solanum tuberosum) crops

摘要

A series of close relationships were established in four cultivars of potatoes between the ratio of actual (AE) : potential (PE) evapotranspiration (ET) and soil moisture deficit (SMD) for different daily ET rates from experiments conducted on sandy loam soils at Cambridge University Farm over the period 1989-93. These showed that there was a limiting SMD at which the ratio of AE : PE decreased rapidly with increasing SMD and this limiting SMD was inversely related to daily ET rate. However, even atsmall SMDs, as daily ET rate increased there was a significant, slow decrease in AE : PE ratio. In order to maintain potential ET rates in conditions of high and extreme demand in the UK (e.g. 5-7 mm day~1), crops need to be maintained at < 25 mm SMD butallowable SMDs can be increased as demand moderates. Irrigation scheduling needs to take account of these findings in order to avoid under- or over-irrigating crops when ET demand is high.