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Water and Nitrogen Management of Young and Maturing Pomegranate Trees

Wang, D., Ayars, J. E., Tirado-Corbala, R., Makus, D., Phene, C. J., Phene, R.
Acta horticulturae 2015 no.1089 pp. 395-401
Mediterranean climate, Punica granatum, ammonium nitrate, field experimentation, flowering, harvesting, irrigation management, leaves, lysimeters, microirrigation, nitrogen, nitrogen content, orchards, pomegranates, rain, soil, soil sampling, summer, trees, California
Commercial production of pomegranate (Punica granatum L.) in California has increased in recent years and the planted area reached 12,148 ha in 2011. The majority of the pomegranate trees are grown in the southern San Joaquin Valley which has a Mediterranean climate with hot dry summers and insignificant rainfall, irrigation is the only source of water for crop growth. As a new emerging minor crop, water and fertilization requirements for young and maturing pomegranate trees are not well understood. The purpose of this project is to determine water and nitrogen requirements of a developing pomegranate crop and follow it until full production. A replicated field experiment is used with two irrigation treatments (surface and subsurface drip) and three nitrogen levels (low, medium, and high). The pomegranate orchard was established in 2010 with a density of 558 trees/ha. A weighing lysimeter is used for irrigation management of the young trees. Leaf and soil sampling are carried out periodically for nitrogen analysis. In 2011, the trees were irrigated and fertilized uniformly to ensure uniform plant development. The first year of production was 2012, and cumulative applied water was 456 mm for the surface drip and 441 mm for the subsurface drip treatment. Nitrogen was applied by continuous injection of urea-sulphuric acid (10% N) and ammonium nitrate (20% N) at 52, 166, 279 kg N/ha. Total nitrogen levels in leaf tissue showed a rapid decline during leaf out, started to recover slowly after flowering but did not fully recover prior to harvest. Soil nitrate concentrations showed a gradual decrease from surface to 50 cm depth then remained nearly constant to 120 cm depth. No yield difference was observed between the nitrogen levels, however, significantly higher yield and larger fruit size was found in the subsurface drip irrigation treatment.