Nitrate-sensitive salinity management: An advanced 4R practice to optimize nutrient and water uptake under microirrigation

Project Summary

This study addresses a specific technical problem that the California almond industry is currently facing: How do you prevent nitrate leaching in micro-irrigated almonds orchards while simultaneously preventing salt accumulation in the root zone? Salinity imposes a significant impact in many areas of the central Valley of California and is greatly exacerbated in drought years when groundwater replaces surface water supplies. Californian agriculture is also now legislatively mandated to reduce nitrate leaching. Salinity has historically been managed by the application of water in excess of plant demand to leach salts (particularly Cl) below the active root-zone, NO₃ however, leaches at essentially the same rate as Cl and hence will also move to the saline periphery of the root zone, where it is subject to loss. The control of salinity buildup by leaching, has not been optimized for the microirrigated context, and requires access to adequate water supplies and thus has a high potential risk of nitrate leaching and groundwater contamination. To develop irrigation and fertigation practices that achieve nitrate-sensitive salinity management, will require a deep understanding of root responses to micro-irrigation and the dynamics of nitrate and salinity uptake and movement in saline affected microirrigated orchards. To address this challenge, we propose an integrated study of root architecture and distribution, root physiology and plasticity, under micro-irrigation in almond. This study places a special focus on determining the ‘right place’ and ‘right time’ so that irrigation and fertigation strategies can be optimized to achieve nitrate-sensitive salinity management.