2013 Annual Report
1a.Objectives (from AD-416):
Overall objective is to optimize water-nitrogen interactions to improve fertilizer use effieiency (FUE) of young and maturing pomegranate.
Specific objectives include:
a. Determine the real time seasonal nitrogen requirements (N) of DI and SDI irrigated maturing pomegranate that improve FUE without yield reduction.
b. Determine the effectiveness of three nitrogen injection rates with DI and SDI on maintaining adequate N levels in maturing pomegranates.
c. Determine the effect of real time seasonal nitrogen injections (N) with DI and SDI irrigated maturing pomegranate on N leaching losses.
d. Develop fertigation management tools that will allow growing to achieve objective "a" and present these results to interested parties.
e. Determine if concentrations of macronutrients (P,K,Ca, Mg) and micronutrients (Zn, Cu, Mn,Fe B and Se) and eventually healthy bioactive compounds in soil, peel, and fruit are influenced by precise irrigation/fertigation management with DI and SDI.
1b.Approach (from AD-416):
Field and laboratory studies will be conducted. The field study will be conducted on a 3.5 field site on the Kearney Agricultural Center that contains a weighing lysimeter. The experimental design is a randomized complete block design with 2 irrigation types and 3 levels of N application with 5 replications. The irrigation systems are surface drip irrigation (DI) and subsurface drip irrigation (SDI). The 3 nitrogen treatments are 70% of adequate, 100% of adequate and 130% of adequate determined using biweekly petiole analysis. The system will be controlled using the weighing lysimeter. Proportional injection of fertilizers will be used to meet the N objectives. Tree and fruit responses will be determined with canopy measurements, pruned plant biomass and bimonthly plant tissue analysis. In the third year flowers, fruit yields, and quality will be measured and statistically analysed.
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. This is the third year of the project that has been guided by Dr. Phene as the on-site manager. The first 2 years were used to install all the monitoring and control equipment, establish the trees and work out the problems with the operation of the fertilizer injection equipment and the operation of the lysimeter. The third year was the first year for complete data collection and harvest of the fruit. We determined the annual water requirement for the crop. A total of 456 and 441 mm of water was applied by the surface and subsurface drip systems respectively. The additional water was applied by the surface drip irrigation to compensate for evaporation from the soil surface. The applied nitrogen was determined to be adequate to meet the N requirements of the plants. A total of 52 kg-N/ha, 166 kg-N/ha and 279 kg-N/ha were applied for the 3 N treatments. There was a large drop in leaf N following leaf out that returned to adequate levels in all three treatments following irrigation and injection of fertilizer. The yields were not impacted by the fertilization levels. The yields were 21.3, 21.7, and 22.9 metric tonnes per ha respectively for the 3 N treatments with no statistical difference in yield between treatments. These data were used to modify the N treatments in 2013. The soil nitrate data have demonstrated the capability of high frequency irrigation to meet crop water requirement and control N placement in the soil. The soil nitrate data show that it was placed within the root zone and did not move deep within the soil profile. As water supplies become limited, the ability to control water placement and meet crop water requirement with little waste will be critical. Nitrate pollution of groundwater is a real and on-going problem with irrigated agriculture, and equipment and management strategies are needed to minimize and potentially eliminate loss of nitrogen to groundwater. High frequency drip irrigation that is being used and demonstrated in this project is one such technology. The data from this year and subsequent years will be used to develop irrigation and fertilization management tools. Initial results do not indicate significant responses on the nutritional components of pomegranate fruit to varying levels of fertilization. Additional studies will be required to confirm this. This project has been funded for 3 additional years.