Location: Water Management ResearchTitle: Biophysical response of young pomegranate trees to surface and sub-surface drip irrigation and deficit irrigation Author
Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2017
Publication Date: 7/6/2017
Citation: Zhang, H., Wang, D., Ayars, J.E., Phene, C.J. 2017. Biophysical response of young pomegranate trees to surface and sub-surface drip irrigation and deficit irrigation. Irrigation Science. 35(5):425-435. https://doi.org/10.1007/s00271-017-0551-y.
DOI: https://doi.org/10.1007/s00271-017-0551-y Interpretive Summary: Pomegranate has recently been recognized for its human nutritional benefits resulting in an increase in production around the world. In general, pomegranate is regarded as a drought tolerant crop. However, limited literature is available on its response to water requirements and types of irrigation systems under commercial conditions. A two-year field study was carried out to characterize crop response to surface and sub-surface drip irrigation and deficit irrigation treatments in two different orchards. Trees receiving less water had higher canopy temperatures than those receiving more irrigation. Tree size was found to correlate with vegetation index and strong correlations were developed to determine crop coefficient. The relationships can be used by farmers and water managers for irrigation management of pomegranate production.
Technical Abstract: Due to recurring agricultural water shortages, many farmers are looking for crops that have both some degree of drought resistance and a higher economic value. Pomegranate has been identified as a crop with potential drought tolerance, and high economic values. To manage limited water effectively, it is necessary to know how pomegranate trees respond to varying levels of applied water and the type of irrigation system used. This study was conducted in experimental orchards located at the University of California Kearney Agricultural Research and Extension (UC KARE) Center and the USDA-ARS San Joaquin Valley Agricultural Sciences Center in Parlier, California. The impact of surface drip (DI) and subsurface drip irrigation (SDI) at the UC KARE orchard and irrigation levels (35, 50, 75, 100% of crop water use) at the USDA-ARS orchard on canopy ground cover (fc), normalized difference vegetation index (NDVI), normalized difference infrared index (NDII), canopy-to-air temperature, and fruit yield were determined during the 2012-2014 growing seasons. There was no difference in tree canopy size between the DI and SDI systems at the UC KARE site; but trees under SDI produced significantly more fruit while saving 10% of water use. At the USDA-ARS site, the 35 and 50% deficit irrigation treatments significantly reduced tree canopy size in 2013 and 2014, compared to the 75 and 100% irrigation treatments. Trees irrigated with 75% of crop water use produced more fruits than trees receiving 35% irrigation. Furthermore, NDVI and NDII were correlated to fc. The relationships between NDVI to fc and fc to crop coefficient have been established and can be used as a potential tool by farmers and water managers to estimate pomegranate tree water use on a field or regional scale using aerial or satellite imagery.