Nitrate sensitive salinity management
University of California Davis
The majority of growers in California have adopted their irrigation system to micro-irrigation systems (drip and micro-spray) in response to the need for improving the management practices for both irrigation and fertigation toward a sustainable agricultural practice. Whereas providing water and nutrient to plants through micro-irrigation system offer a great opportunity to move toward Best Management Practices by reducing the water and nutrient loss through runoff and deep percolation, leaching is an undeniable part of irrigated agricultural practices, since salt accumulation in the root zone adversely affects crop growth and yield. Irrigation strategies, fertigation management, nitrate leaching and salinity management are therefore linked and strategies must be developed that optimize productivity while minimizing nitrate leaching and avoiding salt-induced stress. Perennial species and micro-irrigation impose unique challenges for salinity management and strategies developed for annual crops are not optimized for tree crops. Specifically, 1) for salt sensitive crops (e.g., almond) as water quality diminishes greater leaching volumes will be required, 2) micro-irrigation results in local salt deposition at the lateral and vertical margin of the wetting pattern, and thus water and nitrate within this high salt margin will not be available for uptake, 3) if not conducted properly, strategies that optimize salt leaching to the periphery of the rooted zone will simultaneously leach nitrate. Given the complexity of solute management under micro-irrigation and the lack of information on crop response to salinity and the lack of information on the effects of salinity on root distribution and nitrate uptake it is virtually impossible for growers to make informed irrigation management decisions that satisfy the dual goal of minimizing root zone salinity while simultaneously minimizing nitrate leaching. Therefore, proper irrigation/fertigation management guidelines for grower require a more detailed understanding of patterns of root growth and N uptake in response to non-uniform water and salt distribution. The application of irrigation water and fertigated nutrients, as well as root distribution, and nutrient and water uptake all clearly interact with soil properties and fertilizer source in a complex manner that cannot easily be resolved with ‘experience’ or experimentation alone. we aim to employ an existing and widely used modeling platform, HYDRUS, to conduct numerical simulation for different scenarios for a variety of almond cultivar, soil types, and different level of salinity and combine it with data obtained field/lysimeter experiments to be used as an integrated water and nitrate management tool. This will provide a means to transfer outcome of the treatments and findings of this project to other orchards with other soil types, tree root systems, crop salinity threshold, etc.