Agriculture > Perennial Crop General Approach > Relative yield

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Relative yield

The relative yield is a ratio of the yield per tree divided by the tree's maximum yield (where 0 = no yield, and 1 = maximum yield and yield is represented in pounds/tree). By using relative yield, one can make direct comparisons in yield, irrespective of differing management styles, locations, etc.

For the purpose of the PIleus Project the yield function was used to estimate the impacts of weather and climate across
historical and projected future time frames. In the historical time frame (approximately 1900-2003), yields were estimated at eight sites across the Great Lakes region with observed daily temperatures and precipitation data. At most of the sites considered, relative yields were found to gradually increase with time, generally the result of more favorable weather conditions including lesser frequency of cold injury. These results were unexpected given a perception among growers that relative yields have decreased in recent years due to major spring freeze events such as the April, 2002 cold spell which destroyed a large portion of that year’s production. Our results suggest that losses due to spring freezes with significant yield losses (e.g. 1945) have occurred periodically throughout the past century, with no significant trends in frequency. Trends in the magnitude or severity of freezes over time were unclear.

One other significant trend noted across the study sites was an increase in late winter and early spring temperatures during the past approximately 30 years. This increase in temperature was associated with an earlier onset of the growing season, with early (estimated) tart cherry phenological stages at the most of the study sites tending to occur 7-10 days earlier than they did during the 1960’s and 1970’s.


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