Quantifying the average soil temperatures for a light and heavy soil type in the main apple production areas for application in the apple rootstock trial

Minimum soil temperatures are important at the beginning of the season, with the onset of root growth. In December, two months after full bloom, minimum temperatures in 5 to 10 cm were as low as 10 °C in some areas, which will be a disadvantage for active root growth if it persists for an exists for an extended period.  Average monthly maximum soil temperatures in the top 5 – 10cm for all areas in 2009/10 varied between 22 and 28 °C, except in the Elgin area, where temperatures of 30 °C were experienced. However, this includes spikes of more than 30°C. This temperature range can also influence root development on the long term, although it did not persist during this season (personal observation). The perception that local soils are not suitable for rootstocks from the Cornell Geneva breeding program due to consistently too high temperatures (> 35 ° for extended periods in the top 40 cm) in areas with proper water management, seems unfound for the selected sites in this study.  The data is however only reflecting one season’s temperatures and does not reflect long term trends.