IMPROVING POMEGRANATE FERTIGATION AND NITROGEN USE EFFICIENCY WITH DRIP IRRIGATION SYSTEM
Water Management Research
2012 Annual Report
1a.Objectives (from AD-416):
Determine real time seasonal nitrogen requirements to improve FUE of young and maturing pomegranates using drip and subsurface drip irrigation. Determine required level of nitrogen to maintain N levels in maturing pomegranates. Determine effect of N fertilization on macronutrient concentrations.
1b.Approach (from AD-416):
The project will use a complete randomized design of 2 irrigation treatments and 3 fertilization treatments with 5 replications. The water requirement will be determined by weighing lysimeter and the fertilization will be determined by tissue sampling in years 2 and 3 of the project. This is a field project on 2 acres.
This project supports objective 1 of the parent project. In response to water shortages and rising water and energy costs, California, growers are changing their irrigation practices from flood and furrow irrigation to sprinkler and drip irrigation. However, many growers are still using conventional fertilizer methods such as: soil incorporating and banding methods that apply most fertilizers early in the season when crops need it the least. These fertilizer application methods are not efficient and/or well suited for DI and SDI irrigation methods. This is a report on the activities of the second year of the project. We completed the installation of orchard and control system installation. Baseline soil sampling, water used and applied, evapotranspiration, and basic plant measurements were made. Plant response to fertigation was confirmed and irrigation system operation was confirmed. Trees were irrigated individually with respective water treatment under micro-plot field conditions in Parlier, CA, based in part by weather data collected from CIMIS. The initial results from our nitrogen sampling of plant tissues indicate that pomegranate is very responsive to nitrogen fertilizer. The initial results from the nitrate analysis in the soils demonstrated that we have reasonably uniform nitrogen levels that will not impact the results of the study. The water balance studies demonstrated that the lysimeter system is working very well and will provide adequate data for characterizing the crop water use during the season. A late-season study that characterized the shaded area under the crop demonstrated that the subsurface drip irrigated trees had a larger canopy than the surface drip irrigated trees. Fruits were taken from the trees and discarded to prevent damage to the trees. Next year data will be collected on fruit numbers and size in response to the fertilizer treatments.