Location: Water Management ResearchTitle: Water and nitrogen management of young and maturing pomegranate trees Author
Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 7/31/2013
Publication Date: 7/28/2015
Citation: Wang, D., Phene, C., Phene, R., Ayars, J.E., Tirado-Corbala, R., Makus, D.J. 2015. Water and nitrogen management of young and maturing pomegranate trees. Acta Horticulturae. 1089:395-401. Interpretive Summary: The rising demand for juices with healthy bioactive compounds, mineral nutrients, and high antioxidant contents has led to recent increase in pomegranate acreage. However, the water and nitrogen fertilization requirements of growing pomegranate trees are lacking. We initiated a field trial with the primary focus on determining the water and nitrogen requirements of pomegranate trees. Water requirement was determined with a weighing lysimeter and three levels of nitrogen (low, medium, and high) were used. We found that the average cumulative volume of irrigation water required by the pomegranate tree was 53 liter per tree per day. We also found that total leaf tissue nitrogen content was high in the spring, then showed a sharp decline during leaf out and early flowering stages. Season total pomegranate yield was 22 metric ton per hectare which is comparable to the industry average. No yield and fruit size differences were observed between the three nitrogen levels. Continued monitoring for the same treatment effects will be needed to validate the findings.
Technical Abstract: Commercial production of pomegranate in California has increased drastically in recent years and the planted area reached 12,148 ha in 2011. A majority of the pomegranate trees are grown in the southern San Joaquin Valley which has a Mediterranean climate with hot dry summers and no rainfall, and 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 was to determine water and nitrogen requirements of a developing pomegranate crop and follow it until full production. A replicated field experiment was 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 was used for irrigation management of the young trees. Leaf and soil sampling was 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, and 279 kg N/ha. Total nitrogen levels in leaf tissue showed a rapid decline during leaf out, and 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 and 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