Field investigation of temperature patterns within Oklahoma peach orchards

In Oklahoma the most limiting factor in peach production is the weather - in particular, untimely spring freezes. During the 1990s there were 4 years out of 10 where such freezes resulted in production at or below 8 million pounds. During good years such as 1991 and 1995, production can equal or exceed 30 million pounds. During the 1980 to 1999 period, there were 11 years out of 20 with peach production under 10 million pounds. Thus, the chances of having a "good" or even "average" year for peach production in Oklahoma are less than 50/50. The difficulty in growing peaches due to spring freezes has led to a large decrease in the number of peach trees within Oklahoma from 190,583 trees in 1987 to 82,473 trees in 1997. As of 1997, there were 1244 acres of peaches in the state, with the two largest concentrations being located in the Stratford area (34% of the peach trees) and in the Porter area (21% of the peach trees).

Earlier this year, a multi-year research project was begun to (1) investigate the meteorology within peach orchards in comparison with weather conditions at nearby Oklahoma Mesonet weather monitoring stations, whose data are readily available in near-real-time over the World Wide Web, and to (2) investigate the effectiveness of various freeze protection measures that might help Oklahoma growers ward off spring freeze damage.

With respect to Objective One, it is important, both for real-time freeze protection measures and for models based on weather data, to know how weather conditions being observed at a nearby Mesonet tower relate to those conditions within and above a peach tree canopy in a nearby orchard. For this research focus, three orchard locations near Porter, Oklahoma and two orchard locations near Stratford have been chosen. In each orchard, in a location between two peach trees within a row, we have installed a modified Campbell Scientific weather station (CR10X datalogger) to measure temperatures (15-minute average data) at the 6.5 m level (well above the canopy), at the standard 1.5 m level, and within the tree canopy itself at tree-top, mid- tree, and bottom-tree levels. In addition, relative humidity is measured at 1.5 m, and solar radiation and precipitation are recorded above the tree canopy. Results comparing temperatures and inversion conditions at these sites with conditions at nearby Mesonet towers will be presented, especially for those nights below freezing.

Objective Two, for the first year of this study, will be investigated at one of the three orchards near Porter. A portable oscillating "wind machine" has been purchased and will be tested for its efficacy with the aid of 20+ specially placed Hobo temperature dataloggers within and outside the peach tree block to be tested. Experiments will be conducted during the winter/spring period during nights with inversion conditions and results will be presented at the conference. This device is a most promising freeze protection option for Oklahoma growers, as it only costs about $10,000, is portable, and runs off a 50-80 horsepower tractor.