Open field hydroponics: Concept and application

Abstract

Advanced citrus production systems that combine grove design, size limiting rootstocks, irrigation and nutrient management, and mechanical harvesting have the potential to make citrus more efficient and economically competitive. Recently, the open hydroponic system (OHS) of citrus production has been combined with orchard design to achieve these efficiencies. Open hydroponics are defined as a system of management practices aimed at increased productivity of citrus orchards by continuously applying a balanced nutrient mixture through the irrigation system, limiting the root zone by restricting the number of drippers per tree and maintaining the soil moisture in the rooted zone near field capacity. Concepts of OHS are to maximize water and nutrient use efficiency through improved nutrient availability to concentrate roots in the irrigated zone. These concepts are accomplished through intensive water and nutrient management and results in increased early growth, sustained yields, and reduced nutrient leaching. Additional horticultural principles employed include higher tree density with size-controlling rootstocks grown on soil ridges, if needed, for improved drainage. Limited published information is available for citrus grown under OHS conditions. However, one study reported that orchards on OHS have outgrown trees on conventional production systems and appear to be more productive. Canopy volumes increased by approximately three times and fruit volume by more than five times per unit of N after 4 years of intensive management compared with conventionally grown trees in replicated trials. Yield increases approaching 30% have been reported from several studies in many citrus-producing regions of the world. Use of this advanced production system may maintain higher levels of productivity through improved water and nutrient use efficiencies resulting in improved short- and long-term economic returns, particularly in citrus industries infected with diseases such as Citrus Greening.