Exploration of sub-field microclimates and winter temperatures: Implications for precision agriculture

The field of precision agriculture has brought the concept for "big data" to farming by bringing sensor technology into the field allowing growers to make more efficient management decisions. However much of the research and practice of precision agriculture has focused on soil-related issues while sub-field microclimates have been mostly unstudied despite their known importance to crop production. This study sought to explore the differences in temperature at a sub-field level during an entire season using weather microsensors recording data every minute from 11 Dec 2017 to 11 Apr 2018. Twenty-two cost-effective sensors were placed within a ~ .5 ha area satsuma orange (Citrus unshiu) grove along the Gulf Coast on Baldwin County, Alabama. The sensors were placed in aerated housings in a vertical column on the west face of eleven trees at a height of 1 and 2 m off the ground. We focus on several events where temperatures hovered near 0 °C or near - 7 °C, a temperature known to damage satsuma trees and find that temperatures can vary by as much as 1.5 to 2 °C at the same moment in the same grove. Extreme cold events were also found to be non-uniform within the grove, and the response was seen on a tree-by-tree basis where increased exposure to < - 7 °C temperatures led to increase defoliation (r² = 0.92) and lower fruit count in the following year (r² = 0.71). We discuss the implication of these differences in temperature and what it may mean for the future of precision agriculture.