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Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/15/2013 Publication Date: 8/13/2013 Citation: Zhang, H., Wang, D. 2013. Management of postharvest deficit irrigation of peach trees using infrared canopy temperature. Vadose Zone Journal. 12(3):doi:10.2136/vzj2012.0093. Interpretive Summary: The San Joaquin Valley, one of the major peach growing regions in California, is a semi-arid area. Water supply for irrigation has decreased in recent years due to competition for water demands between residential, industrial, environmental and agricultural usages. It is necessary, therefore, to find management methods to optimize the usage for the limited supply of irrigation water. For early-maturing peach varieties, it has been demonstrated that established peach trees are not sensitive to moderate water stress under deficit irrigation method (i.e., applying less than the full amount) in the non-fruit bearing postharvest growth. However, the margin of error in irrigation management gets more critical. In a three year field study, real time peach tree water stress was monitored using infrared temperature sensors and the information was used to control irrigation management. The field study demonstrated the potential feasibility of managing postharvest deficit irrigation of early season peach trees using infrared canopy temperature measurement. The postharvest deficit irrigation control was reasonably successful with potential water savings of up to 53%. Due to the year to year variability in yield, additional field experimentation is needed to assess the canopy temperature based method for irrigation scheduling. Technical Abstract: Remotely-sensed canopy temperature from infrared thermometer (IRT) sensors has long been shown effective for detecting plant water stress, a vadose zone problem for growing plants. To help alleviate water shortage in the San Joaquin Valley of California, deficit irrigation may be used where the target plants will receive less than full irrigations and come under water stress at certain growth stages, and new irrigation scheduling procedures need to be developed. A field study was conducted from 2009 to 2011 to evaluate the performance of using midday infrared canopy to air temperature difference ('T) to manage postharvest deficit irrigation of early season peach trees. Threshold values of 'T were selected, based on previous years’ stem water potential and 'T measurements, for four irrigation treatments: furrow and surface drip irrigation with or without postharvest water stress. A wired network of 12 IRT sensors was installed in the orchard, above the tree tops, for canopy temperature measurement. Soil water content and stem water potential were also monitored weekly for each treatment. In both growing seasons (2009-2010 and 2010-2011), the measured 'T values showed consistent differences among treatments, which correlated to both soil water content (R2 ˜ 0.47-0.53) and stem water potential readings (R2 ˜ 0.46-0.65). The relationship between fruit weight and postharvest irrigation amount indicated that up to 53% water savings could be achieved without impacting fruit size. The study demonstrated that infrared canopy temperature measured from above the tree top can potentially be used for managing deficit irrigation in peach and possibly other tree crops. Additional research is needed to further validate this approach. |
