1a.Objectives (from AD-416):
Determine real time seasonal N requirements of drip irrigated pomegranates. Determine the effect of three nitrogen injection rates on the N leaching loss.
1b.Approach (from AD-416):
A field experiment will be conducted on 3.3 acres of land with 3 levels of N injection with surface and subsurface. The effects on tree development and fruit quality will be measured.
This project supports research under objective 2 of the in-house project, Developing sustainable water management strategies. Nutrition and irrigation are critical components of sustainable management. This research quantifies the nitrogen requirements for pomegranate. The University of California assists in the management of the pomegranate field, the harvest of the fruit and the required fertilization and pruning through this cooperative agreement. Additionally, the University provides access to the large weighing lysimeter located in the field that is critical for the successful operation of the project. This is the third year of the project that is evaluating the nutrient requirements for maturing pomegranate and quantifying the crop water use. The first 2 years were used to establish the crop and develop the plant architecture to support the fruit. The crop is being grown using both surface and subsurface drip irrigation with 3 levels of applied fertilizer. The fertilizer treatments are characterized as being 50% and 150% of required N. The irrigation is controlled by the weighing lysimeter that measures the crop water use on an hourly basis and initiates irrigation when 1 mm of water has been used by the plant. Fertilizer is injected during the irrigation. All plots are fully irrigated to meet the crop water demand. The fruit were harvested in November and characterized as being either prime or juice. The prime fruit are destined to the fresh fruit market while the juice fruit were supplied to the juice industry. The prime fruit yielded 13 metric tonnes per hectare and the juice fruit yielded 10 metric tonnes per hectare. These values corresponded to typical yields in commercial orchards. There was no statistical difference in yield across the 3 applied nitrogen levels. Of particular note was the ability of the drip irrigation management to control the placement of nitrogen within the soil and to eliminate deep percolation losses. This is the first year for implementation of the N treatments and additional years will be required to confirm the required N levels for production. The Kearney Agricultural Center hosts the data from this project on their website http://kare.ucanr.edu/ under the research section http://ucanr.org/sites/KACLysimeter/. This provides access to the daily crop water use for anyone interested in pomegranate water management. The annual report summarizing the applied water data from 2012 is also available at this site.